Re: [PyOpenGL-Users] ATI Card Flipping FBO Texture

[Mike C. F. <mcf...@vr...>]

Ian Mallett wrote:
> Hello,
>
> I have an NVidia GeForce 8400M GS.  I have recently implemented an
> application that uses FBOs extensively.  The application is available
> here: http://www.mediafire.com/download.php?z2xkwyjmmzm.  It works
> excellently for me.  It should look like:
> http://img7.imageshack.us/img7/6495/image1gsh.png.  My friend, on an
> ATI Mobility Radeon HD 2300, is getting the texture vertically
> flipped: http://img3.imageshack.us/img3/3637/image2sle.png.  I have no
> idea why it is happening.  As a check, I had him manually flip the
> texture, which visually fixed the problem:
> vec2 coords = coord.st/coord.q <http://coord.st/coord.q>;
> value =
> (coord.p/coord.q<=texture2D(shadtex,vec2(coords.x,1.0-coords.y)).r) ?
> 1.0:0.0;
> instead of:
> value = (coord.p/coord.q<=texture2DProj(shadtex,coord).r) ? 1.0:0.0;
> The issue is annoying me.  How can it be "fixed" the real way--e.g.,
> not a hack?
To complicate your hack/workaround, I'm on a Mobility Radeon HD 3650
(Ubuntu Jaunty 9.04 AMD64 w/fglrx drivers) and the code renders
perfectly.  That is, just checking for vendor string doesn't sound like
a solution.

Afraid I don't know of any reason the flip would occur, so I don't have
any real suggestions for how to fix it properly.  You might be able to
hack it by rendering a black/white texture and reading off a pixel
result, but that seems... sub-optimal.

Good luck,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com