More tyre tweaks, chase camera like in GTA 5, basic rigid body interpolation so rendering can run faster than physics and still see everything smoothly

assets/tyre_lateral.csv

@@ -1,12 +1,12 @@
 a
 1.1
--180
-1500
+-200
+1700
 2000
 10
 0
 0
--1
+-0.5
 0
 0
 0

assets/tyre_longitudinal.csv

@@ -1,9 +1,9 @@
 b
-1.4
--120
-1700
-0
-300
+1.2
+-200
+1400
+20
+1
 0
 0
 0

common/emath/math.odin

@@ -0,0 +1,10 @@
+// "Engine" math, to avoid aliasing with core:math
+package emath
+
+import "core:math"
+
+_ :: math
+
+exp_smooth :: proc "contextless" (target: $T, pos: T, speed: f32, dt: f32) -> T {
+	return pos + ((target - pos) * (1.0 - math.exp_f32(-speed * dt)))
+}

game/game.odin

@@ -15,6 +15,7 @@
 package game
 
 import "assets"
+import "common:emath"
 import "common:name"
 import "core:fmt"
 import "core:log"
@@ -27,6 +28,8 @@ import "libs:raylib/rlgl"
 import "libs:tracy"
 import "ui"
 
+_ :: emath
+
 PIXEL_WINDOW_HEIGHT :: 360
 
 Track :: struct {
@@ -115,6 +118,8 @@ World :: struct {
 	player_pos:    rl.Vector3,
 	track:         Track,
 	physics_scene: physics.Scene,
+	// How much time passed in physics scene, can be 0 when paused
+	physics_dt:    f32,
 	pause:         bool,
 	car_handle:    physics.Body_Handle,
 	engine_handle: physics.Engine_Handle,
@@ -149,8 +154,7 @@ Runtime_World :: struct {
 	camera_yaw_pitch:       rl.Vector2,
 	camera_speed:           f32,
 	camera:                 rl.Camera3D,
-	orbit_camera:           Orbit_Camera,
-	camera_mode:            Camera_Mode,
+	game_camera:            Game_Camera,
 	dt:                     f32,
 	rewind_simulation:      bool,
 	commit_simulation:      bool,
@@ -206,11 +210,6 @@ Game_Memory :: struct {
 	free_cam:       bool,
 }
 
-Camera_Mode :: enum {
-	Orbit,
-	Hood,
-}
-
 Track_Edit_State :: enum {
 	// Point selection
 	Select,
@@ -354,7 +353,7 @@ camera_forward_vec :: proc() -> rl.Vector3 {
 
 game_camera_3d :: proc() -> rl.Camera3D {
 	if g_mem.editor || g_mem.free_cam {
-		return free_camera_to_rl(&g_mem.es.camera)
+		return free_camera_to_rl(g_mem.es.camera)
 	}
 
 	return get_runtime_world().camera
@@ -557,7 +556,7 @@ update_world :: proc(world: ^World, dt: f32, config: World_Update_Config) {
 						u32(box_name),
 						physics.Body_Config {
 							name = box_name,
-							initial_pos = {-5 + f32(y) * 1.01, 1, f32(x) * 1.01 + -11.5},
+							initial_pos = {5 + f32(y) * 1.01, 1, f32(x) * 1.01 + -11.5},
 							initial_rot = linalg.QUATERNIONF32_IDENTITY,
 							shapes = {
 								{
@@ -709,7 +708,8 @@ update_world :: proc(world: ^World, dt: f32, config: World_Update_Config) {
 
 		DRIVE_IMPULSE :: 3000
 		BRAKE_IMPULSE :: 10
-		TURN_ANGLE :: -f32(50) * math.RAD_PER_DEG
+		TURN_ANGLE_AT_HIGH_SPEED :: f32(10) * math.RAD_PER_DEG
+		TURN_ANGLE_AT_LOW_SPEED :: f32(30) * math.RAD_PER_DEG
 		// 68% front, 32% rear
 		BRAKE_BIAS :: f32(0.68)
 
@@ -745,7 +745,7 @@ update_world :: proc(world: ^World, dt: f32, config: World_Update_Config) {
 		}
 
 		car_body := physics.get_body(sim_state, world.car_handle)
-		turn_vel_correction := clamp(4.0 / linalg.length(car_body.v), 0, 1)
+		turn_vel_correction := math.smoothstep(f32(90), f32(10), linalg.length(car_body.v) * 3.6)
 
 		turn_input := rl.GetGamepadAxisMovement(0, .LEFT_X)
 		if abs(turn_input) < GAMEPAD_DEADZONE {
@@ -761,7 +761,10 @@ update_world :: proc(world: ^World, dt: f32, config: World_Update_Config) {
 		for wheel_handle in turn_wheels {
 			wheel := physics.get_suspension_constraint(sim_state, wheel_handle)
 
