[PD] GEM: texturing parts of multiple movies

Claude Heiland-Allen claudiusmaximus at goto10.org
Tue Jan 22 15:29:55 CET 2008

Georg Holzmann wrote:
> So my question: is this possible without additional pix_* commands ? 
> (e.g. texturing only a part of the movie onto a rectangle ... ?)
> If yes has someone an idea how ?

You can use awkward maths to change the texture coordinates of the 
rectangle, to display only part of the texture.  The tricky part of the 
maths is due to these things:

1. textures are stored in memory with dimensions rounded up to the 
nearest power of 2 (at least on my gfx card).

2. texture coordinates range from 0 to 1 in "mode 0" (the only mode I 
could get to work on my gfx card...).

3. gl coordinates are not in pixels, but some weird unit where 
height-of-gemwin = 4 or so.

See here (images too big for list):


Hope this helps,


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