View Full Version : finding out the object's center

03-04-2004, 09:51 AM

i am a newbie in OGL and I'm in a problematic situation. you see, i have model with all its co-ordinates but it is not at the origin. so when i rotate it, it revolves around the origin and not about the origin.so i think i should first translate it to the origin and then rotate it and then translate it back to the original positio. the problem is how do i find the displacement between the origin and the model's center to translate it to the origin. please help me.

03-04-2004, 10:25 AM
Just add all vertices of the object and then divide that result by the number of vertices, and then you should have the center of that object.

03-04-2004, 10:48 AM
thanx for your reply, but you see, this is a huge model with many number of vertices ranging to 4000 vertices. so how do i go about it?

03-04-2004, 11:03 AM
the number of vertices shouldn't be a problem, just precalculate the center using Panzer's method and store it with the model information. The only problem I can imagine is if the model's center or rotation isn't at its center of mass, but for most models Panzer's method will work

03-04-2004, 11:11 AM

let me get this right. you're telling me to add all the x , y, z positions seperatley and divide them by the no. of vertices. is that correct?

thanx for the help.

03-04-2004, 11:24 AM
Yes, that's right. But if, as chowe6685 said, your center lies at the objects center of mass then it won't work.
But normally that isn't the case and my method works.

03-04-2004, 03:34 PM
The other way, of course, is to find the min/max for x, y, and z, and use the center of that bounding rectangular solid.