1337 lines
34 KiB
Odin
1337 lines
34 KiB
Odin
package physics
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import "base:runtime"
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import "bvh"
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import "collision"
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import "core:container/bit_array"
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import "core:fmt"
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import "core:log"
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import "core:math"
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import lg "core:math/linalg"
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import "core:math/rand"
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import "core:slice"
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import "game:container/spanpool"
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import "libs:tracy"
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_ :: log
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_ :: rand
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_ :: math
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_ :: fmt
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_ :: slice
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Solver_Config :: struct {
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// Will automatically do fixed timestep
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timestep: f32,
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gravity: Vec3,
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substreps_minus_one: i32,
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}
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Solver_State :: struct {
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accumulated_time: f32,
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// Incremented when simulate is called (not simulate_step)
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simulation_frame: u32,
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// Number of immediate bodies referenced this frame
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num_referenced_bodies: i32,
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num_referenced_suspension_constraints: i32,
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num_referenced_engines: i32,
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immedate_bodies: map[u32]Immedate_State(Body_Handle),
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immediate_suspension_constraints: map[u32]Immedate_State(Suspension_Constraint_Handle),
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immediate_engines: map[u32]Immedate_State(Engine_Handle),
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}
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destroy_solver_state :: proc(state: ^Solver_State) {
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delete(state.immedate_bodies)
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delete(state.immediate_suspension_constraints)
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delete(state.immediate_engines)
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}
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Immedate_State :: struct($T: typeid) {
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handle: T,
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// When was this referenced last time (frame number)
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last_ref: u32,
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}
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MAX_STEPS :: 10
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// TODO: move into scene.odin
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// Copy current state to next
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sim_state_copy :: proc(dst: ^Sim_State, src: ^Sim_State) {
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tracy.Zone()
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convex_container_reconcile(&src.convex_container)
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dst.num_bodies = src.num_bodies
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dst.first_free_body_plus_one = src.first_free_body_plus_one
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dst.first_free_suspension_constraint_plus_one = src.first_free_suspension_constraint_plus_one
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dst.first_free_engine_plus_one = src.first_free_engine_plus_one
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resize(&dst.bodies, len(src.bodies))
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resize(&dst.suspension_constraints, len(src.suspension_constraints))
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resize(&dst.engines, len(src.engines))
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dst.bodies_slice = dst.bodies[:]
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dst.suspension_constraints_slice = dst.suspension_constraints[:]
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for i in 0 ..< len(dst.bodies) {
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dst.bodies[i] = src.bodies[i]
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}
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for i in 0 ..< len(dst.suspension_constraints) {
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dst.suspension_constraints[i] = src.suspension_constraints[i]
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}
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copy(dst.engines[:], src.engines[:])
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contact_container_copy(&dst.contact_container, src.contact_container)
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convex_container_copy(&dst.convex_container, src.convex_container)
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spanpool.copy(&dst.rpm_torque_curves_pool, src.rpm_torque_curves_pool)
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spanpool.copy(&dst.gear_ratios_pool, src.gear_ratios_pool)
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}
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Step_Mode :: enum {
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Accumulated_Time,
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Single,
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}
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// Top Level Acceleration Structure
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TLAS :: struct {
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bvh_tree: bvh.BVH,
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body_aabbs: []bvh.AABB,
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}
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// TODO: free intermediate temp allocs
