I have a question regarding shadowing and shaders.
I have an application which renders streetlamps and projects a spotlight into the scene onto my flat plane ground and onto the sides of houses.
To do this I first of all filter out which polygons are visible to each streetlamp in its spotlights’ immediate area of influencem then I pass those polygons to my cg shader which does the spotlight calculations. Now, because i dont yet have shadowing the ground is also lit underneath the house which of course shouldn’t be happening.
I want to implement shadows and have had some problem with shadow mapping already, and also because I already have sorted out the polygons visible to the light, I thought I should try shadow volumes as I can simply extrude out past the polygons visible to the light.
However one part of the problem is confusing me and I want to clarify it before i start coding it.
If i set up the shadow volume, how will my cg shader be able to perform the relevant stencil tests? i’m sorry if the question is a little vague but i’m really confused on how I’ll do the actual testing against the stencil buffer in my shader.
Can anyone assist me please?