RenderPass

Usage

To draw to the screen in luma.gl, simply create a RenderPass by calling device.beginRenderPass() and start rendering. When done rendering, call renderPass.end()

  // A renderpass without parameters uses the default framebuffer of the device's default CanvasContext 
  const renderPass = device.beginRenderPass();
  model.draw();
  renderPass.end();
  device.submit();

device.getDefaultCanvasContext().getDefaultFramebuffer() returns a special framebuffer that lets you render to screen (into the swap chain). This framebuffer is used by default when a device.beginRenderPass() is called without providing a framebuffer, equivalent to:

  const renderPass = device.beginRenderPass({framebuffer: device.getDefaultCanvasContext().getDefaultFramebuffer()});
  ...

Clearing the screen

Framebuffer attachments are cleared by default when a RenderPass starts. More control is provided via the clearColor parameter, setting this will clear the attachments to the corresponding color. The default clear color is fully transparent [0, 0, 0, 0]. Clearing can also be disabled by setting loadOp='load'.

  const renderPass = device.beginRenderPass({clearColor: [0, 0, 0, 1]});
  model.draw();
  renderPass.end();
  device.submit();

Depth and stencil buffers are also cleared to default values:

  const renderPass = device.beginRenderPass({
    clearColor: [0, 0, 0, 1],
    depthClearValue: 1,
    stencilClearValue: 0
  });
  renderPass.end();
  device.submit();

Viewport size

RenderPassProps.parameters.viewport controls how the rendered graphics is mapped to window pixels / texels (more precisely, the affine transformation of x and y from normalized device coordinates to window coordinates).

If no value for the viewport parameter is provided, the following defaults will be applied.

• If no framebuffer is specified, the size of the canvas drawing buffer will be used (device.getCanvasContext().getDrawingBufferSize())
• If a framebuffer is specified, the width and height of the framebuffer will be used.

Types

RenderPassProps

Property	Type	Default	Description
framebuffer?	Framebuffer	N/A	Provides render target textures and depth/stencil texture
parameters?	Parameters		GPU pipeline parameters
clearColor?	number[] | false	[0, 0, 0, 0]
loadOp?	'load', 'clear'	'clear'	Load operation to perform on texture prior to executing the render pass. Default: 'clear'.
storeOp?	'store', 'discard'	'store'	The store operation to perform on texture after executing the render pass. Default: 'store'.
depthClearValue?	number	1	Value to clear depth component to prior to executing the render pass, if depthLoadOp is "clear". 0.0-1.0.
depthLoadOp?	'load', 'clear'		Load operation to perform on depth component prior to executing the render pass. Default 'clear'.
depthStoreOp?	'store', 'discard'		Store operation` to perform on depth component after executing the render pass. Default 'store'.
depthReadOnly?	boolean		Depth component is read only.
stencilClearValue?	number		Value to clear stencil component to prior to executing the render pass, if stencilLoadOp is "clear".
stencilLoadOp?	'clear', 'load'		Load operation to perform on stencil component prior to executing the render pass. Prefer clearing.
stencilStoreOp?	'store', 'discard'		Store operation to perform on stencil component after executing the render pass.
stencilReadOnly?	boolean		Stencil component is read only.

• Clearing can be disabled by setting loadOp='load' however this may have a small performance cost as GPUs are optimized for clearing.
• WebGL does not support setting storeOp: 'discard' for just some attachments, it is all or nothing.
• Currently luma.gl doesn't support specifying per-rendertarget properties

Members

• device: Device - holds a reference to the Device that created this RenderPass.
• handle: unknown - holds the underlying WebGL or WebGPU shader object
• props: RenderPassProps - holds a copy of the RenderPassProps used to create this RenderPass.

Methods

constructor()

RenderPass is an abstract class and cannot be instantiated directly. Create with device.beginRenderPass(...).

endPass(): void

Must be called after all draw calls have been completed to guarantee rendering. Frees up any GPU resources associated with this render pass.

pushDebugGroup(groupLabel: string): void

Adds a debug group (implementation dependent).

popDebugGroup(): void

Removes a debug group (implementation dependent).

insertDebugMarker(markerLabel: string): void

Adds a debug marker (implementation dependent).