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weighted straight skeleton java implementation

License: Apache License 2.0

Java 100.00%

geometry-library geometry2d java offsets

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is it possible to use it for curved objects?

hi twak,

get results like the ones here:
https://doc.cgal.org/latest/Surface_mesh_skeletonization/index.html

is it possible to represent a curved line of ae shape with vertices close to each other?

thanks!

Everything's fine

Hello,

thanks a lot once again for sharing your implementation.
(just to shows that it is running smoothly on linux)

It seems that you have chosen to avoid "split events" by reducing the length of the median when it crosses an edge. I like the approach.

I've worked on a c++ implementation of straight skeletons, but I had logical issues when solving the intersections. I guess you solved it in your code :)
I'll let you know as soon I'm starting to work again on my code.

All the best,

francois z.

Polygons with holes

yes it works with holes, they have to defined as a separate loop in a backwards direction

I'm following this but I'm unable to get it to behave with holes. I've tried every combination of exterior & interior coordinates directions. Examples:

No hole

Exterior loop CCW, interior loop (hole) CW

Exterior loop CCW, interior loop CCW

Exterior loop CW, interior loop CCW

Exterior loop CW, interior loop CW

Code

Polygon polygon;
Machine speed = new Machine(1); // every edge same speed
Skeleton skeleton;
LoopL<org.twak.camp.Edge> loopL = new LoopL<>(); // list of loops
ArrayList<Corner> corners = new ArrayList<>();
Loop<org.twak.camp.Edge> loop = new Loop<>();

LinearRing exterior = polygon.getExteriorRing();
if (!Orientation.isCCW(exterior.getCoordinates())) {
	exterior = exterior.reverse(); // exterior should be CCW
}

Coordinate[] coords = exterior.getCoordinates();
for (int j = 0; j < coords.length - 1; j++) {
	double a = coords[j].x;
	double b = coords[j].y;
	corners.add(new Corner(a, b));
}
for (int j = 0; j < corners.size() - 1; j++) {
	org.twak.camp.Edge edge = new org.twak.camp.Edge(corners.get(j),
			corners.get((j + 1) % (corners.size() - 1)));
	edge.machine = speed;
	loop.append(edge);
}
loopL.add(loop);

for (int i = 0; i < polygon.getNumInteriorRing(); i++) {
	corners = new ArrayList<>();
	LinearRing hole = polygon.getInteriorRingN(i);
	if (Orientation.isCCW(hole.getCoordinates())) {
		hole = hole.reverse(); // holes should be clockwise
	}
	for (int j = 0; j < hole.getNumPoints() - 1; j++) {
		corners.add(new Corner(hole.getCoordinates()[j].x, hole.getCoordinates()[j].y));
	}
	loop = new Loop<>();
	for (int j = 0; j < corners.size() - 1; j++) {
		org.twak.camp.Edge edge = new org.twak.camp.Edge(corners.get(j),
				corners.get((j + 1) % (corners.size() - 1)));
		edge.machine = speed;
		loop.append(edge);
	}
	loopL.add(loop);
}

How to build a roof like this in a reasonable way?

I want to build roof like

each edge will produce two Face result since there are two different angle section.
how can i generate it using apis in a reasonable way?

Blog Image is missing

http://twak.blogspot.com/2009/05/engineering-weighted-straight-skeleton.html this blog image is missing.(can not find your email so using issue instead)

Jitpack build issue with jutils dependency

I recently had a few projects that rely on camp-skeleton (master branch) fail to build.
After looking into it, I've found it's an issue on jitpack with the current master version of jutils.

campskeleton has a dependency on jutils version master-SNAPSHOT; this label currently points to master-198bbef5f6-1, and this is currently giving problems:

Go to https://jitpack.io/com/github/twak/jutils/master-198bbef5f6-1/ and we see the error:

File not found. Build ok

Hacking: missing twak utils

Missing twak utils in hacking branch.
Thank you

Could not resolve dependecies on maven install.

If I run mvn install I get these message:

The following artifacts could not be resolved:
org.twak.utils:utils:jar:0.0.1-SNAPSHOT,
org.twak.campskeleton:campskeleton:jar:0.0.1-SNAPSHOT

I wonder, because in the past it worked for me.
This happens with other projects like siteplan or chordatlas.

All other dependencies are fetched with maven correctly.

(edges: purple; bones: black; branches: pink)

shrink needs a stopgap too

Hi,
Your OffsetSkeleton code appears to be broken. Running the attached file 
with the current source earns me a ClassCastException.

Exception in thread "main" java.lang.ClassCastException: 
straightskeleton.Edge cannot be cast to straightskeleton.Corner
     at straightskeleton.CornerClone.<init>(CornerClone.java:67)
     at straightskeleton.OffsetSkeleton.<init>(OffsetSkeleton.java:49)
     at straightskeleton.OffsetSkeleton.shrink(OffsetSkeleton.java:249)
     at main.Main.main(Main.java:33)

Looking through debug, I found that LoopL<Corner> input was actually a 
LoopL<Edge>, which was odd. I'd say that ought to be checked somehow but 
I know fuck all about generics. However if you look at 
OffsetSkeleton.shrink you'll notice the LoopL<Edge> in is indeed being 
passed into CornerClone as though it were a LoopL<Corner>.

In your regular Skeleton I noticed the SetupForEdges method and comment, 
and rightly guessed that shrink needed a stopgap as well. A copy/paste 
of that method's body into shrink fixed it for me, and it's now running 
properly.

Just thought you should know. This is the only robust Java 
implementation of inset shapes I've found on the whole internet, and I 
hate installing CGAL/Boost for little things like this.

-Nick Parker

Original issue reported on code.google.com by [email protected] on 4 Dec 2014 at 1:53

Attachments:

Main.java