GLfloat* norm(GLfloat x1, GLfloat y1, GLfloat z1,
		  GLfloat x2, GLfloat y2, GLfloat z2,
		  GLfloat x3, GLfloat y3, GLfloat z3);

GLfloat* norm(GLfloat x1, GLfloat y1, GLfloat z1,
		  GLfloat x2, GLfloat y2, GLfloat z2,
		  GLfloat x3, GLfloat y3, GLfloat z3) {
	GLfloat *normal = new GLfloat[3];
	normal[0] = (y1-y2)*(z1-z3) - (z1-z2)*(y1-y3);
	normal[1] = (x1-x3)*(z1-z2) - (x1-x3)*(z1-z3);
	normal[2] = (x1-x2)*(y1-y3) - (x1-x3)*(y1-y2);
	return normal;
}