In yesterday's post, I introduced my new hobby project Photon Mapping Voxels. Today, I made some more progress, and managed to properly interpolate the shading. The voxel faces in a plane now share vertices. But there is still a matter of ambiguity when shading a quad, which causes the triangle seam to show in the middle of the quad. To alleviate this issue, I added a center vertex in the middle of the quad, and render it as 4 triangles, instead of just 2. The results are below. The animated gif cycles through four renderings: quads, triangles, triangles in wireframe, quads in wireframe. As you can see, there are less discontinuities in the triangle version, at the cost of more vertices, and double the triangles.
Again, this is direct light only. I am getting excited about seeing it with indirect light (bounces) and also colour. Currently, all photons and all voxels are white. Also on the todo list: make it really fast by doing SIMD intersection tests: a ray versus 8 voxels in a single go. This requires AVX though, probably AVX2 even.