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// Creates TLAS using temp allocator
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build_tlas :: proc(sim_state: ^Sim_State, config: Solver_Config) -> TLAS {
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tracy.Zone()
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body_aabbs := make([]bvh.AABB, sim_state.num_bodies, context.temp_allocator)
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body_indices := make([]u16, sim_state.num_bodies, context.temp_allocator)
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{
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aabb_index := 0
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for i in 0 ..< len(sim_state.bodies_slice) {
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body := &sim_state.bodies_slice[i]
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if body.alive {
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aabb := &body_aabbs[aabb_index]
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body_indices[aabb_index] = u16(i)
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aabb_index += 1
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phys_aabb := body_get_aabb(body)
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EXPAND_K :: 2
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expand := lg.abs(EXPAND_K * config.timestep * body.v)
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phys_aabb.extent += expand * 0.5
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aabb.min = phys_aabb.center - phys_aabb.extent
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aabb.max = phys_aabb.center + phys_aabb.extent
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}
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}
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}
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sim_state_bvh := bvh.build_bvh_from_aabbs(body_aabbs, body_indices, context.temp_allocator)
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return TLAS{bvh_tree = sim_state_bvh, body_aabbs = body_aabbs}
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}
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raycast_bodies :: proc(
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sim_state: ^Sim_State,
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tlas: ^TLAS,
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origin, dir: Vec3,
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distance := max(f32),
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) -> (
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t: f32,
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normal: Vec3,
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hit: bool,
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) {
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temp := runtime.default_temp_allocator_temp_begin()
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defer runtime.default_temp_allocator_temp_end(temp)
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t = distance
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ray: bvh.Ray
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ray.origin = origin
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ray.dir = dir
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ray.dir_inv = 1.0 / dir
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it := bvh.iterator_intersect_leaf_ray(&tlas.bvh_tree, ray, distance)
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for leaf_node in bvh.iterator_intersect_leaf_next(&it) {
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for j in 0 ..< leaf_node.prim_len {
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body_idx := tlas.bvh_tree.primitives[leaf_node.child_or_prim_start + j]
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body := get_body(sim_state, index_to_body_handle(int(body_idx)))
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shape := body_get_convex_shape_world(sim_state, body, context.temp_allocator)
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hit_t, _, tmp_normal, _, ok := collision.ray_vs_convex(
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shape,
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ray.origin,
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ray.dir,
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distance,
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)
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if ok && (!hit || hit_t < t) {
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t = hit_t
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normal = tmp_normal
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hit = true
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}
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}
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}
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return
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}
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// TODO: free intermediate temp allocs
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find_new_contacts :: proc(sim_state: ^Sim_State, tlas: ^TLAS) {
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tracy.Zone()
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for i in 0 ..< len(sim_state.bodies_slice) {
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assert(i <= int(max(u16)))
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body_idx := u16(i)
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body := &sim_state.bodies_slice[i]
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if body.alive {
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body_aabb := tlas.body_aabbs[i]
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it := bvh.iterator_intersect_leaf_aabb(&tlas.bvh_tree, body_aabb)
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for leaf_node in bvh.iterator_intersect_leaf_next(&it) {
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for j in 0 ..< leaf_node.prim_len {
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other_body_idx := tlas.bvh_tree.primitives[leaf_node.child_or_prim_start + j]
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prim_aabb := tlas.body_aabbs[other_body_idx]
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pair := make_contact_pair(i32(body_idx), i32(other_body_idx))
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if body_idx != other_body_idx &&
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bvh.test_aabb_vs_aabb(body_aabb, prim_aabb) &&
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!(pair in sim_state.contact_container.lookup) {
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new_contact_idx := len(sim_state.contact_container.contacts)
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resize_soa(&sim_state.contact_container.contacts, new_contact_idx + 1)
