顶点缓冲对象和球体

Question

I have to draw a great collection of spheres in a 3D physical simulation of a "spring-mass" like system.

I would like to know an efficient method to draw spheres without having to compile a display list at every step of my simulation (each step may vary from milliseconds to seconds, depending on the number of bodies involved in the computation).

I've read that vertex-buffer objects are an efficient method to draw objects which need also to be sometimes updated.

Is there any method to draw OpenGL spheres in a way faster than glutSolidSphere?

Answer 1

I would like to know an efficient method to draw spheres without having to compile a display list at every step of my simulation (each step may vary from milliseconds to seconds, depending on the number of bodies involved in the computation).

Why are you generating a display list at all, if the geometry you put into is is dynamic. Display lists are meant for static geometry that never or only seldomly changes.

I've read that vertex-buffer objects are an efficient method to draw objects which need also to be sometimes updated.

Actually VBOs are most efficient with static geometry as well. In general you want to keep the number of actual geometry updates as low as possible. In your case the only thing updating are the positions (and maybe the size) of the spheres. This is a prime example for instanced drawing. However this also works well, with updating only a uniform or the transformation matrix and do the call drawing a sphere.

The idea of Vertex Arrays and VBOs is, that you draw a whole batch of geometry with a single call. A sphere would be such a batch.

Answer 2

Spheres are self-similar; every sphere is just a scaled version of any other sphere. I see no need to regenerate any geometry. Indeed, I see no need to have more than one sphere at all.

It's simply a matter of providing the proper scaling matrix. I would suggest a sphere of radius one centered at the origin for your display list or buffer object mesh. Then you can just transform it to different locations, using a scale to set the new radius.