world coords into camera local coords

I've been trying to write some code to convert an objects position from world coordinates into the cameras local coordinates. the camera can rotate around x and y axes.

This would then allow me to calculate pan and depth values for a sound coming from said object by just taking the x and z lengths.

In pseudo code I have been doing this.

newpos = object.pos - camera.pos

object.rotatexyz(newpos,-camanglex,-camangley,-camanglez)

However this doesn't work. What am I doing wrong?

What you need to do is doing matrix operations:


lposx = cos(angle)*posx + sin(angle)*posy - camx
lposy = -sin(angle)*posx + cos(angle)*posy - camy

This should be the correct equation when I'm not totally wrong.

The first part is a matrix multiplication of world pos with rotation matrix of the camera and substraction of the cam position repositions the world origin into the one of the camera

thats essentially what im doing and it ain't working..

What does your rotate method look like?
With 3 dimensional transformations, it is essential to combine the matrices correctly (ie in the correct order)

ah I think I have cracked it. By putting my opengl camera rotation instructions in the order z,y,x (they were in xyz before)and my "unrotations" in order x,y,z everything seems to work.

Well thats 2 days i'll never see again. I hate these problems where one is basically looking in totally the wrong place for the problem.grrr

Thanks Dreamora for your assistance anyway.