Question

当我在JavaFX中创建我的第一个3D游戏时 - 您可以使用鼠标从零件组装船只。这提出了一个问题，因为JAVAFX似乎没有用于将PerspectiveCamera屏幕2D坐标转换为场景3D空间的原生元素。

以下是我试图实现的目标。鼠标移动的块应在假想的平面上移动，该平面始终相对于摄像机旋转90°： Representation 我试图用三角函数解决问题而没有太大的成功。我没有附加代码段，因为我正在寻找更通用的数学解决方案，但如果需要，我会提供它。

所有帮助将不胜感激！

期望的结果： Before

After

Answer 1

正如@ jdub1581指出的那样，Camera是将鼠标移动与场景中的3D对象绑定的关键。

对于starterts，我们了解公共API PickResult，它允许我们根据从摄像机位置执行的一些光线跟踪技术，使用鼠标选择3D对象。

但是一旦我们有了一个物体，移动它就是一个不同的问题。

寻找这个问题的解决方案（在3D空间中使用2D鼠标移动3D对象）不久前，我在OpenJFX存储库的Toys项目中找到了Camera3D类。

它有一个名为unProjectDirection的承诺方法：

/*
 * returns 3D direction from the Camera position to the mouse
 * in the Scene space 
 */

public Vec3d unProjectDirection(double sceneX, double sceneY, 
                                double sWidth, double sHeight) {
}

由于您要求数学解释，此方法使用您正在寻找的三角学。这将使用私有Vec3d类（我们可以用公共Point3D替换）为您提供基于（x，y）鼠标坐标的3D矢量：

double tanOfHalfFOV = Math.tan(Math.toRadians(camera.getFieldOfView()) * 0.5f);
Vec3d vMouse = new Vec3d(tanOfHalfFOV*(2*sceneX/sWidth-1), tanOfHalfFOV*(2*sceneY/sWidth-sHeight/sWidth), 1);

应用一些进一步的变换来获得场景坐标中的标准化矢量。

下一步将在实际坐标中转换此标准化矢量，仅使用从相机到对象的距离，在拾取结果上给出，并转换对象位置。

基本上，这段代码概述了拖动对象的整个过程：

    scene.setOnMousePressed((MouseEvent me) -> {
        vecIni = unProjectDirection(me.getSceneX(), me.getSceneY(), 
                     scene.getWidth(),scene.getHeight()); 
        distance=me.getPickResult().getIntersectedDistance();           
    });

    scene.setOnMouseDragged((MouseEvent me) -> {
        vecPos = unProjectDirection(mousePosX, mousePosY,
                 scene.getWidth(),scene.getHeight());
        Point3D p=vecPos.subtract(vecIni).multiply(distance);
        node.getTransforms().add(new Translate(p.getX(),p.getY(),p.getZ()));
        vecIni=vecPos;
        distance=me.getPickResult().getIntersectedDistance();
    });

这是一个完整的基本示例：

    public class Drag3DObject extends Application {

    private final Group root = new Group();
    private PerspectiveCamera camera;
    private final double sceneWidth = 800;
    private final double sceneHeight = 600;

    private double mousePosX;
    private double mousePosY;
    private double mouseOldX;
    private double mouseOldY;
    private final Rotate rotateX = new Rotate(-20, Rotate.X_AXIS);
    private final Rotate rotateY = new Rotate(-20, Rotate.Y_AXIS);

    private volatile boolean isPicking=false;
    private Point3D vecIni, vecPos;
    private double distance;
    private Sphere s;

    @Override
    public void start(Stage stage) {
        Box floor = new Box(1500, 10, 1500);
        floor.setMaterial(new PhongMaterial(Color.GRAY));
        floor.setTranslateY(150);
        root.getChildren().add(floor);

        Sphere sphere = new Sphere(150);
        sphere.setMaterial(new PhongMaterial(Color.RED));
        sphere.setTranslateY(-5);
        root.getChildren().add(sphere);

        Scene scene = new Scene(root, sceneWidth, sceneHeight, true, SceneAntialiasing.BALANCED);
        scene.setFill(Color.web("3d3d3d"));

        camera = new PerspectiveCamera(true);
        camera.setVerticalFieldOfView(false);

        camera.setNearClip(0.1);
        camera.setFarClip(100000.0);
        camera.getTransforms().addAll (rotateX, rotateY, new Translate(0, 0, -3000));

        PointLight light = new PointLight(Color.GAINSBORO);
        root.getChildren().add(light);
        root.getChildren().add(new AmbientLight(Color.WHITE));
        scene.setCamera(camera);

        scene.setOnMousePressed((MouseEvent me) -> {
            mousePosX = me.getSceneX();
            mousePosY = me.getSceneY();
            PickResult pr = me.getPickResult();
            if(pr!=null && pr.getIntersectedNode() != null && pr.getIntersectedNode() instanceof Sphere){
                distance=pr.getIntersectedDistance();
                s = (Sphere) pr.getIntersectedNode();
                isPicking=true;
                vecIni = unProjectDirection(mousePosX, mousePosY, scene.getWidth(),scene.getHeight());
            }
        });
        scene.setOnMouseDragged((MouseEvent me) -> {
            mousePosX = me.getSceneX();
            mousePosY = me.getSceneY();
            if(isPicking){
                vecPos = unProjectDirection(mousePosX, mousePosY, scene.getWidth(),scene.getHeight());
                Point3D p=vecPos.subtract(vecIni).multiply(distance);
                s.getTransforms().add(new Translate(p.getX(),p.getY(),p.getZ()));
                vecIni=vecPos;
                PickResult pr = me.getPickResult();
                if(pr!=null && pr.getIntersectedNode() != null && pr.getIntersectedNode()==s){
                    distance=pr.getIntersectedDistance();
                } else {
                    isPicking=false;
                }
            } else {
                rotateX.setAngle(rotateX.getAngle()-(mousePosY - mouseOldY));
                rotateY.setAngle(rotateY.getAngle()+(mousePosX - mouseOldX));
                mouseOldX = mousePosX;
                mouseOldY = mousePosY;
            }
        });
        scene.setOnMouseReleased((MouseEvent me)->{
            if(isPicking){
                isPicking=false;
            }
        });

        stage.setTitle("3D Dragging");
        stage.setScene(scene);
        stage.show();
    }

    /*
     From fx83dfeatures.Camera3D
     http://hg.openjdk.java.net/openjfx/8u-dev/rt/file/5d371a34ddf1/apps/toys/FX8-3DFeatures/src/fx83dfeatures/Camera3D.java
    */
    public Point3D unProjectDirection(double sceneX, double sceneY, double sWidth, double sHeight) {
        double tanHFov = Math.tan(Math.toRadians(camera.getFieldOfView()) * 0.5f);
        Point3D vMouse = new Point3D(tanHFov*(2*sceneX/sWidth-1), tanHFov*(2*sceneY/sWidth-sHeight/sWidth), 1);

        Point3D result = localToSceneDirection(vMouse);
        return result.normalize();
    }

    public Point3D localToScene(Point3D pt) {
        Point3D res = camera.localToParentTransformProperty().get().transform(pt);
        if (camera.getParent() != null) {
            res = camera.getParent().localToSceneTransformProperty().get().transform(res);
        }
        return res;
    }

    public Point3D localToSceneDirection(Point3D dir) {
        Point3D res = localToScene(dir);
        return res.subtract(localToScene(new Point3D(0, 0, 0)));
    }

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

这将允许您在场景中拾取和拖动球体：

dragging 3d

JavaFX在虚拟平面上使用鼠标移动3D对象

1 个答案: