Chapter 479: SSGINode

Core Idea

Post processing node for applying Screen Space Global Illumination (SSGI) to a scene.

References:

The quality and performance of the effect mainly depend on sliceCount and stepCount. The total number of samples taken per pixel is sliceCount * stepCount * 2. Here are some recommended presets depending on whether temporal filtering is used or not.

With temporal filtering (recommended):

Low: sliceCount of 1, stepCount of 12.
Medium: sliceCount of 2, stepCount of 8.
High: sliceCount of 3, stepCount of 16.

Use for a higher slice count if you notice temporal instabilities like flickering. Reduce the sample count then to mitigate the performance lost.

Without temporal filtering:

Low: sliceCount of 2, stepCount of 6.
Medium: sliceCount of 3, stepCount of 8.
High: sliceCount of 4, stepCount of 12.

Key Concepts

aoIntensity : UniformNode.<float>: Power function applied to AO to make it appear darker/lighter. Should be in the range [0, 4].
backfaceLighting : UniformNode.<float>: How much light backface surfaces emit. Should be in the range [0, 1].
beautyNode : TextureNode: A texture node that represents the beauty or scene pass.
depthNode : TextureNode: A node that represents the scene's depth.
expFactor : UniformNode.<float>: Controls samples distribution. It's an exponent applied at each step get increasing step size over the distance. Should be in the range `[1…
giIntensity : UniformNode.<float>: Intensity of the indirect diffuse light. Should be in the range [0, 100].
normalNode : TextureNode: A node that represents the scene's normals. If no normals are passed to the constructor (because MRT is not available), normals can be auto…
radius : UniformNode.<float>: Effective sampling radius in world space. AO and GI can only have influence within that radius. Should be in the range [1, 25].
sliceCount : UniformNode.<uint>: Number of per-pixel hemisphere slices. This has a big performance cost and should be kept as low as possible. Should be in the range `[1, 4…
stepCount : UniformNode.<uint>: Number of samples taken along one side of a given hemisphere slice. This has a big performance cost and should be kept as low as possible. …

Code Examples

import { ssgi } from 'three/addons/tsl/display/SSGINode.js';

What it demonstrates: Typical usage of SSGINode.

Reference Tables

Constructor

Signature
`new SSGINode( beautyNode : TextureNode, depthNode : TextureNode, normalNode : TextureNode, camera : PerspectiveCamera )`

Properties

Property	Description
`.aoIntensity : UniformNode.<float>`	Power function applied to AO to make it appear darker/lighter. Should be in the range `[0, 4]`.
`.backfaceLighting : UniformNode.<float>`	How much light backface surfaces emit. Should be in the range `[0, 1]`.
`.beautyNode : TextureNode`	A texture node that represents the beauty or scene pass.
`.depthNode : TextureNode`	A node that represents the scene's depth.
`.expFactor : UniformNode.<float>`	Controls samples distribution. It's an exponent applied at each step get increasing step size over the distance. Should be in the range `[1, 3]`.
`.giIntensity : UniformNode.<float>`	Intensity of the indirect diffuse light. Should be in the range `[0, 100]`.
`.normalNode : TextureNode`	A node that represents the scene's normals. If no normals are passed to the constructor (because MRT is not available), normals can be automatically reconstructed from depth values in the shader.
`.radius : UniformNode.<float>`	Effective sampling radius in world space. AO and GI can only have influence within that radius. Should be in the range `[1, 25]`.
`.sliceCount : UniformNode.<uint>`	Number of per-pixel hemisphere slices. This has a big performance cost and should be kept as low as possible. Should be in the range `[1, 4]`.
`.stepCount : UniformNode.<uint>`	Number of samples taken along one side of a given hemisphere slice. This has a big performance cost and should be kept as low as possible. Should be in the range `[1, 32]`.
`.thickness : UniformNode.<float>`	Constant thickness value of objects on the screen in world units. Allows light to pass behind surfaces past that thickness value. Should be in the range `[0.01, 10]`.
`.updateBeforeType : string`	The `updateBeforeType` is set to `NodeUpdateType.FRAME` since the node renders its effect once per frame in `updateBefore()`.
`.useLinearThickness : UniformNode.<bool>`	Whether to increase thickness linearly over distance or not (avoid losing detail over the distance).
`.useScreenSpaceSampling : UniformNode.<bool>`	Makes the sample distance in screen space instead of world-space (helps having more detail up close).
`.useTemporalFiltering : boolean`	Whether to use temporal filtering or not. Setting this property to `true` requires the usage of `TRAANode`. This will help to reduce noise although it introduces typical TAA artifacts like ghosting a…

Methods

Method	Description
`.dispose()`	Frees internal resources. This method should be called when the effect is no longer required.
`.getAONode() : PassTextureNode`	Returns the AO result of the effect as a texture node.
`.getGINode() : PassTextureNode`	Returns the GI result of the effect as a texture node.
`.setSize( width : number, height : number )`	Sets the size of the effect.
`.setup( builder : NodeBuilder ) : PassTextureNode`	This method is used to setup the effect's TSL code.
`.updateBefore( frame : NodeFrame )`	This method is used to render the effect once per frame.

Key Takeaways

SSGINode extends: EventDispatcher → Node → TempNode
Most relevant properties: aoIntensity, backfaceLighting, beautyNode, depthNode.
Key methods: dispose, getAONode, getGINode, setSize.

Connects To

EventDispatcher: parent class
Node: parent class
TempNode: parent class
Source: examples/jsm/tsl/display/SSGINode.js