🚀 go-pugleaf

Hello, I'm fairly new to OpenGL programming and am using Borland C++
Builder Pro 4. I have been getting the error "Project main.exe raised
exception class EZeroDivide with message 'Floating point division by
zero'." at various positions/orientations. The error occurs at the
command glEnd().

The only thing I can see in common is when the viewpoint is 'over' a
polygon (ie, a large polygon extending both in front of and behind the
viewpoint). If I disable lighting, everything works fine. Also, if I
disable hardware acceleration (from the Windows Control Panel) it works
fine (albeit very slowly!)

Is OpenGL supposed to cope with such polygons, or am I supposed to do
the clipping myself? Alternatively is it possibly something to do with
my card/driver? (I have a Voodoo 2 Banshee; my CPU is a K6-2). Games
such as Quake 3 run fine.

I have managed to reduce my code down to a simple example which causes
the error (width and height is normally 640x480, but changing it makes
no difference):

glEnable(GL_LIGHTING);
glClearColor(0.0f, 0.0f, 0.0f, 0.5f);    
glClearDepth(1.0f);    
glEnable(GL_DEPTH_TEST);    
glDepthFunc(GL_LEQUAL);        
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);

glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);    
glLoadIdentity();            
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW);

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
GLfloat light[4] = {1.0f,1.0f,1.0f,1.0f};
glLightModelfv(GL_LIGHT_MODEL_AMBIENT,light);
glLoadIdentity();

glTranslatef(-3.0f,-1.8f,-3.0f);
glNormal3f(0.0f,1.0f,0.0f);
glColor3f(1.0f,1.0f,1.0f);
glBegin(GL_POLYGON);
glVertex3f(0,0,0);
glVertex3f(0,0,16);
glVertex3f(16,0,16);
glVertex3f(16,0,0);
glEnd(); // causes error here

SwapBuffers( *hDC );

Another odd thing- if I replace glBegin(GL_POLYGON) and glEnd() with
glBegin(GL_QUADS) this example works, but if I add in a
glRotate3f(180.0f,0.0f,1.0f,0.0f); the error returns! (And if I have the
rotation with GL_POLYGON, it works also). Can anyone help?

Thanks in advance,

Mark