Soft Shadow Technique using XNA 3.0

Question

I am working with XNA 3.0 (sigh, I know) and I am working off a tutorial that helps implement a 3d scene with objects where a spot light hits a torus and projects a hard-edged shadow. Now, I want to know where I can find help (tutorial, source code, snippet) to soften said shadow?

Answer 1

Simplest way would be use Percentage Closer Filtering. Basically it works by taking a few shadow map samples. You can start from an article in GPU Gems.