Point Light Range is very low

Unity Engine
,
1

I am not sure this a bug or if this is the way point lights behave in URP, but the range on point lights seems to be completely unaffected by ranges above a certain threshold. I am using 2019.3b6 and URP 7.12.

I can’t get a 1 intensity light to have any effect on an object 5m away no matter what I set the range to. It simply seems to not matter at all after 4m. However I can raise intensity to get it to effect things at a distance but this is pretty unusable in most situations.

2 Likes
2

Since you gave us source code I felt confident enough to take a look myself. After looking and even step debugging the URP ForwardLightI was pretty confident that the issue wasn’t there. After some messing around I was able to get what looks to be a much much better result in my lights by changing this in the shader:
Lighting.hlsl line 58 (line 7 here):

// Matches Unity Vanila attenuation
// Attenuation smoothly decreases to light range.
float DistanceAttenuation(float distanceSqr, half2 distanceAttenuation)
{
    // We use a shared distance attenuation for additional directional and puctual lights
    // for directional lights attenuation will be 1
    float lightAtten = rcp(1);//was -> float lightAtten = rcp(distanceSqr;

#if SHADER_HINT_NICE_QUALITY
    // Use the smoothing factor also used in the Unity lightmapper.
    half factor = distanceSqr * distanceAttenuation.x;
    half smoothFactor = saturate(1.0h - factor * factor);
    smoothFactor = smoothFactor * smoothFactor;
#else
    // We need to smoothly fade attenuation to light range. We start fading linearly at 80% of light range
    // Therefore:
    // fadeDistance = (0.8 * 0.8 * lightRangeSq)
    // smoothFactor = (lightRangeSqr - distanceSqr) / (lightRangeSqr - fadeDistance)
    // We can rewrite that to fit a MAD by doing
    // distanceSqr * (1.0 / (fadeDistanceSqr - lightRangeSqr)) + (-lightRangeSqr / (fadeDistanceSqr - lightRangeSqr)
    // distanceSqr *        distanceAttenuation.y            +             distanceAttenuation.z
    half smoothFactor = saturate(distanceSqr * distanceAttenuation.x + distanceAttenuation.y);
#endif

    return lightAtten * smoothFactor;
}

Line 58 (line 7 here), from looking at what you were doing in ForwardLight.cs, it looks like all of the smooth falloff was calculated there and you never needed the initial lightAtten to be distanceSqr. I tried 1 and it pretty much works like it did in Standard now.

Hope this helps someone who was having the same issue.

1 Like
3

You’re right.:slight_smile:

4

Changing the value to 1 works for realtime lights, but for lightmapped you need to do this also:

https://docs.unity3d.com/2020.1/Documentation/Manual/ProgressiveLightmapper-CustomFallOff.html

I havn’t been able to figure out how to implement that.

5

I know this is an old post. But I’m running in to the same issue, and editing the Lighting.hlsl file doesn’t seem like a good option, or even to address the issue since whenever I do, Unity rebuilds the package for me overwrites my changes.

Is there an actual solution to this issue?

6

Use an embedded copy of the urp package to make this kind of change to it without letting unity overwrite it.