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contact := &sim_state.contact_container.contacts[new_contact_idx]
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contact^ = Contact {
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a = Body_Handle(i + 1),
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b = Body_Handle(other_body_idx + 1),
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}
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sim_state.contact_container.lookup[pair] = i32(new_contact_idx)
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}
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}
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}
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}
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}
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}
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// Outer simulation loop for fixed timestepping
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simulate :: proc(
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scene: ^Scene,
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state: ^Solver_State,
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config: Solver_Config,
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dt: f32,
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commit := true, // commit = false is a special mode for debugging physics stepping to allow rerunning the same step each frame
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step_mode := Step_Mode.Accumulated_Time,
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) {
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tracy.Zone()
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assert(config.timestep > 0)
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prune_immediate(scene, state)
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sim_state_copy(get_next_sim_state(scene), get_sim_state(scene))
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sim_state := get_next_sim_state(scene)
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num_steps := 0
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switch step_mode {
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case .Accumulated_Time:
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state.accumulated_time += dt
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for state.accumulated_time >= config.timestep {
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num_steps += 1
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state.accumulated_time -= config.timestep
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if num_steps < MAX_STEPS {
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simulate_step(scene, sim_state, config)
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}
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}
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case .Single:
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simulate_step(scene, get_next_sim_state(scene), config)
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num_steps += 1
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}
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if num_steps > 0 && commit {
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flip_sim_state(scene)
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}
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state.simulation_frame += 1
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state.num_referenced_bodies = 0
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state.num_referenced_suspension_constraints = 0
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state.num_referenced_engines = 0
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}
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GLOBAL_PLANE :: collision.Plane {
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normal = Vec3{0, 1, 0},
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dist = 0,
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}
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Contact :: struct {
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a, b: Body_Handle,
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prev_x_a, prev_x_b: Vec3,
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prev_q_a, prev_q_b: Quat,
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manifold: collision.Contact_Manifold,
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applied_corrections: int,
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// For PGS
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total_normal_impulse: [4]f32,
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// xy - tangent and bitangent (linear friction), z - twist friction around normal (rotational impulse only)
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total_friction_impulse: [4]Vec2,
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// XPBD stuff
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lambda_normal: [4]f32,
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lambda_tangent: f32,
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applied_static_friction: bool,
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applied_normal_correction: [4]f32,
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}
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update_contacts :: proc(sim_state: ^Sim_State) {
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tracy.Zone()
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graph_color_bitmask: [4]bit_array.Bit_Array
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for i in 0 ..< len(graph_color_bitmask) {
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bit_array.init(
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&graph_color_bitmask[i],
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len(sim_state.bodies_slice),
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0,
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context.temp_allocator,
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)
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}
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for contact_idx in 0 ..< len(sim_state.contact_container.contacts) {
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contact := &sim_state.contact_container.contacts[contact_idx]
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i, j := i32(contact.a) - 1, i32(contact.b) - 1
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body, body2 := &sim_state.bodies_slice[i], &sim_state.bodies_slice[j]
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assert(body.alive)
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assert(body2.alive)
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old_manifold := contact.manifold
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old_total_normal_impulse := contact.total_normal_impulse
