From 7386a05a0dc50a7580378725bb2d482d0853a701 Mon Sep 17 00:00:00 2001
From: Dzmitry Malyshau <kvarkus@gmail.com>
Date: Fri, 22 Feb 2019 12:59:05 -0500
Subject: [PATCH] Shadow shaders

---
 gfx-examples/Cargo.toml               |  5 +++
 gfx-examples/data/shadow-forward.frag | 51 +++++++++++++++++++++++++--
 gfx-examples/data/shadow-forward.vert | 13 +++----
 gfx-examples/src/cube.rs              |  2 +-
 gfx-examples/src/framework.rs         |  1 +
 gfx-examples/src/shadow.rs            | 12 +++----
 6 files changed, 66 insertions(+), 18 deletions(-)

diff --git a/gfx-examples/Cargo.toml b/gfx-examples/Cargo.toml
index ce4959801a..d8b3698e54 100644
--- a/gfx-examples/Cargo.toml
+++ b/gfx-examples/Cargo.toml
@@ -12,8 +12,13 @@ publish = false
 name = "cube"
 path = "src/cube.rs"
 
+[[bin]]
+name = "shadow"
+path = "src/shadow.rs"
+
 [features]
 default = []
+metal-auto-capture = ["wgpu/metal-auto-capture"]
 metal = ["wgpu/metal"]
 dx11 = ["wgpu/dx11"]
 dx12 = ["wgpu/dx12"]
diff --git a/gfx-examples/data/shadow-forward.frag b/gfx-examples/data/shadow-forward.frag
index 22c79b3e9c..0928adce86 100644
--- a/gfx-examples/data/shadow-forward.frag
+++ b/gfx-examples/data/shadow-forward.frag
@@ -1,10 +1,55 @@
 #version 450
 
+const int MAX_LIGHTS = 10;
+
+layout(location = 0) in vec3 v_Normal;
+layout(location = 1) in vec4 v_Position;
+
 layout(location = 0) out vec4 o_Target;
 
-layout(set = 0, binding = 2) uniform texture2D u_ShadowTexture;
-layout(set = 0, binding = 3) uniform sampler u_ShadowSampler;
+struct Light {
+    mat4 proj;
+    vec4 pos;
+    vec4 color;
+};
+
+layout(set = 0, binding = 0) uniform Globals {
+    mat4 u_ViewProj;
+    uvec4 u_NumLights;
+};
+layout(set = 0, binding = 1) uniform Lights {
+    Light u_Lights[MAX_LIGHTS];
+};
+layout(set = 0, binding = 2) uniform texture2DArray t_Shadow;
+layout(set = 0, binding = 3) uniform samplerShadow s_Shadow;
+
+layout(set = 1, binding = 0) uniform Entity {
+    mat4 u_World;
+    vec4 u_Color;
+};
+
 
 void main() {
-	o_Target = vec4(1.0);
+    vec3 normal = normalize(v_Normal);
+    vec3 ambient = vec3(0.05, 0.05, 0.05);
+    // accumulate color
+    vec3 color = ambient;
+    for (int i=0; i<int(u_NumLights.x) && i<MAX_LIGHTS; ++i) {
+        Light light = u_Lights[i];
+        // project into the light space
+        vec4 light_local = light.proj * v_Position;
+        // compute texture coordinates for shadow lookup
+        light_local.y *= -1.0; // difference in Vulkan target versus texture coordinates...
+        light_local.xyw = (light_local.xyz/light_local.w + 1.0) / 2.0;
+        light_local.z = i;
+        // do the lookup, using HW PCF and comparison
+        float shadow = texture(sampler2DArrayShadow(t_Shadow, s_Shadow), light_local);
+        // compute Lambertian diffuse term
+        vec3 light_dir = normalize(light.pos.xyz - v_Position.xyz);
+        float diffuse = max(0.0, dot(normal, light_dir));
+        // add light contribution
+        color += shadow * diffuse * light.color.xyz;
+    }
+    // multiply the light by material color
+    o_Target = vec4(color, 1.0) * u_Color;
 }
diff --git a/gfx-examples/data/shadow-forward.vert b/gfx-examples/data/shadow-forward.vert
index c100fed42a..5e02939393 100644
--- a/gfx-examples/data/shadow-forward.vert
+++ b/gfx-examples/data/shadow-forward.vert
@@ -3,23 +3,20 @@
 layout(location = 0) in ivec4 a_Pos;
 layout(location = 1) in ivec4 a_Normal;
 
