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How we made the Audi AI:ME’s flying VR experience — Part 3

VR performance challenges and creating realistic fog in Unity

Comparison between in-engine rendering and real life reference

Aims of the Project

an aerial timelapse of the rolling fog by Azad Balabanian

Performance

Draw Calls

Fragment Overdraw

Effect of fragment overdraw on execution times

Textures

Small Improvements

Rendering Realistic Fog in VR

Unity screencap of the final version of the fog implementation

Learning From References

fog blurring the objects behind
dynamic high frequency height fog
Halo around light sources in fog. Photograph by Harald Hoyer

Understanding the Physical Properties of Fog

TL;DR (too long; didn’t read)

Possible Solutions

cloud rendering in Sea of Thieves
Fog rendering in Assassin’s Creed IV: Black Flag
Mie scattering in The Witcher 3

Implementation

finalColor = originalColor * decay(dist, dConst) + inScatteredLight; 
float decay(float distance, float decayConstant)
{
return exp(-distance*decayConstant);
}
graph of e to the power of -distance
inScatteredLight = fogColor*(1.- decay(dist, dConst));
finalColor = originalColor * decay(dist, dConst) + inScatteredLight;

Height Fog

Water rendering in Portal 2
Dynamic objects effecting water in Far Cry. Similar approaches could be done for fog
Left: screen shot in engine, second image a drone shot on site

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Resources and Further Readings

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