/*
 * rotate.c
 *
 * Copyright (C) 1989, 1991, Craig E. Kolb
 * All rights reserved.
 *
 * This software may be freely copied, modified, and redistributed
 * provided that this copyright notice is preserved on all copies.
 *
 * You may not distribute this software, in whole or in part, as part of
 * any commercial product without the express consent of the authors.
 * 
 * There is no warranty or other guarantee of fitness of this software
 * for any purpose.  It is provided solely "as is".
 *
 * $Id: rotate.c,v 4.0.1.1 91/09/29 15:35:38 cek Exp Locker: cek $
 *
 * $Log:	rotate.c,v $
 * Revision 4.0.1.1  91/09/29  15:35:38  cek
 * patch1: Added comments.
 * 
 * Revision 4.0  91/07/17  14:31:18  kolb
 * Initial version.
 * 
 */
#include "common.h"
#include "rotate.h"

TransMethods *iRotateMethods;
void RotationMatrix();

/*
 * Create and return reference to Rotate structure.
 */
Rotate *
RotateCreate()
{
	Rotate *res;

	res = (Rotate *)Malloc(sizeof(Rotate));
	res->x = res->y = res->theta = 0.;
	res->z = 1.;
	return res;
}

/*
 * Return a pointer to collection of methods for the
 * Rotate transformation.
 */
TransMethods *
RotateMethods()
{
	if (iRotateMethods == (TransMethods *)NULL) {
		iRotateMethods = (TransMethods *)Malloc(sizeof(TransMethods));
		iRotateMethods->create = (TransCreateFunc *)RotateCreate;
		iRotateMethods->propagate = RotatePropagate;
	}
	return iRotateMethods;	
}

/*
 * Given a Rotate structure and forward and inverse transformations,
 * propagate the information in the Rotate structure to the
 * transformations.
 */
void
RotatePropagate(rotate, trans, itrans)
Rotate *rotate;
RSMatrix *trans, *itrans;
{
	Vector axis;

	RotationMatrix(rotate->x, rotate->y, rotate->z, deg2rad(rotate->theta), trans);
	/*
	 * Build the inverse...
	 */
	MatrixInvert(trans, itrans);
}

/*
 * Initialize a rotation matrix given an axis of rotation and an
 * angle.  Right-handed rotation is applied.
 */
void
RotationMatrix(x, y, z, theta, trans)
Float x, y, z, theta;
RSMatrix *trans;
{
	Float n1, n2, n3, sintheta, costheta;
	Vector vector;

	MatrixInit(trans);
	vector.x = x;
	vector.y = y;
	vector.z = z;

	if (VecNormalize(&vector) == 0.)
		RLerror(RL_WARN, "Degenerate rotation axis.\n");

	sintheta = sin(theta);
	costheta = cos(theta);

	n1 = vector.x; n2 = vector.y; n3 = vector.z;
	trans->matrix[0][0] = (Float)(n1*n1 + (1. - n1*n1)*costheta);
	trans->matrix[0][1] = (Float)(n1*n2*(1 - costheta) + n3*sintheta);
	trans->matrix[0][2] = (Float)(n1*n3*(1 - costheta) - n2*sintheta);
	trans->matrix[1][0] = (Float)(n1*n2*(1 - costheta) - n3*sintheta);
	trans->matrix[1][1] = (Float)(n2*n2 + (1 - n2*n2)*costheta);
	trans->matrix[1][2] = (Float)(n2*n3*(1 - costheta) + n1*sintheta);
	trans->matrix[2][0] = (Float)(n1*n3*(1 - costheta) + n2*sintheta);
	trans->matrix[2][1] = (Float)(n2*n3*(1 - costheta) - n1*sintheta);
	trans->matrix[2][2] = (Float)(n3*n3 + (1 - n3*n3)*costheta);
}