Intersecting Constraints exception extending path

[ronindev]

Hello!
I'm trying to extend and extrude SVGPath using your great library. But I stuck with some troubles.
Some paths are ok with positive extension values, like extension=1.0, but other works only with negatives, like extension = -1.0.
I've attached 2 tests to show the issue. First test is failing with runtime exception 'Intersecting Constraints', second one is ok. The only one difference is a sign of extension value.
Please can you give me some clarification about it?

import eu.mihosoft.jcsg.ext.path.SVGPath;
import org.junit.Test;

public class tests {

    String path = "m 44.60119,85.333332 c 7.989715,-8.571545 26.84315,-8.29381 29.982173,-21.890636 4.287461,-9.040619 -1.116979,-25.80226 8.789046,-29.988125 19.613851,-3.047385 41.674431,2.373924 54.198871,18.651219 5.47716,6.815747 4.80118,13.009835 -0.17694,22.266232 -5.33515,12.902386 5.65176,30.316308 15.72661,41.123788 9.39009,11.59428 25.61962,17.69247 30.58249,32.65285 1.85847,11.3612 1.14769,23.49796 -2.69912,34.40674 -5.46654,14.84296 -21.89953,20.34395 -36.04556,23.18679 -17.71696,3.46927 -35.63892,6.04663 -53.53514,8.26151 -15.387863,1.04112 -33.096108,0.67095 -44.526702,-11.31777 C 32.693202,187.63749 27.238356,166.86608 22.378749,147.31557 18.594896,130.20764 21.805982,111.29244 33.263521,97.688679 36.711597,93.279609 40.614919,89.25334 44.60119,85.333332 Z";

    @Test(expected = RuntimeException.class)
    public void testFailIntersectingConstraints() {
        // extrude the path
        SVGPath.toCSG(
                path, // svg path
                10.0, //    extrusion height
                0.01, //    step size
                2.0); //    extension
    }

    @Test
    public void testSuccess() {
        // extrude the path
        SVGPath.toCSG(
                path, // svg path
                10.0, //    extrusion height
                0.01, //    step size
                -2.0); //    extension
    }

}

[miho]

Hi, the extension sign depends on the path orientation. In your case -2 will extend the path while +2 will shrink it. Shrinking paths can be tricky since intersections can occur. So either reverse your path or go with negative values to extend your path.

[miho]

In your sample, the extension (-2) looks like this:

[ronindev]

What is right path orientation? How can I detect what I need to reverse path?

[miho]

JCSG provides the method isCCW that can help you with that:

// linearize SVG path
List<Vector3d> linPath = SVGLinearizer.linearizePath(path, 0.01f);
// check orientation
boolean isCCW = Extrude.isCCW(Polygon.fromPoints(linPath));
// determine sign
double sign = isCCW?-1:1;
// compute extension value
double extension = sign*2.0;

Future releases might standardize this process.

[miho]

You can test this behavior by extending both paths, your original path and the reversed path:

String path         = "m 44.60119,85.333332 c 7.989715,-8.571545 26.84315,-8.29381 29.982173,-21.890636 4.287461,-9.040619 -1.116979,-25.80226 8.789046,-29.988125 19.613851,-3.047385 41.674431,2.373924 54.198871,18.651219 5.47716,6.815747 4.80118,13.009835 -0.17694,22.266232 -5.33515,12.902386 5.65176,30.316308 15.72661,41.123788 9.39009,11.59428 25.61962,17.69247 30.58249,32.65285 1.85847,11.3612 1.14769,23.49796 -2.69912,34.40674 -5.46654,14.84296 -21.89953,20.34395 -36.04556,23.18679 -17.71696,3.46927 -35.63892,6.04663 -53.53514,8.26151 -15.387863,1.04112 -33.096108,0.67095 -44.526702,-11.31777 C 32.693202,187.63749 27.238356,166.86608 22.378749,147.31557 18.594896,130.20764 21.805982,111.29244 33.263521,97.688679 36.711597,93.279609 40.614919,89.25334 44.60119,85.333332 Z";

