/*
* ported from p bourke's triangulate.c
* http://astronomy.swin.edu.au/~pbourke/terrain/triangulate/triangulate.c
*
* fjenett, 20th february 2005, offenbach-germany.
* contact: http://www.florianjenett.de/
*
* run like this:
* javac *.java
* java triangulate
*
* to view the output: http://processing.org/
*
*/
class ITRIANGLE {
int p1, p2, p3;
ITRIANGLE() { ; }
}
class IEDGE {
int p1, p2;
IEDGE() { p1=-1; p2=-1; }
}
class XYZ {
double x, y, z;
XYZ() { ; }
XYZ( double _x, double _y, double _z) {
this.x = _x; this.y = _y; this.z = _z;
}
}
public class triangulate {
public static double EPSILON = 0.000001;
/*
Return TRUE if a point (xp,yp) is inside the circumcircle made up
of the points (x1,y1), (x2,y2), (x3,y3)
The circumcircle centre is returned in (xc,yc) and the radius r
NOTE: A point on the edge is inside the circumcircle
*/
static boolean CircumCircle(
double xp, double yp,
double x1, double y1,
double x2, double y2,
double x3, double y3,
/*double xc, double yc, double r*/
XYZ circle
)
{
double m1,m2,mx1,mx2,my1,my2;
double dx,dy,rsqr,drsqr;
double xc, yc, r;
/* Check for coincident points */
if ( Math.abs(y1-y2) < EPSILON && Math.abs(y2-y3) < EPSILON )
{
System.out.println("CircumCircle: Points are coincident.");
return false;
}
if ( Math.abs(y2-y1) < EPSILON )
{
m2 = - (x3-x2) / (y3-y2);
mx2 = (x2 + x3) / 2.0;
my2 = (y2 + y3) / 2.0;
xc = (x2 + x1) / 2.0;
yc = m2 * (xc - mx2) + my2;
}
else if ( Math.abs(y3-y2) < EPSILON )
{
m1 = - (x2-x1) / (y2-y1);
mx1 = (x1 + x2) / 2.0;
my1 = (y1 + y2) / 2.0;
xc = (x3 + x2) / 2.0;
yc = m1 * (xc - mx1) + my1;
}
else
{
m1 = - (x2-x1) / (y2-y1);
m2 = - (x3-x2) / (y3-y2);
mx1 = (x1 + x2) / 2.0;
mx2 = (x2 + x3) / 2.0;
my1 = (y1 + y2) / 2.0;
my2 = (y2 + y3) / 2.0;
xc = (m1 * mx1 - m2 * mx2 + my2 - my1) / (m1 - m2);
yc = m1 * (xc - mx1) + my1;
}
dx = x2 - xc;
dy = y2 - yc;
rsqr = dx*dx + dy*dy;
r = Math.sqrt(rsqr);
dx = xp - xc;
dy = yp - yc;
drsqr = dx*dx + dy*dy;
circle.x = xc;
circle.y = yc;
circle.z = r;
return ( drsqr <= rsqr ? true : false );
}
/*
Triangulation subroutine
Takes as input NV vertices in array pxyz
Returned is a list of ntri triangular faces in the array v
These triangles are arranged in a consistent clockwise order.
The triangle array 'v' should be malloced to 3 * nv
The vertex array pxyz must be big enough to hold 3 more points
The vertex array must be sorted in increasing x values say
qsort(p,nv,sizeof(XYZ),XYZCompare);
int XYZCompare(void *v1,void *v2)
{
XYZ *p1,*p2;
p1 = v1;
p2 = v2;
if (p1->x < p2->x)
return(-1);
else if (p1->x > p2->x)
return(1);
else
return(0);
}
*/
static int Triangulate ( int nv, XYZ pxyz[], ITRIANGLE v[] )
{
boolean complete[] = null;
IEDGE edges[] = null;
int nedge = 0;
int trimax, emax = 200;
int status = 0;
boolean inside;
//int i, j, k;
double xp, yp, x1, y1, x2, y2, x3, y3, xc, yc, r;
double xmin, xmax, ymin, ymax, xmid, ymid;
double dx, dy, dmax;
int ntri = 0;
/* Allocate memory for the completeness list, flag for each triangle */
trimax = 4*nv;
complete = new boolean[trimax];
for (int ic=0; ic<trimax; ic++) complete[ic] = false;
/* Allocate memory for the edge list */
edges = new IEDGE[emax];
for (int ie=0; ie<emax; ie++) edges[ie] = new IEDGE();
/*
Find the maximum and minimum vertex bounds.
This is to allow calculation of the bounding triangle
*/
xmin = pxyz[0].x;
ymin = pxyz[0].y;
xmax = xmin;
ymax = ymin;
for (int i=1;i<nv;i++)
{
if (pxyz[i].x < xmin) xmin = pxyz[i].x;
if (pxyz[i].x > xmax) xmax = pxyz[i].x;
if (pxyz[i].y < ymin) ymin = pxyz[i].y;
if (pxyz[i].y > ymax) ymax = pxyz[i].y;
}
dx = xmax - xmin;
dy = ymax - ymin;
dmax = (dx > dy) ? dx : dy;
xmid = (xmax + xmin) / 2.0;
ymid = (ymax + ymin) / 2.0;
/*
Set up the supertriangle
This is a triangle which encompasses all the sample points.
