From d7378ab5cabc40be419d7bed5882178bf5e06758 Mon Sep 17 00:00:00 2001
From: Verox001 <verox@cimeyclust.com>
Date: Thu, 16 Jan 2025 13:05:57 +0100
Subject: [PATCH] Finished light diffusion

---
 src/lib.rs      | 40 ++++++++++++++++++++++++++--------------
 src/shader.wgsl | 43 +++++++++++++++++++++++++++++++++++++++----
 2 files changed, 65 insertions(+), 18 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 129f9fe..d39814b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -179,22 +179,24 @@ struct Instance {
 
 impl Instance {
     fn to_raw(&self) -> InstanceRaw {
+        let model =
+            cgmath::Matrix4::from_translation(self.position) * cgmath::Matrix4::from(self.rotation);
         InstanceRaw {
-            model: (cgmath::Matrix4::from_translation(self.position)
-                * cgmath::Matrix4::from(self.rotation))
-                .into(),
+            model: model.into(),
+            normal: cgmath::Matrix3::from(self.rotation).into(),
         }
     }
 }
 
 #[repr(C)]
 #[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
+#[allow(dead_code)]
 struct InstanceRaw {
-    #[allow(dead_code)]
     model: [[f32; 4]; 4],
+    normal: [[f32; 3]; 3],
 }
 
-impl InstanceRaw {
+impl model::Vertex for InstanceRaw {
     fn desc() -> wgpu::VertexBufferLayout<'static> {
         use std::mem;
         wgpu::VertexBufferLayout {
@@ -206,11 +208,13 @@ impl InstanceRaw {
             attributes: &[
                 wgpu::VertexAttribute {
                     offset: 0,
+                    // While our vertex shader only uses locations 0, and 1 now, in later tutorials, we'll
+                    // be using 2, 3, and 4 for Vertex. We'll start at slot 5 to not conflict with them later
                     shader_location: 5,
                     format: wgpu::VertexFormat::Float32x4,
                 },
                 // A mat4 takes up 4 vertex slots as it is technically 4 vec4s. We need to define a slot
-                // for each vec4. We don't have to do this in code though.
+                // for each vec4. We don't have to do this in code, though.
                 wgpu::VertexAttribute {
                     offset: mem::size_of::<[f32; 4]>() as wgpu::BufferAddress,
                     shader_location: 6,
@@ -226,6 +230,21 @@ impl InstanceRaw {
                     shader_location: 8,
                     format: wgpu::VertexFormat::Float32x4,
                 },
+                wgpu::VertexAttribute {
+                    offset: mem::size_of::<[f32; 16]>() as wgpu::BufferAddress,
+                    shader_location: 9,
+                    format: wgpu::VertexFormat::Float32x3,
+                },
+                wgpu::VertexAttribute {
+                    offset: mem::size_of::<[f32; 19]>() as wgpu::BufferAddress,
+                    shader_location: 10,
+                    format: wgpu::VertexFormat::Float32x3,
+                },
+                wgpu::VertexAttribute {
+                    offset: mem::size_of::<[f32; 22]>() as wgpu::BufferAddress,
+                    shader_location: 11,
+                    format: wgpu::VertexFormat::Float32x3,
+                },
             ],
         }
     }
@@ -430,14 +449,7 @@ impl<'a> State<'a> {
 
                     let position = cgmath::Vector3 { x, y: 0.0, z };
 
-                    let rotation = if position.is_zero() {
-                        cgmath::Quaternion::from_axis_angle(
-                            cgmath::Vector3::unit_z(),
-                            cgmath::Deg(0.0),
-                        )
-                    } else {
-                        cgmath::Quaternion::from_axis_angle(position.normalize(), cgmath::Deg(45.0))
-                    };
+                    let rotation = cgmath::Quaternion::from_axis_angle((0.0, 1.0, 0.0).into(), cgmath::Deg(180.0));
 
                     Instance { position, rotation }
                 })
diff --git a/src/shader.wgsl b/src/shader.wgsl
index c182e66..5c33ddb 100644
--- a/src/shader.wgsl
+++ b/src/shader.wgsl
@@ -1,5 +1,12 @@
 // Vertex shader
 
+struct Light {
+    position: vec3<f32>,
+    color: vec3<f32>,
+}
+@group(2) @binding(0)
+var<uniform> light: Light;
+
 struct Camera {
     view_proj: mat4x4<f32>,
 }
@@ -9,18 +16,24 @@ var<uniform> camera: Camera;
 struct VertexInput {
     @location(0) position: vec3<f32>,
     @location(1) tex_coords: vec2<f32>,
-}
+    @location(2) normal: vec3<f32>,
+};
 struct InstanceInput {
     @location(5) model_matrix_0: vec4<f32>,
     @location(6) model_matrix_1: vec4<f32>,
     @location(7) model_matrix_2: vec4<f32>,
     @location(8) model_matrix_3: vec4<f32>,
+    @location(9) normal_matrix_0: vec3<f32>,
+        @location(10) normal_matrix_1: vec3<f32>,
+        @location(11) normal_matrix_2: vec3<f32>,
 }
 
 struct VertexOutput {
     @builtin(position) clip_position: vec4<f32>,
     @location(0) tex_coords: vec2<f32>,
-}
+    @location(1) world_normal: vec3<f32>,
+    @location(2) world_position: vec3<f32>,
+};
 
 @vertex
 fn vs_main(
@@ -33,9 +46,18 @@ fn vs_main(
         instance.model_matrix_2,
         instance.model_matrix_3,
     );
+
+    let normal_matrix = mat3x3<f32>(
+        instance.normal_matrix_0,
+        instance.normal_matrix_1,
+        instance.normal_matrix_2,
+    );
     var out: VertexOutput;
     out.tex_coords = model.tex_coords;
-    out.clip_position = camera.view_proj * model_matrix * vec4<f32>(model.position, 1.0);
+    out.world_normal = normal_matrix * model.normal;
+    var world_position: vec4<f32> = model_matrix * vec4<f32>(model.position, 1.0);
+    out.world_position = world_position.xyz;
+    out.clip_position = camera.view_proj * world_position;
     return out;
 }
 
@@ -48,5 +70,18 @@ var s_diffuse: sampler;
 
 @fragment
 fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
-    return textureSample(t_diffuse, s_diffuse, in.tex_coords);
+    let object_color: vec4<f32> = textureSample(t_diffuse, s_diffuse, in.tex_coords);
+
+    let light_dir = normalize(light.position - in.world_position);
+
+    let diffuse_strength = max(dot(in.world_normal, light_dir), 0.0);
+    let diffuse_color = light.color * diffuse_strength;
+
+    // We don't need (or want) much ambient light, so 0.1 is fine
+    let ambient_strength = 0.1;
+    let ambient_color = light.color * ambient_strength;
+
+    let result = (ambient_color + diffuse_color) * object_color.xyz;
+
+    return vec4<f32>(result, object_color.a);
 }
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