GPURenderPassEncoder: drawIndexedIndirect() method

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

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

Syntax

drawIndexedIndirect(indirectBuffer, indirectOffset)

Parameters

• indirectBuffer

  • : A {{domxref("GPUBuffer")}} containing the indexCount, instanceCount, firstIndex, baseVertex, and firstInstance values needed to carry out the drawing operation. The buffer must contain a tightly packed block of five 32-bit unsigned integer values representing the values (20 bytes total), given in the same order as the arguments for {{domxref("GPURenderPassEncoder.drawIndexed()")}}. So for example:

    jsCopy

    const uint32 = new Uint32Array(5);
    uint32[0] = 3; // The indexCount value
    uint32[1] = 1; // The instanceCount value
    uint32[2] = 0; // The firstIndex value
    uint32[3] = 0; // The baseVertex value
    uint32[4] = 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 drawIndexedIndirect() 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("GPURenderPassEncoder")}} 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 GPURenderPassEncoder
const passEncoder = commandEncoder.beginRenderPass(renderPassDescriptor);

// Set pipeline and vertex buffer
passEncoder.setPipeline(renderPipeline);
passEncoder.setVertexBuffer(0, vertexBuffer);
passEncoder.setIndexBuffer(indexBuffer, "uint16");

// Create drawIndexedIndirect values
const uint32 = new Uint32Array(5);
uint32[0] = 3;
uint32[1] = 1;
uint32[2] = 0;
uint32[3] = 0;
uint32[4] = 0;

// Create a GPUBuffer and write the draw values into it
const drawValues = device.createBuffer({
  size: 20,
  usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.INDIRECT,
});
device.queue.writeBuffer(drawValues, 0, uint32, 0, uint32.length);

// Draw the vertices
passEncoder.drawIndexedIndirect(drawValues, 0);

// End the render pass
passEncoder.end();

// End frame by passing array of GPUCommandBuffers to command queue for execution
device.queue.submit([commandEncoder.finish()]);

// …

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• The WebGPU API