256 spp progressive render. I forgot to check the render time but I think it was around 20 minutes. Max bounce count: 64.

128 spp progressive render. Render time was 8 minutes and 26 seconds, which is unfortunately pretty slow. I decreased the chance of terminating a path and the refractive sphere might be slightly less black.

256 spp progressive render. Added Fresnel reflections. Refractive sphere is still too dark.

Fixed some bugs. Also made a couple changes. The first is that blinn normals arent sampled for refractions and the second is that the material based importance sampling is ignored if the materials ray intersects a light. Most pixels here have 176 samples. Render time was almost six minutes.

Most pixels have 48 samples here. Render time: 59 seconds. Sometimes it looks like this and sometimes it looks like the previous image. No changes were made to the code between rendering this image and the previous one.

Progressive renderer that renders pixels with batches of 16 samples. In this image, most pixels have 48 samples. Render time was about 58 seconds. Refractions not working for some reason.