public class Transfos{


    public static double Vol(double[] a, double[] b, double[] c){
	double[] bc = new double[3];
	Outils.crossprod(b,c,bc);
	return(Math.abs(Outils.scalarprod(a,bc,3)));
    }

    public static void Trans(double[] a, double[] v, double[] av){
	int n;
	for(n=0;n<3;n++){
	    av[n] = a[n] + v[n];
	}
    }
    
    public static void Par(double r[], double[] v, double[] rv){
	double[] vpar = new double[3];
	int n;
	
	for(n=0;n<3;n++){
	    vpar[n] = Outils.scalarprod(r,v,3)*r[n];
	    rv[n] = 2.*vpar[n]-v[n];
	}
	

    }

    public static void Rot(double[] r, double[] v, double[] rv, double theta){
	double[] rxv = new double[3];

	Outils.crossprod(r,v,rxv); // Calcul du produit vectoriel r x v 

	double rva, rvb, rvc; 

	rva = (1.-Math.cos(theta))*Outils.scalarprod(r,v,3)*r[0];
	rvb = Math.cos(theta)*v[0];
	rvc = Math.sin(theta)*rxv[0];

	rv[0] = rva + rvb + rvc;

	rva = (1.-Math.cos(theta))*Outils.scalarprod(r,v,3)*r[1];
	rvb = Math.cos(theta)*v[1];
	rvc = Math.sin(theta)*rxv[1];

	rv[1] = rva + rvb + rvc;

	rva = (1.-Math.cos(theta))*Outils.scalarprod(r,v,3)*r[2];
	rvb = Math.cos(theta)*v[2];
	rvc = Math.sin(theta)*rxv[2];

	rv[2] = rva + rvb + rvc;


    }

 			   
}