bullet_move = function(node, sgroot, w, h){
	this.xyz[0] += this.dx;
	this.xyz[1] += this.dy; //+ Math.sin(this.frame) * 500
	this.xyz[2] += this.dz;
	this.frame++;
	if(this.frame > 200){
		this.remove(this);
	}
}

bullet_collision = function(node, sgroot, w, h){
	if(this.xyz[1] > 100){
		this.remove(this);
	}
}