OpenGL camera question, how far back can it render?

Question

I'm working on a very simple program that draws 2 planes. A ground plane and a back ground plane.

I'm attempting to draw both planes using these points ordered in X, Y, Z coordinates.

background plane

point 1 100.000002 100.000002 100.000002
point 2 -100.000002 100.000002 100.000002
point 3 -50.000001 -23.000001 100.000002
point 4 50.000001 -23.000001 100.000002

ground plane

point 1 -50.000001 -23.000001 100.000002
point 2 50.000001 -23.000001 100.000002
point 3 0.352941 -0.352941 0.352941
point 4 -0.352941 -0.352941 0.352941

My GL Setup:

OpenGL lighting is off.
I'm drawing with GL_QUAD in the order the points are listed.
I have not assigned surface normals to the quads.
Camera is centered at (0,0,0) with the Y+ as "up" and the Z axis as depth.

The ground plane renders perfectly (just a sheet of gray), but the background plane isn't rendering at all. So I have to ask:

Should I turn on lighting and compute surface normals?
Do I need to fiddle with the camera and/or view frustrum to see the back plane (does OpenGL "drop off" at a distance of Z = 100+)?

Any help is appreciated. I'm using libSDL with OpenGL.

My OpenGL initialization code looks like this:

if(SDL_Init(SDL_INIT_VIDEO) < 0) {
    return false;
}

SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);   

screenptr = SDL_SetVideoMode(swidth, sheight, sbpp, VIDEO_MODE_OPTIONS);

if( screenptr == NULL) {
    return false;
}

glEnable(GL_TEXTURE_2D);

glClearColor(0,0,0,0);
glClearDepth(1.0f);

glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL); 
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
//gluPerspective(45.0f, SCREEN_WIDTH/SCREEN_HEIGHT, 0.1f, 500.0f);
//gluPerspective( 45.0f, 1.0, 0.1f, 100.0f );
//glFrustum(-500.0f, 500.0f, -500.0f, 500.f, 0.1f, 500.f);
//glFrustum(-1.0, 1.0, -1.0, 1.0, 5, 400);

glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

if(glGetError() != GL_NO_ERROR) {
    return false;
}

Roy T. Roy T. · Accepted Answer · 2011-05-03T14:59:04

You need to take a look at where you create your camera matrix (a call to glPerspective or something similar, I haven't used SDL) and set the near and far-plane to a value such that everything that you want a user to see is further away as the near plane, but closer as the far plane. Everything that is not in between the near and far plane is clipped.

Edit I looked it up, in SDL you create the view matrix like this:

/* Create our projection matrix with a 45 degree field of view
 * a width to height ratio of 1.0 and view from .1 to 100 infront of us */
perspective(projectionmatrix, 45.0, 1.0, 0.1, 100.0);

Don't ever set the near plane to 0 (will result in a devision by zero exception) or the far plane to Float.Max (might cause weird problems)

Also take a look at this view frustum picture for a perspective projection:

OpenGL camera question, how far back can it render?

2 Answers