Re: Identifying just the one triangle that the user clicked on?

Flark wrote:

> Hi,
> 
> I'm drawing tens of 1000s of triangles and the user is going to
> click on the screen. I want to identify just the one that the
> user has clicked on. I figure select mode would be overkill
> since I'd have to establish tens of 1000s of names, one per
> triangle. Can anyone tell me of an efficient way to do this?

Doing it with OpenGL:

Assuming you can draw with 8 bits per channel there are 2^24
values you can address using the colour buffer. Just give each
triangle a colour that maps to a number, to a glReadPixels on
the mouse position and you're done.

Doing it not with OpenGL:

Use some space partitioning structure to accelerate ray-triangle
intersection. Or use a ready to use library. Google
for "collision detection". I can recommend OPCODE
<http://www.codercorner.com/Opcode.htm>

Wolfgang Draxinger
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