View Full Version : rendering refractions only...

05 May 2003, 12:00 AM
here is my problem...

if i have an image plane that i want seen in refractions of objects in my scene, BUT NOT RENDERED, how do i do that? all i want is the objects, with their refractions... (they are glass spheres btw)

Please don't say render two passes and use the second as an alpha in my comp package, i know that trick... i am really trying to avoid two render passes here, the sequence is over two minutes long and will take too long to render twice...

Also, the image plane is a video sequence, so i can't get away with just one frame and comping it in either...

thanks in advance for any suggestions

05 May 2003, 05:48 AM
I got it!!!

I've tried to do this before but couldn't figure it out! But today it occured to me that perhaps if you changed the Image Plane's Depth to somewhere beyond the camera's clipping plane, it would still appear in the refractions etc but not actually render!

And it works! The only thing is that you have to scale the Image Plane up to counter the fact that it's far away.

Here's the image I got:

05 May 2003, 06:20 AM
So, you're not working with true image planes, then? Because it shouldn't have to ever be scaled, no matter what you set your depth at....


05 May 2003, 06:37 AM
Yeah I thought that was weird too, but it is a real Image Plane.

Maybe it has something to do with how Maya calculates refraction?? :shrug:

05 May 2003, 06:46 AM
OOOH, oh oh oh....

So, the image place is still filling the background like it should without being scaled.... But it just seems to be small inside the refraction? Well, that makes sense. I thought you were implying that the image plane itself was getting smaller as you pushed it back.

The reason you have to scale it is because the sphere is acting like a super-wide-angle lens. In order to take up more real estate in the lens, the thing has to cover more of the lens's field of vision. Kinda like the difference between sitting 10 feet away from a 20 inch TV and 10 feet away from an IMax screen.

Anyway, I'm sure you already understand that completely... Just rambling. Working it all out for myself, you know. :)


05 May 2003, 07:09 AM
Hehe, yes that's exactly right.


05 May 2003, 12:53 PM
thanks joz,

been puzzling over that for a while now, and as is typical... you come through.

i am glad that i finally have a solution

BTW... joz is the render lead for a project i am working on. Check it out at we haven't gotten past modelling for scene 1 yet, but we will soon, and then we will actually have some content!!! for the time being we do have a bulletin board, so feel free to register and chat with the crew, or even join the crew if you wish

05 May 2003, 10:45 PM
Go Opus! Go!


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