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Unity-GeoAO

Fast ambient occlusion in Unity baked at runtime.

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For URP please check the URP branch here

Explanations

Unity does not allow to compute ambient occlusion on generated mesh at runtime and SSAO does not always provide the quality we deserve.

This small project shows how to quickly compute AO for each vertex in Unity. For N samples positions of camera around the mesh, a depth map is generated by Unity and vertex positions are sent to a shader that reads the depth map and tests if vertices are visible or not. The output colors for each vertex are blended with the result of all the samples.

Another shader is set to the meshes that reads the value for each vertex and darkens it accordingly.

This is an implementation of this technique in Unity : https://github.com/wwwtyro/geo-ambient-occlusion

To make it fast, one of the hack I have to use is to move all the meshes at the origin position (0,0,0) and with the rotation (0,0,0) and scale (1,1,1) to avoid computing the real vertex positions in world space.

~~You have to disable all other objects of the scene when computing the AO or play with layers because everything that will write to the depth map can interfere with the AO computation.~~

To compute AO, objects layers are set to AOLayer during computation and restored to the previous layer after the work is done.

Computing AO for a 500k vertices Stanford dragon with 256 samples is done 0.15s on my computer (770 GTX + i7 4790k).

System

Tested on Windows DX11, DX12 and OpenGL, macOS with OpenGL and Metal, Linux with OpenGL

Now works with Universal Render Pipeline (URP)

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