PBR

src/camera.rs

@@ -3,6 +3,7 @@ use std::time::Instant;
 use winit::event::{ElementState, VirtualKeyCode};
 
 pub trait Camera {
+    fn get_eye(&self) -> [f32; 4];
     fn get_vp(&self) -> [[f32; 4]; 4];
 }
 
@@ -148,6 +149,10 @@ impl Flycam {
 }
 
 impl Camera for Flycam {
+    fn get_eye(&self) -> [f32; 4] {
+        self.position.extend(0.0).to_array()
+    }
+
     fn get_vp(&self) -> [[f32; 4]; 4] {
         let orientation = Quat::from_euler(glam::EulerRot::XYZ, self.tilt, self.pan, 0.0);
         let rotation = Mat4::from_quat(orientation);

src/model.rs

@@ -93,8 +93,10 @@ impl ObjModel {
 
         let albedo = on_load.load_texture(&albedo_data);
 
-        let material_data = MaterialData { albedo };
-        let material_handle = on_load.load_material(&material_data);
+        let material_handle = on_load.load_material(&MaterialData {
+            albedo,
+            metallic_roughness: albedo, // TODO better placeholder MR texture
+        });
 
         let mesh = BasicMesh {
             mesh_handle,
@@ -201,7 +203,13 @@ impl<'a, T: OnLoad> GltfLoader<'a, T> {
         let base_color = pbr.base_color_texture().unwrap().texture();
         let albedo = self.load_texture(base_color);
 
-        self.on_load.load_material(&MaterialData { albedo })
+        let metallic_roughness = pbr.metallic_roughness_texture().unwrap().texture();
+        let metallic_roughness = self.load_texture(metallic_roughness);
+
+        self.on_load.load_material(&MaterialData {
+            albedo,
+            metallic_roughness,
+        })
     }
 
     pub fn load_texture(&mut self, texture: gltf::Texture) -> TextureHandle {

src/pool.rs

@@ -145,6 +145,7 @@ impl TexturePool {
 
 pub struct MaterialData {
     pub albedo: TextureHandle,
+    pub metallic_roughness: TextureHandle,
 }
 
 pub struct Material {
@@ -158,6 +159,17 @@ pub struct MaterialPool {
 
 impl MaterialPool {
     pub fn new(device: &wgpu::Device) -> Self {
+        let texture_entry = wgpu::BindGroupLayoutEntry {
+            binding: u32::MAX,
+            visibility: wgpu::ShaderStages::FRAGMENT,
+            ty: wgpu::BindingType::Texture {
+                multisampled: false,
+                view_dimension: wgpu::TextureViewDimension::D2,
+                sample_type: wgpu::TextureSampleType::Float { filterable: true },
+            },
+            count: None,
+        };
+
         let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
             entries: &[
                 wgpu::BindGroupLayoutEntry {
@@ -168,13 +180,11 @@ impl MaterialPool {
                 },
                 wgpu::BindGroupLayoutEntry {
                     binding: 1,
-                    visibility: wgpu::ShaderStages::FRAGMENT,
-                    ty: wgpu::BindingType::Texture {
-                        multisampled: false,
-                        view_dimension: wgpu::TextureViewDimension::D2,
-                        sample_type: wgpu::TextureSampleType::Float { filterable: true },
-                    },
-                    count: None,
+                    ..texture_entry
+                },
+                wgpu::BindGroupLayoutEntry {
+                    binding: 2,
+                    ..texture_entry
                 },
             ],
             label: Some("Texture Bind Group Layout"),
@@ -193,6 +203,7 @@ impl MaterialPool {
         data: &MaterialData,
     ) -> MaterialHandle {
         let albedo_view = &texture_pool.textures[data.albedo.id].texture_view;
+        let mr_view = &texture_pool.textures[data.metallic_roughness.id].texture_view;
 
         let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
             layout: &self.bind_group_layout,
@@ -205,6 +216,10 @@ impl MaterialPool {
                     binding: 1,
                     resource: wgpu::BindingResource::TextureView(albedo_view),
                 },
+                wgpu::BindGroupEntry {
+                    binding: 2,
+                    resource: wgpu::BindingResource::TextureView(mr_view),
+                },
             ],
             label: None,
         });

src/renderer.rs

@@ -61,7 +61,7 @@ impl Renderer {
                 entries: &[
                     wgpu::BindGroupLayoutEntry {
                         binding: 0,
-                        visibility: wgpu::ShaderStages::VERTEX,
+                        visibility: wgpu::ShaderStages::VERTEX_FRAGMENT,
                         ty: wgpu::BindingType::Buffer {
                             ty: wgpu::BufferBindingType::Uniform,
                             has_dynamic_offset: false,
@@ -378,17 +378,20 @@ impl OnLoad for &mut Renderer {
 #[repr(C)]
 #[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
 struct CameraUniform {
+    eye: [f32; 4],
     vp: [[f32; 4]; 4],
 }
 
 impl CameraUniform {
     pub fn new() -> Self {
         Self {
+            eye: [0.0; 4],
             vp: glam::Mat4::IDENTITY.to_cols_array_2d(),
         }
     }
 
     pub fn update(&mut self, camera: &impl Camera) {
+        self.eye = camera.get_eye();
         self.vp = camera.get_vp();
     }
 }

src/shader.wgsl

@@ -1,4 +1,5 @@
 struct CameraUniform {
+  eye: vec4<f32>;
   vp: mat4x4<f32>;
 };
 
