Hi there!
I am just trying to migrate a small OpenGL application from Unix to Windows using the Cygwin environment for development. I was able to get my code running without any significant changes.
Now I wish to apply convolution which is OpenGL 1.2 functionality. It took some time to realize that anything above version 1.1 is not directly supported by Windows but that one must obtain function pointers via wglGetProcAddress(). Unfortunately, it only returns a null pointer – why?
Here’s a minimal example to produce that behavior:
#include <stdio.h>
#include <windows.h>
#include <GL/glut.h>
#include <GL/glext.h>
void display(void)
{
PFNGLGETCONVOLUTIONPARAMETERIVPROC glGetConvolutionParameteriv;
printf("VENDOR : %s
", glGetString(GL_VENDOR));
printf("RENDERER : %s
", glGetString(GL_RENDERER));
printf("VERSION : %s
", glGetString(GL_VERSION));
glGetConvolutionParameteriv = (PFNGLGETCONVOLUTIONPARAMETERIVPROC)
wglGetProcAddress("glGetConvolutionParameteriv");
printf("address = %p
", glGetConvolutionParameteriv);
printf("error = %d
", GetLastError());
exit(0);
}
int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutCreateWindow(“Testwindow”);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
The compiler is run like this:
$ gcc example.c -o example -lglut32 -lopengl32
And the output is like this:
VENDOR : ATI Technologies Inc.
RENDERER : Radeon 7500 DDR x86/SSE2
VERSION : 1.3.3038 Win2000 Release
address = 0x0
error = 127
The error code is
127 The specified procedure could not be found. ERROR_PROC_NOT_FOUND
So why doesn’t this work? The OpenGL version available is 1.3 so glGetConvolutionParameteriv() should be available!?
Bye,
Wolfgang
