Really I've just been trying to get as accurate refractions as I can get for the sake of seeing if I can. But you are correct, I think I will just push this one aside - being a natural engineer, I tend to become obsessed with the little details sometimes too much - although that's what got me into graphics programming in the first place.
More importantly though, I do need to work out a way of either getting more accurate cone-traced soft shadows, or somehow masking the very voxelized core of the shadow that is closest to the occluder. I think the latter will be more achievable:
My idea is to render a shadow map and this would be blended in with the cone traced soft shadow. What I would start off doing is to fade out the shadow map at a certain distance away from each occluder. I remember being able to do this with Unreal Engine 3 shadows, however I never understood the technical specifics of it. I'd like to know if anyone knows of a way of doing this?
[attachment=13839:givox7.jpg]
Another thing I have to resolve is - if you look at the translucent cube, you will notice its shadow is incorrect. This is related to the issue in the following image, where the reflection of the red box only shows the top and side voxels as opaque and anything in shadow is transparent:
[attachment=13840:gibox0-1.jpg]
Technically, the base mip should be completely opaque with an alpha value of 1 - even when I try forcing the base mip alpha values to 1 the problem still persists.
A thing that might be worth exploring more is voxel anti aliasing. If your mesh partially covers a voxel space, might it be better to have that voxel "partially" filled?
So currently, my voxels are just blended together and when I sample for the cone trace, I take a voxel offset for six directions:
[attachment=13841:givox8.jpg]
which pretty much achieves what you are saying - unless you are referring to something else? Anyhow, I have heard an octree structure might be able to provide more accurate voxel antialiasing - which is something I will implement later down the track.