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# updating world coords

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### #1taybrin  Members

Posted 10 October 2001 - 06:43 PM

okay i have this car defined in its own coordinate system. I then use OpenGL to rotate, move, scale it down to the world coordinate system. My problem is that I am trying to do some simple point in polygon collision detection, but I need to take my description of the car in its local system and make it have a set of world coordinate points. I figured I could just mimic what OpenGL does and scale, rotate and translate it. The only point of the car that I do update this way and that works is its center point. Then I call glTranslatef(cenx, ceny, 0); glRotatef(somedirection, 0, 0, 1); glScalef(sx, sy, 1); This is how i draw the car, some my question is, how do i accurately keep a copy of the rest of teh car''s points in world space. I hope this makes sense, if anyone needs clarification please let me know, i have been toiling at this for some time now . . .

### #2Jankey  Members

Posted 10 October 2001 - 08:27 PM

If i checked what you mean, you scale, rotate & translate your object ... and want to use Collision Detection for your object,

If you load your Object, Scale it in Loading time ( by Updateing the Vertex Array, or the triangle list )

If you have a good understanding of vectors ... translate & rotate the Vector to the Car system ( so you dont have to Rotate & Translate the whole object! ) it should work

J@nkey ... if you have questions ... mail me!

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