On Wed, 5 Jul 2006, Robert Osfield wrote:
Hi Eric,
On 7/5/06, Eric Sokolowsky <[EMAIL PROTECTED]> wrote:
I have determined that when reading a texture back, Image::_pixelFormat
and Image::_internalTextureFormat should be set to the same value, which
is obtained with a call to glGetTexLevelParameteriv(textureMode, 0,
GL_TEXTURE_INTERNAL_FORMAT, ...). That is fine. But I still haven't
found a way to get the pixel format from OpenGL. Perhaps we need to add
something to the osg::State to track this.
I'm afraid I'm too cold on this topic to provide much insight.
Well, the call to glGetTexImage() asks for a format and a type. The
format parameter can be obtained from OpenGL, but the type cannot be.
Therefore, it seems reasonable to add a "type" argument to
osg::Image::readImageFromCurrentTexture, instead of arbitrarily mandating
one type or another. The current implementation is buggy in that it
sets the type parameter to the same internal format that is used as the
format parameter.
This should also help Brad Colbert with his texture read precision problem.
A changed file is forthcoming.
BTW, the set of images I was having trouble with were not a multiple of
four in size. OpenGL will report an error when trying to use a
compressed texture with glTexSubImage2D() if the subloaded texture is
not of a multiple of four in both dimensions. Is this something that
should be checked for by OSG? I have a workaround in my application that
will disable texture compression on images that are not a multiple of
four in size.
I believe the limit of a multiple of 4 is something related to the
S3TC compression where it uses blocks of pixels as its block to do the
compression.
Yes, this is exactly the reason. The question is, is it worthwhile coding
a check for this condition in OSG? I don't want to code it if it stands
little success for inclusion in OSG proper. I already have a workaround for
my application that deals with this situation, but the general solution
might be useful to others as well. The change would merely disable the
compression request for images that are not a multiple of four in either
dimension, when glTexSubImage2D() is called.
--
____ __ Eric Sokolowsky (GST) NASA Goddard Space Flight Center
/ __/__/_/__ Visualization Programmer Scientific Visualization Studio
/ __/ _/ / _/ 301.286.3751 Mailstop 610.3 Bldg 28 Rm E102
/___/_//_/__/ [EMAIL PROTECTED] Greenbelt, MD 20771
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