From 83b9d6423554bcbf5d0c08789b9283eb7225b495 Mon Sep 17 00:00:00 2001
From: sergeypdev <sergeypoznyak@protonmail.com>
Date: Mon, 4 Mar 2024 16:10:15 +0400
Subject: [PATCH] Add shadowmap frustum culling. Fix too large shadow bias

---
 assets/shaders/mesh.glsl |  5 ++---
 src/Render.zig           | 21 ++++++++++++++++-----
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/assets/shaders/mesh.glsl b/assets/shaders/mesh.glsl
index f088d9b..a39a1a5 100644
--- a/assets/shaders/mesh.glsl
+++ b/assets/shaders/mesh.glsl
@@ -186,9 +186,9 @@ vec3 microfacetModel(Material mat, int light_idx, Light light, vec3 P, vec3 N) {
   float NDotV = dot(N, V);
 
   float normal_offset_scale = clamp(1 - NDotL, 0, 1);
-  normal_offset_scale *= 12; // constant
+  normal_offset_scale *= 10; // constant
 
-  float constant_bias = 0.003;
+  float constant_bias = 0.001;
   float shadow_mult = 1;
   vec4 shadow_offset = vec4(VertexOut.wNormal * normal_offset_scale, 0);
   if (point == 1) {
@@ -229,7 +229,6 @@ vec3 microfacetModel(Material mat, int light_idx, Light light, vec3 P, vec3 N) {
     texcoord.z = 0; // First shadow map
 
     float sum = 0;
-
     for (float y = -1.5; y <= 1.5; y += 1) {
       for (float x = -1.5; x <= 1.5; x += 1) {
         sum += texture(shadow_maps, vec4(texcoord.xy + vec2(x, y) * shadow_map_texel_size, texcoord.zw));
diff --git a/src/Render.zig b/src/Render.zig
index 50d0b5a..e149687 100644
--- a/src/Render.zig
+++ b/src/Render.zig
@@ -318,7 +318,10 @@ pub fn finish(self: *Render) void {
                         Vec3.up(),
                     ),
                 };
-                light.shadow_vp = camera_matrix.projection.mul(camera_matrix.view);
+
+                const shadow_view_proj = camera_matrix.projection.mul(camera_matrix.view);
+                const light_frustum = math.Frustum.new(shadow_view_proj);
+                light.shadow_vp = shadow_view_proj;
 
                 gl.namedBufferSubData(self.shadow_matrices_buffer, 0, @sizeOf(CameraMatrices), std.mem.asBytes(&self.shadow_matrices));
                 checkGLError();
@@ -326,7 +329,7 @@ pub fn finish(self: *Render) void {
                 gl.clear(gl.DEPTH_BUFFER_BIT);
                 gl.bindBufferBase(gl.UNIFORM_BUFFER, UBO.CameraMatrices.value(), self.shadow_matrices_buffer);
 
-                self.renderShadow();
+                self.renderShadow(&light_frustum);
             } else {
                 // Point Light
                 gl.useProgram(self.assetman.resolveShaderProgram(a.ShaderPrograms.shaders.cube_shadow).program);
@@ -353,6 +356,9 @@ pub fn finish(self: *Render) void {
                             cam_dir.up,
                         ),
                     };
+
+                    const shadow_view_proj = camera_matrix.projection.mul(camera_matrix.view);
+                    const light_frustum = math.Frustum.new(shadow_view_proj);
                     light.near_far = near_far;
                     gl.uniform2f(Uniform.NearFarPlanes.value(), near_far.x(), near_far.y());
 
@@ -362,7 +368,7 @@ pub fn finish(self: *Render) void {
                     gl.clear(gl.DEPTH_BUFFER_BIT);
                     gl.bindBufferBase(gl.UNIFORM_BUFFER, UBO.CameraMatrices.value(), self.shadow_matrices_buffer);
 
-                    self.renderShadow();
+                    self.renderShadow(&light_frustum);
                 }
             }
         }
@@ -485,7 +491,7 @@ pub fn finish(self: *Render) void {
         );
     }
 
-    std.log.debug("Total draws {}, frustum culled draws {}\n", .{ self.command_count, rendered_count });
+    //std.log.debug("Total draws {}, frustum culled draws {}\n", .{ self.command_count, rendered_count });
 
     self.gl_fences[self.tripple_buffer_index] = gl.fenceSync(gl.SYNC_GPU_COMMANDS_COMPLETE, 0);
     c.SDL_GL_SwapWindow(ginit.window);
@@ -531,9 +537,14 @@ const cube_camera_dirs = [6]CubeCameraDir{
     },
 };
 
-fn renderShadow(self: *Render) void {
+fn renderShadow(self: *Render, frustum: *const math.Frustum) void {
     for (self.command_buffer[0..self.command_count]) |*cmd| {
         const mesh = self.assetman.resolveMesh(cmd.mesh);
+        const aabb = math.AABB.fromMinMax(mesh.aabb.min, mesh.aabb.max);
+
+        if (!frustum.intersectAABB(aabb.transform(cmd.transform))) {
+            continue;
+        }
 
         gl.uniformMatrix4fv(Uniform.ModelMatrix.value(), 1, gl.FALSE, @ptrCast(&cmd.transform.data));
         mesh.positions.bind(Render.Attrib.Position.value());