Realtime GI - Voxel cone tracing

Question

Recently Ive been researching realtime GI techniques like Light Propagation Volumes, Reflective Shadow Mapping, Imperfect Shadow Mapping etc. But the one that really caught my attention was of course Sparse Octree Voxel Cone Tracing. It has it all : GI, approximated specular reflections, can be easily integrated into deferred rendering pipeline, has no noise, doesnt rely on polygonal heaviness of the models being involved into calculations/ The one thing that really bothers me is transparency. How does one achieve proper illumination of semi-transparent voxels? (like coloured glass or semi-transparent curtains)?

Is it possible? Any ideas? Thank you!

Answer 1

To achieve alpha blending-like transparency an idea is to:

• store alpha values in the voxels

• use a multiplicative (1-alpha) accumulation when filtering the voxels and after encountering a voxel during light accumulation

• step along the cone to accumulate light while multiplying the result with alpha

• stop if alpha is zero

For refraction, you need to refract the cone (the BRDF is replaced with a BTDF)

You should consider contacting the author for a better answer