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old_total_friction_impulse := contact.total_friction_impulse
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contact.prev_x_a = body.x
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contact.prev_x_b = body2.x
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contact.prev_q_a = body.q
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contact.prev_q_b = body2.q
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contact.manifold = {}
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contact.total_normal_impulse = 0
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contact.total_friction_impulse = 0
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contact.lambda_normal = 0
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contact.lambda_tangent = 0
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contact.applied_static_friction = false
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contact.applied_normal_correction = 0
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aabb1, aabb2 := body_get_aabb(body), body_get_aabb(body2)
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// TODO: extract common math functions into a sane place
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if !collision.test_aabb_vs_aabb(
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{min = aabb1.center - aabb1.extent, max = aabb1.center + aabb1.extent},
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{min = aabb2.center - aabb2.extent, max = aabb2.center + aabb2.extent},
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) {
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continue
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}
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m1, m2 :=
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body_get_convex_shape_world(sim_state, body),
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body_get_convex_shape_world(sim_state, body2)
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// Raw manifold has contact points in world space
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raw_manifold, collision := collision.convex_vs_convex_sat(m1, m2)
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if collision {
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assert(raw_manifold.points_len > 0)
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manifold := &contact.manifold
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manifold^ = raw_manifold
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// Convert manifold contact from world to local space
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for point_idx in 0 ..< manifold.points_len {
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manifold.points_a[point_idx] = body_world_to_local(
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body,
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manifold.points_a[point_idx],
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)
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manifold.points_b[point_idx] = body_world_to_local(
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body2,
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manifold.points_b[point_idx],
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)
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}
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preserve_impulse :=
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old_manifold.points_len == raw_manifold.points_len &&
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old_manifold.type == raw_manifold.type
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if preserve_impulse {
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contact.total_normal_impulse = old_total_normal_impulse
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for point_idx in 0 ..< manifold.points_len {
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contact.total_friction_impulse[point_idx].x = lg.dot(
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old_total_friction_impulse[point_idx].x * old_manifold.tangent,
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manifold.tangent,
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)
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contact.total_friction_impulse[point_idx].y = lg.dot(
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old_total_friction_impulse[point_idx].y * old_manifold.bitangent,
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manifold.bitangent,
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)
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}
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}
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}
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}
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}
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calculate_soft_constraint_params :: proc(
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natural_freq, damping_ratio, dt: f32,
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) -> (
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bias_rate: f32,
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mass_coef: f32,
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impulse_coef: f32,
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) {
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omega := 2.0 * math.PI * natural_freq // angular frequency
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a1 := 2.0 * damping_ratio + omega * dt
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a2 := dt * omega * a1
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a3 := 1.0 / (1.0 + a2)
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bias_rate = omega / a1
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mass_coef = a2 * a3
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impulse_coef = a3
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return
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}
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pgs_solve_contacts :: proc(
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sim_state: ^Sim_State,
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config: Solver_Config,
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dt: f32,
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inv_dt: f32,
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apply_bias: bool,
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) {
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bias_rate, mass_coef, impulse_coef := calculate_soft_constraint_params(30, 0.8, dt)
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if !apply_bias {
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mass_coef = 1
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bias_rate = 0
