View Full Version : OpenGL overlay

04-02-2004, 01:35 AM
Hi everyone!
Is it possible to draw an overlay using opengl?
what I wan't to do is draw over a window where graphics is already drawed, so I don't want to use opengl in that actual window. you get it?

04-11-2004, 12:55 PM
I'm an opengl newbie myself, first post and all, but I did something like this awhile back.

Only way I could find at the time was :

1.) grab a handle to the window you need to draw on
2.) either use setpixel (slow)
3.) getpixel works (slow)
4.) BitBlt works as well, to and from a memDC

so as to printing out a window inside an already open , OpenGL window... I guess you could either 'create' a window lookalike on the current hdc, or memDC, and bitblt it over.. it's not that slow..

well, hope I helped a little..


04-11-2004, 12:58 PM

I forgot to mention the flicker. If you decide to try that, the screen where you are drawing on the OpenGL window, will flicker.. Due to buffering. Wish I knew how to fix that, but it's been awhile since I messed with it.

Maybe some sort of buffer, have no idea how to access the opengl buffer. If anyone else knows that , I myself would be happy to see it work :)