Using GPU Parameters

luma.gl provides a unified API for controlling GPU parameters providing control of GPU pipeline features such as culling, depth and stencil buffers, blending, clipping etc.

Usage

To set up depth testing

const value = device.createRenderPipeline({
  parameters: {
    depthWriteEnabled: true,
    depthCompare: 'less-equal'
  },

const value = device.createRenderPipeline({
  parameters: {
    depthWriteEnabled: true,
    depthCompare: 'less-equal'
  },
  targets: [
    {
      blendColor: ...,

    }
  ]
});

const framebuffer = device.createFramebuffer({
  colorAttachments: {clearColor: [1, 0, 0]},
})

const device.beginRenderPass({
  framebuffer,
  parameters: {

  }
})

renderPass.setPipeline(pipeline);
renderPass.setParameters({viewport: MAIN_MAP})
renderPass.draw();
renderPass.setParameters({viewport: MINI_MAP})
renderPass.draw();

GPU Pipeline Overview

Parameters control the GPU pipeline and can be GPU Pipeline Stages

Describes luma.gl setting names and values

0. Vertex Fetch (buffers)
1. Vertex Shader
2. Primitive assembly (topology)
3. Rasterization (multisampling parameters)
4. Fragment shader Framebuffer
5. Stencil test and operation (stencil parameters)
6. Depth test and write (depth parameters)
7. Output merging, controlled by Framebuffer

Parameter Mutability

Most luma.gl parameters are stored on the RenderPipeline or RenderPass classes which are either fully or partially immutable, meaning that parameters are fixed when these objects are created, and cannot be changed without creating new resources. The following table summarizes the situation:

Parameter Mutability	Examples	Constraint
Dynamic RenderPass parameters	viewport, scissor, blendConstant	Can be freely changed between draw calls.
Fixed RenderPass parameters	clearColors, discard, depthClearValue...	Can not be changed. A new RenderPass must be created.
Fixed RenderPipeline parameters	cullMode, frontFace, depthWriteEnabled, ...	Can not be changed. A new RenderPipeline must be created.

Dynamic RenderPass Parameters

The only parameters that can be changed at any time (using renderPass.setParameters()) are viewport size, scissor rectangle, and blend constant

Fixed RenderPass Parameters

A RenderPass holds parameters specifying how color and depth / stencil attachments should be cleared (clear colors, values), discarded etc.

Note that there is no explicit clear function in the luma.gl v9 API. Instead attachments are cleared when a RenderPass is created (begins),