String pathReversed = "M 44.60119,85.333332 C 40.614919,89.25334 36.711597,93.279609 33.263521,97.688679 21.805982,111.29244 18.594896,130.20764 22.378749,147.31557 c 4.859607,19.55051 10.314453,40.32192 24.518169,55.37036 11.430594,11.98872 29.138839,12.35889 44.526702,11.31777 17.89622,-2.21488 35.81818,-4.79224 53.53514,-8.26151 14.14603,-2.84284 30.57902,-8.34383 36.04556,-23.18679 3.84681,-10.90878 4.55759,-23.04554 2.69912,-34.40674 -4.96287,-14.96038 -21.1924,-21.05857 -30.58249,-32.65285 -10.07485,-10.80748 -21.06176,-28.221402 -15.72661,-41.123788 4.97812,-9.256397 5.6541,-15.450485 0.17694,-22.266232 C 125.04684,35.828495 102.98626,30.407186 83.372409,33.454571 73.466384,37.640436 78.870824,54.402077 74.583363,63.442696 71.44434,77.039522 52.590905,76.761787 44.60119,85.333332 Z";

[ronindev]

Thank you very much!

[ronindev]

Can you help me again?
Now I got that exception without extensions, just extrude that path:

M355.506 251.515c-8.888-12.821-21.24-23.226-34.849-30.74 -13.776-7.609-29.784-12.329-45.61-10.509 -12.757 1.467-24.164 7.819-32.752 17.264 -5.176 5.69-8.979 12.034-10.557 19.617 -1.623 7.803-0.817 16.116 2.138 23.5 0.092 0.229 0.753 0.571 0.704 0.116 -0.382-3.526-0.382-7.396 1.862-10.346 1.757-2.311 4.727-3.239 7.451-3.792 6.825-1.384 13.858-0.932 20.549-3.125 6.183-2.026 10.396-6.402 13.429-12.019 2.822-5.227 4.53-11.036 7.839-16.002 1.662-2.495 3.841-4.561 6.603-5.775 3.747-1.647 8.102-1.262 11.995-0.445 -0.038-0.215-0.075-0.429-0.113-0.645 -10.263-0.371-14.339 13.217-13.199 21.448 0.028 0.218 0.487 0.662 0.674 0.344 3.465-5.877 8.443-10.551 15.204-12.176 6.34-1.524 13.065 0.001 19.001 2.353 11.006 4.359 21.379 12.18 29.078 21.147 0.286 0.335 0.84 0.104 0.497-0.296 -8.045-9.372-18.856-17.343-30.39-21.791 -5.867-2.262-12.343-3.428-18.56-2.059 -6.841 1.504-11.998 6.453-15.462 12.333 0.224 0.114 0.449 0.229 0.675 0.344 -1.093-7.898 2.728-21.35 12.686-20.987 0.463 0.016 0.188-0.582-0.114-0.645 -5.967-1.252-12.151-1.045-16.762 3.381 -4.067 3.905-5.984 9.721-8.232 14.744 -2.608 5.831-5.854 11.467-11.664 14.59 -6.442 3.464-14.064 3.337-21.137 4.177 -3.469 0.411-7.177 1.098-9.854 3.512 -3.156 2.845-3.194 7.645-2.772 11.53 0.235 0.039 0.468 0.077 0.703 0.115 -3.985-9.961-3.907-21.425 0.45-31.255 3.756-8.478 11.322-15.92 19.008-20.906 14.106-9.15 31.51-9.637 47.309-5.173 21.144 5.975 41.047 20.254 53.56 38.305C355.108 251.963 355.805 251.945 355.506 251.515L355.506 251.515z

java.lang.RuntimeException: Intersecting Constraints
at eu.mihosoft.jcsg.ext.org.poly2tri.DTSweep.flipEdgeEvent(DTSweep.java:60)

Path is seems be ok, it's opens with visualisation tools correctly. For now I can't determine the core of that issue

[miho]

The error message tells exactly what's wrong with the path. The path contains intersections. For visualization purposes this isn't a problem. But you can't extrude such a path with JCSG. Please check that your path meets this criterion. Maybe you have overlapping versions of the same path etc. which are not visible in the rendered image.

[ronindev]

Ok, I'll check the path, thanks

[ronindev]

Can I ask for your help here another once?
I have a path, extend it for 0.8, extrude, after it I make difference between that figure and extrusion without extension (making hollow with 0.8 walls).
The problem is strange produced polygons:

The sanitizing tool also detects many errors:
Non-manifold edges

Intersect faces

Zero faces

Can I do something to reduce errors in the model?

[miho]

Have you tried https://github.com/miho/JCSG-MeshExtensions ?

[ronindev]

Wow.. I'll check it out, thanks!