fix: Rebuild gsplat work buffer render targets for runtime-added streams

src/scene/gsplat-unified/gsplat-work-buffer.js

@@ -168,6 +168,14 @@ class GSplatWorkBuffer {
     /** @type {GSplatWorkBufferRenderPass} */
     colorRenderPass;
 
+    /**
+     * Stream-set version the render targets were created for.
+     *
+     * @type {number}
+     * @private
+     */
+    _renderTargetsVersion = -1;
+
     /**
      * GPU frustum culler for octree node visibility.
      *
@@ -317,6 +325,7 @@ class GSplatWorkBuffer {
 
         // Collect all textures in order for MRT
         const colorBuffers = this.streams.getTexturesInOrder();
+        this._renderTargetsVersion = this.streams._formatVersion;
         // viewport rects used to fill the work buffer must address identical texel rows on all
         // graphics APIs, matching the WebGL layout
         this.renderTarget = new RenderTarget({
@@ -345,11 +354,13 @@ class GSplatWorkBuffer {
      * Call this before rendering to ensure all streams have textures.
      */
     syncWithFormat() {
-        const prevVersion = this.streams._formatVersion;
         this.streams.syncWithFormat(this.format);
 
-        // If format changed, recreate render targets to include new textures
-        if (prevVersion !== this.streams._formatVersion) {
+        // Recreate the render targets when they were built for an older stream set. Compared
+        // against the version the targets were built for, not the streams' version before this
+        // call: getTexture() syncs the streams on its own, so by the time this runs they can
+        // already be up to date while the targets still lack the new textures.
+        if (this._renderTargetsVersion !== this.streams._formatVersion) {
             this._createRenderTargets();
         }
     }

test/scene/gsplat-unified/gsplat-work-buffer.test.mjs

@@ -0,0 +1,49 @@
+import { expect } from 'chai';
+
+import { PIXELFORMAT_R8 } from '../../../src/platform/graphics/constants.js';
+import { NullGraphicsDevice } from '../../../src/platform/graphics/null/null-graphics-device.js';
+import { GSplatParams } from '../../../src/scene/gsplat-unified/gsplat-params.js';
+import { GSplatWorkBuffer } from '../../../src/scene/gsplat-unified/gsplat-work-buffer.js';
+
+describe('GSplatWorkBuffer#syncWithFormat', function () {
+    let device;
+    let workBuffer;
+
+    beforeEach(function () {
+        device = new NullGraphicsDevice({ width: 1, height: 1 });
+    });
+
+    afterEach(function () {
+        workBuffer?.destroy();
+        workBuffer = null;
+        device.destroy();
+    });
+
+    it('attaches a stream added after creation', function () {
+        const params = new GSplatParams(device);
+        workBuffer = new GSplatWorkBuffer(device, params.format);
+        const before = workBuffer.renderTarget.colorBufferCount;
+
+        params.format.addExtraStreams([{ name: 'testStream', format: PIXELFORMAT_R8 }]);
+        workBuffer.syncWithFormat();
+
+        expect(workBuffer.renderTarget.colorBufferCount).to.equal(before + 1);
+        expect(workBuffer.renderTarget.getColorBuffer(before)).to.equal(workBuffer.getTexture('testStream'));
+    });
+
+    it('attaches a stream added after creation even if getTexture() synced the streams first', function () {
+        const params = new GSplatParams(device);
+        workBuffer = new GSplatWorkBuffer(device, params.format);
+        const before = workBuffer.renderTarget.colorBufferCount;
+
+        params.format.addExtraStreams([{ name: 'testStream', format: PIXELFORMAT_R8 }]);
+
+        // a renderer binding textures by name syncs the streams on its own
+        const texture = workBuffer.getTexture('testStream');
+        expect(texture).to.not.equal(undefined);
+
+        workBuffer.syncWithFormat();
+        expect(workBuffer.renderTarget.colorBufferCount).to.equal(before + 1);
+        expect(workBuffer.renderTarget.getColorBuffer(before)).to.equal(texture);
+    });
+});