Comments on: Collision Detection with Occlusion Queries Redux

By: kometbomb

kometbomb — Thu, 06 Oct 2011 18:59:09 +0000

If you really want do use this in a server-client situation, I guess the only (easy) way is to draw as usual on the server. I am not sure but it might be possible to “draw” to hidden viewports and whatnot if it really is important to have stuff invisible. I am not sure if the pixel counts that the collision method discussed here update if the GPU doesn’t physically draw something. I suggest you find a more suitable method to check collisions, though.

By: Varacsix

Varacsix — Thu, 06 Oct 2011 14:24:45 +0000

I was wondering, if I wanted to do a server-client game using this technique, would the server have to run a graphical simulation to use the stencil buffer to check for collisions? Or is there something you can do with opengl to simulate the stencil buffer without emulating the graphics?

By: akr

akr — Wed, 28 Jul 2010 11:27:08 +0000

Hi, I implemented this algorithm. Also using stencil buffer. Works. But performance is low. This was a suprise for me……..

By: iliak

iliak — Wed, 16 Jun 2010 12:36:40 +0000

You have to set alpha test on and set AlphaFunction to greater than a treshold :

Display.AlphaTest = true;
Display.AlphaFunction(AlphaFunction.Greater, 0.1f);

BTW great article !!!

By: kometbomb

kometbomb — Sun, 02 May 2010 19:25:37 +0000

Try debugging by drawing the “collision screen” on the actual visible screen. You should see only the overlapping area being drawn (because of the stencil.)

By: wondersonic

wondersonic — Sat, 01 May 2010 09:18:27 +0000

Hello
First, thank you very much for this very interesting article!

I’ve coded this feature using LWJGL framework and ARBOcclusionQuery class.

My problem is that when I draw 2 quads both 16×16 pixels, with some transparent areas (PNG with alpha channel), I always get as a result 256 whereas I should get (if I’ve understood the feature) the number of pixels that “collided”.

Do you know any Open GL setup that could result in such a behaviour?

Regards,
WS

By: Hardware-accelerated 2D collision detection in OpenGL - kometbomb

Hardware-accelerated 2D collision detection in OpenGL - kometbomb — Wed, 23 Jul 2008 15:39:51 +0000

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