Smaller epsilon for triangle intersection

I just found that while the program in general can use a relative large Epsilon (e.g. 1e-5), triangle intersection benefits from a smaller value, say 1e-9 or less. With models that have many small triangles a large Epsilon may cause false misses and lead to visual artifacts.

The model below (100,000 triangles, here rendered in 76 seconds at 64 samples per pixel) improved noticeably with the smaller Epsilon.