Vorlesungsskript Computergraphik II - IWR

2.3. C FOR GRAPHICS 35
static CGprofile
static CGprogram
cg_fragment_profile;
cg_fragment_program;
static CGparameter cg_parameter_vertex_scale_factor;
static CGparameter cg_parameter_vertex_rotation;
static CGparameter cg_parameter_fragment_color;
// Error checking routine for Cg:
static void checkForCgError(const char *situation) {
CGerror error;
const char *string = cgGetLastErrorString(&error);
}
if (error != CG_NO_ERROR) {
printf("%s: %s\n", situation, string);
if (error == CG_COMPILER_ERROR) {
printf("%s\n", cgGetLastListing(cg_context));
}
exit(1);
}
// keyboard callback:
void keyboard(unsigned char key, int x, int y) {
switch (key) {
case 27: // Escape
case ’q’:
cgDestroyProgram(cg_vertex_program);
cgDestroyProgram(cg_fragment_program);
cgDestroyContext(cg_context);
exit(0);
break;
}
}
// display function:
void display() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
cgGLBindProgram(cg_vertex_program);
checkForCgError("binding vertex program");
cgGLEnableProfile(cg_vertex_profile);
checkForCgError("enabling vertex profile");
// Hier werden die Werte der einheitlichen Parameter "scale_factor", "vertex_rotation" festgesetzt:
cgGLSetParameter1f(cg_parameter_vertex_scale_factor, 0.7);
cgGLSetParameter1f(cg_parameter_vertex_rotation, 1.509);
cgGLBindProgram(cg_fragment_program);
checkForCgError("binding fragment program");
cgGLEnableProfile(cg_fragment_profile);
checkForCgError("enabling fragment profile");
GLfloat color[] = {0.2, 0.7, 0.3};
cgGLSetParameter3fv(cg_parameter_fragment_color, color);
// Rendern eines Dreiecks. Hierfuer wurde keine Farbe ausgewaehlt!
glBegin(GL_TRIANGLES);
glVertex2f(-0.8, 0.8);
glVertex2f(0.8, 0.8);
glVertex2f(0.0, -0.8);
glEnd();
cgGLDisableProfile(cg_vertex_profile);
checkForCgError("disabling vertex profile");
cgGLDisableProfile(cg_fragment_profile);
checkForCgError("disabling fragment profile");