Question

I’m new to OpenGL. I’ve successfully drawn cubes, and tried to improve the code, came up with this, but this only draws the first face of the cube:

glPushMatrix();
glColor3d(1,0,0);
glRotatef(45,0,1,0);
glTranslatef(0,0,3);

for(int i=0;i<6;i++){
   glBegin(GL_QUADS);
   glVertex3f(0,0,0);
   glVertex3f(3,0,0);
   glVertex3f(3,3,0);
   glVertex3f(0,3,0);
   glEnd();
   if(i<4)
    glRotatef(90,0,1,0);
   if(i=4)
    glRotatef(90,1,0,0);
   if(i=5)
    glRotatef(180,1,0,0);
}

glRotatef(90,1,0,0);

glPopMatrix();

The iteration doesn’t seem to work at all! Am I missing something basic about the way how OpenGL works?

Answer 1

First answer is: You’re using an archaic version of OpenGL. Nowadays you don’t send vertices one by one, but instead:

• create a memory buffer with some vertices
• send that buffer to a buffer (VBO) in the GPU memory
• render directly from there using glDrawArrays or glDrawElements.

Try it sometime, works drastically faster 🙂

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And on what’s wrong with your example- Did you perhaps mean this…?

if (i == 4)

and

if (i == 5)

Please enable your compiler warnings so that you’ll catch that. (I didn’t see it either, by the way – my compiler did :-))