Controllable ambient light color (#852)

Control ambient light color via resource

The AmbientLight resource now controls the ambient light color in the
pbr fragment shader.

crates/bevy_pbr/src/lib.rs

@@ -32,7 +32,8 @@ impl Plugin for PbrPlugin {
             .add_system_to_stage(
                 stage::POST_UPDATE,
                 shader::asset_shader_defs_system::<StandardMaterial>.system(),
-            );
+            )
+            .init_resource::<AmbientLight>();
         let resources = app.resources();
         let mut render_graph = resources.get_mut::<RenderGraph>().unwrap();
         add_pbr_graph(&mut render_graph, resources);

crates/bevy_pbr/src/light.rs

@@ -53,3 +53,17 @@ impl LightRaw {
         }
     }
 }
+
+// Ambient light color.
+#[derive(Debug)]
+pub struct AmbientLight {
+    pub color: Color,
+}
+
+impl Default for AmbientLight {
+    fn default() -> Self {
+        Self {
+            color: Color::rgb(0.05, 0.05, 0.05),
+        }
+    }
+}

crates/bevy_pbr/src/render_graph/forward_pipeline/forward.frag

@@ -19,6 +19,7 @@ layout(set = 0, binding = 0) uniform Camera {
 };
 
 layout(set = 1, binding = 0) uniform Lights {
+    vec3 AmbientColor;
     uvec4 NumLights;
     Light SceneLights[MAX_LIGHTS];
 };
@@ -42,9 +43,8 @@ void main() {
 
 # ifdef STANDARDMATERIAL_SHADED
     vec3 normal = normalize(v_Normal);
-    vec3 ambient = vec3(0.05, 0.05, 0.05);
     // accumulate color
-    vec3 color = ambient;
+    vec3 color = AmbientColor;
     for (int i=0; i<int(NumLights.x) && i<MAX_LIGHTS; ++i) {
         Light light = SceneLights[i];
         // compute Lambertian diffuse term

crates/bevy_pbr/src/render_graph/lights_node.rs

@@ -1,5 +1,5 @@
 use crate::{
-    light::{Light, LightRaw},
+    light::{AmbientLight, Light, LightRaw},
     render_graph::uniform,
 };
 use bevy_core::{AsBytes, Byteable};
@@ -78,16 +78,19 @@ pub struct LightsNodeSystemState {
 pub fn lights_node_system(
     mut state: Local<LightsNodeSystemState>,
     render_resource_context: Res<Box<dyn RenderResourceContext>>,
+    ambient_light_resource: Res<AmbientLight>,
     // TODO: this write on RenderResourceBindings will prevent this system from running in parallel with other systems that do the same
     mut render_resource_bindings: ResMut<RenderResourceBindings>,
     query: Query<(&Light, &GlobalTransform)>,
 ) {
     let state = &mut state;
     let render_resource_context = &**render_resource_context;
 
+    let ambient_light: [f32; 4] = ambient_light_resource.color.into();
+    let ambient_light_size = std::mem::size_of::<[f32; 4]>();
     let light_count = query.iter().count();
     let size = std::mem::size_of::<LightRaw>();
-    let light_count_size = std::mem::size_of::<LightCount>();
+    let light_count_size = ambient_light_size + std::mem::size_of::<LightCount>();
     let light_array_size = size * light_count;
     let light_array_max_size = size * state.max_lights;
     let current_light_uniform_size = light_count_size + light_array_size;
@@ -128,8 +131,12 @@ pub fn lights_node_system(
         staging_buffer,
         0..current_light_uniform_size as u64,
         &mut |data, _renderer| {
+            // ambient light
+            data[0..ambient_light_size].copy_from_slice(ambient_light.as_bytes());
+
             // light count
-            data[0..light_count_size].copy_from_slice([light_count as u32, 0, 0, 0].as_bytes());
+            data[ambient_light_size..light_count_size]
+                .copy_from_slice([light_count as u32, 0, 0, 0].as_bytes());
 
             // light array
             for ((light, global_transform), slot) in query