Category : C Source Code
Archive   : GRAFGEM3.ZIP
Filename : NDLINE.C

/* Badouel / Wuthrich "Face Connected Line Segment Generation in an
N-dimensional Space"
*/
/******************************************************************************
Data structure for n-dimensional line segment generation. Initialized by the
procedure Init() and used by the procedure Incr().
******************************************************************************/

#define DIM 4 /* number of dimensions */

typedef struct {
int D[DIM]; /* counter for each of the N dimensions */
int N[DIM]; /* increment for each of the N dimensions */
int S[DIM]; /* orientation for each of the N dimensions */
int cm; /* common multiple */
} Nline;

Nline line;

/******************************************************************************
Init(): initializes the data structure in order to generate the discrete
path between the point P and the point Q in an n-dimensional space.

This procedure should be called once before using Incr().

Entry: P - origin point
Q - destination point
line - line segment data structure
******************************************************************************/

void Init (P, Q, line)
int *P, *Q;
Nline *line;
{
int i, v;

line->cm = 1;
for (i=0; i v = Q[i] - P[i];
if (v < 0) {
line->S[i] = -1; line->N[i] = -v;
} else {
line->S[i] = 1; line->N[i] = v;
}
if (line->N[i] != 0) line->cm *= line->N[i];
}
for (i=0; i if (line->N[i] == 0)
line->D[i] = 2*line->cm;
else {
line->D[i] = line->cm/line->N[i];
line->N[i] = 2*line->D[i];
}
}
}

/******************************************************************************
Incr(): generates one step of a discrete segment line in an n-dimensional
space. Indicate the end of the generation with the returned value -1 for
the direction.

The procedure Init() must be called once before using Incr().

Entry: line - line segment data structure
Exit: d - current step direction
s - current step orientation
******************************************************************************/

int Incr (line, d, s)
Nline *line;
int *d, *s;
{
int i, v = 2*line->cm;

*d = -1;
for (i=0; i if (line->D[i] < v) {
v = line->D[i];
*d = i;
}
}
line->D[*d] += line->N[*d];
*s = line->S[*d];
return *d;
}