Fix generated texture code for multi-texturing (#430)

Ensure the bind points are unique for all textures used.

Fixes #421

Author: djeedai

CHANGELOG.md

@@ -62,6 +62,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed a bug with opaque effects not rendering.
 - Fixed a bug in `ParticleLayout` where some fields may not have been aligned according to the WGSL rules.
 - Added a workaround for a `wgpu` bug on macOS/Metal backend related to `ParticleLayout` alignment.
+- Fixed a bug where only 1 texture could be used due to incorrectly generated shader code. (#421)
 
 ### Removed
 
@@ -78,7 +79,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Removed `EffectAsset::ribbon_group` as well as `with_trails()` and `with_ribbons()`.
   Use the `Attribute::RIBBON_ID` instead to assign a per-particle ribbon ID.
 - Removed `ParticleEffectBundle`. Use `ParticleEffect` directly instead.
-- Removed `ParticleEffect::z_layer_2d`. Use the Z coordinate of the effect's `Tranform` to order effects.
+- Removed `ParticleEffect::z_layer_2d`. Use the Z coordinate of the effect's `Tranform` to order effects. (#423)
 
 ## [0.14.0] 2024-12-09
 

assets/ramp.png

@@ -22,6 +22,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 }
 
 fn setup(
+    asset_server: Res<AssetServer>,
     mut commands: Commands,
     mut images: ResMut<Assets<Image>>,
     mut effects: ResMut<Assets<EffectAsset>>,
@@ -40,6 +41,9 @@ fn setup(
     let anim_img = make_anim_img(sprite_size, sprite_grid_size, Vec3::new(0.1, 0.1, 0.1));
     let texture_handle = images.add(anim_img);
 
+    // Also use a serialized asset
+    let texture_handle2 = asset_server.load("ramp.png");
+
     // The sprites form a grid, with a total animation frame count equal to the
     // number of sprites.
     let frame_count = sprite_grid_size.x * sprite_grid_size.y;
@@ -105,9 +109,11 @@ fn setup(
     let update_sprite_index = SetAttributeModifier::new(Attribute::SPRITE_INDEX, sprite_index);
 
     let texture_slot = writer.lit(0u32).expr();
+    let texture_slot2 = writer.lit(1u32).expr();
 
     let mut module = writer.finish();
     module.add_texture_slot("color");
+    module.add_texture_slot("shape");
 
     let effect = effects.add(
         EffectAsset::new(32768, Spawner::burst(32.0.into(), 8.0.into()), module)
@@ -121,6 +127,10 @@ fn setup(
                 texture_slot: texture_slot,
                 sample_mapping: ImageSampleMapping::ModulateOpacityFromR,
             })
+            .render(ParticleTextureModifier {
+                texture_slot: texture_slot2,
+                sample_mapping: ImageSampleMapping::ModulateRGB,
+            })
             .render(FlipbookModifier { sprite_grid_size })
             .render(ColorOverLifetimeModifier { gradient })
             .render(SizeOverLifetimeModifier {
@@ -150,7 +160,7 @@ fn setup(
     commands.spawn((
         ParticleEffect::new(effect),
         EffectMaterial {
-            images: vec![texture_handle],
+            images: vec![texture_handle, texture_handle2],
         },
         Name::new("effect"),
     ));

examples/circle.rs

@@ -1116,12 +1116,16 @@ fn append_spawn_events_{0}(particle_index: u32, count: u32) {{
                 texture_layout
             );
             let mut material_bindings_code = String::new();
+            let mut bind_index = 0;
             for (slot, _) in texture_layout.layout.iter().enumerate() {
+                let tex_index = bind_index;
+                let sampler_index = bind_index + 1;
                 material_bindings_code.push_str(&format!(
-                    "@group(2) @binding(0) var material_texture_{slot}: texture_2d<f32>;
-@group(2) @binding(1) var material_sampler_{slot}: sampler;
+                    "@group(2) @binding({tex_index}) var material_texture_{slot}: texture_2d<f32>;
+@group(2) @binding({sampler_index}) var material_sampler_{slot}: sampler;
 "
                 ));
+                bind_index += 2;
             }
 
             (

src/lib.rs

@@ -44,16 +44,18 @@ pub enum ImageSampleMapping {
     ModulateOpacityFromR,
 }
 
-impl ToWgslString for ImageSampleMapping {
-    fn to_wgsl_string(&self) -> String {
+impl ImageSampleMapping {
+    /// Convert this mapping to shader code for the given texture slot.
+    pub fn to_shader_code(&self, texture_slot: &str) -> String {
         match *self {
-            ImageSampleMapping::Modulate => "color = color * texColor;",
+            ImageSampleMapping::Modulate => format!("color = color * texColor{texture_slot};"),
             ImageSampleMapping::ModulateRGB => {
-                "color = vec4<f32>(color.rgb * texColor.rgb, color.a);"
+                format!("color = vec4<f32>(color.rgb * texColor{texture_slot}.rgb, color.a);")
+            }
+            ImageSampleMapping::ModulateOpacityFromR => {
+                format!("color.a = color.a * texColor{texture_slot}.r;")
             }
-            ImageSampleMapping::ModulateOpacityFromR => "color.a = color.a * texColor.r;",
         }
-        .to_string()
     }
 }
 
@@ -118,7 +120,7 @@ impl ParticleTextureModifier {
     ) -> Result<String, ExprError> {
         let texture_slot = module.try_get(self.texture_slot)?;
         let texture_slot = texture_slot.eval(module, context)?;
-        let sample_mapping = self.sample_mapping.to_wgsl_string();
+        let sample_mapping = self.sample_mapping.to_shader_code(&texture_slot[..]);
 
         let sample_mapping_name = format!("{:?}", self.sample_mapping);
 
@@ -129,15 +131,15 @@ impl ParticleTextureModifier {
         let mut code = String::with_capacity(1024);
         code += &format!(
             "    // ParticleTextureModifier
-    var texColor: vec4<f32>;
+    var texColor{texture_slot}: vec4<f32>;
     switch ({texture_slot}) {{\n"
         );
         let count = module.texture_layout().layout.len() as u32;
         for index in 0..count {
             let wgsl_index = index.to_wgsl_string();
-            code += &format!("      case {wgsl_index}: {{ texColor = textureSample(material_texture_{index}, material_sampler_{index}, uv); }}\n");
+            code += &format!("      case {wgsl_index}: {{ texColor{texture_slot} = textureSample(material_texture_{index}, material_sampler_{index}, uv); }}\n");
         }
-        code += "      default: {{ texColor = vec4<f32>(0.0); }}\n";
+        code += &format!("      default: {{ texColor{texture_slot} = vec4<f32>(0.0); }}\n");
         code += &format!(
             "    }}
     // Sample mapping: {sample_mapping_name}

src/modifier/output.rs

@@ -1992,13 +1992,6 @@ impl SpecializedRenderPipeline for ParticlesRenderPipeline {
 
         if let Some(material_bind_group_layout) = self.get_material(&key.texture_layout) {
             layout.push(material_bind_group_layout.clone());
-            // //  @location(1) vertex_uv: vec2<f32>
-            // vertex_buffer_layout.attributes.push(VertexAttribute {
-            //     format: VertexFormat::Float32x2,
-            //     offset: 12,
-            //     shader_location: 1,
-            // });
-            // vertex_buffer_layout.array_stride += 8;
         }
 
         // Key: LOCAL_SPACE_SIMULATION