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impulse_coef = 0
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}
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random_order := make([]i32, len(sim_state.contact_container.contacts), context.temp_allocator)
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{
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for i in 0 ..< len(random_order) {
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random_order[i] = i32(i)
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}
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// for i in 0 ..< len(random_order) - 1 {
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// j := rand.int_max(len(random_order))
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// slice.swap(random_order, i, j)
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// }
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}
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for i in 0 ..< len(sim_state.contact_container.contacts) {
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contact := &sim_state.contact_container.contacts[random_order[i]]
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manifold := &contact.manifold
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body1, body2 := get_body(sim_state, contact.a), get_body(sim_state, contact.b)
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for point_idx in 0 ..< manifold.points_len {
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p1, p2 :=
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body_local_to_world(body1, manifold.points_a[point_idx]),
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body_local_to_world(body2, manifold.points_b[point_idx])
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p_diff_normal := lg.dot(p2 - p1, manifold.normal)
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separation := min(p_diff_normal, 0)
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if separation < 0 {
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// r1, r2 := p1 - body1.x, p2 - body2.x
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v1 := body_velocity_at_point(body1, p1)
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v2 := body_velocity_at_point(body2, p2)
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w1 := get_body_inverse_mass(body1, manifold.normal, p1)
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w2 := get_body_inverse_mass(body2, manifold.normal, p2)
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w := w1 + w2
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if w == 0 {
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continue
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}
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inv_w := 1.0 / w
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delta_v := v2 - v1
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{
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delta_v_norm := lg.dot(delta_v, manifold.normal)
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bias := f32(0.0)
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MAX_BAUMGARTE_VELOCITY :: 4.0
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if separation > 0 {
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bias = separation * inv_dt
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} else if apply_bias {
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bias = lg.max(bias_rate * separation, -MAX_BAUMGARTE_VELOCITY)
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}
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incremental_impulse :=
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-inv_w * mass_coef * (delta_v_norm + bias) -
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impulse_coef * contact.total_normal_impulse[point_idx]
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new_total_impulse := max(
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contact.total_normal_impulse[point_idx] + incremental_impulse,
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0,
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)
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applied_impulse := new_total_impulse - contact.total_normal_impulse[point_idx]
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contact.total_normal_impulse[point_idx] = new_total_impulse
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applied_impulse_vec := applied_impulse * manifold.normal
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apply_velocity_correction(body1, -applied_impulse_vec, p1)
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apply_velocity_correction(body2, applied_impulse_vec, p2)
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}
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{
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DYNAMIC_FRICTION :: 0.6
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STATIC_FRICTION :: 0.8
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STATIC_FRICTION_VELOCITY_THRESHOLD :: 0.01
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delta_v_tang := Vec2 {
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lg.dot(delta_v, manifold.tangent),
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lg.dot(delta_v, manifold.bitangent),
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}
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use_static_friction :=
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lg.dot(delta_v_tang, delta_v_tang) <
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STATIC_FRICTION_VELOCITY_THRESHOLD * STATIC_FRICTION_VELOCITY_THRESHOLD
|
|
friction: f32 = use_static_friction ? STATIC_FRICTION : DYNAMIC_FRICTION
|
|
friction_clamp := contact.total_normal_impulse[point_idx] * friction
|
|
|
|
incremental_impulse := -inv_w * delta_v_tang
|
|
|
|
new_total_impulse: Vec2 = lg.clamp(
|
|
contact.total_friction_impulse[point_idx] + incremental_impulse,
|
|
Vec2(-friction_clamp),
|
|
Vec2(friction_clamp),
|
|
)
|
|
|
|
applied_impulse :=
|
|
new_total_impulse - contact.total_friction_impulse[point_idx]
|
|
contact.total_friction_impulse[point_idx] = new_total_impulse
|
|
|
|
applied_impulse_vec :=
|
|
applied_impulse.x * manifold.tangent +
|
|
applied_impulse.y * manifold.bitangent
|
|
|
|
apply_velocity_correction(body1, -applied_impulse_vec, p1)
|
|
apply_velocity_correction(body2, applied_impulse_vec, p2)
|
|
}
|
|
} else {
|
|
contact.total_normal_impulse[point_idx] = 0
|
|
contact.total_friction_impulse[point_idx] = 0
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Returns index into the gear ratios array
|
|
// -1 (revers) mapped to 0
|
|
// 1..N mapped to 0..N-1
|
|
lookup_gear_ratio :: #force_inline proc(gear_ratios: []f32, gear: i32) -> (ratio: f32) {
|
|
assert(len(gear_ratios) > 1)
|
|
if gear == 0 {
|
|
return 0
|
|
} else {
|
|
index := int(gear + 1)
|
|
