How to extend camera mapping around the edge?

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  03 March 2013
How to extend camera mapping around the edge?

Ok, imagine a white sphere in front of a red plane. I then have a red texture that I am camera mapping onto the sphere so that everything appears red from the camera's point of view. Then (in my animation) the sphere rotates around, revealing the white on the other side of the sphere. I do the rotation after baking the object/texture. In C4D, this works great.

The problem is that I need to export this 'effect' into a realtime engine. The fringe, where the camera mapping ends, is perfectly invisible in a cinema render, but is quite obvious in realtime once the object is baked. What would be ideal is to "bleed" the camera mapped texture just a little over the edge of the sphere, so the white creeps more into the red. This will eventually have to apply to a grid of spheres, all using the same camera as a mapping source, so I can't do something as simple as say, just using a gradient going down Z. It has to be based on the camera angle, but go OVER the horizon of the sphere(s).

Sorry if that's really confusing. Any help appreciated!
 
  03 March 2013
So you're baking the texture and bringing that resulting geometry into a game engine? Which one?

It sounds like an issue related to a straight vs pre multiplied alpha. Do you have a screenshot or a scene file to look at?

I should add that with camera mapping, you can't extend the image past what the camera sees. You'd need another camera mapped image with a different view, another material assigned to the unseen portion of the geometry, or by generating UVs to the object and texturing/painting in the extra areas on your texture map.
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Last edited by demafleez : 03 March 2013 at 09:03 PM.
 
  03 March 2013
IIRC there is a "border" option when baking maps, which extends the color by a few pixels outside the UV islands, but that's usually to prevent mipmap scaling issues, don't know if that would fix your problem.

If not, my best bet would be to add another projection camera to add coverage (see projection man) I guess or to do fix it manually in bodypaint.
 
  03 March 2013
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