-			wheel.turn_angle = TURN_ANGLE * turn_vel_correction * turn_input
+			wheel.turn_angle =
+				TURN_ANGLE_AT_HIGH_SPEED +
+				(TURN_ANGLE_AT_LOW_SPEED - TURN_ANGLE_AT_HIGH_SPEED) * turn_vel_correction
+			wheel.turn_angle *= -turn_input
 		}
 
 		immediate_scene(world, &world.main_scene, "assets/blender/test_level_blend/Scene.scn")
@@ -788,7 +791,7 @@ update_world :: proc(world: ^World, dt: f32, config: World_Update_Config) {
 			)
 		}
 
-		physics.simulate(
+		world.physics_dt = physics.simulate(
 			&world.physics_scene,
 			SOLVER_CONFIG,
 			dt,
@@ -816,7 +819,7 @@ update_world :: proc(world: ^World, dt: f32, config: World_Update_Config) {
 	}
 }
 
-update_runtime_world :: proc(runtime_world: ^Runtime_World, dt: f32) {
+runtime_world_update :: proc(runtime_world: ^Runtime_World, dt: f32) {
 	cur_world := runtime_world_current_world(runtime_world)
 
 	runtime_world.dt = dt
@@ -856,6 +859,24 @@ Orbit_Camera :: struct {
 	distance:   f32,
 }
 
+Car_Follow_Camera :: struct {
+	// Params
+	body:       physics.Body_Handle,
+	com_offset: rl.Vector3,
+	distance:   f32,
+
+	// State
+	pos:        rl.Vector3,
+	target:     rl.Vector3,
+	up:         rl.Vector3,
+}
+
+Game_Camera :: union {
+	Free_Camera,
+	Orbit_Camera,
+	Car_Follow_Camera,
+}
+
 GAMEPAD_DEADZONE :: f32(0.07)
 
 collect_camera_input :: proc() -> (delta: rl.Vector2, sense: f32) {
@@ -929,6 +950,60 @@ orbit_camera_to_rl :: proc(camera: Orbit_Camera) -> rl.Camera3D {
 	return result
 }
 
+follow_camera_update :: proc(world: ^World, camera: ^Car_Follow_Camera, dt: f32) {
+	body := physics.get_interpolated_body(&world.physics_scene, SOLVER_CONFIG, camera.body)
+
+	camera.target = body.x + physics.Vec3{0, 2.5, 0}
+
+	// forward := physics.body_local_to_world_vec(body, physics.Vec3{0, 0, 1})
+	// up := physics.body_local_to_world_vec(body, physics.Vec3{0, 1, 0})
+
+	dir := linalg.normalize0(camera.pos - camera.target)
+	if dir == 0 {
+		dir = {0, 0, -1}
+	}
+	distance := f32(8)
+	pos_target := camera.target + dir * distance
+	log.debugf("pos_target: {}", pos_target)
+
+	camera.pos = emath.exp_smooth(pos_target, camera.pos, 40, dt)
+}
+
+follow_camera_to_rl :: proc(camera: Car_Follow_Camera) -> rl.Camera3D {
+	return rl.Camera3D {
+		position = camera.pos,
+		target = camera.target,
+		up = rl.Vector3{0, 1, 0},
+		fovy = 50,
+		projection = .PERSPECTIVE,
+	}
+}
+
+game_camera_update :: proc(world: ^World, camera: ^Game_Camera, dt: f32) {
+	switch &c in camera {
+	case Free_Camera:
+		free_camera_update(&c)
+	case Orbit_Camera:
+		orbit_camera_update(&c)
+	case Car_Follow_Camera:
+		follow_camera_update(world, &c, dt)
+	}
+}
+
+game_camera_to_rl :: proc(camera: Game_Camera) -> rl.Camera3D {
+	result: rl.Camera3D
+	switch c in camera {
+	case Free_Camera:
+		result = free_camera_to_rl(c)
+	case Orbit_Camera:
+		result = orbit_camera_to_rl(c)
+	case Car_Follow_Camera:
+		result = follow_camera_to_rl(c)
+	}
+	return result
+}
+
+
 Matrix3 :: # row_major matrix[3, 3]f32
 
 free_camera_rotation :: proc(camera: Free_Camera) -> linalg.Matrix3f32 {
@@ -971,8 +1046,8 @@ free_camera_update :: proc(camera: ^Free_Camera) {
 	camera.pos += (input.x * right + input.y * forward) * camera.speed
 }
 
