[Sidefx-houdini-list] Refraction Artifacts

Robert Thomas shinyaryart.sidefx at gmail.com
Wed Sep 5 23:03:19 EDT 2007

Hi everyone,

I'm trying to make a refractive cloaking effect on a model I made.  I render
out the animation of the ship to a sequence of pngs, import them into COPs
for a quick blurring, and then use the COPs image to drive displacement of a
grid that is positioned directly in front of the camera.  This grid has a
shader that does nothing but refract.

I'm satisfied with the effect for now, but I'm getting these weird artifacts
from the refraction as you can see here (sorry about the poor quality; I'm
still a student, so money for server space is hard to come by):


At frame 6 there is an artifact on the ship itself, and later on there are
artifacts on the terrain.  Somehow the refractive shader is letting me see
parts of the background.

Can someone tell me what they are and how to get rid of them?



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