From c676907f6540de4709c6ac204fb1c90e87217b6e Mon Sep 17 00:00:00 2001
From: Jordan Orelli <jordanorelli@gmail.com>
Date: Sun, 11 Jun 2023 16:11:59 -0500
Subject: [PATCH] adding a solid shader

---
 assets/shaders/solid.frag | 19 +++++++++++++++
 src/main.rs               | 51 ++++++++++++++++++++++-----------------
 src/materials.rs          |  3 +++
 src/materials/solid.rs    | 34 ++++++++++++++++++++++++++
 4 files changed, 85 insertions(+), 22 deletions(-)
 create mode 100644 assets/shaders/solid.frag
 create mode 100644 src/materials.rs
 create mode 100644 src/materials/solid.rs

diff --git a/assets/shaders/solid.frag b/assets/shaders/solid.frag
new file mode 100644
index 0000000..54b61cf
--- /dev/null
+++ b/assets/shaders/solid.frag
@@ -0,0 +1,19 @@
+#version 450
+
+// I don't know what these inputs actually are, but the shader doesn't compile
+// if we don't actually consume them. It doesn't seem to matter what type I use
+// to describe each field, so I just picked vec2.
+//
+// I think these are probably declared in the derived AsBindGroup trait that
+// binds data between the Rust application and the shader?
+layout(location = 0) in vec2 _;
+layout(location = 1) in vec2 _;
+layout(location = 2) in vec2 _;
+
+layout(location = 0) out vec4 o_Target;
+
+void main() {
+    o_Target = vec4(1.0, 0.0, 1.0, 1.0);
+}
+
+// vim: set ft=glsl:
diff --git a/src/main.rs b/src/main.rs
index db0fd40..250e3e6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,5 @@
+mod materials;
+
 use bevy::{
     pbr::{MaterialPipeline, MaterialPipelineKey},
     prelude::*,
@@ -16,26 +18,34 @@ fn startup(
     mut meshes: ResMut<Assets<Mesh>>,
     mut materials: ResMut<Assets<StandardMaterial>>,
     mut tiled_materials: ResMut<Assets<RepeatMaterial>>,
+    mut solid_materials: ResMut<Assets<materials::SolidMaterial>>,
 ) {
-    //
-    let texture = assets.load("grid-texture.png");
-
-    // This is a solid texture
-    let material = materials.add(StandardMaterial {
-        base_color_texture: Some(texture.clone()),
-        alpha_mode: AlphaMode::Opaque,
-        unlit: true,
-        ..default()
+    let grid_texture = assets.load("grid-texture.png");
+
+    let grid_material = tiled_materials.add(RepeatMaterial {
+        color: Color::BLUE,
+        color_texture: Some(grid_texture.clone()),
+        alpha_mode: AlphaMode::Blend,
     });
 
-    // ground plane
-    commands.spawn(PbrBundle {
+    // Standard material with opaque grid texture (stretched)
+    // let material = materials.add(StandardMaterial {
+    //     base_color_texture: Some(grid_texture.clone()),
+    //     alpha_mode: AlphaMode::Opaque,
+    //     unlit: true,
+    //     ..default()
+    // });
+
+    let solid_material = solid_materials.add(materials::SolidMaterial{});
+
+    // a ground plane
+    commands.spawn(MaterialMeshBundle {
         mesh: meshes.add(shape::Plane::from_size(5.0).into()),
-        material,
+        material: solid_material,
         ..default()
     });
 
-    // a subject cube
+    // a solid colored cube
     commands.spawn(PbrBundle {
         mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
         material: materials.add(Color::rgb(0.8, 0.7, 0.6).into()),
@@ -43,27 +53,23 @@ fn startup(
         ..default()
     });
 
-    let grid_tile = tiled_materials.add(RepeatMaterial {
-        color: Color::BLUE,
-        color_texture: Some(texture.clone()),
-        alpha_mode: AlphaMode::Blend,
-    });
-
+    // a unit cube using our shader
     commands.spawn(MaterialMeshBundle {
         mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
-        material: grid_tile.clone(),
+        material: grid_material.clone(),
         transform: Transform::from_xyz(2.0, 0.5, 0.0),
         ..default()
     });
 
+    // a doubly large cube using our shader to test texture tiling (not yet working!!!)
     commands.spawn(MaterialMeshBundle {
         mesh: meshes.add(Mesh::from(shape::Cube { size: 2.0 })),
-        material: grid_tile.clone(),
+        material: grid_material.clone(),
         transform: Transform::from_xyz(-2.0, 1.0, 0.0),
         ..default()
     });
 
-    // single light source
+    // a single light source
     commands.spawn(PointLightBundle {
         point_light: PointLight {
             intensity: 1500.0,
@@ -128,6 +134,7 @@ fn main() {
     App::new()
         .add_plugins(DefaultPlugins)
         .add_plugin(MaterialPlugin::<RepeatMaterial>::default())
+        .add_plugin(MaterialPlugin::<materials::SolidMaterial>::default())
         .add_startup_system(startup)
         .run();
 }
diff --git a/src/materials.rs b/src/materials.rs
new file mode 100644
index 0000000..4f42d1f
--- /dev/null
+++ b/src/materials.rs
@@ -0,0 +1,3 @@
+mod solid;
+
+pub use solid::SolidMaterial;
diff --git a/src/materials/solid.rs b/src/materials/solid.rs
new file mode 100644
index 0000000..d3b5687
--- /dev/null
+++ b/src/materials/solid.rs
@@ -0,0 +1,34 @@
+use bevy::{
+    pbr::{Material, MaterialPipeline, MaterialPipelineKey},
+    reflect::TypeUuid,
+    render::{
+        mesh::MeshVertexBufferLayout,
+        render_resource::{
+            AsBindGroup, RenderPipelineDescriptor, ShaderRef, SpecializedMeshPipelineError,
+        },
+    },
+};
+
+#[derive(AsBindGroup, Clone, TypeUuid)]
+#[uuid = "6dd176cf-c8c2-4cc5-8163-0df87c53139a"]
+pub struct SolidMaterial {}
+
+impl Material for SolidMaterial {
+    fn fragment_shader() -> ShaderRef {
+        "shaders/solid.frag".into()
+    }
+
+    fn specialize(
+        _: &MaterialPipeline<Self>,
+        descriptor: &mut RenderPipelineDescriptor,
+        _: &MeshVertexBufferLayout,
+        _: MaterialPipelineKey<Self>,
+    ) -> Result<(), SpecializedMeshPipelineError> {
+        let mut frag = descriptor
+            .fragment
+            .as_mut()
+            .expect("should have a fragment entry point here");
+        frag.entry_point = "main".into();
+        Ok(())
+    }
+}