GPURenderBundleEncoder: drawIndirect() method

{{APIRef("WebGPU API")}}{{SecureContext_Header}}{{AvailableInWorkers}}

The drawIndirect() method of the {{domxref("GPURenderBundleEncoder")}} interface draws primitives using parameters read from a {{domxref("GPUBuffer")}}.

[!NOTE] This method is functionally identical to its equivalent on {{domxref("GPURenderPassEncoder")}} — {{domxref("GPURenderPassEncoder.drawIndirect", "drawIndirect()")}}.

Syntax

drawIndirect(indirectBuffer, indirectOffset)

Parameters

• indirectBuffer

  • : A {{domxref("GPUBuffer")}} containing the vertexCount, instanceCount, firstVertex, and firstInstance values needed to carry out the drawing operation. The buffer must contain a tightly packed block of four 32-bit unsigned integer values representing the values (16 bytes total), given in the same order as the arguments for {{domxref("GPURenderBundleEncoder.draw()")}}. So for example:

    jsCopy

    const uint32 = new Uint32Array(4);
    uint32[0] = 3; // The vertexCount value
    uint32[1] = 1; // The instanceCount value
    uint32[2] = 0; // The firstVertex value
    uint32[3] = 0; // The firstInstance value
    
    // Write values into a GPUBuffer
    device.queue.writeBuffer(buffer, 0, uint32, 0, uint32.length);
    

    [!NOTE] The indirect-first-instance feature needs to be enabled for non-zero firstInstance values to be used. If the indirect-first-instance feature is not enabled and firstInstance is not zero, the drawIndirect() call will be treated as a no-op.

• indirectOffset

  • : The offset, in bytes, into indirectBuffer where the value data begins.

Return value

None ({{jsxref("Undefined")}}).

Validation

The following criteria must be met when calling drawIndirect(), otherwise a {{domxref("GPUValidationError")}} is generated and the {{domxref("GPURenderBundleEncoder")}} becomes invalid:

• indirectBuffer's {{domxref("GPUBuffer.usage")}} contains the GPUBufferUsage.INDIRECT flag.
• indirectOffset + the total size specified by the value parameters in the indirectBuffer is less than or equal to the indirectBuffer's {{domxref("GPUBuffer.size")}}.
• indirectOffset is a multiple of 4.

Examples

// …

// Create GPURenderBundleEncoder
const bundleEncoder = device.createRenderBundleEncoder(descriptor);

// Set pipeline and vertex buffer
bundleEncoder.setPipeline(renderPipeline);
bundleEncoder.setVertexBuffer(0, vertexBuffer);

// Create drawIndirect values
const uint32 = new Uint32Array(4);
uint32[0] = 3;
uint32[1] = 1;
uint32[2] = 0;
uint32[3] = 0;

// Create a GPUBuffer and write the draw values into it
const drawValues = device.createBuffer({
  size: 16,
  usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.INDIRECT,
});
device.queue.writeBuffer(drawValues, 0, uint32, 0, uint32.length);

// Draw the vertices
bundleEncoder.drawIndirect(drawValues, 0);

// End the bundle recording
const renderBundle = bundleEncoder.finish();

// …

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• The WebGPU API