Shadow attenuation issue on URP spot light in custom lighting.

Unity Engine
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1

Hi there !

I am making a URP shader for HairStudio, with custom lighting and unlit master node. I’m facing an issue with shadow attenuation that does not seem to be taken into account.

I have a custom node with this code:

int lightCount = GetAdditionalLightsCount();
for (int i = 0; i < lightCount; ++i)
{
    Light light = GetAdditionalLight(i, position);
    float3 attenuatedLightColor = light.color * light.distanceAttenuation * light.shadowAttenuation;
    color += GetMySpecular(light.direction, attenuatedLightColor);
}

And here is the result:

6075150--658902--upload_2020-7-10_11-35-47.png
6075150--658902--upload_2020-7-10_11-35-47.png801×734 50.9 KB

As we can see, the shadow attenuation works well on all surfaces, but not at all on the hair using this custom lighting. It only concerns shadow attenuation, because if I move the spot light back and forth, I can see that the distance attenuation is taken into account on both the hair and surfaces.

Is there something I’m doing wrong?

1 Like
2

The shadow was not working with the main directional light either, so I changed the code to add shadow sampling.

This code allows me to receive shadows from the main light with unlit master node.

float4 shadowCoord = TransformWorldToShadowCoord(position);
Light mainLight = GetMainLight(shadowCoord);

ShadowSamplingData shadowSamplingData = GetMainLightShadowSamplingData();
half shadowStrength = GetMainLightShadowStrength();
float mlShadowAtten = SampleShadowmap(shadowCoord, TEXTURE2D_ARGS(_MainLightShadowmapTexture, sampler_MainLightShadowmapTexture), shadowSamplingData, shadowStrength, false);
  
float attenuatedLightColor = mainLight.color * mainLight.distanceAttenuation * mlShadowAtten;
  
color = GetMySpecular(mlDirection, attenuatedLightColor);

I don’t use the mainLight.shadowAttenuation because it is always at 1. As I understand things, this is due to the fact that I use the unlit master node. Using this node, I’m telling that I don’t need light data, therefore shadows are not ready to use for performance purpose. Calling the SampleShadowmap manually is mandatory to create the data I need.

(If I’m right, then it would be great to have a CustomLighting master node, with main light and additionnal light ready to use.)

Anyway I tried that for additionnal lights as well, but the shadow attenuation still has no effect after a manual sampling. This code leads to the same result as in the original post.

int lightCount = GetAdditionalLightsCount();
for (int i = 0; i < lightCount; ++i)
{
    Light light = GetAdditionalLight(i, position);

    ShadowSamplingData shadowSamplingData = GetAdditionalLightShadowSamplingData();
    float shadowStrength = GetAdditionalLightShadowStrenth(i);
    float shadowAtten = SampleShadowmap(shadowCoord, TEXTURE2D_ARGS(_AdditionalLightsShadowmapTexture, sampler_AdditionalLightsShadowmapTexture), shadowSamplingData, shadowStrength, false);

    float3 attenuatedLightColor = light.color * light.distanceAttenuation* shadowAtten;
    color += GetMySpecular(mlDirection, attenuatedLightColor);
}
3

For me, for some reason, light.distanceAttenuation does not work when using LIT shader when I do a build (but it does work whilst in the Editor)

Unity 2019.4.2f1
URP 7.4.1

4

So, is there a way to obtain additionnal lights shadow attenuation with unlit master node?

Or another master node that can allow a custom lighting?