[PD] GEM : GLSL Mixer - working 2 channel video mixer example

Alexandre Quessy listes at sourcelibre.com
Wed Jan 2 17:21:35 CET 2008

Super nice !
I didn't know about the "texunit 0" message you can send to
pix_texture. Are there other things I should know regarding
[pix_texture] before I start over again my texture storage
abstractions ?

Regarding texture coordinates, we can not access gl_MultiTexCoord1 due
to a bug in [glsl_program] ? That means that it is ok as long as we
use simple coordinates like from (0,0) to (1,1) on a rectangle ?
That's a starting point. At least we can do overlay blending and so

And happy new 2008.


2007/12/24, vade <doktorp at mac.com>:
> Hello
> Here is a 2 channel mixer using overlay blend mode with GLSL. This
> works, is decently fast and gives me the expected result.
> If you want more blend modes, feel free to grab them from http://001.vade.info
>   (or elsewhere, most are trivial to figure out)- the glsl shaders for
> the mixers use the same subroutine layout in the glsl, so it is
> trivial to swap. I did not include them out of sheer laziness.
> Caveats with PD 0.4.03 Extended nightly from Dec 24th (Mac OS X
> 10.5.1, QT 7.3, Intel):
>   - had to edit the GLSL program to fix multitexture coordinate issue.
> Only can use the texture dims from the zeroths texture unit.
>   - could not get sampler2DRect working at all - only had a single
> texel mapped it seemed.
>   - had weird issue where I would sometimes have to close the gemwin
> (0, destroy) and then re create it to see the textures assigned to
> texture units.
>         this happened most often after closing and re-opening the patch.
> Please see the included question(s) within the PD patch concerning
> using framebuffer to grab the output of the rendered shader and send
> it to yet another shader. Ive included an exposure shader in an
> attempt to make a chain of GLSL effects. I however could not get
> gemframebuffer to output any usable texture after using glslprogram.
> Thanks, hope this is helpful to those out there
> FUDDLE DUDDLE !@#!@#!@#()*!@#(*@#
> :)
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Alexandre Quessy

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