Plane.java

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package eu.mihosoft.vrl.v3d;
 
// # class Plane
import java.util.ArrayList;
import java.util.List;
 
// TODO: Auto-generated Javadoc
public class Plane {
    private static IPolygonDebugger debugger = null;
    private static boolean useDebugger = false;
    public static final double EPSILON =    1.0e-9;
    public static final double EPSILON_Point =  EPSILON;
    public static final double EPSILON_duplicate =  1.0e-4;
    public static final Plane XY_PLANE = new Plane(Vector3d.Z_ONE, 1);
    public static final Plane XZ_PLANE = new Plane(Vector3d.Y_ONE, 1);
    public static final Plane YZ_PLANE = new Plane(Vector3d.X_ONE, 1);
 
    public Vector3d normal;
    public double dist;
 
    public Plane(Vector3d normal, double dist) {
        this.normal = normal.normalized();
        this.dist = dist;
    }
 
    public static Plane createFromPoints(Vector3d a, Vector3d b, Vector3d c) {
        Vector3d n = b.minus(a).cross(c.minus(a)).normalized();
        return new Plane(n, n.dot(a));
    }
 
    /* (non-Javadoc)
     * @see java.lang.Object#clone()
     */
    @Override
    public Plane clone() {
        return new Plane(normal.clone(), dist);
    }
 
    public void flip() {
        normal = normal.negated();
        dist = -dist;
    }
 
    public void splitPolygon(
            Polygon polygon,
            List<Polygon> coplanarFront,
            List<Polygon> coplanarBack,
            List<Polygon> front,
            List<Polygon> back) {
        final int COPLANAR = 0;
        final int FRONT = 1;
        final int BACK = 2;
        final int SPANNING = 3; // == some in the FRONT + some in the BACK
        if(debugger!=null && useDebugger) {
//          debugger.display(polygon);
//          debugger.display(coplanarFront);
//          debugger.display(coplanarBack);
//          debugger.display(front);
//          debugger.display(back);
        }
        // search for the epsilon values of the incoming plane
        double negEpsilon = -Plane.EPSILON;
        double posEpsilon = Plane.EPSILON;
        for (int i = 0; i < polygon.vertices.size(); i++) {
            double t = polygon.plane.normal.dot(polygon.vertices.get(i).pos) - polygon.plane.dist; 
            if(t>posEpsilon) {
                //System.err.println("Non flat polygon, increasing positive epsilon "+t);
                posEpsilon=t+Plane.EPSILON;
            }
            if(t<negEpsilon) {
                //System.err.println("Non flat polygon, decreasing negative epsilon "+t);
                negEpsilon=t-Plane.EPSILON;
            }
        }
        int polygonType = 0;
        List<Integer> types = new ArrayList<>();
        boolean somePointsInfront = false;
        boolean somePointsInBack = false;
        for (int i = 0; i < polygon.vertices.size(); i++) {
            double t = this.normal.dot(polygon.vertices.get(i).pos) - this.dist; 
            int type = (t < negEpsilon) ? BACK : (t > posEpsilon) ? FRONT : COPLANAR;
            //polygonType |= type;
            if(type==BACK)
                somePointsInBack=true;
            if(type==FRONT)
                somePointsInfront = true;
            types.add(type);
        }
        if(somePointsInBack && somePointsInfront)
            polygonType=SPANNING;
        else if(somePointsInBack) {
            polygonType=BACK;
        }else if(somePointsInfront)
            polygonType=FRONT;
 
        //System.out.println("> switching");
        // Put the polygon in the correct list, splitting it when necessary.
        switch (polygonType) {
            case COPLANAR:
                //System.out.println(" -> coplanar");
                (this.normal.dot(polygon.plane.normal) > 0 ? coplanarFront : coplanarBack).add(polygon);
                break;
            case FRONT:
                //System.out.println(" -> front");
                front.add(polygon);
                break;
            case BACK:
                //System.out.println(" -> back");
                back.add(polygon);
                break;
            case SPANNING:
                //System.out.println(" -> spanning");
                List<Vertex> f = new ArrayList<>();
                List<Vertex> b = new ArrayList<>();
                for (int i = 0; i < polygon.vertices.size(); i++) {
                    int j = (i + 1) % polygon.vertices.size();
                    int ti = types.get(i);
                    int tj = types.get(j);
                    Vertex vi = polygon.vertices.get(i);
                    Vertex vj = polygon.vertices.get(j);
                    if (ti != BACK) {
                        f.add(vi);
                    }
                    if (ti != FRONT) {
                        b.add(ti != BACK ? vi.clone() : vi);
                    }
                    if ((ti | tj) == SPANNING) {
                        double t = (this.dist - this.normal.dot(vi.pos))
                                / this.normal.dot(vj.pos.minus(vi.pos));
                        Vertex v = vi.interpolate(vj, t);
                        f.add(v);
                        b.add(v.clone());
                    }
                }
                if (f.size() >= 3) {
                    front.add(new Polygon(f, polygon.getStorage()));
                }else {
                    System.out.println("Front Clip Fault!");
                }
                if (b.size() >= 3) {
                    back.add(new Polygon(b, polygon.getStorage()));
                }else {
                    System.out.println("Back Clip Fault!");
                }
                break;
        }
    }
 
    public static IPolygonDebugger getDebugger() {
        return debugger;
    }
 
    public static void setDebugger(IPolygonDebugger debugger) {
        Plane.debugger = debugger;
    }
 
    public static boolean isUseDebugger() {
        return useDebugger;
    }
 
    public static void setUseDebugger(boolean useDebugger) {
        Plane.useDebugger = useDebugger;
    }
}