Screen-Space Reflections

Reflect visible scene lighting from glossy and rough surfaces using depth, surface normals, roughness, and temporal reprojection. createSSRShaderPassPipeline traces reflection rays through the current frame and resolves them into a stabilized specular contribution.

GitHub

At a Glance

Property	Value
Export	createSSRShaderPassPipeline
Backend	WebGPU
Render passes	Six: reflection trace, temporal resolve, depth history, two spatial filters, and composite
Required bindings	depthTexture, normalTexture, and velocityTexture
Persistent state	rgba16float reflection and depth history
Reflection coverage	Visible scene color and first-layer screen depth

Usage

import {ShaderPassRenderer} from '@luma.gl/engine';
import {createSSGIShaderPassPipeline, createSSRShaderPassPipeline} from '@luma.gl/effects';

const renderer = new ShaderPassRenderer(device, {
  colorFormat: 'rgba16float',
  shaderPasses: [
    createSSGIShaderPassPipeline({resolutionScale: 0.5}),
    createSSRShaderPassPipeline({resolutionScale: 0.5})
  ]
});

renderer.renderToScreen({
  sourceTexture: litSceneTexture,
  bindings: gBuffer.getShaderPassBindings(),
  uniforms: {
    ssrTrace: {
      projectionMatrix,
      inverseProjectionMatrix,
      intensity: 1.35,
      maxDistance: 60,
      thickness: 0.45,
      sampleCount: 48,
      maxRoughness: 0.88,
      frameIndex
    },
    ssrTemporal: {inverseProjectionMatrix, historyWeight: 0.86, depthThreshold: 0.018}
  }
});

Parameters

Parameter	Default	Range or purpose
resolutionScale	1	Relative resolution of reflection tracing, history, and spatial filtering.
intensity	1.35	Strength of traced specular reflection before final composition.
maxDistance	60	Maximum view-space reflection-ray travel distance.
thickness	0.45	Accepted depth thickness when testing a possible screen-space hit.
sampleCount	48	Ray-march budget; supported range is 8 to 96.
maxRoughness	0.88	Highest surface roughness that can contribute reflections.
historyWeight	0.86	Contribution from depth-validated reflection history.
depthThreshold	0.018	Temporal rejection threshold for disoccluded reflected surfaces.
strength	1	Final ssrComposite contribution blended into scene color.

Quality and Limitations

SSR cannot reflect geometry outside the current viewport, hidden behind the first visible depth layer, or absent from the already-lit source color. Roughness-aware spatial filtering broadens reflections and rejects unrelated depth/normal surfaces. Lowering sampleCount or resolutionScale saves GPU work but can increase missed intersections or soften thin details.

Trace reflections after direct lighting and Screen-Space Global Illumination when the reflected image should include their contributions. Reset history after camera cuts or changes to attachment dimensions.

Related Effects

• Screen-Space Global Illumination gathers diffuse rather than specular light.
• GTAO provides complementary ambient visibility.
• Bloom spreads intense reflected highlights later in the HDR pipeline.