   Using GLEXT - Urgent Help Needed
  I'm trying to use the Convolution2D call in the glext library, but for some reason they kept saying "identifier not found". So i added in the following code, hoping to get it working:typedef void (APIENTRY * PFNGLCONVOLUTIONFILTER2DPROC)(GLenum target, GLenum internalformat, GLsizei width, GLsizei height, GLenum format, GLenum type, const GLvoid *image);PFNGLCONVOLUTIONFILTER2DPROC glConvolutionFilter2D;glConvolutionFilter2D = (PFNGLCONVOLUTIONFILTER2DPROC)wglGetProcAddress("glConvolutionFilter2DEXT");But now I have a new set of errors (along with all the old ones):missing type specifier - int assumed. 'glConvolutionFilter2DEXT' : redefinition; different type modifierserror C2440: 'initializing' : cannot convert from 'PFNGLCONVOLUTIONFILTER2DEXTPROC' to 'int'   
  Are you sure you want to use that call? Is not hardware accelerated.   ;  To be honest, I don't have much of a preference. I just want this piece of code to work:extern GLubyte*  readImage(const char*, GLsizei*, GLsizei*);GLubyte  *pixels;GLsizei   width, height;GLfloat  laplacian[3][3] = {    { -0.125, -0.125, -0.125 },    { -0.125,  1.0  , -0.125 },    { -0.125, -0.125, -0.125 },};void init(void){   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);   glClearColor(0.0, 0.0, 0.0, 0.0);   printf("Using the horizontal filter\n");   glConvolutionFilter2D(GL_CONVOLUTION_2D, GL_LUMINANCE, 3, 3, GL_LUMINANCE, GL_FLOAT, horizontal);   glEnable(GL_CONVOLUTION_2D);}void display(void){   glClear(GL_COLOR_BUFFER_BIT);   glRasterPos2i( 1, 1);   glDrawPixels(width, height, GL_RGB, GL_UNSIGNED_BYTE, pixels);   glFlush();}Is there a better way of doing convolution like this? I know we can do it through the accummulation buffer, but i dont really understand that method.Thanks!   ;  Hey Guys,Sorry for the double post but I really do need help with this.I don't think the method I'm using above is optimised, so can anyone recommended a method of doing convolution filters? Specifically the sobel filter? 