View Full Version : undistorting and premultiplication

05 May 2008, 11:55 PM
hi !

i have this weird problem.

i rendered out a series of elements (UNdistorted to matchMove) in maya with premult on, saved as .tif. (opened in photoshop, the areas with alpha are transparent with the little squares)

like this, the composite is perfect. the file in's color channel just looks perfect without any cut out alpha areas.

but after i distorted the elements back (in photoshop) to match the plate and use the same setup in shake, it seems the premultiplication is destroyed in photoshop.

05 May 2008, 12:48 AM
well, for the specific shot i don't need an alpha since i have rendered it out in an other pass

so the basic question ..

how can i remove remove the transparency (squares) in that photoshop layer ?

is there a checkbox for the layers or display somewhere ?

05 May 2008, 01:15 AM
i just found out that i can skip the photoshop batch for undistorting by just adding a lensWarp node to each fileIn node. saves also a great amount of disk space !

the question is obsolete now, but it'd be great to have an answer anyway...

06 June 2008, 11:54 AM
You'd be far better off compositing your elements together when undistorted and then just doing the LensWarp before compositing the result with your plate.

06 June 2008, 02:13 PM
A nice little trick is to undistort your background plate with the LensWarp node but don't composite over this setup.

Make your regular undistord comp without the background, then take a clone of the lenswarp node and use that to warp your comp and comp the whole over the original, undistorted background. This way you'll avoid blurring your background plate.

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06 June 2008, 02:13 PM
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