Fix Z-fighting between overlay and stencil with OpenGL wgpu back-end.

Cargo.toml

@@ -20,6 +20,7 @@ bevy = { version = "0.10", default-features = false, features = [
 bitfield = "0.14"
 interpolation = "0.2"
 thiserror = "1.0"
+wgpu-types = "0.15"
 
 [dev-dependencies]
 bevy = { version = "0.10", default-features = false, features = [

src/draw.rs

@@ -3,7 +3,9 @@ use bevy::prelude::*;
 use bevy::render::render_asset::RenderAssets;
 use bevy::render::render_phase::{DrawFunctions, RenderPhase, SetItemPipeline};
 use bevy::render::render_resource::{PipelineCache, SpecializedMeshPipelines};
+use bevy::render::renderer::RenderAdapterInfo;
 use bevy::render::view::{ExtractedView, RenderLayers};
+use wgpu_types::Backend;
 
 use crate::node::{OpaqueOutline, StencilOutline, TransparentOutline};
 use crate::pipeline::{OutlinePipeline, PassType, PipelineKey};
@@ -32,6 +34,7 @@ pub(crate) fn queue_outline_stencil_mesh(
     mut pipelines: ResMut<SpecializedMeshPipelines<OutlinePipeline>>,
     pipeline_cache: Res<PipelineCache>,
     render_meshes: Res<RenderAssets<Mesh>>,
+    adapter_info: Res<RenderAdapterInfo>,
     material_meshes: Query<(
         Entity,
         &Handle<Mesh>,
@@ -52,7 +55,8 @@ pub(crate) fn queue_outline_stencil_mesh(
 
     let base_key = PipelineKey::new()
         .with_msaa(*msaa)
-        .with_pass_type(PassType::Stencil);
+        .with_pass_type(PassType::Stencil)
+        .with_opengl_workaround(adapter_info.0.backend == Backend::Gl);
 
     for (view, mut stencil_phase, view_mask) in views.iter_mut() {
         let rangefinder = view.rangefinder3d();
@@ -105,6 +109,7 @@ pub(crate) fn queue_outline_volume_mesh(
     mut pipelines: ResMut<SpecializedMeshPipelines<OutlinePipeline>>,
     pipeline_cache: Res<PipelineCache>,
     render_meshes: Res<RenderAssets<Mesh>>,
+    adapter_info: Res<RenderAdapterInfo>,
     material_meshes: Query<(
         Entity,
         &Handle<Mesh>,
@@ -129,7 +134,9 @@ pub(crate) fn queue_outline_volume_mesh(
         .get_id::<DrawOutline>()
         .unwrap();
 
-    let base_key = PipelineKey::new().with_msaa(*msaa);
+    let base_key = PipelineKey::new()
+        .with_msaa(*msaa)
+        .with_opengl_workaround(adapter_info.0.backend == Backend::Gl);
 
     for (view, mut opaque_phase, mut transparent_phase, view_mask) in views.iter_mut() {
         let view_mask = view_mask.copied().unwrap_or_default();

src/fragment.wgsl

@@ -1,24 +1,32 @@
-#ifdef VOLUME
+struct FragmentOutput {
+    @location(0) colour: vec4<f32>,
+#ifdef OPENGL_WORKAROUND
+    @builtin(frag_depth) frag_depth: f32,
+#endif
+};
 
 struct OutlineFragmentUniform {
     @align(16)
     colour: vec4<f32>,
 };
 
+#ifdef VOLUME
 @group(3) @binding(1)
 var<uniform> fstage: OutlineFragmentUniform;
-
-@fragment
-fn fragment() -> @location(0) vec4<f32> {
-    return fstage.colour;
-}
-
-#else
-// Stencil
-
-@fragment
-fn fragment() {
-    return;
-}
-
 #endif
+
+@fragment
+#ifdef OPENGL_WORKAROUND
+fn fragment(@location(0) normalised_depth: f32) -> FragmentOutput {
+#else
+fn fragment() -> FragmentOutput {
+#endif
+    var out: FragmentOutput;
+#ifdef VOLUME
+    out.colour = fstage.colour;
+#endif
+#ifdef OPENGL_WORKAROUND
+    out.frag_depth = normalised_depth; 
+#endif
+    return out;
+}

src/outline.wgsl

@@ -12,6 +12,13 @@ struct VertexInput {
 #endif
 };
 
+struct VertexOutput {
+    @builtin(position) position: vec4<f32>,
+#ifdef OPENGL_WORKAROUND
+    @location(0) normalised_depth: f32,
+#endif
+};
+
 struct OutlineViewUniform {
     @align(16)
     scale: vec2<f32>,
@@ -53,7 +60,7 @@ fn model_origin_z(plane: vec3<f32>, view_proj: mat4x4<f32>) -> f32 {
 }
 
 @vertex
-fn vertex(vertex: VertexInput) -> @builtin(position) vec4<f32> {
+fn vertex(vertex: VertexInput) -> VertexOutput {
 #ifdef SKINNED
     let model = skin_model(vertex.joint_indexes, vertex.joint_weights);
 #else
@@ -72,5 +79,10 @@ fn vertex(vertex: VertexInput) -> @builtin(position) vec4<f32> {
     let ndc_delta = vstage.offset * normalize(clip_norm.xy) * view_uniform.scale * clip_pos.w;
     let out_xy = clip_pos.xy + ndc_delta;
 #endif
-    return vec4<f32>(out_xy, out_z, clip_pos.w);
+    var out: VertexOutput;
+    out.position = vec4<f32>(out_xy, out_z, clip_pos.w);
+#ifdef OPENGL_WORKAROUND
+    out.normalised_depth = 0.5 + 0.5 * (out_z / clip_pos.w);
+#endif
+    return out;
 }

src/pipeline.rs

@@ -56,6 +56,7 @@ impl PipelineKey {
         depth_mode_int, set_depth_mode_int: 12, 11;
         pub offset_zero, set_offset_zero: 13;
         pub hdr_format, set_hdr_format: 14;
+        pub opengl_workaround, set_opengl_workaround: 15;
     }
 
     pub(crate) fn new() -> Self {
@@ -129,6 +130,11 @@ impl PipelineKey {
         self.set_hdr_format(hdr_format);
         self
     }
+
+    pub(crate) fn with_opengl_workaround(mut self, opengl_workaround: bool) -> Self {
+        self.set_opengl_workaround(opengl_workaround);
+        self
+    }
 }
 
 #[derive(Resource)]
@@ -294,6 +300,11 @@ impl SpecializedMeshPipeline for OutlinePipeline {
                 bind_layouts.push(self.outline_volume_bind_group_layout.clone());
             }
         }
+        if key.opengl_workaround() {
+            let val = ShaderDefVal::from("OPENGL_WORKAROUND");
+            vertex_defs.push(val.clone());
+            fragment_defs.push(val);
+        }
         let buffers = vec![mesh_layout.get_layout(&buffer_attrs)?];
         Ok(RenderPipelineDescriptor {
             vertex: VertexState {