feat(rendering): add bounded virtual draw fallback

Author: proggeramlug

native/shared/shaders/virtual_geometry/visibility_raster.wgsl

@@ -14,10 +14,9 @@ fn bloom_invalid_virtual_vertex() -> VirtualVisibilityVertexOut {
     return VirtualVisibilityVertexOut(vec4<f32>(2.0, 2.0, 2.0, 1.0), 0u, 0u);
 }
 
-@vertex
-fn vs_virtual_visibility(
-    @builtin(vertex_index) corner: u32,
-    @builtin(instance_index) selected_index: u32,
+fn bloom_virtual_visibility_vertex(
+    selected_index: u32,
+    corner: u32,
 ) -> VirtualVisibilityVertexOut {
     if (selected_index >= arrayLength(&virtual_selected.records)) {
         return bloom_invalid_virtual_vertex();
@@ -61,6 +60,14 @@ fn vs_virtual_visibility(
     );
 }
 
+@vertex
+fn vs_virtual_visibility(
+    @builtin(vertex_index) corner: u32,
+    @builtin(instance_index) selected_index: u32,
+) -> VirtualVisibilityVertexOut {
+    return bloom_virtual_visibility_vertex(selected_index, corner);
+}
+
 @fragment
 fn fs_virtual_visibility(
     in: VirtualVisibilityVertexOut,

native/shared/shaders/virtual_geometry/visibility_raster_binned.wgsl

@@ -0,0 +1,22 @@
+// Bounded fallback for adapters without indirect-count submission. GPU
+// compaction writes selected indices into 22 power-of-two triangle bins, so
+// this path issues a constant 22 draws and invokes fewer than twice the exact
+// number of cluster vertices.
+
+struct VirtualBinnedSelectionIndices { records: array<u32>, };
+@group(0) @binding(5) var<storage, read> virtual_binned_selection_indices:
+    VirtualBinnedSelectionIndices;
+
+@vertex
+fn vs_virtual_visibility_binned(
+    @builtin(vertex_index) corner: u32,
+    @builtin(instance_index) binned_index: u32,
+) -> VirtualVisibilityVertexOut {
+    if (binned_index >= arrayLength(&virtual_binned_selection_indices.records)) {
+        return bloom_invalid_virtual_vertex();
+    }
+    return bloom_virtual_visibility_vertex(
+        virtual_binned_selection_indices.records[binned_index],
+        corner,
+    );
+}