View more

View more

View more

### Image of the Day Submit

IOTD | Top Screenshots

### The latest, straight to your Inbox.

Subscribe to GameDev.net Direct to receive the latest updates and exclusive content.

Sign up now

# delaunay triangulation code

Old topic!

Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.

4 replies to this topic

### #1mike74  Members

Posted 30 August 2005 - 09:14 AM

Hi. I've been experimenting with the Delaunay triangulation code on page 187 of the book Computational Geometry in C (1998 edition), and it doesn't seem to work properly. In particular, it doesn't seem to find all the triangles of the Delaunay triangulation. Here's my code, which is slightly modififed from the book:

double rand01(void)
{
double num = double(rand())/double(RAND_MAX);
return num;
}

void drawdelaun(void)
{
float x[NMAX], y[NMAX], z[NMAX];
int n;
int i, j, k, m;
float xn, yn, zn;
int flag;
glBegin(GL_LINES);

n = 30;
for (int ctr = 0; ctr < n; ctr++)
{
x[ctr] = rand01()*2-1;
y[ctr] = rand01()*2-1;
z[ctr] = x[ctr] * x[ctr] + y[ctr] * y[ctr];
}

for (i = 0; i < n - 2; i++)
for (j = i + 1; j < n; j++)
for (k = i + 1; k < n; k++)
if ( j != k) {
xn = (y[j]-y[i])*(z[k]-z[i]) - (y[k]-y[i])*(z[j]-z[i]);
yn = (x[k]-x[i])*(z[j]-z[i]) - (x[j]-x[i])*(z[k]-z[i]);
zn = (x[j]-x[i])*(y[k]-y[i]) - (x[k]-x[i])*(y[j]-y[i]);

if (flag = (zn < 0))
for (m = 0; m < n; m++)
flag = flag && ((x[m] - x[i])*xn + (y[m] - y[i])*yn +
(z[m] - z[i])*zn <= 0);

if (flag) {
glColor3f(1, 1, 1);
glVertex2f(x[i], y[i]);
glVertex2f(x[j], y[j]);
glVertex2f(x[j], y[j]);
glVertex2f(x[k], y[k]);
glVertex2f(x[k], y[k]);
glVertex2f(x[i], y[i]);
}

}
glEnd();
}

Anyone have any ideas?

Thanks.

mike
http://www.coolgroups.com/

### #2Aph3x  Members

Posted 31 August 2005 - 08:37 AM

Hmm dunno, but here's my code that works:


for (unsigned int i=0; i<mNodeCount-2; i++)
{
for (unsigned int j=i+1; j<mNodeCount-1; j++)
{
for (unsigned int k=j+1; k<mNodeCount; k++)
{
if (!c.CircumCircle(pts[i], pts[j], pts[k]))
{
// Slight Hax0r: move (last) point a bit so not collinear.
LOG("Warning: had to shift collinear network point.");
pts[k] += pts[k]*0.0001f;

if (!c.CircumCircle(pts[i], pts[j], pts[k]))
{
LOG("Error: can't create triangulation!");
return false;
}
}

pointValid = true;
for (unsigned int l=0; l<mNodeCount; l++)
{
if (l != i  &&  l != j  &&  l != k)
{
if (c.IsPointInside(pts[l]))
{
pointValid = false;
break;
}
}
}

if (pointValid)
{
// Add triangle as graph links
Node(i).AddLink(Node(j));
Node(j).AddLink(Node(k));
Node(k).AddLink(Node(i));
}
}
}
}



### #3mike74  Members

Posted 31 August 2005 - 11:02 AM

Interesting. How did you come up with that?

Can you tell me what the object c represents and what the IsPointInside function does?

Thanks.

mike
http://www.coolgroups.com/

### #4Aph3x  Members

Posted 15 September 2005 - 03:23 AM

Whoops sorry, been away for a while...

Code was sort of from here (the java code, not the Guibas-Stolfi stuff).

c is my circle class.
CircumCircle() creates the circle with the 3 given points on its circumference.
IsPointInside returns whether the given point is inside the circle.

If you're working with any sort of geometry, a good circle class can simplify/reduce/encapsulate a lot of work for you!

### #5Gl_Terminator  Members

Posted 16 August 2011 - 12:45 PM

Here is a link for a 2D delaunay triangulation example in C# http://vasilydev.blogspot.com/2011/08/delaunay-triangulation-example-in-c.html

Old topic!

Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.