View Full Version : glDrawPixels problem

02-01-2002, 06:39 AM
At the moment I'm working on a project wich draws thumpnails via OpenGL. I'm using glDrawPixels to draw the thumpnails and it works quite nice, but whenever I try to draw a thumpnail which lays partly outside the view, it won't show up.
So for example, if the thumpnail is 100 pixels width and I draw it at x-positon -50 so that only the half of the image is visible, it won't show up.
I'm using glRasterPos2d to set the current drawing position.

Does anyone know a way around this problem?

I can't use textures, because of the power of 2 limitation and because of the thumpnails changing themselves from time to time. (weird project http://www.opengl.org/discussion_boards/ubb/wink.gif

02-01-2002, 07:36 AM
Read the spec. I'm pretty sure that is the correct behavior of rasterPos() (ie don't draw if the raster position is outside of visible range).

02-01-2002, 07:39 AM
It sounds like you have an invalid RasterPos.

You can get around this by first setting a valid rasterPos inside your current viewport and then using glBitmap to set a rasterPos that is outside the viewport but still valid.

To do this call glBitmap with a NULL bitmap and then modify the current raster position using the xmove & ymove parameters.

Hope this helps

02-02-2002, 02:55 AM
Yes, Errin, you are right. It is the correct behavior of glRasterPos() it's just that I tryed to find a way around this limitation.

So thanks Ledge, because your way works really good. It helped a lot.
I have wrote I nice glRasterPosHack() function, which calls glRasterPos with a valid position and change it afterwards with glBitmap.