URP Linear and custom lighting calculations

Unity Engine
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1

All the flexibility of the past seems to have been lost in URP. OK you can write a custom render pipeline in theory but not got the time!

Not being able to have linear falloff lights from builtin is a real issue for lighting procedural geometry that is not lightmapped. We should get some control of the falloff.

And before you could replace the whole lighting pipeline which I guess is only possible now by customizing the package - has anyone done?

URP is not just for realistic games with realistic lighting - so we need the flexibility!

2

So the current solution to change all lighting is to modify one lighting file in the URP package: RealtimeLights.hlsl in ShaderLibrary\RealtimeLights
Find the function DistanceAttenuation
To use linear lighting I think you can just sqrt the distanceSqr that comes into that function to go back to linear!!

Here is the function with some comments:

float DistanceAttenuation(float distanceSqr, half2 distanceAttenuation)
{
    //Note: Add this line for linear lighting! Dumb but works?!
    distanceSqr = sqrt(distanceSqr);//back to linear from squared

    // We use a shared distance attenuation... this is as provided
    float lightAtten = rcp(distanceSqr);
    //Note: what is this?! I mean is half2 not adjusted to be a float in most cases anyway - never seen this!
    float2 distanceAttenuationFloat = float2(distanceAttenuation);

    // XX Use the smoothing factor also used in the Unity lightmapper.
    // Note: What exactly does this smoothing factor do?! Not easy to see visually!
    half factor = half(distanceSqr * distanceAttenuationFloat.x);
    half smoothFactor = saturate(half(1.0) - factor * factor);
    smoothFactor = smoothFactor * smoothFactor;

    return lightAtten * smoothFactor;
}
3

Updated post to show currently known solution - thanks to Custom Dynamic Lighting Attenuation - Community Showcases - Unity Discussions

Here is the effect of adding one line to hlsl to get linear lighting:

image