Re: [PyOpenGL-Users] couple of queries

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

Prashant Saxena wrote:

> 1. Which is better (VBO or display list) when you have to show large 
> number of 3d geometrical objects in terms of efficiency and smooth 
> viewport navigation?

There's no general answer to that -- it depends on what you're
doing and what environment you're doing it in.

I have no experience with VBOs, but I've had very good results
using display lists from Python, because they let you draw
arbitrarily large amounts of just about anything using a
single Python call. Since Python function calls are probably
the bottleneck when using OpenGL from Python, this is a
huge win.

You may get similar results using VBOs, but I'd expect that
to be true only if you're drawing a few objects with very
large numbers of vertices each. But as I said, I haven't
tried using VBOs myself, so that's just theorising. The only
way to find out is to try both and see which works better for
you in your situation.

> 2. Method for picking (large number of 3d geometrical objects)
>     a) color based (it'll work only when you draw each objects in 
> wireframe mode and gives unique color to each object. AFAIK)
>     b)Default Selection Mode GL rendering(I am sure it'll be slow)
>     c) Any other?

Personally I prefer to do my own calculations to find picked
objects, and not use OpenGL's picking functions at all.

> 3. If you do have a professional graphic card then performance will be 
> increased using pyOpenGL or no performance gain?

Again, no general answer. Depends on whether GPU activity is
the bottleneck. The only way to find that out is by profiling
your code.

-- 
Greg