本章主要介绍，javaFX 3D库中的PickResult API。

PickResult API 早就在2D的视角相机中就可用了，然而，当用到深度缓存的时候依旧有点限制，PickResult类在javafx。scene。input包

下，它是选择事件的容器。

创建PickResult对象

// Creates a pick result for a 2D case where no additional information
// is needed. Converts the given scene coordinates to the target's local
// coordinate space andstores the value as the intersected point. Sets 
// intersected node to the giventarget, distance to 1.0, face to 
// FACE_UNDEFINED and texCoord to null
PickResult(EventTarget target, double sceneX, double sceneY)

// Creates a new instance of PickResult for a non-3d-shape target. Sets face
// to FACE_UNDEFINED and texCoord to null.
PickResult(Node node, Point3D point, double distance)

// Creates a new instance of PickResult
PickResult(Node node, Point3D point, double distance, int face, 
           Point2D texCoord)

PickResult对象的方法

// Returns the intersected node. Returns null if there was no intersection
// with any node and the scene was picked.
public final Node getIntersectedNode()

// Returns the intersected point in local coordinate of the picked Node. If
// no node was picked, it returns the intersected point with the ion 
// plane.
public final Point3D getIntersectedPoint()

// Returns the intersected distance between camera position and the 
// intersected point
public final double getIntersectedDistance()

// Returns the intersected face of the picked Node, FACE_UNDEFINED if the
//  node doesn't have user-specified faces or was picked on bounds.
public final int getIntersectedFace()
 
// Return the intersected texture coordinates of the picked 3d shape. If the
// picked target is not Shape3D or has pickOnBounds==true, it returns null. 
// Returns new Point2D presenting the intersected TexCoord
public final Point2D getIntersectedTexCoord()

PcikResult的实例

下面的例子展示了PickResult对象和方法得使用。这个实例展示了怎么从PickResult对象中获取信息，当你的鼠标在网格上移动的时候，

鼠标的位置就会显示在上边，

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package com.chu.helloworld;

import javafx.application.Application;
import javafx.application.ConditionalFeature;
import javafx.application.Platform;
import javafx.event.EventHandler;
import javafx.geometry.Point2D;
import javafx.geometry.Point3D;
import javafx.geometry.VPos;
import javafx.scene.Camera;
import javafx.scene.DepthTest;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.PerspectiveCamera;
import javafx.scene.PointLight;
import javafx.scene.Scene;
import javafx.scene.SceneAntialiasing;
import javafx.scene.SubScene;
import javafx.scene.input.KeyEvent;
import javafx.scene.input.MouseEvent;
import javafx.scene.input.PickResult;
import javafx.scene.layout.HBox;
import javafx.scene.paint.Color;
import javafx.scene.paint.PhongMaterial;
import javafx.scene.shape.CullFace;
import javafx.scene.shape.DrawMode;
import javafx.scene.shape.MeshView;
import javafx.scene.shape.Rectangle;
import javafx.scene.shape.Shape3D;
import javafx.scene.shape.TriangleMesh;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.scene.text.TextAlignment;
import javafx.stage.Stage;

/**
 * A Simple Picking Example
 */
public class PickMesh3D extends Application {

    MeshView meshView;
    final static float minX = -10;
    final static float minY = -10;
    final static float maxX = 10;
    final static float maxY = 10;

    static TriangleMesh buildTriangleMesh(int subDivX, int subDivY, float scale) {

        final int pointSize = 3;
        final int texCoordSize = 2;
        // 3 point indices and 3 texCoord indices per triangle
        final int faceSize = 6;
        int numDivX = subDivX + 1;
        int numVerts = (subDivY + 1) * numDivX;
        float points[] = new float[numVerts * pointSize];
        float texCoords[] = new float[numVerts * texCoordSize];
        int faceCount = subDivX * subDivY * 2;
        int faces[] = new int[faceCount * faceSize];

        // Create points and texCoords
        for (int y = 0; y <= subDivY; y++) {
            float dy = (float) y / subDivY;
            double fy = (1 - dy) * minY + dy * maxY;

            for (int x = 0; x <= subDivX; x++) {
                float dx = (float) x / subDivX;
                double fx = (1 - dx) * minX + dx * maxX;

                int index = y * numDivX * pointSize + (x * pointSize);
                points[index] = (float) fx * scale;
                points[index + 1] = (float) fy * scale;
                points[index + 2] = 0.0f;

                index = y * numDivX * texCoordSize + (x * texCoordSize);
                texCoords[index] = dx;
                texCoords[index + 1] = dy;
            }
        }

        // Create faces
        for (int y = 0; y < subDivY; y++) {
            for (int x = 0; x < subDivX; x++) {
                int p00 = y * numDivX + x;
                int p01 = p00 + 1;
                int p10 = p00 + numDivX;
                int p11 = p10 + 1;
                int tc00 = y * numDivX + x;
                int tc01 = tc00 + 1;
                int tc10 = tc00 + numDivX;
                int tc11 = tc10 + 1;

                int index = (y * subDivX * faceSize + (x * faceSize)) * 2;
                faces[index + 0] = p00;
                faces[index + 1] = tc00;
                faces[index + 2] = p10;
                faces[index + 3] = tc10;
                faces[index + 4] = p11;
                faces[index + 5] = tc11;

                index += faceSize;
                faces[index + 0] = p11;
                faces[index + 1] = tc11;
                faces[index + 2] = p01;
                faces[index + 3] = tc01;
                faces[index + 4] = p00;
                faces[index + 5] = tc00;
            }
        }

