Can you file a bug report on this. Please attach a sample application
also.
haroon
On Feb 20, 2005, at 4:29 PM, R. Scott Thompson wrote:
On Feb 20, 2005, at 2:19 PM, R. Scott Thompson wrote:
I'm trying to render graphics into a Quartz context created by
CGGLContextCreate, but I have found precious little documentation of
its behavior, and no sample code to speak of.
To the routine I am passing the context returned to me by
aglCreateContext (a double buffering context OpenGL context whose
drawable is set to a window). I pass in the size of my viewport and
use NULL for the color space (which is supposed to choose the
default RGB color space).
I've tried drawing the Quartz graphics before and after the call to
aglSwapBuffer but the Quartz Graphics don't show up.
Are there limitations to the support for GLContexts in Panther? (can
they only be used with CGL contexts, full screen contexts, only if
the software renderer is being used... something like that?)
If I'm using a double buffered GL context.. should I draw the Quartz
graphics before or after the buffers are swapped?
To respond to my own post.
My expectation was that when you created a CGContext on top of an
OpenGL context, that you would end up with a CGContext that happened
to share a memory buffer with the GL context. In other words, when
you drew into the CGContext it would simply take the current color
buffer and use it as the drawing destination (much the same way a
QuickDraw port and a CGContext can share a PixMap).
What it appears is happening, instead, is when you issue CGContext
graphics commands, the computer translates those commands into actual
3D geometry and asks OpenGL to render that geometry. In order to get
my graphics to show up as I expected it to, I had to reset the
projection matrix to an orthographic projection and turn off the
lighting calculations (so the colors weren't affected by lighting
calculations).
For the most part things seem to be working pretty well, but I am
still seeing some unexpected behavior. At the moment I'm drawing two
Quartz 2D primitives, a line and a square. The line is a simple,
stroked, moveto/lineto path (one segment) and draws as expected. The
square, however, does not draw in the region where the bounding box
of the line and the square intersect.
You can see a picture of this at
<http://homepage.mac.com/easco/QuartzGLDrawing.jpg>
The really odd thing, however, is if I reverse the order of the line
and rectangle drawing (so the rectangle is drawn first) then the
rectangle draws as expected, the line draws everywhere except where
the rectangle is, and none of my 3D content draws at all.
This would imply (to me at least) that the Quartz 2D drawing may be
changing something in the GL State that I'm not expecting. Not being
too terribly familiar with OpenGL, I don't have enough experience to
be able to guess what setting that might be. Can someone suggest what
GL state variables could be changed by the Quartz 2D drawing that I
need to save and restore around my Quartz 2D drawings?
Scott
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haroon sheikh هارون شيخ
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