View Full Version : Alpha Channel issue

07-30-2004, 09:18 PM
What I want:
Render my yacht out in a different pass then the ocean.

Alpha channel has holes in it

Why do I get this distorded alpha channel when I put the option "Unseen by alpha channel" on for the yacht? No transparency is on...



07-31-2004, 01:37 PM
Does anybody has the same issues?

07-31-2004, 05:44 PM
Are you sure you need an alpha for the ocean? The yacht would just cover it up anyway...

Is the yacht object intersecting the ocean object?

show us the rgb so we can see what you're trying to do

07-31-2004, 06:23 PM
Thanks for your reply.

This is the image when I render out both the yacht and water at the same time.

My goal is to render them out at the same time and make the water transparent (to save valuable render time) and control the yacht and water seperate. Also, I want to be able to control other settings of the water and yacht individually in AFX.
Since the yacht intersects I can't simply render both objects seperately...

I know a way arround this issue (render out with max. luminosity in black/white) but this creates extra render time.

Any suggestions?



07-31-2004, 06:39 PM
This is the composited render. I had to cheat with the alpha channel creation.

By rendering out the solid water and make it transparent in AFX, I save over 75 percent of render tim...

Thanks for future advice regarding my alpha channel issue!


08-01-2004, 12:59 PM
I see, we're looking up from underwater -

I don't think the ocean's alpha should get messed up just from intersecting with other geometry. Have you checked your models for non-planar or duplicate polygons? Is the ocean a subpatch model?

08-02-2004, 12:32 PM
Dear Tobey,

Thanks for reply.

Indeed, this is weird...
I tried replacing the yacht with a regular sphere and it had the same issues.

The water is indeed subdivided.

How can I make non planar poly's planar?



08-02-2004, 09:26 PM
Check the ship first - if it has non-planar polygons, open it in modeler, hit 'w' for the stats window, click the '+' next to 'non-planar', then press shift-'T' to triple them / make them triangles.

If that doesn't do it, try changing the subdivision order of the ocean, in Layout. If you still can't find a good combination, you'll have to open the ocean in modeler, freeze it, then triple it.