Yeah, I was mistaken when looking at the frist pic, I was tired, and I thought I was seeing polygons casting individual shadows and overlapping as if you flattened a mesh on a plane and made it transparent. But he's just got multiple light sources.
So the only problem here is that he's not casting shadows from every object. Is there a way to avoid that? I don't know. In his example there, with the light casting a shadow onto the floor, the only way you make it look "correct" would be for there to be no shadow on the floor. So he would just want a shadow on the wall.
Maybe he could set a clipping plane to clip the object's shadow volume at some fixed distance from the object. But honestly, I can't think of ANY shadow system which would avoid this specific issue without clamping the distance at which the shadow can go. It would look the same in my shadow system, or even a zbuffer shadow system.
The only thing he could do maybe is right now he doesn't have shadow maps being rendered. If he rendered all his shadow maps black and the stencil shadows black in a first pass, and all the light sources were fixed in the same locations as they were to create the shadow maps, then the stencil shadows would blend with the shadow maps. It would look a bit funny with the sharp shadows and the blurrier shaow maps, but he'd get a scene somewhat similar to what you've shown, without the cost of rendering stencil shadows for nonmoving objects. His objects however would cast shadows onto eachother, but the world would not cast shadows onto them so there'd be a potential glitch there. And he would not want to use those stencils for that nonmoving light as in his example.
So the only problem here is that he's not casting shadows from every object. Is there a way to avoid that? I don't know. In his example there, with the light casting a shadow onto the floor, the only way you make it look "correct" would be for there to be no shadow on the floor. So he would just want a shadow on the wall.
Maybe he could set a clipping plane to clip the object's shadow volume at some fixed distance from the object. But honestly, I can't think of ANY shadow system which would avoid this specific issue without clamping the distance at which the shadow can go. It would look the same in my shadow system, or even a zbuffer shadow system.
The only thing he could do maybe is right now he doesn't have shadow maps being rendered. If he rendered all his shadow maps black and the stencil shadows black in a first pass, and all the light sources were fixed in the same locations as they were to create the shadow maps, then the stencil shadows would blend with the shadow maps. It would look a bit funny with the sharp shadows and the blurrier shaow maps, but he'd get a scene somewhat similar to what you've shown, without the cost of rendering stencil shadows for nonmoving objects. His objects however would cast shadows onto eachother, but the world would not cast shadows onto them so there'd be a potential glitch there. And he would not want to use those stencils for that nonmoving light as in his example.