if index > 0 {
|
|
index -= 1
|
|
}
|
|
index = clamp(index, 0, len(gear_ratios) - 1)
|
|
return gear_ratios[index]
|
|
}
|
|
}
|
|
|
|
pgs_solve_engines :: proc(sim_state: ^Sim_State, config: Solver_Config, dt: f32, inv_dt: f32) {
|
|
for &engine in sim_state.engines {
|
|
if engine.alive {
|
|
rpm_torque_curve := get_engine_curve(sim_state, engine.rpm_torque_curve)
|
|
gear_ratios := get_gear_ratios(sim_state, engine.gear_ratios)
|
|
|
|
// Unstall impulse
|
|
{
|
|
engine_lowest_velocity := rpm_to_angular_velocity(engine.lowest_rpm)
|
|
|
|
delta_omega := engine_lowest_velocity - engine.w
|
|
|
|
inv_w := engine.inertia
|
|
|
|
incremental_impulse := inv_w * delta_omega
|
|
new_total_impulse := max(engine.unstall_impulse + incremental_impulse, 0)
|
|
applied_impulse := new_total_impulse - engine.unstall_impulse
|
|
engine.unstall_impulse = new_total_impulse
|
|
|
|
engine.w += applied_impulse / engine.inertia
|
|
}
|
|
|
|
rpm := angular_velocity_to_rpm(engine.w)
|
|
throttle := engine.throttle
|
|
|
|
if engine.rev_limit_time < 0.0 {
|
|
engine.rev_limit_time += dt
|
|
throttle = 0
|
|
} else if (rpm >= engine.rev_limit_rpm) {
|
|
engine.rev_limit_time = -engine.rev_limit_interval
|
|
throttle = 0
|
|
}
|
|
|
|
|
|
// Throttle
|
|
{
|
|
|
|
{
|
|
torque: f32
|
|
|
|
idx, _ := slice.binary_search_by(
|
|
rpm_torque_curve,
|
|
rpm,
|
|
proc(a: [2]f32, k: f32) -> slice.Ordering {
|
|
return slice.cmp(a[0], k)
|
|
},
|
|
)
|
|
|
|
if idx > 0 && idx < len(rpm_torque_curve) - 1 {
|
|
cur_point := rpm_torque_curve[idx]
|
|
next_point := rpm_torque_curve[idx + 1]
|
|
rpm_diff := next_point[0] - cur_point[0]
|
|
alpha := (rpm - cur_point[0]) / rpm_diff
|
|
|
|
torque = math.lerp(cur_point[1], next_point[1], alpha)
|
|
} else {
|
|
torque = rpm_torque_curve[math.clamp(idx, 0, len(rpm_torque_curve) - 1)][1]
|
|
}
|
|
|
|
// log.debugf("torque: %v Nm", torque)
|
|
torque *= throttle
|
|
|
|
engine.w += (torque / engine.inertia) * dt
|
|
}
|
|
}
|
|
|
|
// Internal Friction
|
|
{
|
|
delta_omega := -engine.w
|
|
|
|
inv_w := engine.inertia
|
|
|
|
friction :=
|
|
math.pow(max(engine.w - rpm_to_angular_velocity(engine.lowest_rpm), 0), 2) *
|
|
0.0001 *
|
|
engine.internal_friction +
|
|
engine.internal_friction
|
|
|
|
// Not physically based, but we assume when throttle is open there is no friction
|
|
friction *= (1.0 - throttle)
|
|
|
|
incremental_impulse := inv_w * delta_omega
|
|
new_total_impulse := math.clamp(
|
|
engine.friction_impulse + incremental_impulse,
|
|
-friction,
|
|
friction,
|
|
)
|
|
applied_impulse := new_total_impulse - engine.friction_impulse
|
|
engine.friction_impulse = new_total_impulse
|
|
|
|
engine.w += applied_impulse / engine.inertia
|
|
}
|
|
|
|
// Transmission
|
|
{
|
|
gear_ratio := lookup_gear_ratio(gear_ratios, engine.gear)
|
|
|
|
if engine.gear != 0 {
|
|
ratio := gear_ratio * engine.axle.final_drive_ratio
|
|
inv_ratio := f32(1.0 / (ratio))
|
|
|
|
drive_wheel1 := &engine.axle.wheels[0]
|
|
wheel1 := get_suspension_constraint(sim_state, drive_wheel1.wheel)
|
|
|
|
drive_wheel2 := &engine.axle.wheels[1]
|
|
wheel2 := get_suspension_constraint(sim_state, drive_wheel2.wheel)
|
|
|
|
w1 := f32(1.0 / (engine.inertia * ratio * ratio))
|
|
w2 := wheel1.inv_inertia
|
|
w3 := wheel2.inv_inertia
|
|
|
|
w := w1 + w2 + w3
|
|
inv_w := f32(1.0 / w)
|
|
|
|
avg_wheel_vel := (wheel1.w + wheel2.w) * 0.5
|
|
|
|
delta_omega := avg_wheel_vel * ratio - (-engine.w)
|
|
|
|
incremental_impulse := -inv_w * delta_omega
|
|
engine.axle.engine_impulse += incremental_impulse
|
|
|
|
engine.w += incremental_impulse * w1
|
|
wheel1.w += incremental_impulse * w2 * inv_ratio
|
|
wheel2.w += incremental_impulse * w3 * inv_ratio
|
|
}
|
|
}
|
|
|
|
// Diff
|
|
{
|
|
switch engine.axle.diff_type {
|
|
case .Open:
|
|
case .Fixed:
|
|
drive_wheel1 := &engine.axle.wheels[0]
|
|
wheel1 := get_suspension_constraint(sim_state, drive_wheel1.wheel)
|
|
|
|
drive_wheel2 := &engine.axle.wheels[1]
|
|
wheel2 := get_suspension_constraint(sim_state, drive_wheel2.wheel)
|
|
|
|
w1 := wheel1.inv_inertia
|
|
w2 := wheel2.inv_inertia
|
|
|
|
w := w1 + w2
|
|
inv_w := f32(1.0 / w)
|
|
|
|
delta_omega := wheel2.w - wheel1.w
|
|
|
|
incremental_impulse := -inv_w * delta_omega
|
|
engine.axle.diff_impulse += incremental_impulse
|
|
|
|
wheel1.w += -incremental_impulse * wheel1.inv_inertia
|
|
wheel2.w += incremental_impulse * wheel2.inv_inertia
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
pgs_solve_suspension :: proc(
|
|
sim_state: ^Sim_State,
|
|
tlas: ^TLAS,
|
|
config: Solver_Config,
|
|
dt: f32,
|
|
inv_dt: f32,
|
|
) {
|
|
// Solve suspension velocity
|
|
for _, i in sim_state.suspension_constraints {
|
|
v := &sim_state.suspension_constraints_slice[i]
|
|
if v.alive {
|
|
body := get_body(sim_state, v.body)
|
|
|
|
if body.alive {
|
|
wheel_world_pos := body_local_to_world(body, v.rel_pos)
|
|
dir := body_local_to_world_vec(body, v.rel_dir)
|
|
v.hit_t, v.hit_normal, v.hit = raycast_bodies(
|
|
sim_state,
|
|
tlas,
|
|
wheel_world_pos,
|
|
dir,
|
|
v.rest,
|
|
)
|
|
// log.debugf("hit_t: %v, hit: %v", v.hit_t, v.hit)
|
|
v.hit_point = wheel_world_pos + dir * v.hit_t
|
|
|
|
forward := wheel_get_forward_vec(body, v)
|
|
right := wheel_get_right_vec(body, v)
|
|
|
|
body_vel_at_contact_patch := body_velocity_at_point(body, v.hit_point)
|
|
|
|
w_normal := get_body_angular_inverse_mass(body, dir)
|
|
inv_w_normal := 1.0 / w_normal
|
|
|
|
// Drive force
|
|
if true {
|
|
total_impulse := -v.drive_impulse
|
|
|
|
v.w += v.inv_inertia * total_impulse * dt
|
|
}
|
|
|
|
// Brake force
|
|
if true {
|
|
// How strong is brake pad pushing against brake disc
|
|
brake_pad_impulse := v.brake_impulse
|
|
|
|
if brake_pad_impulse != 0 {
|
|
// TODO: figure out what's the realistic value
|
|
brake_friction := f32(1.0)
|
|
friction_clamp := brake_pad_impulse * brake_friction
|
|
|
|
incremental_impulse := (1.0 / v.inv_inertia) * -v.w
|
|
new_total_impulse := clamp(
|
|
v.brake_friction_impulse + incremental_impulse,
|
|
-friction_clamp,
|
|
friction_clamp,
|
|
)
|
|
applied_impulse := new_total_impulse - v.brake_friction_impulse
|
|
v.brake_friction_impulse = new_total_impulse
|
|
|
|
v.w += v.inv_inertia * applied_impulse
|
|
} else {
|
|
v.brake_friction_impulse = 0
|
|
}
|
|
}
|
|
|
|
if v.hit {
|
|
|
|
// Spring force
|
|
{
|
|
bias_coef, mass_coef, impulse_coef := calculate_soft_constraint_params(
|
|
v.natural_frequency,
|
|
v.damping,
|
|
dt,
|
|
)
|
|
|
|
vel := lg.dot(body_velocity_at_point(body, wheel_world_pos), dir)
|
|
x := v.hit_t
|
|
separation := v.rest - x
|
|
|
|
incremental_impulse :=
|
|
-inv_w_normal * mass_coef * (vel + separation * bias_coef) -
|
|
impulse_coef * v.spring_impulse
|
|
v.spring_impulse += incremental_impulse
|
|
|
|
apply_velocity_correction(body, incremental_impulse * dir, wheel_world_pos)
|
|
}
|
|
|
|
// Positive means spinning forward
|
|
wheel_spin_vel := -v.radius * v.w
|
|
ground_vel_x := lg.dot(body_vel_at_contact_patch, right)
|
|
ground_vel_y := lg.dot(body_vel_at_contact_patch, forward)
