[GEM-dev] pix_crop y coordinates

[IOhannes m zmoelnig]

On 2010-03-18 17:35, Matteo Sisti Sette wrote:
> chris clepper escribió:
> 
>> OpenGL absolutely allows for platform specific behavior, 
> 
> Wow, really sad
> 

but it doesn't mean that one has to make an application behave
differently on different plaforms.

sometimes there are reasons: e.g. performance (that's the reason why it
is like it is)

on OSX we have upside-down textures by default for performance reasons;
we also use rectangle textures for performance reasons (and because they
are guaranteed to work on osx); on other platforms (w32, linux)
rectangle textures might be not faster than normalized texs (or even
slower) AND depending on the hardware or drivers installed, rectangle
textures might not even be supported at all.

there are some good news, however:
- in future releases all pixes will have top-down orientation (because
there are virtually no codecs that provide bottom-up video material, and
for images the performance penalty is not so big (and is blananced by
the performance gain for videos)
- the user will be able to set the default texture type on their systems
in a central place (so they can guarantee themselves that they always
have rectangle textures (if supported, that is)
- eventually we will find a way to use texture matrices to unify
texcoords for shaders and complex geometries (therefore: always
premultiply your texcoords with the current texture matrix in your
shader - even if it doesn't do anything right now)

fgmasdr
IOhannes

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