Question

I’m experimenting with pyOpenGL and I’ve had trouble getting the camera to work properly.

def Draw():

     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
     glMatrixMode(GL_MODELVIEW)
     glLoadIdentity()

     glRotatef(roty,1,0,0)
     glRotatef(rotx,0,1,0)
     glTranslate(0,0,eyez)

     glPushMatrix()

     glTranslate(0,0,-80)

     glBegin(GL_QUADS)
     glColor(0,1,0)
     glVertex3f(-50,-5,10)
     glVertex3f(-50,50,10)
     glVertex3f(50,50,10)
     glVertex3f(50,-5,10)

     glColor(1,0,0)
     glVertex3f(-50,-5,10)
     glVertex3f(-50,50,10)
     glVertex3f(-50,50,70)
     glVertex3f(-50,-5,70)
     glEnd()

     glPopMatrix()

     glutSwapBuffers()

These rotations work great but I am not able to move forward in the direction the camera is facing. When I have modified the code to be able to move forward in this way the scene will not rotate correctly. What will happen is that the scene will rotate in a circle if I back up far enough.

Answer 1

If you are writing an application that has the concept of the camera moving (and rotating too I suppose) then rather than operating on the object with glRotate and glTranslate consider looking into gluLookAt, which allows you to set things up in a camera-centered way, so to speak.

By the way, gluLookAt is deprecated, even though some people have said they “miss it a lot.” If you wish to stay away from this deprecated utility function, see the source of this function and roll your own matrix on the CPU.