-free_camera_to_rl :: proc(camera: ^Free_Camera) -> (result: rl.Camera3D) {
-	rotation := free_camera_rotation(camera^)
+free_camera_to_rl :: proc(camera: Free_Camera) -> (result: rl.Camera3D) {
+	rotation := free_camera_rotation(camera)
 	forward := -rotation[2]
 
 	result.position = camera.pos
@@ -1008,16 +1083,6 @@ update :: proc() {
 		// g_mem.es.world.player_pos = g_mem.runtime_world.camera.position
 	}
 
-	if rl.IsKeyPressed(.F2) && !g_mem.free_cam {
-		cam_mode := &get_runtime_world().camera_mode
-		switch cam_mode^ {
-		case .Orbit:
-			cam_mode^ = .Hood
-		case .Hood:
-			cam_mode^ = .Orbit
-		}
-	}
-
 	dt := rl.GetFrameTime()
 
 	// Debug BVH traversal
@@ -1056,33 +1121,25 @@ update :: proc() {
 	if g_mem.editor {
 		update_editor(get_editor_state(), dt)
 	} else {
-		update_runtime_world(get_runtime_world(), dt)
+		runtime_world_update(get_runtime_world(), dt)
 		world := runtime_world_current_world(get_runtime_world())
 
 		if g_mem.free_cam {
 			free_camera_update(&g_mem.es.camera)
 		} else {
-			switch get_runtime_world().camera_mode {
-			case .Orbit:
-				orbit_camera_update(&get_runtime_world().orbit_camera)
-				get_runtime_world().camera = orbit_camera_to_rl(get_runtime_world().orbit_camera)
-			case .Hood:
-				car := physics.get_body(
-					physics.get_sim_state(&world.physics_scene),
-					world.car_handle,
-				)
-
-				cam: rl.Camera3D
-				cam.position = physics.body_local_to_world(car, physics.Vec3{0, 0.9, 2})
-				cam.target =
-					cam.position + physics.body_local_to_world_vec(car, physics.Vec3{0, 0, 1})
-				cam.up = physics.body_local_to_world_vec(car, physics.Vec3{0, 1, 0})
-				cam.fovy = 60
-				cam.projection = .PERSPECTIVE
-
-
-				get_runtime_world().camera = cam
+			game_cam := &get_runtime_world().game_camera
+			if _, ok := game_cam.(Car_Follow_Camera); !ok {
+				game_cam^ = Car_Follow_Camera{}
+				log.debugf("overwriting cam")
 			}
+			car_follow_cam := &game_cam.(Car_Follow_Camera)
+			car_follow_cam.body = world.car_handle
+
+			if world.physics_dt == 0 {
+				log.debugf("phys dt == 0")
+			}
+			game_camera_update(world, &get_runtime_world().game_camera, dt)
+			get_runtime_world().camera = game_camera_to_rl(get_runtime_world().game_camera)
 		}
 	}
 }
@@ -1125,7 +1182,11 @@ draw_world :: proc(world: ^World) {
 	phys_debug_state: physics.Debug_State
 	physics.init_debug_state(&phys_debug_state)
 
-	car_body := physics.get_body(sim_state, world.car_handle)
+	car_body := physics.get_interpolated_body(
+		&world.physics_scene,
+		SOLVER_CONFIG,
+		world.car_handle,
+	)
 	engine := physics.get_engine(sim_state, world.engine_handle)
 
 	{
@@ -1187,8 +1248,9 @@ draw_world :: proc(world: ^World) {
 
 
 	car_matrix := rl.QuaternionToMatrix(car_body.q)
-	car_matrix =
-		(auto_cast linalg.matrix4_translate_f32(physics.body_get_shape_pos(car_body))) * car_matrix
+	// TODO: figure out how to use helper funcs that take Body_Ptr for interpolated body which is just Body
+	car_pos := linalg.quaternion_mul_vector3(car_body.q, car_body.shape_offset) + car_body.x
+	car_matrix = (auto_cast linalg.matrix4_translate_f32(car_pos)) * car_matrix
 
 	// basic_shader := assets.get_shader(
 	// 	&g_mem.assetman,
@@ -1532,7 +1594,10 @@ game_hot_reloaded :: proc(mem: rawptr) {
 	render.init(&g_mem.assetman)
 	ui.rl_init()
 
-	g_mem.runtime_world.orbit_camera.distance = 6
+	orbit, ok := &g_mem.runtime_world.game_camera.(Orbit_Camera)
+	if ok {
+		orbit.distance = 6
+	}
 	log.debugf("hot reloaded")
 }
 

game/physics/scene.odin

@@ -3,11 +3,14 @@ package physics
 import "bvh"
 import "collision"
 import "common:name"
+import "core:log"
 import lg "core:math/linalg"
 import "game:assets"
 import "game:container/spanpool"
 import "libs:tracy"
 
