glOrtho

So I'm learning OpenGL right now and trying to use glOrtho to scale my sprites correctly, but it doesn't seem to be working. No matter what arguments I pass to glOrtho, it always defaults back to (-1, 1, -1, 1). I checked for GL errors and got nothing. Here is my test code:

void Draw() {
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-100.0, 100.0, -100.0, 100.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);
    glLoadIdentity();
    glBegin(GL_QUADS);
        glColor3f(1.0f, 0.0f, 0.0f);
        glVertex2f(-1.0f, 1.0f);
        glVertex2f(1.0f, 1.0f);
        glVertex2f(1.0f, -1.0f);
        glVertex2f(-1.0f, -1.0f);
    glEnd();
}

The quad I draw should be tiny, but it covers the entire viewport. Halp!

Maybe try     glOrtho(-100.0, 100.0, -100.0, 100.0, 0.0, 1.0);
Or just use gluOrtho2D.

I do this before glutMainLoop()

void init() {
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(-2.0, 10.0, -2.0, 5.0);
  glMatrixMode(GL_MODELVIEW);

  glClearColor(1.0, 1.0, 1.0, 1.0);

  glEnable(GL_POINT_SMOOTH);
}

Oh, I think you should put glOrtho before you do the main loop. Not in your display function.

OP here. I've tried gluOrtho2D, tried changing the near and far clipping plane, and also my glOrtho call was originally before the main loop. I just put it there for the code sample. None of it makes any difference =\

You have to be in GL_MODELVIEW when you draw.

Switching to GL_MODELVIEW didn't change anything. I thought that was only for 3D drawing anyways, right? This is all 2D.

You should start with working code. Here is an example from a graphics course. http://www.cse.nd.edu/courses/cse40166/www/resources/triforce.tar.gz

>>7
2D in opengl is really 3D orthographic projection.

When you do that second glLoadIdentity, you're undoing your glOrtho.

Pronounced 'glor-fo'.

>>10
I'll project your ortho, NOMSAYN?

>>10
Not OP, but now I am confused. How is it that the quad still gets rendered like you would in ortho projection?

learning OpenGL
FFP
Nope.

>>13
You're not “in” a projection, you apply a projection to an existing space.  The view doesn't vanish just because you haven't transformed it.

>>1
As >>10 said: glLoadIdentity() undos glOrtho() as it resetts your current view Matrix. So you have to call glOrtho() in a different MATRIX like this:

...
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(...)
...
glMatrixMode(GL_MODELVIEW);
glLoadLibrary();
...
Btw go read a decent OpenGL Tutorial. Like this:
http://www.opengl.org/documentation/red_book/