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HELP!!! Simple glOrtho problem! - Printable Version

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HELP!!! Simple glOrtho problem! - Marvin - Jun 26, 2007 01:34 PM

Hey,

can anyone explain to me why this code doesn't generate a visible red line from the left bottom to the top right corner of my window?



Code:
void initGL()
{
glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Black background
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.f, 1.f, 0.f, 1.f, 0.f, 1.f);
glMatrixMode(GL_MODELVIEW);
}

void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear screen and depth buffer
glColor4f(1.0f, 0.0f, 0.0f, 1.0f);
glBegin(GL_LINES);
glVertex3f(0.0f, 0.0f, 0.0f);
glVertex3f(1.0f, 1.0f, 1.0f);
glEnd();
glFlush();
}

int main(int argc, char** argv) // Create main function for bringing it all together
{

glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB); // Display mode
glutInitWindowSize(500, 500);
glutCreateWindow("Aufgabe ?");
initGL();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutKeyboardFunc(key); // callback for key input
// glutIdleFunc(display); // If continuous animation is required
glutMainLoop(); // Initialize the main loop

}



As you can see, I have specified the viewable volume as a cube of length one, one corner at (0, 0, 0), the other one at (1, 1, 1). I'm drawing the diagonal line through these two corners, so what I should expect on the 2D window surface is a diagonal line across the window. Why isn't this happening? My window remains BLACK.

Please help. This is such a simple thing, and I'm stuck at this already.

Cheers
Marvin


HELP!!! Simple glOrtho problem! - reubert - Jun 26, 2007 03:05 PM

try
glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);

and

glVertex3f(0.0f, 0.0f, 0.0f);
glVertex3f(1.0f, 1.0f, 0.0f);

my guess is that your vertices are both getting culled


HELP!!! Simple glOrtho problem! - Realization - Jun 26, 2007 06:29 PM

Could you post your reshape function? Maybe you're not looking in the right place.


HELP!!! Simple glOrtho problem! - Marvin - Jun 27, 2007 10:23 AM

Hey folks, problem solved!

Didn't know GL_MODELVIEW is by default made to look down the negative z-Axis. Made the necessary adjustments.

As for my reshape function, it just calls the display function


Thanks

Marvin