CGTalk - Refraction problem

Pate

01-11-2003, 08:18 AM

Hi!

I am having a problem in my scene. If I use a refraction index of anything besides 1.0, my glass objects (that use the material in question) mostly stop being transparent, and generate all sorts of weird artifacts. If I use the index of 1.0, the objects lose their illusion of thickness.

I was hoping some of you might have some ideas about how to avoid the artifacts.. I created a stripped-down scene file that illustrates the problem. If you feel like it, you could download the file and see what I am talking about by changing the refraction index of the material "Glass03" and re-rendering.

The file is at:

http://www.co.jyu.fi/~ap/RefProb.c4d

It is about 470 kilobytes, made with C4D R7.

Thanks!

Pate

VestanPance

01-11-2003, 08:45 AM

It's because your starfield sphere is 2000000000 m. This is way too big. The glass is refracting just fine...it's just that it is like pointing a telescope into the sky at night and having to search for a star...cause it is so far away. OK that probably didn't make sense. (Sorry it's late)

This image is with a field (sphere) at only 2000 m. That is probaly too small for what you need but that was the problem anyways.

Hope that helps. Post the scene when you are finished!

SP(VP)

Pate

01-11-2003, 09:33 AM

Originally posted by VestanPance
It's because your starfield sphere is 2000000000 m.
...

Hope that helps. Post the scene when you are finished!

SP(VP)

Wow, that was fast!

I was afraid that might be the problem.. I believe I need astronomical scale as it is an astronomical scene, though.. :)

I'll see if I can cheat in some way, or else I just need to use a non-refracting glass where ever I run into this problem.

This is for an animation I'm working on (have been for the last 6 months, actually), I will certainly post a heads-up when I eventually get something worth showing done.

Thanks for the help!

Pate

Bucko

01-12-2003, 10:06 PM

A starfield should appear infinitely far away from the viewer which is what the Sky object does. Add a sky object, add your starscape texture (just use the Illumination channel). When you apply it to the sky object you should use cubic mapping to avoid ugly pinching at the poles. Also, consider scaling it up (set tiles to 0.25 or so) to give you fewer stars.

Would be cool with a starscape procedural with some control of star color, size, distribution etc.

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