        TriangleMesh triangleMesh = new TriangleMesh();
        triangleMesh.getPoints().setAll(points);
        triangleMesh.getTexCoords().setAll(texCoords);
        triangleMesh.getFaces().setAll(faces);

        return triangleMesh;
    }
    
    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) {
        if (!Platform.isSupported(ConditionalFeature.SCENE3D)) {
            throw new RuntimeException("*** ERROR: common conditional SCENE3D is not supported");
        }

        stage.setTitle("JavaFX 3D Simple Picking demo");

        final PerspectiveCamera camera = new PerspectiveCamera();

        Node pickResultPanel = createOverlay();

        Group root = new Group();
        root.getChildren().addAll(pickResultPanel, createSubScene(camera));
        Scene scene = new Scene(root, 800, 800);
        scene.setFill(Color.color(0.2, 0.2, 0.2));
        scene.setOnKeyTyped(new EventHandler<KeyEvent>() {
            @Override
            public void handle(KeyEvent e) {
                switch (e.getCharacter()) {
                    case "L":
                        System.err.print("L ");
                        boolean wireframe = meshView.getDrawMode() == DrawMode.LINE;
                        meshView.setDrawMode(wireframe ? DrawMode.FILL : DrawMode.LINE);
                        break;
                }
            }
        });
        stage.setScene(scene);
        stage.show();

        stage.requestFocus();
    }

    private Node createSimpleMesh() {

        TriangleMesh triangleMesh = buildTriangleMesh(2, 2, 30);
        meshView = new MeshView(triangleMesh);
        activateShape(meshView, "Simple Mesh");

        meshView.setDrawMode(DrawMode.FILL);
        meshView.setCullFace(CullFace.NONE);

        PhongMaterial material = new PhongMaterial();
        material.setDiffuseColor(Color.GOLD);
        material.setSpecularColor(Color.rgb(30, 30, 30));
        meshView.setMaterial(material);        
  
        Node group = new Group(meshView);
        group.setTranslateX(550);
        group.setTranslateY(550);

        return group;
    }

    private void activateShape(final Shape3D shape, final String name) {

        shape.setId(name);

        EventHandler<MouseEvent> moveHandler = new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                PickResult res = event.getPickResult();
                setState(res);
                event.consume();
            }
        };

        shape.setOnMouseMoved(moveHandler);
        shape.setOnMouseDragOver(moveHandler);

        shape.setOnMouseEntered(new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                PickResult res = event.getPickResult();
                if (res == null) {
                    System.err.println("Mouse entered has not pickResult");
                }
                setState(res);
            }
        });

        shape.setOnMouseExited(new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                PickResult res = event.getPickResult();
                if (res == null) {
                    System.err.println("Mouse exited has not pickResult");
                }
                setState(res);
                event.consume();
            }
        });
    }

    Text caption, data;
    private Node createOverlay() {
        HBox hBox = new HBox(10);

        caption = new Text("Node:\n\nPoint:\nTexture Coord:\nFace:\nDistance:");
        caption.setFont(Font.font("Times New Roman", 18));
        caption.setTextOrigin(VPos.TOP);
        caption.setTextAlignment(TextAlignment.RIGHT);

        data = new Text("-- None --\n\n\n\n");
        data.setFont(Font.font("Times New Roman", 18));
        data.setTextOrigin(VPos.TOP);
        data.setTextAlignment(TextAlignment.LEFT);

        Rectangle rect = new Rectangle(300, 150, Color.color(0.2, 0.5, 0.3, 0.8));
        hBox.getChildren().addAll(caption, data);
        return new Group(rect, hBox);
    }

    private  SubScene createSubScene(Camera camera) {
        final Node simpleMesh = createSimpleMesh();

        final Group parent = new Group(simpleMesh);
        parent.setTranslateZ(600);
        parent.setTranslateX(-150);
        parent.setTranslateY(-200);
        parent.setScaleX(0.8);
        parent.setScaleY(0.8);
        parent.setScaleZ(0.8);

        final PointLight pointLight = new PointLight(Color.ANTIQUEWHITE);
        pointLight.setTranslateX(100);
        pointLight.setTranslateY(100);
        pointLight.setTranslateZ(-300);

        final Group root = new Group(parent, pointLight, new Group(camera));
        root.setDepthTest(DepthTest.ENABLE);

        final SubScene subScene = new SubScene(root, 800, 800, true, SceneAntialiasing.BALANCED);
        subScene.setCamera(camera);
        subScene.setFill(Color.TRANSPARENT);

        subScene.setId("SubScene");

        return subScene;
    }

 <strong>   final void setState(PickResult result) {
        if (result.getIntersectedNode() == null) {
            data.setText("Scene\n\n"
                    + point3DToString(result.getIntersectedPoint()) + "\n"
                    + point2DToString(result.getIntersectedTexCoord()) + "\n"
                    + result.getIntersectedFace() + "\n"
                    + String.format("%.1f", result.getIntersectedDistance()));
        } else {
            data.setText(result.getIntersectedNode().getId() + "\n"
                    + getCullFace(result.getIntersectedNode()) + "\n"
                    + point3DToString(result.getIntersectedPoint()) + "\n"
                    + point2DToString(result.getIntersectedTexCoord()) + "\n"
                    + result.getIntersectedFace() + "\n"
                    + String.format("%.1f", result.getIntersectedDistance()));
        }
    }</strong>

    private static String point3DToString(Point3D pt) {
        if (pt == null) {
            return "null";
        }
        return String.format("%.1f; %.1f; %.1f", pt.getX(), pt.getY(), pt.getZ());
    }

    private static String point2DToString(Point2D pt) {
        if (pt == null) {
            return "null";
        }
        return String.format("%.2f; %.2f", pt.getX(), pt.getY());
    }

    private static String getCullFace(Node n) {
        if (n instanceof Shape3D) {
            return "(CullFace." + ((Shape3D) n).getCullFace() + ")";
        }
        return "";
    }
}

运行显示如下：