+_ :: log
+
 MAX_CONTACTS :: 1024 * 16
 
 Vec3 :: [3]f32
@@ -122,7 +125,7 @@ Sim_State :: struct {
 }
 
 DEV_BUILD :: #config(DEV, false)
-NUM_SIM_STATES :: 2 when DEV_BUILD else 1
+NUM_SIM_STATES :: 2
 
 Scene :: struct {
 	assetman:               ^assets.Asset_Manager,
@@ -537,6 +540,40 @@ get_body :: proc(sim_state: ^Sim_State, handle: Body_Handle) -> Body_Ptr {
 	return &sim_state.bodies_slice[index]
 }
 
+get_interpolated_body :: proc(
+	scene: ^Scene,
+	solver_config: Solver_Config,
+	handle: Body_Handle,
+) -> Body {
+	prev_sim_state := get_prev_sim_state(scene)
+	sim_state := get_sim_state(scene)
+
+	prev_body := get_body(prev_sim_state, handle)
+	body := get_body(sim_state, handle)
+
+	result: Body = Body {
+		q = lg.QUATERNIONF32_IDENTITY,
+	}
+
+	if prev_body.alive && body.alive {
+		// interpolate
+		t := scene.solver_state.accumulated_time / solver_config.timestep
+		log.debugf("t = {}", t)
+		result = prev_body^
+		result.x = body.x * t + (1.0 - t) * prev_body.x
+		result.q = lg.quaternion_slerp_f32(prev_body.q, body.q, t)
+		result.v = lg.lerp(prev_body.v, body.v, t)
+		// I don't think that's right, but not going to be used anyway probably
+		result.w = lg.lerp(prev_body.w, body.w, t)
+	} else if prev_body.alive {
+		result = prev_body^
+	} else if body.alive {
+		result = body^
+	}
+
+	return result
+}
+
 remove_shape :: proc(sim_state: ^Sim_State, idx: i32) {
 	cur_idx := idx
 	for {

game/physics/simulation.odin

@@ -696,6 +696,8 @@ simulate :: proc(
 	dt: f32,
 	commit := true, // commit = false is a special mode for debugging physics stepping to allow rerunning the same step each frame
 	step_mode := Step_Mode.Accumulated_Time,
+) -> (
+	accumulated_dt: f32,
 ) {
 	tracy.Zone()
 	assert(config.timestep > 0)
@@ -704,31 +706,37 @@ simulate :: proc(
 
 	prune_immediate(scene)
 
-	copy_sim_state(get_next_sim_state(scene), get_sim_state(scene))
+	did_copy := false
 	sim_state := get_next_sim_state(scene)
 
-	// runtime.DEFAULT_TEMP_ALLOCATOR_TEMP_GUARD()
-
 	sim_cache: Sim_Cache
 	sim_cache.level_geom_asset_bvh = make_map(
 		map[Level_Geom_Handle]assets.Loaded_BVH,
 		context.temp_allocator,
 	)
 
+	simulated_dt := f32(0)
+
 	num_steps := 0
 	switch step_mode {
 	case .Accumulated_Time:
 		state.accumulated_time += dt
 
 		for state.accumulated_time >= config.timestep {
+			if !did_copy {
+				did_copy = true
+				copy_sim_state(get_next_sim_state(scene), get_sim_state(scene))
+			}
 			num_steps += 1
 			state.accumulated_time -= config.timestep
+			simulated_dt += config.timestep
 
 			if num_steps < MAX_STEPS {
 				simulate_step(scene, sim_state, &sim_cache, config)
 			}
 		}
 	case .Single:
+		copy_sim_state(get_next_sim_state(scene), get_sim_state(scene))
 		simulate_step(scene, get_next_sim_state(scene), &sim_cache, config)
 		num_steps += 1
 	}
@@ -742,6 +750,8 @@ simulate :: proc(
 	state.immediate_suspension_constraints.num_items = 0
 	state.immediate_engines.num_items = 0
 	state.immediate_level_geoms.num_items = 0
+
+	return simulated_dt
 }
 
 GLOBAL_PLANE :: collision.Plane {
@@ -1332,7 +1342,7 @@ pgs_solve_suspension :: proc(
 						) *
 						math.sign(lateral_to_longitudinal_relation)
 
-					v.turn_assist = drift_amount * math.PI * 0.1
+					v.turn_assist = drift_amount * math.PI * 0.15
 				}