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Ehsan Kamrani
05-20-2005, 01:54 AM
Does the values of the function glRasterPos2*() affect the function glReadPixels?
As an example if we use from the following code:
glRasterPos2i( xi, yi );
glReadPixels(x,y,...);

Is it correct that the bottom-left of the rectangle that we want to read is (xi+x, yi+y)?

What does happen if the width and height values of the function glReadPixels() are greater than the with and height of the screen?--Does the OpenGL clamp them?Or do we see any logical error?

-Ehsan-

05-20-2005, 03:43 AM
Originally posted by Ehsan Kamrani:
Does the values of the function glRasterPos2*() affect the function glReadPixels?
No. glReadPixel() does not depend on the current raster position.

Be carefull with glRasterPos() calls tho, if the position is invalid all sucessive OpenGL commands that rely on the raster position like for example glDrawPixels() will be ignored.


Originally posted by Ehsan Kamrani:
What does happen if the width and height values of the function glReadPixels() are greater than the with and height of the screen?--Does the OpenGL clamp them?Or do we see any logical error?
From the glReadPixels() documentation:

"Values for pixels that lie outside the window connected to the current OpenGL context are undefined."