Fixes

[e2002e]

Hello @luboslenco,
In this pull request:

• add more offset to the starting position when conetracing to avoid self occlusion.
• fix voxels refractions view vector which was inverted.
• use fresnel term for ssr / ssrefr.
• use rgba8 image for voxels final sampling targets (rgba16 cannot be properly wiped for 3D images).