mesh - 莫比乌斯带有缝! Java3D

Question

我正在用 Java3D 创建莫比乌斯带。我有一条缝，我似乎无法摆脱它!我假设它与法线有关，而且连接边之间的角度差在技术上是 180 度。谁能帮我去掉这个接缝？

这是我的代码:

    public class MobiusStrip extends Applet {
        public static void main(String[] args){
            new MainFrame(new MobiusStrip(), 800, 600);      
        }

        @Override
        public void init(){
            GraphicsConfiguration gc = SimpleUniverse.getPreferredConfiguration();
            Canvas3D canvas = new Canvas3D(gc);
            this.setLayout(new BorderLayout());
            this.add(canvas, BorderLayout.CENTER);
            SimpleUniverse su = new SimpleUniverse(canvas);
            su.getViewingPlatform().setNominalViewingTransform();
            BranchGroup bg = createSceneGraph();
            bg.compile();
            su.addBranchGraph(bg);
        }

        private BranchGroup createSceneGraph(){
            BranchGroup root = new BranchGroup();       
            Shape3D shape = new Shape3D();
            shape.setGeometry(mobius().getIndexedGeometryArray());
            //Scaling transform
            Transform3D tr = new Transform3D();
            tr.setScale(0.5);

            //Spin transform group
            TransformGroup spin = new TransformGroup();
            spin.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
            root.addChild(spin);

            //Set appearance
            Appearance ap = new Appearance();
            PointAttributes pa = new PointAttributes(10, true);
            ap.setPointAttributes(pa);
            ap.setPolygonAttributes(new PolygonAttributes
                    (PolygonAttributes.POLYGON_FILL, 
                    PolygonAttributes.CULL_NONE, 0));

            //Set materials
            Material mat = new Material();
            mat.setLightingEnable(true);
            mat.setShininess(30);
            ap.setMaterial(mat);

            //Overarching Transform group
            TransformGroup tg = new TransformGroup(tr);
            tg.addChild(shape);
            spin.addChild(tg);
            shape.setAppearance(ap);                

            //Set rotation
            Alpha alpha = new Alpha(-1, 6000);
            RotationInterpolator rotate = new RotationInterpolator(alpha, spin);
            BoundingSphere bounds = new BoundingSphere();
            rotate.setSchedulingBounds(bounds);
            spin.addChild(rotate);

            //Set background
            Background background = new Background(1.0f, 1.0f, 1.0f);
            background.setApplicationBounds(bounds);
            root.addChild(background);

            //Set lighting
            AmbientLight light = new AmbientLight(true, new Color3f(Color.BLACK));
            light.setInfluencingBounds(bounds);
            root.addChild(light);

            PointLight ptlight = new PointLight(new Color3f(Color.white),
            new Point3f(0.5f,0.5f,1f),
            new Point3f(1f,0.2f,0f));
            ptlight.setInfluencingBounds(bounds);
            root.addChild(ptlight);

            return root;
        }//Close branchgroup method

        //Create the Mobius shape
        private GeometryInfo mobius()
          {
            int m = 100; //number of row points
            int n = 100; //number of col points
            int p = 4*((m-1)*(n-1)); //faces * points per face

            IndexedQuadArray iqa = new IndexedQuadArray(m*n, 
                          GeometryArray.COORDINATES, p);
            Point3d[] vertices = new Point3d[m*n];
            int index = 0;

            //Create vertices
            for(int i = 0; i < m; i++)
            {
                for(int j = 0; j < n; j++)
                 {
                    double u = i * (2*(Math.PI))/(m - 1);
                    double v = -0.3 + (j * (0.6/(n-1)));
                    double x=(1+v*Math.cos(u/2))*Math.cos(u);
                    double y=(1+v*Math.cos(u/2))*Math.sin(u);
                    double z=v*Math.sin(u/2);
                    vertices[index]=new Point3d(x,y,z);
                    index++;
                }//close nested for loop
             }//close for loop

            iqa.setCoordinates(0, vertices);
            index = 0;

            //set index for coordinates
            for(int i = 0; i < m-1; i++){
                for(int j = 0; j < n-1; j++){
                    iqa.setCoordinateIndex(index, i*m+j);
                    index++;
                    iqa.setCoordinateIndex(index, i*m+j+1);
                    index++;
                    iqa.setCoordinateIndex(index, (i+1)*m+j+1);
                    index++;
                    iqa.setCoordinateIndex(index, (i+1)*m+j);
                    index++;
                }//close nested for loop
            }//close for loop

            //create geometry info and generate normals for shape
            GeometryInfo gi = new GeometryInfo(iqa);
            NormalGenerator ng = new NormalGenerator();
            ng.generateNormals(gi);
            return gi;
        }
    }

Answer 1

参见 this question更多解释。您需要进行两项更改:

ap.setPolygonAttributes(new PolygonAttributes(PolygonAttributes.POLYGON_FILL, PolygonAttributes.CULL_BACK, 0));

double u = i * (4 * (Math.PI)) / (m - 1);