Hi guys!
I am using tile based shading in my project. I am adding shadows contribution to the shading pass and I am getting strange errors when compiling the pixel shader.
Below is a code snippet of the pixel shader.
float3 pointLightsContrib = float3(0.0f, 0.0f, 0.0f);
for (uint lightIndexPerTile = pointLightIndexPerTileStart; lightIndexPerTile < pointLightIndexPerTileEnd; ++lightIndexPerTile)
{
uint lightIndex = g_PointLightIndexPerTileBuffer[lightIndexPerTile];
float3 lightWorldSpacePos = g_PointLightWorldBoundsBuffer[lightIndex].center;
// Plus rest of the code
float3 lightContrib = CalcPointLightContribution(lightWorldSpacePos, lightColor, lightRange,
worldSpaceDirToViewer, worldSpacePos, worldSpaceNormal, diffuseAlbedo, specularAlbedo, shininess);
// Plus rest of the code
float lightVisibility = CalcPointLightVisibility(g_VarianceShadowMapSampler, g_PointLightTiledVarianceShadowMap,
lightViewProjMatrix, lightViewNearPlane, lightRcpViewClipRange, worldSpacePos);
pointLightsContrib += lightVisibility * lightContrib;
}And there are helper functions used from the pixel shader above.
float VSM(SamplerState shadowSampler, Texture2D<float2> varianceShadowMap, float2 shadowMapCoords, float receiverDepth)
{
float2 moments = varianceShadowMap.Sample(shadowSampler, shadowMapCoords).xy;
return ChebyshevUpperBound(moments, receiverDepth);
}
float CalcPointLightVisibility(SamplerState shadowSampler, Texture2D<float2> varianceShadowMap,
float4x4 lightViewProjMatrix, float lightViewNearPlane, float lightRcpViewClipRange, float3 worldSpacePos)
{
float4 lightClipSpacePos = mul(lightViewProjMatrix, float4(worldSpacePos, 1.0f));
float3 lightPostWDivideProjSpacePos = lightClipSpacePos.xyz / lightClipSpacePos.w;
float2 shadowMapCoords = float2(0.5f * (lightPostWDivideProjSpacePos.x + 1.0f), 0.5f * (1.0f - lightPostWDivideProjSpacePos.y));
float lightSpaceDepth = lightClipSpacePos.w;
float normalizedLightSpaceDepth = (lightSpaceDepth - lightViewNearPlane) * lightRcpViewClipRange;
return VSM(shadowSampler, varianceShadowMap, shadowMapCoords, normalizedLightSpaceDepth);
}When I compile the shader, I get the following warning and error.
Warning: warning X3570: gradient instruction used in a loop with varying iteration, attempting to unroll the loop
Error: error X3511: unable to unroll loop, loop does not appear to terminate in a timely manner (210 iterations) or unrolled loop is too large, use the [unroll(n)] attribute to force an exact higher number
The warning points to the line "float2 moments = varianceShadowMap.Sample(shadowSampler, shadowMapCoords).xy;" of VSM function
and the error points to the line "for (uint lightIndexPerTile = pointLightIndexPerTileStart; lightIndexPerTile < pointLightIndexPerTileEnd; ++lightIndexPerTile)".
If I change implementation of VSM function to simply { return 1.0f } it compiles fine.
What is going on?
