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 [0, 0, 0, 1]. 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],
    clearDepth: 1,
    clearStencil: 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

RenderPassProps extends ResourceProps and accepts the following fields.

Property	Type	Default	Description
framebuffer?	Framebuffer | null	null	Render target that receives the output of the pass. When omitted, the default canvas framebuffer is used.
parameters?	RenderPassParameters	undefined	Mutable pipeline parameters such as viewport, scissor rectangle, blend constant and stencil reference.
clearColor?	NumberArray4 | TypedArray | false	[0, 0, 0, 1]	Color used to clear the default color attachment. Set to false to preserve the previous value.
clearColors?	(TypedArray | false)[]	undefined	Per-attachment clear values for multiple color attachments. Takes precedence over clearColor when provided.
clearDepth?	number | false	1	Depth value used when clearing the depth attachment. Set to false to preserve the previous depth.
clearStencil?	number | false	0	Stencil value used when clearing the stencil attachment. Set to false to preserve the previous stencil.
depthReadOnly?	boolean	false	Marks the depth attachment as read-only for the duration of the pass.
stencilReadOnly?	boolean	false	Marks the stencil attachment as read-only for the duration of the pass.
discard?	boolean	false	Disables rasterization output when set to true.
occlusionQuerySet?	QuerySet	undefined	Query set that records occlusion query results generated by the pass.
timestampQuerySet?	QuerySet	undefined	Query set that will receive timestamps at the beginning and end of the pass.
beginTimestampIndex?	number	undefined	Query set index that records the timestamp when the pass begins.
endTimestampIndex?	number	undefined	Query set index that records the timestamp when the pass ends.

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(...).

end(): 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).