Filter size

[jcyuan]

about calculating the filter size, we need to first calculate the estimation:
imo, to calculate the penumbra size, we can do:

penumbraSize = (dReceiver - dBlocker) / dBlocker * lightSize

actually my questions are from your code:

float SearchWidth(float uvLightSize, float receiverDistance)
{
	return uvLightSize * (receiverDistance - NEAR) / eyePosition.z;
}

for the search area width, i don't know why you use eyePosition.z instead of the shadow space z here, what is the reason? is the eyePosition the main camera in the scene? could you please elaborate?) (http://developer.download.nvidia.com/whitepapers/2008/PCSS_DirectionalLight_Integration.pdf is not available now...)

also, what is the reason you use NEAR / shadowCoords.z here?

float penumbraWidth = (shadowCoords.z - blockerDistance) / blockerDistance;
float uvRadius = penumbraWidth * uvLightSize * NEAR / shadowCoords.z;

Thanks!