Matte the Fill, THEN Interpolate?

[chepmedia]

I have a ton of hand-painted (by someone else) texture images where there are "garbage" pixels jusssst outside where the matte cuts out the picture. In programs like Photoshop or After Effects those garbage pixels are "under" completely black (100% transparent) matte pixels and aren't visible once matted. The matted edges appear "clean".

Here's the problem I'm having in Softimage though. Those garbage pixels are showing up on the fringe of edges. I don't know anything about the mental ray pipeline but I'm starting to wonder if mental ray interpolates the fill BEFORE the matte kicks in as opposed to first matting, THEN interpolating. I think the "how far do I look to interpolate this pixel" is including those garbage pixels.

I'm using an Image node piped into a Sprite to use the alpha channel matte that comes with each texture. I've tried every sampling permutation including altering the filters (Box, Gaussian etc.) to see if they help but they don't.

Is there a way I can force mr to matte my textures BEFORE interpolating so the interpolation isn't "aware" of the garbage pixels once the matte mattes them out? And no, I do not know how much wood a woodchuck would chuck.

Thanks,

Marc

[FXDude]

Maybe it's a premultuply thing? you can check and play with render setting for that. But would you mind posting an illustrative image?

cheers,

[chepmedia]

LOL - actually, I think it's the "garbage" generated by a straight (no premultiplied) fill that's the problem.

I know the white garbage pixels are "close" to the edge of the matte but I keep thinking like a computer ... "does the matte turn off that pixel? Yes? Then it should be 'off'. Not, 'maybe'. Or 'sometimes'."

(Sorry if the picts are confusing - the best shot for showing the noisy pixels was a horizontal section ... the best shot for showing the results in Soft was a vertical section, but it's all the same area.)

Here's what the fill looks like...

The Fill of the texture image

Here's what the matte looks like...

The Matte of the texture image

And here's the result in Softimage...

What the result looks like in Softimage

[chepmedia]

Here's a quick mockup in After Effects using the same fill and matte. Again, a little "apples versus oranges" but thought I'd show...

[FXDude]

Sorry, I referred to render settings, but you mentioned that they were from drawings.

Yet it does seem to be a premultiply thing, so using your image with the alpha as alpha,
here is composited straight, and premutiplied

(I think AE Pre-mutiplies everything by default)



So you can Premultiply them before applying them as textures,
(usually is a "premult" anywhere including in the FXTree, but it's essentially multiplying RGB by Alpha without touching the alpha)


You can also do it "live" on the image clips themselves in the FXtree without writing them first.
(using "Clips" top menu to get and process clips)

[chepmedia]

That FXTree idea worked out. Thank you.

Marc