luma.gl/docs/api-guide/parameters.md

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.

A number of parameters are set when certain GPU objects are created, and cannot be changed without creating a new object.

Parameter "Type"	Comments
RenderPipeline constructor	RenderPipeline is created.
RenderPass constructor	Render targets, clear colors etc. To vary these parameters, additional RenderPasses would need to be created.
RenderPass method	(viewport, scissor and blendConstant) can be changed dynamically between draw calls in the same RenderPass.

Note that there are certain types of parameters affecting GPU operation that are not handled by

Parameters	Comments
Sampler	How to sample from textures is controlled by Sampler objects.
Framebuffer	luma.gl uses Framebuffer objects to collect render targets and also certain per-render-target settings, such as clearColors.

Dynamic Parameters

The only parameters that can be changed at any time are viewport parameters, blend constant and stencil reference.

Parameter	Description	Values
viewport	Specifying viewport size	number (0xffffffff)
scissor	Specifyi	number (0xffffffff)	gl.frontFace
blendConstant	Sets color referenced by pipeline targets using blend factors constant, one-minus-constant
stencilReference

Usage

To set up depth testing

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

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

    }
  ]
});

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

const device.createRenderPass({
  parameters: {

  }
})

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

Parameters by GPU Pipeline Stages

Describes luma.gl setting names and values

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

Primitive Assembly Parameters (RenderPipeline)

Note: topology must be specified on a RenderPipeline to describe the layout of vertex buffers.

Rasterization Parameters (RenderPipeline)

These parameters control the primitive assembly stage (which happens before fragment shader runs).

Function	How to set	Description	Values	WebGL counterpart
cullMode	Which face to cull	'none', 'front', 'back'
frontFace	Which triangle winding order is front	ccw, cw

Multisample Parameters (RenderPipeline)

Function	Description	Values
sampleCount		1
sampleMask		0xFFFFFFFF
alphaToCoverageEnabled		false

Blending

Parameter	How to set	Description
blendColor	RenderPass.setParameters()
blendEquation	createRenderPipeline({targets: ...})
blendOperation	createRenderPipeline({targets}).
blendSrcFactor	createRenderPipeline({targets}).
blendDstFactor	createRenderPipeline({targets}).

Stencil Test (RenderPipeline)

After the fragment shader runs, optional stencil tests are performed, with resulting operations on the the stencil buffer.

Function	Description	Values
stencilReadMask	createRenderPipeline()	Binary mask for reading stencil values	number (0xffffffff)
stencilWriteMask	createRenderPipeline()	Binary mask for writing stencil values	number (0xffffffff)	gl.frontFace
stencilCompare	createRenderPipeline()	How the mask is compared	always, not-equal, ...	gl.stencilFunc
stencilPassOperation	createRenderPipeline()		'keep'	gl.stencilOp
stencilDepthFailOperation	createRenderPipeline()		'keep'	gl.stencilOp
stencilFailOperation	createRenderPipeline()		'keep'	gl.stencilOp

Stencil Test Functions

stencilCompare Value	Description
'always'	Always pass
'never'	Never pass
'less'	Pass if (ref & mask) < (stencil & mask)
'equal'	Pass if (ref & mask) = (stencil & mask)
'lequal'	Pass if (ref & mask) <= (stencil & mask)
'greater'	Pass if (ref & mask) > (stencil & mask)
'notequal'	Pass if (ref & mask) != (stencil & mask)
'gequal'	Pass if (ref & mask) >= (stencil & mask)

Stencil Operations (RenderPipeline)

stencil<>Operation	Description
'keep'	Keeps current value
'zero'	Sets stencil buffer value to 0
'replace'	Sets stencil buffer value to reference value per stencilFunc
'invert'	Inverts stencil buffer value bitwise
'increment-clamp'	Increments stencil buffer value. Clamps to max value
'increment-wrap'	Increments stencil buffer value. Wraps to zero
'decrement-clamp'	Decrements stencil buffer value. Clamps to 0
'decrement-wrap'	Decrements stencil buffer value, wraps to max unsigned value

Action when the stencil test fails

• stencil test fail action,
• depth test fail action,
• pass action

Remarks:

• By using binary masks, an 8 bit stencil buffer can effectively contain 8 separate masks or stencils
• The luma.gl API currently does not support setting stencil operations separately for front and back faces.

Depth Test Parameters (RenderPipeline)

After the GPU completes stencil tests, depth tests and writes are performed. These can be controlled by the following parameters:

Function	Description	Values	WebGL counterpart
depthWriteEnabled	Whether depth buffer is updated	boolean true	gl.depthMask
depthCompare	If and how depth testing is done	always, ...	gl.depthFunc
depthBias	Small depth offset for polygons	float	gl.polygonOffset
depthBiasSlopeScale	Small depth factor for polygons	float	gl.polygonOffset
depthBiasClamp	Max depth offset for polygons	float	N/A
unclippedDepth	Disable depth value clipping to [0, 1]	false boolean	N/A - Requires depth-clip-control

• Depth Bias - Sometimes referred to as "polygon offset". Adds small offset to fragment depth values (by factor × DZ + r × units). Usually used as a heuristic to avoid z-fighting, but can also be used for effects like applying decals to surfaces, and for rendering solids with highlighted edges. The semantics of polygon offsets are loosely specified by the WebGL standard and results can thus be driver dependent.

Render Targets (Framebuffers)

Clear Color

Function	Sets parameters
clearColor	createRenderPass({colorAttachments})