Re: [Boost-users] gil and OpenGL

Subject: Re: [Boost-users] gil and OpenGL
From: Kenny Riddile (kfriddile_at_[hidden])
Date: 2010-01-12 09:52:48

Ruben Lopez wrote:
> Kenny Riddile wrote:
>> Kenny Riddile wrote:
>>>
>>> I do this to load GIL images as OpenGL textures and it works fine for 
>>> me:
>>>
>>> reinterpret_cast<const char*>( 
>>> interleaved_view_get_raw_data(imageView) )
>>
>> Also, I've noticed that OpenGL interprets the image data upside down, 
>> so I flip it prior to calling glTexImage2D using flipped_up_down_view. 
>> Flipping the image data seems to be common practice when loading 
>> OpenGL textures based on what I've read online.
> You can flip the image, but it is more efficient to flip the texture 
> coordinates on Y (or T) axis. If you have a lot of texture coordinates, 
> you can set a texture matrix (glMatrixMode(GL_TEXTURE)) that flips them 
> on hardware.

Thanks!  I was actually looking for a convenient way to flip all texture 
coordinates...I'm still somewhat unfamiliar with OpenGL.  I see GLSL 
also gives me access to the texture matrices for each texture unit in 
the vertex shader, which is exactly what I need :)