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Index › Programming Questions & Help › OpenGL and 3D Libraries › Masking layer over background image
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Masking layer over background image (Read 1632 times)
willmarshall
Masking layer over background image
Sep 12th, 2009, 6:36pm  
Hi,

I'm using OpenGL and processing to play a series of images.

I'd like add a layer over these images, that is a mostly black canvas with elliptical areas of transparency at various X,Y coords.

I've managed to draw transparent ellipses over the images: but I can't work out how to generate a mostly-black canvas with transparent patches to render.

Can anyone help me?

Cheers,
Will.
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willmarshall
Re: Masking layer over background image
Reply #1 - Sep 12th, 2009, 7:16pm  
Note: I've got this working using a P3D offscreen graphics buffer which I use to mask a black PImage and then render: but this is awfully slow and OpenGL won't let me use offscreen buffers.
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ben_hem
Re: Masking layer over background image
Reply #2 - Sep 12th, 2009, 9:44pm  
I don't know if this will be fast enough for your purposes either, but in this thread:
http://processing.org/discourse/yabb2/num_1251260591.html
Cedric mentions "breakShape" which would seem to fit your purpose.  But as we discovered, it doesn't work in GL mode, so you'd have to create a secondary PGraphics object with P2D rendering mode in order to generate the mask image.  -- Ben
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Cedric
Re: Masking layer over background image
Reply #3 - Sep 13th, 2009, 1:43pm  
if that doesnt work, i would just create an transparent PNG and overlay it. There you can also add a smooth blurry transparency transition. That should do the job
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