The ‘ray epsilon’ pin in the kernel nodes is used to ensure that geometry does not cast shadows on itself, so provides a gap between surfaces when calculating shadows. For close-up rendering, it should be set low, so that these gaps are not visible. For ‘distance’ renders, where the camera is a long way from the rendered geometry, the ‘ray epsilon’ will need to be increased, since the geometry being rendered will be a long way from the camera and the vertices will appear to the Octane renderer to be at the same points in space (and thus cause shadow artifacts with a low ‘ray epsilon’).
In summary:
Note: A ‘ray epsilon’ of 0.075 = 7.5cms.
Figure 1: Left image has Ray Epsilon 0, right image has Ray Epsilon 0.00047 .