|
|
// contact_patch_linear_vel :=
|
|
// body_vel_at_contact_patch + (v.radius * v.w * forward)
|
|
|
|
slip_ratio :=
|
|
ground_vel_y == 0 ? 0 : clamp(wheel_spin_vel / ground_vel_y - 1, -1, 1) * 100.0
|
|
|
|
slip_angle :=
|
|
-lg.angle_between(Vec2{0, 1}, Vec2{ground_vel_x, ground_vel_y}) *
|
|
math.DEG_PER_RAD
|
|
|
|
v.slip_ratio = slip_ratio
|
|
v.slip_angle = slip_angle
|
|
|
|
MAX_SLIP_LEN :: f32(2.0)
|
|
|
|
slip_vec := Vec2 {
|
|
slip_angle / PACEJKA94_LATERAL_PEAK_X / MAX_SLIP_LEN,
|
|
slip_ratio / PACEJKA94_LONGITUDINAL_PEAK_X / MAX_SLIP_LEN,
|
|
}
|
|
|
|
slip_len := lg.length(slip_vec)
|
|
slip_len = slip_len == 0 ? 0 : min(slip_len, 1) / slip_len
|
|
slip_vec *= slip_len
|
|
|
|
v.slip_vec = slip_vec
|
|
|
|
// log.debugf("slip_vec: %v", slip_vec)
|
|
|
|
long_friction :=
|
|
abs(
|
|
pacejka_94_longitudinal(
|
|
v.pacejka_long,
|
|
slip_ratio,
|
|
max(abs(v.spring_impulse), 0.001) * inv_dt * 0.001,
|
|
),
|
|
) *
|
|
abs(slip_vec.y)
|
|
lat_friction :=
|
|
abs(
|
|
pacejka_94_lateral(
|
|
v.pacejka_lat,
|
|
slip_angle,
|
|
max(abs(v.spring_impulse), 0.001) * inv_dt * 0.001,
|
|
0.0,
|
|
),
|
|
) *
|
|
abs(slip_vec.x)
|
|
|
|
// Longitudinal friction
|
|
if true {
|
|
// Wheel linear velocity relative to ground
|
|
relative_vel := ground_vel_y - wheel_spin_vel
|
|
|
|
friction_clamp := abs(v.spring_impulse) * long_friction
|
|
|
|
w_body := get_body_inverse_mass(body, forward, v.hit_point)
|
|
|
|
w_long := w_body + v.inv_inertia
|
|
inv_w_long := 1.0 / w_long
|
|
|
|
incremental_impulse := -inv_w_long * relative_vel
|
|
new_total_impulse := clamp(
|
|
v.longitudinal_impulse + incremental_impulse,
|
|
-friction_clamp,
|
|
friction_clamp,
|
|
)
|
|
applied_impulse := new_total_impulse - v.longitudinal_impulse
|
|
v.longitudinal_impulse = new_total_impulse
|
|
|
|
apply_velocity_correction(body, applied_impulse * forward, v.hit_point)
|
|
v.w += v.inv_inertia * applied_impulse
|
|
}
|
|
// Lateral friction
|
|
if true {
|
|
vel_contact := body_vel_at_contact_patch
|
|
|
|
lateral_vel := lg.dot(right, vel_contact)
|
|
friction_clamp := abs(v.spring_impulse) * lat_friction
|
|
|
|
incremental_impulse := -inv_w_normal * lateral_vel
|
|
new_total_impulse := clamp(
|
|
v.lateral_impulse + incremental_impulse,
|
|
-friction_clamp,
|
|
friction_clamp,
|
|
)
|
|
applied_impulse := new_total_impulse - v.lateral_impulse
|
|
v.lateral_impulse = new_total_impulse
|
|
|
|
apply_velocity_correction(body, applied_impulse * right, v.hit_point)
|
|
}
|
|
} else {
|
|
v.lateral_impulse = 0
|
|
v.spring_impulse = 0
|
|
v.longitudinal_impulse = 0
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
pgs_substep :: proc(
|
|
sim_state: ^Sim_State,
|
|
tlas: ^TLAS,
|
|
config: Solver_Config,
|
|
dt: f32,
|
|
inv_dt: f32,
|
|
) {
|
|
for i in 0 ..< len(sim_state.bodies_slice) {
|
|
body := &sim_state.bodies_slice[i]
|
|
|
|
if body.alive {
|
|
body.v += config.gravity * dt * (body.inv_mass == 0 ? 0 : 1) // special case for gravity, TODO
|
|
}
|
|
}
|
|
|
|
// Warm start
|
|
if true {
|
|
for i in 0 ..< len(sim_state.contact_container.contacts) {
|
|
contact := &sim_state.contact_container.contacts[i]
|
|
manifold := &contact.manifold
|
|
|
|
body1, body2 := get_body(sim_state, contact.a), get_body(sim_state, contact.b)
|
|
|
|
for point_idx in 0 ..< manifold.points_len {
|
|
p1, p2 :=
|
|
body_local_to_world(body1, manifold.points_a[point_idx]),
|
|
body_local_to_world(body2, manifold.points_b[point_idx])
|
|
total_normal_impulse := contact.total_normal_impulse[point_idx] * manifold.normal
|
|
|
|
apply_velocity_correction(body1, -total_normal_impulse, p1)
|
|
apply_velocity_correction(body2, total_normal_impulse, p2)
|
|
|
|
total_tangent_impulse :=
|
|
contact.total_friction_impulse[point_idx].x * manifold.tangent +
|
|
contact.total_friction_impulse[point_idx].y * manifold.bitangent
|
|
|
|
apply_velocity_correction(body1, -total_tangent_impulse, p1)
|
|
apply_velocity_correction(body2, total_tangent_impulse, p2)
|
|
}
|
|
}
|
|
|
|
for i in 0 ..< len(sim_state.engines) {
|
|
e := &sim_state.engines[i]
|
|
|
|
if e.alive {
|
|
gear_ratios := get_gear_ratios(sim_state, e.gear_ratios)
|
|
e.w += e.unstall_impulse / e.inertia
|
|
|
|
e.w += e.friction_impulse / e.inertia
|
|
|
|
// Warm start engine torque
|
|
if false {
|
|
drive_wheel1 := &e.axle.wheels[0]
|
|
wheel1 := get_suspension_constraint(sim_state, drive_wheel1.wheel)
|
|
|
|
drive_wheel2 := &e.axle.wheels[1]
|
|
wheel2 := get_suspension_constraint(sim_state, drive_wheel2.wheel)
|
|
|
|
gear_ratio := lookup_gear_ratio(gear_ratios, e.gear)
|
|
|
|
if e.gear != 0 {
|
|
ratio := gear_ratio * e.axle.final_drive_ratio
|
|
inv_ratio := f32(1.0 / (ratio))
|
|
|
|
w1 := f32(1.0 / (e.inertia * ratio * ratio))
|
|
w2 := wheel1.inv_inertia
|
|
w3 := wheel2.inv_inertia
|
|
|
|
e.w += e.axle.engine_impulse * w1
|
|
wheel1.w += e.axle.engine_impulse * w2 * inv_ratio
|
|
wheel2.w += e.axle.engine_impulse * w3 * inv_ratio
|
|
}
|
|
|
|
// Warmp start diff impulse
|
|
if false {
|
|
switch e.axle.diff_type {
|
|
case .Open:
|
|
case .Fixed:
|
|
wheel1.w += -e.axle.diff_impulse * wheel1.inv_inertia
|
|
wheel2.w += e.axle.diff_impulse * wheel2.inv_inertia
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
for i in 0 ..< len(sim_state.suspension_constraints) {
|
|
s := &sim_state.suspension_constraints_slice[i]
|
|
|
|
if s.hit {
|
|
body := get_body(sim_state, s.body)
|
|
p := body_local_to_world(body, s.rel_pos)
|
|
hit_p := body_local_to_world(body, s.rel_pos + s.rel_dir * s.hit_t)
|
|
forward := wheel_get_forward_vec(body, s)
|
|
right := wheel_get_right_vec(body, s)
|
|
|
|
apply_velocity_correction(
|
|
body,
|
|
s.spring_impulse * body_local_to_world_vec(body, s.rel_dir),
|
|
p,
|
|
)
|
|
apply_velocity_correction(body, s.lateral_impulse * right, p)
|
|
|
|
apply_velocity_correction(body, s.longitudinal_impulse * forward, hit_p)
|
|
s.w += s.inv_inertia * s.longitudinal_impulse
|
|
}
|
|
|
|
s.w += s.inv_inertia * s.brake_friction_impulse
|
|
}
|
|
}
|
|
|
|
apply_bias := true
|
|
pgs_solve_contacts(sim_state, config, dt, inv_dt, apply_bias)
|
|
pgs_solve_engines(sim_state, config, dt, inv_dt)
|
|
pgs_solve_suspension(sim_state, tlas, config, dt, inv_dt)
|
|
|
|
for i in 0 ..< len(sim_state.bodies_slice) {
|
|
body := &sim_state.bodies_slice[i]
|
|
|
|
if body.alive {
|
|
body.x += body.v * dt
|
|
|
|
// NOTE: figure out how this works https://fgiesen.wordpress.com/2012/08/24/quaternion-differentiation/
|
|
q := body.q
|
|
|
|
w := body.w
|
|
delta_rot := quaternion(x = w.x, y = w.y, z = w.z, w = 0)
|
|
delta_rot = delta_rot * q
|
|
q.x += 0.5 * dt * delta_rot.x
|
|
q.y += 0.5 * dt * delta_rot.y
|
|
q.z += 0.5 * dt * delta_rot.z
|
|
q.w += 0.5 * dt * delta_rot.w
|
|
q = lg.normalize0(q)
|
|
|
|
body.q = q
|
|
}
|
|
}
|
|
|
|
for i in 0 ..< len(sim_state.engines) {
|
|
e := &sim_state.engines[i]
|
|
|
|
e.q = math.mod_f32(e.q + 0.5 * e.w * dt, math.PI * 2)
|
|
}
|
|
|
|
for i in 0 ..< len(sim_state.suspension_constraints_slice) {
