Artifacts in Glass or user error?

[JeffPatton]

I'm noticing some artifacts in glass objects (black lines).  I thought it may be my geometry but found that even a torus knot primitive in 3ds Max exhibits the issue I'm running into.

I've tried it with the various render engine options in Corona render but it seems to show up on all of them.  Have I failed to configure something properly?  Attached the image and scene for reference.

Thanks!

[Ondra]

I'll take a look

[maru]

Mystery solved. I wonder if anybody else will crack it. :)

hint: eQuestria

[Ludvik Koutny]

Mystery solved. I wonder if anybody else will crack it. :)

hint: eQuestria

? :)

[Ludvik Koutny]

I am starting to get afraid this is what it's supposed to look like.

I created iRay scene, and in Arch&Design material, i did set up same ray depth for refraction as the one corona uses (25) Then i replicated the scene, and this is iRay output:

It's probably the torus knot refracting itself many times over what creates this illusion :)

I am attaching the stripped down Corona scene (removed reflection and reset settings to defaults in order to eliminate any other shading components that could interfere).

I would also suggest not to use Bidir/VCM renderer. It is highly experimental and far from production ready. :) Progressive or Bucket ones are way to go ;)

[romullus]

It's geometry that causing problems. Your torus knot has double sided walls. Try to play with P and Q parametters a bit, until your torus gets untangled :]

edit: sorry maru, i can't torture people, like you do ;]

[Ludvik Koutny]

Ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh...

now i feel silly :D

[maru]

It's geometry that causing problems. Your torus knot has double sided walls. Try to play with P and Q parametters a bit, until your torus gets untangled :]

Yup. Basically it's two objects overlapping. It happens if you set Q to 10 (or some other values), hence my hint. ;) You can add edit poly modifier and see double vertices.

[JeffPatton]

D'oh!  Geeesh, it's been one of those days.  Thanks for clearing that up!