glRasterPos() & glPixelZoom()

OpenGL OpenGL: Basic Coding
1

Hi All,

We are drawing the same 32x32 bitmap (rounded corner) at each viewport corner inverting it with glPixelZoom().

If the viewport is 100x100 pixel, is it allowes to do:

glRasterPos(100,100);
glZoomPixel(-1,-1);
gl.DrawPixel(...);

Looks like on some hardwares it works only with:

glRasterPos(99,99);
glZoomPixel(-1,-1);
gl.DrawPixel(...);

Otherwise it flickers…

Thanks,

Alberto

2

if the viewport is 100x100, then each coordinate is valid when in [0;99] range, so indeed 100 is invalid.

Did you read this section “9. Careful Updating that Raster Position” here :
http://www.opengl.org/resources/features/KilgardTechniques/oglpitfall/

3

I was suspecting it, thanks!

Alberto