|
|
s := &sim_state.suspension_constraints_slice[i]
|
|
|
|
s.q = math.mod_f32(s.q + 0.5 * s.w * dt, math.PI * 2)
|
|
}
|
|
|
|
apply_bias = false
|
|
pgs_solve_contacts(sim_state, config, dt, inv_dt, apply_bias)
|
|
// pgs_solve_suspension(sim_state, config, dt, inv_dt, apply_bias)
|
|
}
|
|
|
|
simulate_step :: proc(scene: ^Scene, sim_state: ^Sim_State, config: Solver_Config) {
|
|
tracy.Zone()
|
|
|
|
substeps := config.substreps_minus_one + 1
|
|
|
|
dt := config.timestep / f32(substeps)
|
|
inv_dt := 1.0 / dt
|
|
|
|
|
|
tlas := build_tlas(sim_state, config)
|
|
|
|
{
|
|
tracy.ZoneN("simulate_step::remove_invalid_contacts")
|
|
i := 0
|
|
for i < len(sim_state.contact_container.contacts) {
|
|
contact := sim_state.contact_container.contacts[i]
|
|
|
|
aabb_a := tlas.body_aabbs[int(contact.a) - 1]
|
|
aabb_b := tlas.body_aabbs[int(contact.b) - 1]
|
|
|
|
if !bvh.test_aabb_vs_aabb(aabb_a, aabb_b) {
|
|
removed_pair := make_contact_pair(i32(contact.a) - 1, i32(contact.b) - 1)
|
|
delete_key(&sim_state.contact_container.lookup, removed_pair)
|
|
|
|
unordered_remove_soa(&sim_state.contact_container.contacts, i)
|
|
|
|
if i < len(sim_state.contact_container.contacts) {
|
|
moved_contact := &sim_state.contact_container.contacts[i]
|
|
moved_pair := make_contact_pair(
|
|
i32(moved_contact.a) - 1,
|
|
i32(moved_contact.b) - 1,
|
|
)
|
|
sim_state.contact_container.lookup[moved_pair] = i32(i)
|
|
}
|
|
} else {
|
|
i += 1
|
|
}
|
|
}
|
|
}
|
|
|
|
find_new_contacts(sim_state, &tlas)
|
|
|
|
update_contacts(sim_state)
|
|
|
|
Solver :: enum {
|
|
XPBD,
|
|
PGS,
|
|
}
|
|
|
|
solver := Solver.PGS
|
|
|
|
switch solver {
|
|
case .XPBD:
|
|
for _ in 0 ..< substeps {
|
|
xpbd_substep(sim_state, config, dt, inv_dt)
|
|
}
|
|
case .PGS:
|
|
for _ in 0 ..< substeps {
|
|
pgs_substep(sim_state, &tlas, config, dt, inv_dt)
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
body_solve_velocity :: #force_inline proc(
|
|
body: Body_Ptr,
|
|
prev_x: Vec3,
|
|
prev_q: Quat,
|
|
inv_dt: f32,
|
|
) {
|
|
body.v = (body.x - prev_x) * inv_dt
|
|
|
|
delta_q := body.q * lg.quaternion_inverse(prev_q)
|
|
body.w = Vec3{delta_q.x, delta_q.y, delta_q.z} * 2.0 * inv_dt
|
|
|
|
if delta_q.w < 0 {
|
|
body.w = -body.w
|
|
}
|
|
}
|
|
|
|
calculate_constraint_params1 :: proc(
|
|
dt: f32,
|
|
body: Body_Ptr,
|
|
compliance: f32,
|
|
error: f32,
|
|
error_gradient: Vec3,
|
|
pos: Vec3,
|
|
other_combined_inv_mass: f32,
|
|
) -> (
|
|
lambda: f32,
|
|
w: f32,
|
|
correction: Vec3,
|
|
ok: bool,
|
|
) {
|
|
if error == 0 {
|
|
return
|
|
}
|
|
|
|
w = get_body_inverse_mass(body, error_gradient, pos)
|
|
w += other_combined_inv_mass
|
|
|
|
if w == 0 {
|
|
return
|
|
}
|
|
|
|
ok = true
|
|
|
|
alpha := compliance / dt / dt
|
|
lambda = -error / (w + alpha)
|
|
correction = -error_gradient * -lambda
|
|
|
|
return
|
|
}
|
|
|
|
calculate_constraint_params2 :: proc(
|
|
dt: f32,
|
|
body1: Body_Ptr,
|
|
body2: Body_Ptr,
|
|
compliance: f32,
|
|
error: f32,
|
|
error_gradient: Vec3,
|
|
pos1: Vec3,
|
|
pos2: Vec3,
|
|
) -> (
|
|
lambda: f32,
|
|
correction1: Vec3,
|
|
correction2: Vec3,
|
|
ok: bool,
|
|
) {
|
|
if error == 0 {
|
|
return
|
|
}
|
|
|
|
w := get_body_inverse_mass(body1, error_gradient, pos1)
|
|
w += get_body_inverse_mass(body2, error_gradient, pos2)
|
|
|
|
if w == 0 {
|
|
return
|
|
}
|
|
|
|
ok = true
|
|
|
|
alpha := compliance / dt / dt
|
|
lambda = -error / (w + alpha)
|
|
correction1 = -error_gradient * -lambda
|
|
correction2 = error_gradient * -lambda
|
|
|
|
return
|
|
}
|
|
|
|
apply_constraint_correction_unilateral :: proc(
|
|
dt: f32,
|
|
body: Body_Ptr,
|
|
compliance: f32,
|
|
error: f32,
|
|
error_gradient: Vec3,
|
|
pos: Vec3,
|
|
other_combined_inv_mass: f32 = 0,
|
|
) -> (
|
|
lambda: f32,
|
|
) {
|
|
w: f32
|
|
correction: Vec3
|
|
ok: bool
|
|
lambda, w, correction, ok = calculate_constraint_params1(
|
|
dt,
|
|
body,
|
|
compliance,
|
|
error,
|
|
error_gradient,
|
|
pos,
|
|
other_combined_inv_mass,
|
|
)
|
|
|
|
if ok {
|
|
apply_position_correction(body, correction, pos)
|
|
}
|
|
|
|
return
|
|
}
|
|
|
|
multiply_inv_intertia :: proc(body: Body_Ptr, vec: Vec3) -> (result: Vec3) {
|
|
q := body.q
|
|
inv_q := lg.quaternion_normalize0(lg.quaternion_inverse(q))
|
|
|
|
result = lg.quaternion_mul_vector3(inv_q, vec)
|
|
result *= body.inv_inertia_tensor
|
|
result = lg.quaternion_mul_vector3(q, result)
|
|
|
|
return result
|
|
}
|
|
|
|
apply_velocity_correction :: #force_inline proc "contextless" (
|
|
body: Body_Ptr,
|
|
impulse: Vec3,
|
|
pos: Vec3,
|
|
) {
|
|
apply_velocity_correction_linear(body, impulse)
|
|
|
|
angular_impulse := lg.cross(pos - body.x, impulse)
|
|
|
|
apply_velocity_correction_angular(body, angular_impulse)
|
|
}
|
|
|
|
apply_velocity_correction_linear :: #force_inline proc "contextless" (
|
|
body: Body_Ptr,
|
|
impulse: Vec3,
|
|
) {
|
|
body.v += impulse * body.inv_mass
|
|
}
|
|
|
|
apply_velocity_correction_angular :: #force_inline proc "contextless" (
|
|
body: Body_Ptr,
|
|
angular_impulse: Vec3,
|
|
) {
|
|
q := body.q
|
|
inv_q := lg.quaternion_normalize0(lg.quaternion_inverse(q))
|
|
delta_omega := lg.quaternion_mul_vector3(inv_q, angular_impulse)
|
|
delta_omega *= body.inv_inertia_tensor
|
|
delta_omega = lg.quaternion_mul_vector3(q, delta_omega)
|
|
|
|
body.w += delta_omega
|
|
}
|
|
|
|
apply_position_correction :: proc(body: Body_Ptr, corr: Vec3, pos: Vec3) {
|
|
body.x += corr * body.inv_mass
|
|
|
|
q := body.q
|
|
inv_q := lg.quaternion_normalize0(lg.quaternion_inverse(q))
|
|
delta_omega := pos - body.x
|
|
delta_omega = lg.cross(delta_omega, corr)
|
|
delta_omega = lg.quaternion_mul_vector3(inv_q, delta_omega)
|
|
delta_omega *= body.inv_inertia_tensor
|
|
delta_omega = lg.quaternion_mul_vector3(q, delta_omega)
|
|
|
|
delta_rot := quaternion(x = delta_omega.x, y = delta_omega.y, z = delta_omega.z, w = 0)
|
|
delta_rot *= q
|
|
q.x += 0.5 * delta_rot.x
|
|
q.y += 0.5 * delta_rot.y
|
|
q.z += 0.5 * delta_rot.z
|
|
q.w += 0.5 * delta_rot.w
|
|
q = lg.normalize0(q)
|
|
|
|
body.q = q
|
|
}
|
|
|
|
// Total inverse mass (linear + angular)
|
|
get_body_inverse_mass :: proc(body: Body_Ptr, normal, pos: Vec3) -> f32 {
|
|
linear, angular := get_body_inverse_mass_separate(body, normal, pos)
|
|
|
|
return linear + angular
|
|
}
|
|
|
|
get_body_inverse_mass_separate :: proc(
|
|
body: Body_Ptr,
|
|
normal, pos: Vec3,
|
|
) -> (
|
|
linear: f32,
|
|
angular: f32,
|
|
) {
|
|
q := body.q
|
|
inv_q := lg.quaternion_normalize0(lg.quaternion_inverse(q))
|
|
|
|
rn := pos - body.x
|
|
rn = lg.cross(rn, normal)
|
|
rn = lg.quaternion_mul_vector3(inv_q, rn)
|
|
|
|
linear = body.inv_mass
|
|
angular = lg.dot(rn, rn * body.inv_inertia_tensor)
|
|
|
|
return
|
|
}
|
|
|
|
get_body_angular_inverse_mass :: proc(body: Body_Ptr, normal: Vec3) -> f32 {
|
|
q := body.q
|
|
inv_q := lg.quaternion_normalize0(lg.quaternion_inverse(q))
|
|
|
|
n := lg.quaternion_mul_vector3(inv_q, normal)
|
|
|
|
return lg.dot(n, n * body.inv_inertia_tensor)
|
|
}
|