@@ -44,6 +45,76 @@ var<storage,read> meshes: MeshData;
 
 [[group(2), binding(0)]] var m_sampler: sampler;
 [[group(2), binding(1)]] var m_albedo: texture_2d<f32>;
+[[group(2), binding(2)]] var m_metallic_roughness: texture_2d<f32>;
+
+let PI: f32 = 3.141592;
+
+fn D_GGX(NoH: f32, roughness: f32) -> f32 {
+  let a = roughness * roughness;
+  let a2 = a * a;
+  let NoH2 = NoH * NoH;
+  let f = NoH * (a2 - 1.0) + 1.0;
+  return a2 / (PI * f * f);
+}
+
+fn g1(NoV: f32, roughness: f32, k: f32) -> f32 {
+  let denom = NoV * (1.0 - k) + k;
+  return NoV / denom;
+}
+
+fn G_SmithGGXCorrelated(NoV: f32, NoL: f32, roughness: f32) -> f32 {
+  let r = roughness + 1.0;
+  let k = (r * r) / 8.0;
+
+  let g1l = g1(NoV, roughness, k);
+  let g1v = g1(NoL, roughness, k);
+
+  return g1l * g1v;
+}
+
+fn F_Schlick(u: f32, f0: vec3<f32>) -> vec3<f32> {
+  let f = pow(1.0 - u, 5.0);
+  return f + f0 * (1.0 - f);
+}
+
+fn BRDF(
+  l: vec3<f32>,      // normalized light direction
+  n: vec3<f32>,      // normalized surface normal
+  v: vec3<f32>,      // normalized view direction
+  albedo: vec3<f32>, // surface albedo
+  metallic: f32,     // surface metallic
+  roughness: f32,    // surface roughness
+) -> vec3<f32> {
+  let h = normalize(v + l);
+  let NoL = max(dot(n, l), 0.0);
+  let NoV = max(dot(n, v), 0.0);
+  let NoH = max(dot(n, h), 0.0);
+  let LoH = max(dot(l, h), 0.0);
+
+  // calculate reflectance at surface incidence
+  let f0 = mix(vec3<f32>(0.04), albedo, metallic);
+
+  // specular BRDF
+  let D = D_GGX(NoH, roughness);
+  let G = G_SmithGGXCorrelated(NoV, NoL, roughness);
+  let F = F_Schlick(LoH, f0);
+
+  let numerator = (D * G) * F;
+  let denominator = 4.0 * NoV * NoL;
+
+  let Fr = numerator / max(denominator, 0.01);
+
+  // diffuse BRDF
+  let diffuse_fresnel =
+    (vec3<f32>(1.0) - F_Schlick(NoL, f0)) *
+    (vec3<f32>(1.0) - F_Schlick(NoV, f0));
+
+  let lambertian = albedo / PI;
+  let Fd = diffuse_fresnel * lambertian;
+
+  // TODO multiple scattering
+  return (Fr + Fd) * NoL;
+}
 
 [[stage(vertex)]]
 fn vs_main(
@@ -68,14 +139,27 @@ fn fs_main(
 ) -> [[location(0)]] vec4<f32> {
   let albedo = textureSample(m_albedo, m_sampler, frag.tex_coords).rgb;
   let normal = normalize(frag.normal);
+  let view = normalize(camera.eye.xyz - frag.position);
+
+  let metallic_roughness = textureSample(m_metallic_roughness, m_sampler, frag.tex_coords).bg;
+  let metallic = metallic_roughness.x;
+  let roughness = metallic_roughness.y;
 
   var lum = vec3<f32>(0.0);
   for(var i = 0; i < 4; i = i + 1) {
     let light = point_lights.lights[i];
-    let light_relative = light.center.xyz - frag.position;
-    let received = dot(normal, normalize(light_relative));
-    let diffuse = (albedo * received) / dot(light_relative, light_relative);
-    lum = lum + (diffuse * light.intensity.rgb);
+    let light_position = light.center.xyz - frag.position;
+    let light_intensity = light.intensity.rgb;
+    let light_direction = normalize(light_position);
+
+    let radiance = light_intensity / dot(light_position, light_position);
+
+    let reflected = BRDF(
+      light_direction, normal, view,
+      albedo, metallic, roughness
+    );
+
+    lum = lum + (radiance * reflected);
   }
 
   return vec4<f32>(lum, 1.0);