Re: [pygame] Collision Detection with Pygame/OpenGL Surfaces

["Dave LeCompte (really)" <dave@xxxxxxxxxxxx>]

"Michael George" <mdgeorge@xxxxxxxxxxxxxx> wrote:
> Just out of curiousity, have you compared your approach the gluPick and
> the selection buffer infrastructure in openGL?

I haven't done performance tests, but several of my concerns about
glReadPixel from the color buffer remain valid with the selection buffer
approach:

- I'm really nervous about having OpenGL code in my controller logic, that
seems like a really good clue my controller is relying on graphics code
too heavily.

- the selection buffer is kept in main memory, right? That means I'd be
using OpenGL as a software renderer. The selection buffer wouldn't be the
entire screen, but still, it seems like if you've got a well organized
spacial partition, you can skip a lot of the work that OpenGL would be
doing to generate the selection buffer data.

- doing a ray/sphere intersection is pretty fast. Rendering a sphere to a
selection buffer seems like it would have to be slower (at absolute best,
your selection buffer would be a single pixel, in which case, it could be
as fast as the intersection test, but no faster).

- doing all those state changes to set up the render properties for your
selection render pass and then switching back doesn't seem like it'd be
any fun to write. You could probably cut and paste the code from somewhere
else, and probably not have to do much maintenance on it, but still, it
seems like a lot of code (and potentially some slow operations on the
hardware).


-Dave LeCompte