docs: void compute_Rv() {
  		double t = Math.sqrt(v1*v1 + v2*v2);
  		double s = Math.sqrt(t*t + 1);
  		double cosT = 1.0/s;
  		double sinT = Math.sqrt(1-1.0/(s*s));
  
  		K_x.data[0] = 0;   K_x.data[1] = 0;   K_x.data[2] = v1;
  		K_x.data[3] = 0;   K_x.data[4] = 0;   K_x.data[5] = v2;
  		K_x.data[6] = -v1; K_x.data[7] = -v2; K_x.data[8] = 0;
  		CommonOps_DDRM.divide(K_x,t);
  		CommonOps_DDRM.setIdentity(R_v);
  		CommonOps_DDRM.addEquals(R_v,sinT,K_x);
  		CommonOps_DDRM.multAdd(1.0-cosT,K_x,K_x,R_v);
  	}