How does 3D picking work in JavaFX 8 - javafx-8

Question

Unfortunately I could not find any good tutorial for picking api.
Can anyone give me a brief tutorial about it or some useful links?
Update
world.setOnMouseClicked((event)->{
PickResult res = event.getPickResult();
System.out.println("res "+res);
//you can get a reference to the clicked node like this
if (res.getIntersectedNode() instanceof Node){
((Node)res.getIntersectedNode()).setTranslateZ(-50);
}
});
The code above only work on the first node that I click.
Does anyone know what is the problem?

Answer 1

It seems to work just fine without much understanding. My guess is it takes the element closest to the camera (ie. in front) in the 2D representation of where you clicked. It doesn't matter which face you click, it always gets the right node.
The code is very simple. I've made a scene with a Parent called world that has 3D elements.
package simple3dboxapp;
import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Parent;
import javafx.scene.PerspectiveCamera;
import javafx.scene.Scene;
import javafx.scene.SubScene;
import javafx.scene.control.Label;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.input.PickResult;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.paint.Material;
import javafx.scene.paint.PhongMaterial;
import javafx.scene.shape.Box;
import javafx.scene.text.Text;
import javafx.scene.transform.Rotate;
import javafx.scene.transform.Translate;
import javafx.stage.Stage;
public class Simple3dBoxApp extends Application {
public Rotate rx = new Rotate();
{ rx.setAxis(Rotate.X_AXIS); }
public Rotate ry = new Rotate();
{ ry.setAxis(Rotate.Y_AXIS); }
public Rotate rz = new Rotate();
{ rz.setAxis(Rotate.Z_AXIS); }
Translate t = new Translate();
private final PerspectiveCamera camera = new PerspectiveCamera(true);
{camera.getTransforms().addAll(t, rz, ry, rx);}
Label data = new Label();{data.setWrapText(true);data.setPrefHeight(200);}
public Parent createContent() {
Group root = new Group();
for(int i = 0; i<10; i++){
Box box = new Box(50, 50, 50);
Text text = new Text("Hi "+i);
ImageView iv = new ImageView("file:apple-touch-icon.png");
Image im = iv.getImage();
Material m = new PhongMaterial(Color.CYAN, im, null, null, null);
box.setMaterial(m);
box.getTransforms().add(new Translate(-250 + i * 50 , -100, -100 + i * 50));
text.getTransforms().add(new Translate(-250 + i * 50 , 0, -100 + i * 50));
iv.getTransforms().add(new Translate(-250 + i * 50 , +100, -100 + i * 50));
root.getChildren().addAll(box,text,iv);
}
camera.setNearClip(1);
camera.setFarClip(2000);
camera.setFieldOfView(100);
// Use a SubScene
SubScene subScene = new SubScene(root, 500,500);
subScene.setFill(Color.ALICEBLUE);
subScene.setCamera(camera);
Group group = new Group();
group.getChildren().add(subScene);
return group;
}
#Override
public void start(Stage stage) {
VBox vbox = new VBox();
Parent world = createContent();
world.setFocusTraversable(true);
vbox.getChildren().addAll(world,data);
Scene scene = new Scene(vbox);
stage.setScene(scene);
stage.show();
world.setOnKeyPressed((evt)->{
switch (evt.getCode()){
case UP:
rx.setAngle(rx.getAngle()+5);
break;
case DOWN:
rx.setAngle(rx.getAngle()-5);
break;
case RIGHT:
t.setX(t.getX()+10);
//camera.setTranslateX(camera.getTranslateX()+10);
break;
case LEFT:
t.setX(t.getX()-10);
//camera.setTranslateX(camera.getTranslateX()-10);
break;
case Z:
double zoom = evt.isShortcutDown()?-10:+10;
t.setZ(t.getZ()+zoom);
//camera.setTranslateZ(camera.getTranslateZ()+zoom);
break;
}
});
world.setOnMouseClicked((event)->{
PickResult res = event.getPickResult();
data.setText("res "+res);
if (res.getIntersectedNode() instanceof Box){
((Box)res.getIntersectedNode()).setMaterial(
new PhongMaterial(event.isShiftDown() ? Color.BLACK : Color.RED));
}
});
}
public static void main(String[] args) {launch(args);}
}
And this is the result from clicking a Box
res PickResult [node = Box#1dc02a4, point = Point3D [x = 12.361420184603276, y = 15.984395060669844, z = -5.0], distance = 1866.0254037844388, texCoord = Point2D [x = 0.6236142018460328, y = 0.8196879012133969]
PickResult javadoc