Use viewport size and pos or use scale and rotate?

[jean]

Hi,


I’m making my first animation after I’ve studied and tried some examples of the book iPhone 3D programming.


In the examples I’ve seen so far in the book objects are moved changing viewport-position e viewport-size, I suppose that I can obtain the same result with viewport-size that get the whole scene and using scale and rotate, right?


Is there a more preferable approach between these? Why?





In my animation now I want to move in circle an airplane, the solutions are two:


- move in circle the viewport-position that contains only the airplane


- scale and translate the airplane in circle inside the viewport-size (that get the whole scene)


In these case which is the better approach?


I think the second because with the first to obtain a circle with a specific center and radius I need to consider that the viewport is drawn from the bottom-left corner and then the computation of the viewport-position is more complex, with the second solution the computation is simpler because the airplane is translated using the origin. My consideration are right?





Thanks.


Jean