既然你说它是一个多面体,堆垛机的链接(http://softsurfer.com/Archive/algorithm_0101/algorithm_0101.htm)适用。
这是我针对您的情况对 C 代码的大致 C# 翻译:
// NOTE: The original code contained the following notice:
// ---------------------------------------
// Copyright 2000 softSurfer, 2012 Dan Sunday
// This code may be freely used and modified for any purpose
// providing that this copyright notice is included with it.
// iSurfer.org makes no warranty for this code, and cannot be held
// liable for any real or imagined damage resulting from its use.
// Users of this code must verify correctness for their application.
// ---------------------------------------
// area3D_Polygon(): computes the area of a 3D planar polygon
// Input: int n = the number of vertices in the polygon
// Point[] V = an array of n+2 vertices in a plane
// with V[n]=V[0] and V[n+1]=V[1]
// Point N = unit normal vector of the polygon's plane
// Return: the (float) area of the polygon
static float
area3D_Polygon( int n, Point3D[] V, Point3D N )
{
float area = 0;
float an, ax, ay, az; // abs value of normal and its coords
int coord; // coord to ignore: 1=x, 2=y, 3=z
int i, j, k; // loop indices
// select largest abs coordinate to ignore for projection
ax = (N.x>0 ? N.x : -N.x); // abs x-coord
ay = (N.y>0 ? N.y : -N.y); // abs y-coord
az = (N.z>0 ? N.z : -N.z); // abs z-coord
coord = 3; // ignore z-coord
if (ax > ay) {
if (ax > az) coord = 1; // ignore x-coord
}
else if (ay > az) coord = 2; // ignore y-coord
// compute area of the 2D projection
for (i=1, j=2, k=0; i<=n; i++, j++, k++)
switch (coord) {
case 1:
area += (V[i].y * (V[j].z - V[k].z));
continue;
case 2:
area += (V[i].x * (V[j].z - V[k].z));
continue;
case 3:
area += (V[i].x * (V[j].y - V[k].y));
continue;
}
// scale to get area before projection
an = Math.Sqrt( ax*ax + ay*ay + az*az); // length of normal vector
switch (coord) {
case 1:
area *= (an / (2*ax));
break;
case 2:
area *= (an / (2*ay));
break;
case 3:
area *= (an / (2*az));
break;
}
return area;
}