The supertriangle coordinates are added to the end of the
vertex list. The supertriangle is the first triangle in
the triangle list.
*/
pxyz[nv+0].x = xmid - 2.0 * dmax;
pxyz[nv+0].y = ymid - dmax;
pxyz[nv+0].z = 0.0;
pxyz[nv+1].x = xmid;
pxyz[nv+1].y = ymid + 2.0 * dmax;
pxyz[nv+1].z = 0.0;
pxyz[nv+2].x = xmid + 2.0 * dmax;
pxyz[nv+2].y = ymid - dmax;
pxyz[nv+2].z = 0.0;
v[0].p1 = nv;
v[0].p2 = nv+1;
v[0].p3 = nv+2;
complete[0] = false;
ntri = 1;
/*
Include each point one at a time into the existing mesh
*/
for (int i=0;i<nv;i++) {
xp = pxyz[i].x;
yp = pxyz[i].y;
nedge = 0;
/*
Set up the edge buffer.
If the point (xp,yp) lies inside the circumcircle then the
three edges of that triangle are added to the edge buffer
and that triangle is removed.
*/
XYZ circle = new XYZ();
for (int j=0;j<ntri;j++)
{
if (complete[j])
continue;
x1 = pxyz[v[j].p1].x;
y1 = pxyz[v[j].p1].y;
x2 = pxyz[v[j].p2].x;
y2 = pxyz[v[j].p2].y;
x3 = pxyz[v[j].p3].x;
y3 = pxyz[v[j].p3].y;
inside = CircumCircle( xp, yp, x1, y1, x2, y2, x3, y3, circle );
xc = circle.x; yc = circle.y; r = circle.z;
if (xc + r < xp) complete[j] = true;
if (inside)
{
/* Check that we haven't exceeded the edge list size */
if (nedge+3 >= emax)
{
emax += 100;
IEDGE[] edges_n = new IEDGE[emax];
for (int ie=0; ie<emax; ie++) edges_n[ie] = new IEDGE();
System.arraycopy(edges, 0, edges_n, 0, edges.length);
edges = edges_n;
}
edges[nedge+0].p1 = v[j].p1;
edges[nedge+0].p2 = v[j].p2;
edges[nedge+1].p1 = v[j].p2;
edges[nedge+1].p2 = v[j].p3;
edges[nedge+2].p1 = v[j].p3;
edges[nedge+2].p2 = v[j].p1;
nedge += 3;
v[j].p1 = v[ntri-1].p1;
v[j].p2 = v[ntri-1].p2;
v[j].p3 = v[ntri-1].p3;
complete[j] = complete[ntri-1];
ntri--;
j--;
}
}
/*
Tag multiple edges
Note: if all triangles are specified anticlockwise then all
interior edges are opposite pointing in direction.
*/
for (int j=0;j<nedge-1;j++)
{
//if ( !(edges[j].p1 < 0 && edges[j].p2 < 0) )
for (int k=j+1;k<nedge;k++)
{
if ((edges[j].p1 == edges[k].p2) && (edges[j].p2 == edges[k].p1))
{
edges[j].p1 = -1;
edges[j].p2 = -1;
edges[k].p1 = -1;
edges[k].p2 = -1;
}
/* Shouldn't need the following, see note above */
if ((edges[j].p1 == edges[k].p1) && (edges[j].p2 == edges[k].p2))
{
edges[j].p1 = -1;
edges[j].p2 = -1;
edges[k].p1 = -1;
edges[k].p2 = -1;
}
}
}
/*
Form new triangles for the current point
Skipping over any tagged edges.
All edges are arranged in clockwise order.
*/
for (int j=0;j<nedge;j++)
{
if (edges[j].p1 == -1 || edges[j].p2 == -1)
continue;
if (ntri >= trimax) return -1;
v[ntri].p1 = edges[j].p1;
v[ntri].p2 = edges[j].p2;
v[ntri].p3 = i;
complete[ntri] = false;
ntri++;
}
}
/*
Remove triangles with supertriangle vertices
These are triangles which have a vertex number greater than nv
*/
for (int i=0;i<ntri;i++)
{
if (v[i].p1 >= nv || v[i].p2 >= nv || v[i].p3 >= nv)
{
v[i] = v[ntri-1];
ntri--;
i--;
}
}
return ntri;
}
public static void main (String[] args)
{
int nv = 20;
if (args.length > 0 && args[0] != null) nv = new Integer(args[0]).intValue();
if (nv <= 0 || nv > 1000) nv = 20;
//System.out.println("Creating " + nv + " random points.");
XYZ[] points = new XYZ[ nv+3 ];
for (int i=0; i<points.length; i++)
points[i] = new XYZ( i*4.0, 400.0 * Math.random(), 0.0 );
ITRIANGLE[] triangles = new
