Octree boundary artifacts

I have traced the small artifacts that were popping up in the renders, to issues caused by octree leaf borders. It turns out that an octree border cutting through a smooth surface causes a slice to appear on the surface. This can be seen in the images below. At level 10, there are several small octree nodes, and they cause a large number of slices to appear on the surface. At level 4, there are very few borders of octree nodes, and therefore, we see no artifacts in the render. A more serious side effect is that rays start 'leaking' through the surface at these border points, and cause holes to appear on the surface. In animations, these holes pop in and out in a very distracting manner.


10 level octree (1.2 seconds to render)

8 level octree (1.3 seconds to render)

6 level octree (5 seconds to render)

4 level octree (80 seconds to render)

I don't have a solution to this problem yet, but I am thinking along the lines of adding splats to multiple octree leaves, or checking multiple nearby octree leaves while shading (rather than a single octree leaf).