/****************************************************************************
*                vector.h
*
*  This module contains macros to perform operations on vectors.
*
*  from Persistence of Vision Raytracer 
*  Copyright 1992 Persistence of Vision Team
*---------------------------------------------------------------------------
*  Copying, distribution and legal info is in the file povlegal.doc which
*  should be distributed with this file. If povlegal.doc is not available
*  or for more info please contact:
*
*       Drew Wells [POV-Team Leader] 
*       CIS: 73767,1244  Internet: 73767.1244@compuserve.com
*       Phone: (213) 254-4041
* 
* This program is based on the popular DKB raytracer version 2.12.
* DKBTrace was originally written by David K. Buck.
* DKBTrace Ver 2.0-2.12 were written by David K. Buck & Aaron A. Collins.
*
*****************************************************************************/


/* Misc. Vector Math Macro Definitions */

extern DBL VTemp;

/* Vector Add */
#define VAdd(a, b, c) {(a).x=(b).x+(c).x;(a).y=(b).y+(c).y;(a).z=(b).z+(c).z;}

/* Vector Subtract */
#define VSub(a, b, c) {(a).x=(b).x-(c).x;(a).y=(b).y-(c).y;(a).z=(b).z-(c).z;}

/* Scale - Multiply Vector by a Scalar */
#define VScale(a, b, k) {(a).x=(b).x*(k);(a).y=(b).y*(k);(a).z=(b).z*(k);}

/* Inverse Scale - Divide Vector by a Scalar */
#define VInverseScale(a, b, k) {(a).x=(b).x/(k);(a).y=(b).y/(k);(a).z=(b).z/(k);}

/* Dot Product - Gives Scalar angle (a) between two vectors (b) and (c) */
#define VDot(a, b, c) {a=(b).x*(c).x+(b).y*(c).y+(b).z*(c).z;}

/* Cross Product - returns Vector (a) = (b) x (c) 
   WARNING:  a must be different from b and c.*/
#define VCross(a,b,c) {(a).x=(b).y*(c).z-(b).z*(c).y; \
(a).y=(b).z*(c).x-(b).x*(c).z; \
                       (a).z=(b).x*(c).y-(b).y*(c).x;}

/* Evaluate - returns Vector (a) = Multiply Vector (b) by Vector (c) */
#define VEvaluate(a, b, c) {(a).x=(b).x*(c).x;(a).y=(b).y*(c).y;(a).z=(b).z*(c).z;}

/* Square a Vector */
#define	VSqr(a) {(a).x*(a).x;(a).y*(a).y;(a).z*(a).z;}

/* Simple Scalar Square Macro */
#define	Sqr(a)	((a)*(a))

/* Square a Vector (b) and Assign to another Vector (a) */
#define VSquareTerms(a, b) {(a).x=(b).x*(b).x;(a).y=(b).y*(b).y;(a).z=(b).z*(b).z;}

/* Vector Length - returs Scalar Euclidean Length (a) of Vector (b) */
#define VLength(a, b) {a=sqrt((b).x*(b).x+(b).y*(b).y+(b).z*(b).z);}

/* Normalize a Vector - returns a vector (length of 1) that points at (b) */
#define VNormalize(a,b) {VTemp=sqrt((b).x*(b).x+(b).y*(b).y+(b).z*(b).z);(a).x=(b).x/VTemp;(a).y=(b).y/VTemp;(a).z=(b).z/VTemp;}

/* Compute a Vector (a) Halfway Between Two Given Vectors (b) and (c) */
#define VHalf(a, b, c) {(a).x=0.5*((b).x+(c).x);(a).y=0.5*((b).y+(c).y);(a).z=0.5*((b).z+(c).z);}