View Full Version : 2018.0.3 Dielectric Refraction Artifacts

04-05-2018, 09:29 AM
How do I get rid of some very serious refraction artifacts in a single, dielectric shaded (default settings), single-sided poly in 2018.0.3, as seen in the video link below (I get an invalid file error when uploading the mp4 to the forum's attach system)?

I obtained the same results after giving the dial's glass polygon a little bit of thickness, but then I had to enable double-sided in order for the refraction to bend the rays.

The artifacts also happen exactly the same using PBDSF or Standard with any value of transparency and with any value of Refraction Index, even 1.0 (no refraction).

The video below is a VPR preview at draft and half rez. Full F9 render is no different. Increasing the various ray recursions values or ray precision in Render Globals did nothing. The artifacts only happen when the flat poly or a disc with thickness comes in very close proximity to other polys, "dissolving" in the closer it gets. The last frame has the poly about 0.5mm from the UV mapped dial face poly. The poly is rotating to show that the patterns are NOT REFLECTIONS or refractions of some other geometry. Scale is animated to show the edges of the poly and that the pattern is not mapped or a texture.


04-06-2018, 06:38 AM
HA! Facebook Lightwave Wiki Group beats the Forum again. Ken Nign suggested setting Polygon Intersection Mode from default Watertight to Double Precision in Render Globals. This totally eliminated the artifacts!

This is all the manual says:

"There are three intersection modes with increasing precision:
Fastest - This is the speediest of the three, but can sometimes return dots where edges between polygons don't line up precisely
Watertight - Should work in all cases, but still uses single precision math that might fail in extreme situations
Double Precision - Bulletproof but not as fast"

But WHAT does it MEAN? Define "fast" and "extreme situations," because I wouldn't call this scene and use of a flat polygon as a gauge's glass window anywhere close to "extreme." Yet, here we are with show stopping artifacts that require a vague, unquantified hit to render time to fix.