UeSSAOPass

UeSSAOPass implements Screen Space Ambient Occlusion, a technique used to approximate local ambient occlusion in real-time. It adds depth and realism to the scene by darkening crevices, corners, and areas where objects are close to each other.

This pass is designed to work efficiently in both Forward and Deferred rendering paths.

warning

This feature is experimental and does not works yet.

Constructor

new UeSSAOPass(data?)

• data (optional): A struct containing configuration properties.
  • radius: float (default: 0.5) - The radius of the occlusion sampling.
  • bias: float (default: 0.025) - The bias to prevent self-occlusion artifacts.
  • power: float (default: 1.0) - The exponent applied to the occlusion factor.
  • intensity: float (default: 1.0) - The overall strength of the effect.

Properties

• radius: float - The sampling radius in view-space units. Larger values create broader shadows but may lose detail.
• bias: float - A small offset to avoid "acne" or self-occlusion on flat surfaces.
• power: float - Controls the falloff of the occlusion. Higher values make the shadows darker and more concentrated.
• intensity: float - Blending factor for the final composition. 0.0 means no AO, 1.0 means full AO.

How it works

The SSAO pass performs several internal steps to generate the effect:

1. Normal Pre-pass: If not already available (like in Forward Rendering), the pass renders the opaque objects of the scene to a separate buffer to extract View-Space Normals.
2. Occlusion Generation: Using the Depth Buffer and the Normal Map, the shader reconstructs the view-space position of each pixel and samples a random kernel of 32 points within a hemisphere oriented along the surface normal.
3. Bilateral Blur: The raw occlusion output is noisy due to the random sampling. A bilateral blur is applied to smooth the result while preserving sharp edges by comparing depth differences.
4. Composition: The final smoothed occlusion map is multiplied with the original scene color.

🛠️ Integration with Forward Rendering

In Forward Rendering, UeSSAOPass automatically leverages surface_get_texture_depth() to avoid an extra depth pass. It only performs one additional geometry pass for normals, making it highly efficient.

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Example

var composer = new UeEffectComposer(renderer);

// Standard render pass
composer.addPass(new UeRenderPass(scene, camera));

// Add SSAO
var ssao = new UeSSAOPass({
    radius: 0.8,
    intensity: 1.5,
    power: 2.0
});
composer.addPass(ssao);