[Fluxus] texture types (was Re: png diagonal oddness)

[David Griffiths]

Hi all

On Thu, 2011-01-20 at 22:17 +0200, David Griffiths wrote:
> > Both are 750x160 .png files (like the one already send). One glitches,
> > the other doesn't. I don't know enough about the anatomy of .png files
> > to say anything sensible about this but I do know that this means
> > there is some non-trivial weirdness here or at the very least that
> > dimensions in pixels aren't the only thing that affects whether or not
> > a given texture displays correctly.
> 
> Just a quick guess - does one have alpha and the other not?

Oh yes, you attached the textures to the bug report :)

Yeah, I think that could be the problem. The annoying thing is that it
looks like it's passing the right thing to OpenGL (desc.InternalFormat,
TexturePainter.cpp, lines 266 and 272). I'll have a closer look.

Also, on the power of two issue - my thinking on this was that if you
were generating mipmaps (the default in fluxus) gluBuild2DMipmaps[1]
should take care of this for you by scaling up/down and correcting. If
you have mipmap generation off then it's going a much lower level route,
so you are on your own with these calculations.

All of this gloriously missing from the documentation I suspect...

cheers,

dave

[1] http://www.opengl.org/sdk/docs/man/xhtml/gluBuild2DMipmaps.xml