#include <math.h>

/* C=A+B */
#define ADD2(C,A,B)								\
	( C[0] = A[0] + B[0],						\
	  C[1] = A[1] + B[1],						\
	  C[2] = A[2] + B[2],						\
	  C )

/* C=A-B */
#define SUB2(C,A,B)								\
	( C[0] = A[0] - B[0],						\
	  C[1] = A[1] - B[1],						\
	  C[2] = A[2] - B[2],						\
	  C )

/* A=B */
#define COPY(A,B) \
  ( A[0] = B[0], A[1] = B[1], A[2] = B[2] )

/* C=AxB */
#define CROSS2(C,A,B)							\
	( C[0] = A[1]*B[2] - A[2]*B[1],				\
	  C[1] = A[2]*B[0] - A[0]*B[2],				\
	  C[2] = A[0]*B[1] - A[1]*B[0],				\
	  C )

/* n=n/|n| */
#define NORMALIZE(n)							\
{												\
  GLfloat s;									\
												\
  s = sqrt(n[0]*n[0] + n[1]*n[1] + n[2]*n[2]);	\
  n[0] /= s;									\
  n[1] /= s;									\
  n[2] /= s;									\
}

/* |n| */
#define LENGTH(n) \
   sqrt(n[0]*n[0] + n[1]*n[1] + n[2]*n[2])

/* a==b? */
#define EQUAL(a,b) \
   (a[0] == b[0] && a[1] == b[1] && a[2] == b[2])

/* print 3vec */
#define PRINT(a)  \
   printf("%s=[%.2f %.2f %.2f] ", #a, a[0], a[1], a[2])