Category : C Source Code
Archive   : GRAFGEM2.ZIP
Filename : FASTUPDA.C

/*
* Author: Filippo Tampieri
*/

#define FALSE 0
#define TRUE 1
#define DOT(A,B) (A[0] * B[0] + A[1] * B[1] + A[2] * B[2])

/*
vertexIsBehindPlane returns TRUE if point P is behind the
plane of normal N and coefficient d, FALSE otherwise.
*/
vertexIsBehindPlane(P, N, d)
float P[3], N[3], d;
{
return(DOT(N, P) + d <= 0. ? TRUE : FALSE);
}

/*
boxIsBehindPlane returns TRUE if the axis-aligned box of
minimum corner Cmin and maximum corner Cmax is behind the
plane of normal N and coefficient d, FALSE otherwise.
*/
boxIsBehindPlane(Cmin, Cmax, N, d)
float Cmin[3], Cmax[3], N[3], d;
{
register int i;
float P[3];

/*
assign to P the corner further away
along the direction of normal N
*/
for(i = 0; i < 3; i++)
P[i] = N[i] >= 0. ? Cmax[i] : Cmin[i];

/* test P against the input plane */
return(vertexIsBehindPlane(P, N, d));
}