Support full-object assignment to array indices

Author: davepagurek

src/strands/strands_node.js

@@ -197,6 +197,17 @@ export class StrandsNode {
       throw new Error('set() can only be used on storage buffers with an identifier');
     }
 
+    // If value is a plain object (struct literal), expand to per-field assignments
+    // e.g. buf[idx] = { position: pos, velocity: vel }
+    // becomes buf[idx].position = pos; buf[idx].velocity = vel;
+    if (value !== null && typeof value === 'object' && !value.isStrandsNode && this._schema) {
+      const proxy = createStructArrayElementProxy(this.strandsContext, this, index, this._schema);
+      for (const [fieldName, fieldValue] of Object.entries(value)) {
+        proxy[fieldName] = fieldValue;
+      }
+      return this;
+    }
+
     // Create array assignment node: buffer.set(index, value) -> buffer[index] = value
     // This creates an ASSIGNMENT node and records it in the CFG basic block
     // CFG preserves sequential order, preventing reordering of assignments

test/unit/visual/cases/webgpu.js

@@ -1353,5 +1353,45 @@ visualSuite("WebGPU", function () {
         await screenshot();
       }
     );
+
+    visualTest(
+      'Compute shader writes a whole struct element as an object literal',
+      async function(p5, screenshot) {
+        await p5.createCanvas(50, 50, p5.WEBGPU);
+
+        const particles = p5.createStorage([
+          { position: [0, 0], velocity: [15, -10] },
+        ]);
+
+        const computeShader = p5.buildComputeShader(() => {
+          const buf = p5.uniformStorage('buf', particles);
+          const idx = iteration.index.x;
+          let pos = buf[idx].position;
+          let vel = buf[idx].velocity;
+          pos = pos + vel;
+          buf[idx] = { position: pos, velocity: vel };
+        }, { p5, particles });
+        p5.compute(computeShader, 1);
+
+        const sphereShader = p5.baseMaterialShader().modify(() => {
+          const buf = p5.uniformStorage('buf', particles);
+          p5.getWorldInputs((inputs) => {
+            const pos = buf[0].position;
+            inputs.position.x += pos.x;
+            inputs.position.y += pos.y;
+            return inputs;
+          });
+        }, { p5, particles });
+
+        const geo = p5.buildGeometry(() => p5.sphere(5));
+        p5.background(200);
+        p5.noStroke();
+        p5.fill(255, 0, 0);
+        p5.shader(sphereShader);
+        p5.model(geo, 1);
+
+        await screenshot();
+      }
+    );
   });
 });

test/unit/visual/screenshots/WebGPU/Compute shaders/Compute shader writes a whole struct element as an object literal/000.png

@@ -0,0 +1,3 @@
+{
+  "numScreenshots": 1
+}