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View Full Version : Do I not understand Matteobject or is it broken.



stib
09-28-2006, 11:21 PM
I'm trying to use some semi-transparent objects as mattes in my scenes. As you do. I've checked the matte object box, and I've got use surface opacity as the alpha channel. Now I think this should mean that the surface opacity of the object (ie semi-transparent) is preserved in the alpha channel as per the surface settings, while the colour is set to my matte colour, regardless of any surface setting.

But what it seems to mean is the same as if I set it to constant white, because all I get is solid white alpha in the areas where the matte objects are. This means that I have to make matte versions of all my matte objects and swap them into my scene. A touch tedious.

Or have I got something fundamentally wrong with my understanding of the "use Surface Opacity" setting?

stib
09-28-2006, 11:42 PM
Pics:

http://www.pureandapplied.com.au/images/temp/normalObjectRGB.png
the image as it renders without a matte object

http://www.pureandapplied.com.au/images/temp/normalObjectAlpha.png
the alpha channel of the above, showing semi transparent grey alpha

http://www.pureandapplied.com.au/images/temp/MatteObjectRGB.png
the RGB when I turn on Matte object (I probably should have used another colour apart from black as my matte colour)
Note that the transparencey doesn't work here either, instead of the Matte object being a semi transparent matte it's a fully opaque one

http://www.pureandapplied.com.au/images/temp/MatteObjectAlpha.png
The Alpha Channel, showing solid white for my matte.

toby
09-29-2006, 03:51 AM
I don't understand what you're trying to do! Never heard of a semi-transparent matte object before!
But I just know there's a way to do it. First I would render your objects without Matte object checked, to see exactly what kind of alpha you're getting with and without - because it depends on whether you're raytracing or not.

The 'Constant' alpha value in the surface editor is another option, you can set the alpha to whatever value you want, and using dissolve in object properties might might be another option.

stib
09-29-2006, 04:03 AM
Ok a real world example. I'm doing a logo animation and there's some nice particle spritey things that are whizzing around some other logo objects that happen to be semi transparent. Some of the particles are in front, some behind. Now I want to break this up into passes, so I can ad sparkly effects to my sprites, and so I can tweak colours etc seperately.

If I render without the semi transparent logo objects, my sprites will appear as though they were in front even when they should be behind the logo. If I use the logo as a matte object, then my sprites will disappear entirely when they go behind it. Get it? I need my sprites to be partially obscured (and if possible refracted, reflected etc) by the logo, but I don't want to see the logo.

I can do it by making replacement matte objects, I was only hoping there would be a one button solution.

BeeVee
09-29-2006, 04:55 AM
Are you using the Perspective Camera? Have you tried with the Classic?

B