Hi, i want to implement a weapon in my first person shooter. The problem is, i don´t know how to get the projectile particles fired in the direction the weapon (or player) looks/points. I have tried to multiply the vertices of the particles with the inverse modelview matrix, but this does not the job... And i don´t want to use open gl´s transform routines, since i need to change my vertices directly (for collision detection). What do i need to do to get it working? Thanks for any help, Gammastrahler

You probably want to start the projectile at the location of the player, and sets the projectile's velocity according to their direction (ie. vx = speed * cos(theta), vy = speed * sin(theta) where theta is the player's current rotation angle, for a Doom-type game. There's a couple more sines and cosines involved for a mouselook-type game. :)

To translate the particle into position for drawing, you need its position and orientation. Then you build a new modelview matrix for the particle based on these - basically you'll be writing your own versions of glRotate(), glTranslate() etc. which are useful to have around anyway.