WIP support for vertex pulling

Author: MiiBond

packages/dev/core/src/Engines/WebGPU/webgpuCacheRenderPipeline.ts

@@ -175,7 +175,7 @@ export abstract class WebGPUCacheRenderPipeline {
     public readonly mrtTextureArray: InternalTexture[];
     public readonly mrtTextureCount: number = 0;
 
-    public getRenderPipeline(fillMode: number, effect: Effect, sampleCount: number, textureState = 0): GPURenderPipeline {
+    public getRenderPipeline(fillMode: number, effect: Effect, sampleCount: number, textureState = 0, useVertexPulling: boolean = false): GPURenderPipeline {
         sampleCount = WebGPUTextureHelper.GetSample(sampleCount);
 
         if (this.disabled) {
@@ -196,7 +196,7 @@ export abstract class WebGPUCacheRenderPipeline {
         this._setRasterizationState(fillMode, sampleCount);
         this._setColorStates();
         this._setDepthStencilState();
-        this._setVertexState(effect);
+        this._setVertexState(effect, useVertexPulling);
         this._setTextureState(textureState);
 
         this.lastStateDirtyLowestIndex = this._stateDirtyLowestIndex;
@@ -777,13 +777,13 @@ export abstract class WebGPUCacheRenderPipeline {
         }
     }
 
-    private _setVertexState(effect: Effect): void {
+    private _setVertexState(effect: Effect, useVertexPulling: boolean = false): void {
         const currStateLen = this._statesLength;
         let newNumStates = StatePosition.VertexState;
 
         const webgpuPipelineContext = effect._pipelineContext as WebGPUPipelineContext;
-        const attributes = webgpuPipelineContext.shaderProcessingContext.attributeNamesFromEffect;
-        const locations = webgpuPipelineContext.shaderProcessingContext.attributeLocationsFromEffect;
+        const attributes = useVertexPulling ? [] : webgpuPipelineContext.shaderProcessingContext.attributeNamesFromEffect;
+        const locations = useVertexPulling ? [] : webgpuPipelineContext.shaderProcessingContext.attributeLocationsFromEffect;
 
         let currentGPUBuffer;
         let numVertexBuffers = 0;

packages/dev/core/src/Engines/abstractEngine.ts

@@ -225,6 +225,9 @@ export abstract class AbstractEngine {
     /** @internal */
     public _videoTextureSupported: boolean;
 
+    /** @internal */
+    public _useVertexPulling: boolean = false;
+
     protected _compatibilityMode = true;
     /** @internal */
     public _pointerLockRequested: boolean;

packages/dev/core/src/Engines/webgpuEngine.ts

@@ -319,6 +319,8 @@ export class WebGPUEngine extends ThinWebGPUEngine {
 
     private _commandBuffers: GPUCommandBuffer[] = [null as any, null as any];
 
+    private _dummyVertexBuffer: DataBuffer;
+
     // Frame Buffer Life Cycle (recreated for each render target pass)
 
     private _mainRenderPassWrapper: IWebGPURenderPassWrapper = {
@@ -3690,7 +3692,9 @@ export class WebGPUEngine extends ThinWebGPUEngine {
 
         this._currentMaterialContext.textureState = textureState;
 
-        const pipeline = this._cacheRenderPipeline.getRenderPipeline(fillMode, this._currentEffect!, this.currentSampleCount, textureState);
+        // If vertex pulling, get a cached pipeline with empty vertex layout
+        // Pass a boolean here to getRenderPipeline that will cause the vertex layout to be empty
+        const pipeline = this._cacheRenderPipeline.getRenderPipeline(fillMode, this._currentEffect!, this.currentSampleCount, textureState, this._useVertexPulling);
         const bindGroups = this._cacheBindGroups.getBindGroups(webgpuPipelineContext, this._currentDrawContext, this._currentMaterialContext);
 
         if (!this._snapshotRendering.record) {
@@ -3717,6 +3721,13 @@ export class WebGPUEngine extends ThinWebGPUEngine {
             );
         }
 
+        // If vertex pulling, bind a cached empty vertex buffer
+        if (this._useVertexPulling) {
+            if (!this._dummyVertexBuffer) {
+                this._dummyVertexBuffer = this.createVertexBuffer(new Float32Array(0), false, "DummyVertexPullingBuffer");
+            }
+            renderPass2.setVertexBuffer(0, this._dummyVertexBuffer.underlyingResource, 0, 0);
+        }
         const vertexBuffers = this._cacheRenderPipeline.vertexBuffers;
         for (let index = 0; index < vertexBuffers.length; index++) {
             const vertexBuffer = vertexBuffers[index];

packages/dev/core/src/Meshes/abstractMesh.ts

@@ -956,6 +956,9 @@ export abstract class AbstractMesh extends TransformNode implements IDisposable,
     /** @internal */
     public _unIndexed = false;
 
+    /** @internal */
+    public _useVertexPulling = false;
+
     /** @internal */
     public _lightSources = new Array<Light>();
 

packages/dev/core/src/Meshes/mesh.ts

@@ -1999,6 +1999,11 @@ export class Mesh extends AbstractMesh implements IGetSetVerticesData {
         } else if (fillMode == Material.WireFrameFillMode) {
             // Triangles as wireframe
             engine.drawElementsType(fillMode, 0, subMesh._linesIndexCount, this.forcedInstanceCount || instancesCount);
+        } else if (this._useVertexPulling) {
+            // We're rendering the number of indices in the index buffer but the vertex shader is handling the data itself.
+            engine._useVertexPulling = true;
+            engine.drawArraysType(fillMode, subMesh.indexStart, subMesh.indexCount, this.forcedInstanceCount || instancesCount);
+            engine._useVertexPulling = false;
         } else {
             engine.drawElementsType(fillMode, subMesh.indexStart, subMesh.indexCount, this.forcedInstanceCount || instancesCount);
         }