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07-09-2003, 04:37 AM
Hello

I wonder what do I get from multiplying
projection and modelview matrix. I get
a pack o 16 numbers but what do they mean?
I know I can get many information about
for example frustrum but how?

Thanks

starman
07-09-2003, 06:17 AM
I found this description by googling on comp.graphics.api.opengl:

OpenGL has the following (and I assume you are interested in OpenGL, since
this is the OpenGL newsgroup)...

Object coordinates
multiply by ModelView matrix to get...
Eye Coordinates
multiply by Projection matrix to get...
Clip Coordinates
multiply by 1/W to get...
Normalized Device Coordinates
scale/translate according to the specified viewport to get...
Device Coordinates


[This message has been edited by starman (edited 07-09-2003).]

07-10-2003, 08:10 AM
Originally posted by starman:
I found this description by googling on comp.graphics.api.opengl:

OpenGL has the following (and I assume you are interested in OpenGL, since
this is the OpenGL newsgroup)...

Object coordinates
multiply by ModelView matrix to get...
Eye Coordinates
multiply by Projection matrix to get...
Clip Coordinates
multiply by 1/W to get...
Normalized Device Coordinates
scale/translate according to the specified viewport to get...
Device Coordinates


[This message has been edited by starman (edited 07-09-2003).]

Woow. Thanks.

Really I was interested how to use it for frustrum culling. Multiplying modelview matrix by projection matix gives ... something. And on www.gametutorials.com (http://www.gametutorials.com) the use this 'something' to cull objects.
What do you think about that?

Thanx

starman
07-10-2003, 11:15 AM
The application I'm working on is pretty small scale...only a handful of objects. I haven't had the need to do frustum culling yet. However, I did research it months back as was pointed to this article. I think you might find it helpful:
http://www.markmorley.com/opengl/frustumculling.html

[This message has been edited by starman (edited 07-10-2003).]

07-11-2003, 01:47 AM
Thanks!