Just be warned that the colors you get when reading from a pixel may not be exactly the same as the colors you put in a minute earlier. That is why keeping your own frame buffer around is handy.
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Sasha Pachev Sent: Tuesday, February 04, 2003 12:16 PM To: [EMAIL PROTECTED]; Lars Olson Subject: Re: [uug] OpenGL help On Saturday 01 February 2003 06:22 pm, Lars Olson wrote: > Correction: I just looked up the function prototype (found one at > http://www.cevis.uni-bremen.de/~uwe/opengl/glReadPixels.html, google > returned several others) and if you use GL_RGB (or GL_RGBA) it will > return all the color components. > > e.g.: > float rgb[3]; > glReadPixels(x, y, 1, 1, GL_RGB, GL_FLOAT, rgb); > > One caveat: as I recall, you actually had to flush the buffer before it > would read correctly, otherwise it would always return (0,0,0) (black). > This caused my floodfill to be extreeeeemely slow. The wrapper > function idea would definitely work faster. (Anyone know if there's a > way to check the frame buffer without having to redraw the screen?) Disclaimer - I have very little experience with OpenGL, this answer is based just on a little bit of common sense. It seems to me that glReadPixels() will read the entire polygon into an array. Assuming I am right, then a good strategy for floodfill should be to call glReadPixels() on the rectangle that covers the area you are trying to floodfill, then perform the floodfill in memory on the array you have read, and then call glWritePixels() to send it back to the screen. -- MySQL Development Team For technical support contracts, visit https://order.mysql.com/?ref=mspa __ ___ ___ ____ __ / |/ /_ __/ __/ __ \/ / Sasha Pachev <[EMAIL PROTECTED]> / /|_/ / // /\ \/ /_/ / /__ MySQL AB, http://www.mysql.com/ /_/ /_/\_, /___/\___\_\___/ Provo, Utah, USA <___/ MySQL Users Conference and Expo http://www.mysql.com/events/uc2003/ ____________________ BYU Unix Users Group http://uug.byu.edu/ ___________________________________________________________________ List Info: http://phantom.byu.edu/cgi-bin/mailman/listinfo/uug-list ____________________ BYU Unix Users Group http://uug.byu.edu/ ___________________________________________________________________ List Info: http://phantom.byu.edu/cgi-bin/mailman/listinfo/uug-list
