tangent basis

code/intermediate/tutorial11-normals/src/shader.wgsl

@@ -34,9 +34,11 @@ struct InstanceInput {
 struct VertexOutput {
     @builtin(position) clip_position: vec4<f32>,
     @location(0) tex_coords: vec2<f32>,
-    @location(1) tangent_position: vec3<f32>,
-    @location(2) tangent_light_position: vec3<f32>,
-    @location(3) tangent_view_position: vec3<f32>,
+    @location(1) world_position: vec3<f32>,
+    @location(2) world_tangent: vec3<f32>,
+    @location(3) world_bitangent: vec3<f32>,
+    @location(4) world_normal: vec3<f32>,
+
 }
 
 @vertex
@@ -55,25 +57,16 @@ fn vs_main(
         instance.normal_matrix_1,
         instance.normal_matrix_2,
     );
-
-    // Construct the tangent matrix
-    let world_normal = normalize(normal_matrix * model.normal);
-    let world_tangent = normalize(normal_matrix * model.tangent);
-    let world_bitangent = normalize(normal_matrix * model.bitangent);
-    let tangent_matrix = transpose(mat3x3<f32>(
-        world_tangent,
-        world_bitangent,
-        world_normal,
-    ));
-
-    let world_position = model_matrix * vec4<f32>(model.position, 1.0);
+    let world_position: vec4<f32> = model_matrix * vec4<f32>(model.position, 1.0);
 
     var out: VertexOutput;
     out.clip_position = camera.view_proj * world_position;
     out.tex_coords = model.tex_coords;
-    out.tangent_position = tangent_matrix * world_position.xyz;
-    out.tangent_view_position = tangent_matrix * camera.view_pos.xyz;
-    out.tangent_light_position = tangent_matrix * light.position;
+    out.world_position = world_position.xyz;
+    out.world_tangent = normalize(normal_matrix * model.tangent);
+    out.world_bitangent = normalize(normal_matrix * model.bitangent);
+    out.world_normal = normalize(normal_matrix * model.normal);
+
     return out;
 }
 
@@ -97,19 +90,19 @@ fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
     let ambient_strength = 0.1;
     let ambient_color = light.color * ambient_strength;
 
-    // Create the lighting vectors
-    let tangent_normal = object_normal.xyz * 2.0 - 1.0;
-    let light_dir = normalize(in.tangent_light_position - in.tangent_position);
-    let view_dir = normalize(in.tangent_view_position - in.tangent_position);
+    let tangent_basis = mat3x3<f32>(in.world_tangent, in.world_bitangent, in.world_normal);
+    let world_normal = tangent_basis * (object_normal.xyz * 2.0 - 1.0);
+    let light_dir = normalize(light.position - in.world_position);
+    let view_dir = normalize(camera.view_pos.xyz - in.world_position);
     let half_dir = normalize(view_dir + light_dir);
 
-    let diffuse_strength = max(dot(tangent_normal, light_dir), 0.0);
+    let diffuse_strength = max(dot(world_normal, light_dir), 0.0);
     let diffuse_color = light.color * diffuse_strength;
 
-    let specular_strength = pow(max(dot(tangent_normal, half_dir), 0.0), 32.0);
+    let specular_strength = pow(max(dot(world_normal, half_dir), 0.0), 32.0);
     let specular_color = specular_strength * light.color;
 
     let result = (ambient_color + diffuse_color + specular_color) * object_color.xyz;
 
     return vec4<f32>(result, object_color.a);
-}
+}