1 reply to this topic

[TiagoCosta]

Currently I select the CSM split to sample from using a loop and conditional

for(int i = 0; i < numCascades; i++)
{
	 if(viewPos.z < splitEnd[i])
	 {
		   //transform using *i* split proj matrix
		   break;
	 }
}

However I'm looking for faster methods to do the selection because loops/conditionals are usually slow inside pixel shaders.

Can someone explain a faster method? Thanks.

P.S. I calculate each split projection matrix by creating a tight sphere around the world space corners of the view frustum split.

Edited by TiagoCosta, 01 September 2012 - 10:55 AM.

[MJP]

I usually do it like this:

uint cascadeIdx = 0;

[unroll]
for(uint i = 0; i < NumCascades - 1; ++i)
{
	[flatten]
	if(depthVS > CascadeSplits[i])
		cascadeIdx = i + 1;
}

Where "depthVS" is the view-space Z value of the pixel, and CascadeSplits are the linear view-space Z values of the cascade partitions.

Edited by MJP, 01 September 2012 - 12:32 PM.