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View Full Version : Refraction problems!!

ndeboar
08-12-2005, 03:42 AM
Hey,

Im having a really annoying problem with a shot im working on, check this out:
http://forums.cgsociety.org/attachment.php?attachmentid=77902&stc=1

It's a work in progress, the final should be way sexier. The prob is the black bits in the refraction at the base of the water tubes. I know this is normally a refraction limit issue (i had it in other shots and fixed them by just increasing my refraction limit). This scene was rendered with Mental ray:

Renderglobals:
Refractions: 100
Max Trace Depth: 100

Phong shader:
Refractive index: 1.33
Refraction limit: 100

Ive tried even boosting these values to 1000+ and i still get the black stuff. I turned off relfections and i still got it, so im pretty sure its a refraction prob. I know its not my scene, ive tried adding basic enviroment maps and still get it. Could it be a light setting?

Any ideas would be greatly appricated! I was supposed to have this done yesterday ;)

Cheers guys,

Nick D
www.thepra.com.au (http://www.thepra.com.au)
Sphere♥
08-12-2005, 12:38 PM
Could you have surfaces/faces in the water? Water should only have one continuous surface on the outside with normals pointing out, no geometry inside it, unless you want air bubbles. Refraction happens everytime it hits a new face.
bmcaff
08-12-2005, 12:57 PM
This is probably "total internal reflection" and trace depth won't help. The ray effectively Is trapped with in the object.. it's a real phenomenon and you can search it on google. Sometimes if you change the camera environment to white or even put a texture in there then it fill in the black.. It's worth a try anyway.
ndeboar
08-13-2005, 03:09 AM
total internal reflection. i think your on to somthing. It is one continous face. I did a quick google and it seems to happen when the light hits at a particular angle, ill try moving my light around. Woudl it help if i post the model for that frame?
bmcaff
08-13-2005, 10:50 AM
Sure, post a model someone will be able to find a work around. Moving the light around shoud not have any effect as what you are seeing is refraction rays rather than direct light rays. These are shot from the camera and are traced through the object. I'll have a look at your file if you post it.
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