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KurtCob
01-25-2001, 11:12 AM
Hi people,

I have a model that is scanned in slices, and in each slice I Have two edges, how can I detect the point where these edges are ?

Thank you
Best regards
Kurt

Ps.: I can send a picture.

chennes
01-25-2001, 12:50 PM
I'm a bit confused by what you mean by "edge". Are you talking about an area with a high color gradient?

Chris

KurtCob
01-25-2001, 01:40 PM
No, Itīs like a corner ... you know ? I have a cloud of points, and I want to know the corners.

Thank you
Best regards
Kurt

Rob
01-25-2001, 01:52 PM
I'm still not at all clear what you're trying to do? Something like a convex hull of the point cloud?

Osku
01-25-2001, 07:51 PM
Hello

Calculate the delta between two adjacent points and if it is big enough then it is a corner. If you have "noise" in the points try using the delta between a point and another point maybe 5 points away...

Pseudo code :

for(x=0;x<n-1;x++)
{
if (abs(p(x)-p(x+1))>delta)
return x;
}

KurtCob
01-26-2001, 05:01 AM
Hello guys,

Rob.: I could send you some picture, do you want ?

Osku.: Could you be more clear, I don't understand what you explain.

Thank you for the moment
Best regards
Kurt

chennes
01-26-2001, 06:03 AM
Wait... you have a 3D set of points in space that define some shape, and you want the outer perimeter of the shape? Like a 3D version of a convex hull algorithm?

If you get a minute, send me a picture while you're at it - I'm currently doing a lot of work with models that are input in planes as well.

Chris

Rob
01-26-2001, 10:19 AM
Sure, you can send me a picture and I'll try to take a look at it.
rblanding@hotmail.com

Osku
01-26-2001, 02:24 PM
As I understand you have a collection of points that is like a graph? Please send a picture and maybe I can help you.

Osku

chennes
01-27-2001, 11:13 AM
If you have the points ordered sequentially this is fairly easy... loop through all the points and get the slopes of each pair of adjacent points. If the slope differs by a large enough amount, then you have found your corner.

If they're not ordered sequentially, sort them first.

Chris