-struct Light {
-	mat4 proj;
-	vec4 color;
-};
+layout(location = 0) out vec3 v_Normal;
+layout(location = 1) out vec4 v_Position;
 
 layout(set = 0, binding = 0) uniform Globals {
     mat4 u_ViewProj;
     uvec4 u_NumLights;
 };
-layout(set = 0, binding = 1) uniform Lights {
-    Light u_Lights[];
-};
 layout(set = 1, binding = 0) uniform Entity {
     mat4 u_World;
     vec4 u_Color;
 };
 
 void main() {
-    gl_Position = u_ViewProj * u_World * vec4(a_Pos);
+    v_Normal = mat3(u_World) * vec3(a_Normal.xyz);
+    v_Position = u_World * vec4(a_Pos);
+    gl_Position = u_ViewProj * v_Position;
 }
diff --git a/gfx-examples/src/cube.rs b/gfx-examples/src/cube.rs
index 09e1b079a8..b58e2a7acf 100644
--- a/gfx-examples/src/cube.rs
+++ b/gfx-examples/src/cube.rs
@@ -98,7 +98,7 @@ impl Example {
         let mx_view = cgmath::Matrix4::look_at(
             cgmath::Point3::new(1.5f32, -5.0, 3.0),
             cgmath::Point3::new(0f32, 0.0, 0.0),
-            cgmath::Vector3::unit_z(),
+            -cgmath::Vector3::unit_z(),
         );
         mx_projection * mx_view
     }
diff --git a/gfx-examples/src/framework.rs b/gfx-examples/src/framework.rs
index dec148427b..e5cb1a319a 100644
--- a/gfx-examples/src/framework.rs
+++ b/gfx-examples/src/framework.rs
@@ -123,5 +123,6 @@ pub fn run<E: Example>(title: &str) {
 
         let frame = swap_chain.get_next_texture();
         example.render(&frame, &mut device);
+        running &= !cfg!(feature = "metal-auto-capture");
     }
 }
diff --git a/gfx-examples/src/shadow.rs b/gfx-examples/src/shadow.rs
index f0dd5ce404..5200f6da93 100644
--- a/gfx-examples/src/shadow.rs
+++ b/gfx-examples/src/shadow.rs
@@ -172,11 +172,11 @@ impl Example {
     };
 
     fn generate_matrix(aspect_ratio: f32) -> cgmath::Matrix4<f32> {
-        let mx_projection = cgmath::perspective(cgmath::Deg(45f32), aspect_ratio, 1.0, 10.0);
+        let mx_projection = cgmath::perspective(cgmath::Deg(45f32), aspect_ratio, 1.0, 20.0);
         let mx_view = cgmath::Matrix4::look_at(
-            cgmath::Point3::new(1.5f32, -5.0, 3.0),
+            cgmath::Point3::new(3.0f32, -10.0, 6.0),
             cgmath::Point3::new(0f32, 0.0, 0.0),
-            cgmath::Vector3::unit_z(),
+            -cgmath::Vector3::unit_z(),
         );
         mx_projection * mx_view
     }
@@ -219,7 +219,7 @@ impl framework::Example for Example {
             bindings: &[                     
                 wgpu::BindGroupLayoutBinding {
                     binding: 0,
-                    visibility: wgpu::ShaderStageFlags::VERTEX,
+                    visibility: wgpu::ShaderStageFlags::VERTEX | wgpu::ShaderStageFlags::FRAGMENT,
                     ty: wgpu::BindingType::UniformBuffer,
                 },
             ],
@@ -447,8 +447,8 @@ impl framework::Example for Example {
                 rasterization_state: wgpu::RasterizationStateDescriptor {
                     front_face: wgpu::FrontFace::Cw,
                     cull_mode: wgpu::CullMode::Back,
-                    depth_bias: 0,
-                    depth_bias_slope_scale: 0.0,
+                    depth_bias: 2,
+                    depth_bias_slope_scale: 1.0,
                     depth_bias_clamp: wgpu::MAX_DEPTH_BIAS_CLAMP,
                 },
                 primitive_topology: wgpu::PrimitiveTopology::TriangleList,