Re: [PyOpenGL-Users] Newbe question on pyopengl

[Greg E. <gre...@ca...>]

duncan duncan wrote:
> So what are the correct way ? Rotate the object or move the camera ?

There isn't really any difference between these -- they're
just two different ways of thinking about the same thing.
If thinking in terms of rotating the object works for you,
then there's nothing wrong with that.

However, as you develop your application further, you
may find it helpful to think of the object-to-camera
transformation as consisting of two stages:

   1) Transform from object to world coordinates

   2) Transform from world to camera coordinates

Then you can implement operations such as "move the
object along the x axis" by changing the object-to-world
part of the transformation, and not have to worry about
what direction the x axis is pointing relative to the
camera.

Setting up such a 2-stage transformation would go something
like

   glMatrixMode(GL_PROJECTION)
   glLoadIdentity()
   gluPerspective(...) # or gluOrtho for an orthographic projection
   glMatrixMode(GL_MODELVIEW)
   glLoadIdentity()
   gluLookAt(...) # Establish world-to-camera transform
   glMultMatrixd(object_to_world_transform)
   # Render object

Note that gluLookAt is used on the modelview matrix, not
the projection matrix.

--
Greg