Hi RJ, glCopyPixels will be doing a round trip to the CPU. You might be able to help out by using a PixelBuffer object for reading and writing, but as general advice I have to say absolutely don't code the problem in the way your are doing as it will be slow. Use FBO to render a texture and then render a quad screen aligned, don't use glCopyPixels and glDrawPixels at all.
Robert. On 9/24/07, Rahul Jain <[EMAIL PROTECTED]> wrote: > Hi Guys, > This question is not directly related to OSG, but I hope the OSG users > must have answer to this problem and the reason i am asking this on this > forum is that because the OSG has most number of OpenGL experts.;) > > I am transfering data from one pbuffer to other pbuffer using > glCopyPixel and the transfer rate is two slow, 1MB/sec on my Nvidia > Quadro 4600 (512MB) graphics card. > Can some one tell me what can be the problem. The detail description of > what i am doing is given below. > > The two pbuffers i have created using glXCreatePbuffer > with GLXFBConfig atributes as mentioned below > > int attrib[] = > { > GLX_DOUBLEBUFFER, True, > GLX_RED_SIZE, 8, > GLX_GREEN_SIZE, 8, > GLX_BLUE_SIZE, 8, > GLX_ALPHA_SIZE, 8, > GLX_RENDER_TYPE, GLX_RGBA_BIT, > GLX_DRAWABLE_TYPE, GLX_PBUFFER_BIT, > None > } > The attributes of the pbuufer are > > int pbufAttrib[] = > { > GLX_PBUFFER_WIDTH, 512, > GLX_PBUFFER_HEIGHT, 512, > GLX_LARGEST_PBUFFER, True, > GLX_PRESERVED_CONTENTS,True, > None > } > > Now i created a context (contx0) and made the context current w.r.t > pbuffer0. > > Now using glDrawPixel i draw an image in pbuffer0. > > Now using glXMakeContextCurrent(display,pbuufer1(drawable), > pbuffer0(readable), contx0); > i set the context so that pixelBuffer1 is my drawable and pixelBuffer0 > is my readable buffer. > > Now i am copying tha data from pixelBuffer0 to PixelBufer1 using > glCopyPixel() and that is where i am getting the performace hit. > Since i am transfering data from GPU to GPU the transfer rate should be > very high (GB/sec) > but i am getting aroung 1MB/sec. > > Thanks in advance > rj > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org