Hello, > I'm working on a wood working design and manufacturing software based on > Trimble Sketchup. > What i'm planning currently, is trying to move some board connecting > detection from Sketchup > plugin side ( based on some Sketchup 3D api in ruby ) to server side (in > java, of course). Commons > Geometry is the best 3D lib i can find in java world.
Glad to hear it! Feel free to report any bugs you find or features you feel would be useful on JIRA [1]. Good luck on your project! Regards, Matt J [1] https://issues.apache.org/jira/projects/GEOMETRY On Sat, Sep 17, 2022 at 10:57 PM Bai Song <baisongm...@163.com> wrote: > > Hi, > > > Alex, thanks for your reply, saved me a lot of time! > > > Matt, thanks for your detailed demo of 3D pop down to 2D, this helps me a > lot! I'll do more trial in > > this way. > > > > I'm working on a wood working design and manufacturing software based on > Trimble Sketchup. > > What i'm planning currently, is trying to move some board connecting > detection from Sketchup > > plugin side ( based on some Sketchup 3D api in ruby ) to server side (in > java, of course). Commons > > Geometry is the best 3D lib i can find in java world. > > > > Thanks again for your work! > > > Regards, > Bai Song > > At 2022-09-17 10:58:33, "Matt Juntunen" <matt.a.juntu...@gmail.com> wrote: > >Hello, > > > >Alex is correct in that the intersection operation you are attempting > >to perform will only work in 2D. When you constructed bsp1 and bsp2 > >from the faces, what you ended up with was 2 half spaces of infinite > >size. > > > > List<ConvexPolygon3D> list1 = new ArrayList<>(); > > list1.add(face1); > > RegionBSPTree3D bsp1 = RegionBSPTree3D.from(list1); // this is > >an infinite half space > > > > List<ConvexPolygon3D> list2 = new ArrayList<>(); > > list2.add(face2); > > RegionBSPTree3D bsp2 = RegionBSPTree3D.from(list2); // this is > >also an infinite half-space and is actually identical to the first one > > > >(The reason for this has to do with the way BSP trees represent > >regions. I suggest taking a look at the BSP tree tutorial on the > >commons-geometry site [1].) > > > >The intersection of those two infinite half-spaces is itself an > >infinite half-space. Regions of infinite size do not have a defined > >centroid, which is why the centroid in your example is null. > > > >In order to compute the intersection of the two polygons in your > >example, we have to use 2D space. We can either do the entire thing in > >2D (as Alex demonstrated), or we can start in 3D and pop down to 2D > >when needed. This is the approach that I will show here. We'll start > >with the same 3D convex polygons that you had: > > > > List<Vector3D> pts1 = Arrays.asList( > > Vector3D.of(0, 10, 0), > > Vector3D.of(30, 10, 0), > > Vector3D.of(30, 20, 0), > > Vector3D.of(0, 20, 0)); > > ConvexPolygon3D face1 = Planes.convexPolygonFromVertices(pts1, > >precision); > > > > List<Vector3D> pts2 = Arrays.asList( > > Vector3D.of(10, 0, 0), > > Vector3D.of(20, 0, 0), > > Vector3D.of(20, 30, 0), > > Vector3D.of(10, 30, 0)); > > ConvexPolygon3D face2 = Planes.convexPolygonFromVertices(pts2, > >precision); > > > >Now, in order to perform the 2D intersection, we will first access the > >2D geometries that are embedded in the 3D planes of the > >ConvexPolygon3D instances. You can picture a ConvexPolygon3D (and any > >other PlaneSubset subclass) as a 2D sticker stuck to a pane of glass > >(the infinite 3D plane). In the lines below, we are extracting the 2D > >"sticker" in order to work with it directly. > > > > ConvexArea area1 = face1.getEmbedded().getSubspaceRegion(); > > ConvexArea area2 = face2.getEmbedded().getSubspaceRegion(); > > > >We can now compute the intersection in 2D: > > > > RegionBSPTree2D areaBsp = RegionBSPTree2D.empty(); > > areaBsp.intersection(area1.toTree(), area2.toTree()); > > > >This gives us a finite 2D region with the expected centroid: > > > > Vector2D centroid2d = areaBsp.getCentroid(); > > System.out.println(centroid2d); // prints (15.000000000000002, > >-15.000000000000002) > > > >If we wish to take this 2D centroid back up to 3D, we can again use > >the subspace embedding information from the faces. In this case, we > >only need to use one of the faces: > > > > Vector3D centroid3d = face1.getEmbedded().toSpace(centroid2d); > > System.out.println(centroid3d); // prints (15.000000000000002, > >15.000000000000002, 0.0) > > > >I hope this helps. Thank you for your interest in this project and > >feel free to reach out if you have any more questions. > > > >Regards, > >Matt J > > > >[1] > >https://commons.apache.org/proper/commons-geometry/tutorials/bsp-tree.html > > > >On Fri, Sep 16, 2022 at 6:10 AM Alex Herbert <alex.d.herb...@gmail.com> > >wrote: > >> > >> This may be related to the fact that you are using the 3D API with 2D > >> areas. Since the shapes have no volume the intersection may not be defined. > >> > >> This does work as expected in 2D: > >> > >> Precision.DoubleEquivalence precision = > >> Precision.doubleEquivalenceOfEpsilon(1e-6); > >> > >> List<Vector2D> pts1 = new ArrayList<>(); > >> pts1.add(Vector2D.of(0, 10)); > >> pts1.add(Vector2D.of(30, 10)); > >> pts1.add(Vector2D.of(30, 20)); > >> pts1.add(Vector2D.of(0, 20)); > >> ConvexArea face1 = ConvexArea.convexPolygonFromVertices(pts1, > >> precision); > >> > >> List<Vector2D> pts2 = new ArrayList<>(); > >> pts2.add(Vector2D.of(10, 0)); > >> pts2.add(Vector2D.of(20, 0)); > >> pts2.add(Vector2D.of(20, 30)); > >> pts2.add(Vector2D.of(10, 30)); > >> ConvexArea face2 = ConvexArea.convexPolygonFromVertices(pts2, > >> precision); > >> > >> RegionBSPTree2D bsp1 = RegionBSPTree2D.from(face1.getBoundaries()); > >> > >> RegionBSPTree2D bsp2 = RegionBSPTree2D.from(face2.getBoundaries()); > >> > >> RegionBSPTree2D result = RegionBSPTree2D.empty(); > >> result.intersection(bsp1, bsp2); > >> > >> System.out.println("Hello, Geometry! Centroid: " + > >> result.getCentroid()); > >> > >> Result: > >> > >> Hello, Geometry! Centroid: (15.000000000000002, 15.000000000000002) > >> > >> There may be a setting for the 3D equivalent to allow intersections on the > >> plane to be returned. I could not find anything obvious in the API. > >> > >> Regards, > >> > >> Alex > >> > >> > >> > >> On Fri, 16 Sept 2022 at 10:03, Bai Song <baisongm...@163.com> wrote: > >> > >> > Hi, Geometry Team > >> > > >> > I'm learning this interesting project and facing some difficulties when i > >> > did a little experiment. > >> > > >> > I created two ConvexPolygon3D instances (2 white rectangles in below > >> > image) on the same plane, and try to get the overlaping area(blue part) > >> > by > >> > RegionBSPTree3D intersection operation. > >> > > >> > > >> > But i got null when getting the centroid of the intersection. It looks > >> > that this test of intersection failed. > >> > Could you tell me how can i fix this? > >> > > >> > Thanks for your contribution to this project! > >> > > >> > //---------my test codes---------- > >> > public class TestIntersection > >> > { > >> > public static void main(String args[]) > >> > { > >> > Precision.DoubleEquivalence precision = > >> > Precision.doubleEquivalenceOfEpsilon(1e-6); > >> > > >> > List<Vector3D> pts1 = new ArrayList<>(); > >> > pts1.add(Vector3D.of(0, 10, 0)); > >> > pts1.add(Vector3D.of(30, 10, 0)); > >> > pts1.add(Vector3D.of(30, 20, 0)); > >> > pts1.add(Vector3D.of(0, 20, 0)); > >> > ConvexPolygon3D face1=Planes.convexPolygonFromVertices(pts1, > >> > precision); > >> > > >> > List<Vector3D> pts2 = new ArrayList<>(); > >> > pts2.add(Vector3D.of(10, 0, 0)); > >> > pts2.add(Vector3D.of(20, 0, 0)); > >> > pts2.add(Vector3D.of(20, 30, 0)); > >> > pts2.add(Vector3D.of(10, 30, 0)); > >> > ConvexPolygon3D face2 = Planes.convexPolygonFromVertices(pts2, > >> > precision); > >> > > >> > List<ConvexPolygon3D> list1 = new ArrayList<>(); > >> > list1.add(face1); > >> > RegionBSPTree3D bsp1 = RegionBSPTree3D.from(list1); > >> > > >> > List<ConvexPolygon3D> list2 = new ArrayList<>(); > >> > list2.add(face2); > >> > RegionBSPTree3D bsp2 = RegionBSPTree3D.from(list2); > >> > > >> > RegionBSPTree3D result = RegionBSPTree3D.empty(); > >> > result.intersection(bsp1, bsp2); > >> > > >> > System.out.println("Hello, Geometry! Centroid: > >> > "+result.getCentroid()); //expect (15,15,0), but got null actually > >> > } > >> > } > >> > > >> > > > > >--------------------------------------------------------------------- > >To unsubscribe, e-mail: user-unsubscr...@commons.apache.org > >For additional commands, e-mail: user-h...@commons.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: user-unsubscr...@commons.apache.org For additional commands, e-mail: user-h...@commons.apache.org
