javafx collision issue between path(line) with thick stroke and circle

Question

I am using JavaFx 8 library.

My task is simple: I want to check if circle collides with a path that has a thick stroke around it. The problem is that both functions Path.intersect() and Shape.intersect() ignores the stroke around a path/line.

Path tempPath = new Path(player.getPath().getElements());
//player.getDot() is Circle
if(tempPath.intersects(player.getDot().getBoundsInParent())){
   Shape intersect = Shape.intersect(tempPath, player.getDot());
   if(intersect.getBoundsInLocal().getWidth() != -1){
      System.out.println("Path Collision occurred"); 
   }
}

My path is made out of many LineTo objects. The format is this:

/** Creates path and player dot */
private void createPath() {
    this.path = new Path();
    this.path.setStrokeWidth(20);
    this.path.setStroke(Color.RED);
    this.path.setStrokeLineCap(StrokeLineCap.ROUND);
    this.path.setStrokeLineJoin(StrokeLineJoin.ROUND);

    this.dot = new Circle(10, Color.BLUE);
    this.dot.setOpacity(1);
}

How could I implement a successful collision detection?

score 3 · Accepted Answer · answered Jun 08 '15 at 15:40

The collision detection works just fine:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.shape.Circle;
import javafx.scene.shape.ClosePath;
import javafx.scene.shape.LineTo;
import javafx.scene.shape.MoveTo;
import javafx.scene.shape.Path;
import javafx.scene.shape.Shape;
import javafx.scene.shape.StrokeLineCap;
import javafx.scene.shape.StrokeLineJoin;
import javafx.stage.Stage;

public class Main extends Application {
    @Override
    public void start(Stage primaryStage) {

        BorderPane root = new BorderPane();

        Circle circle = new Circle(100, 100, 30);
        Path path = new Path();

        double x = 144;

        path.getElements().add(new MoveTo(x, 140));
        path.getElements().add(new LineTo(500, 100));
        path.getElements().add(new ClosePath());

        path.setStrokeWidth(60);
        path.setStrokeLineCap(StrokeLineCap.ROUND);
        path.setStrokeLineJoin(StrokeLineJoin.ROUND);

        Shape shape = Shape.intersect(circle, path);

        boolean intersects = shape.getBoundsInLocal().getWidth() != -1;

        System.out.println("Intersects: " + intersects);

        Pane pane = new Pane();
        pane.getChildren().addAll(circle, path);
        root.setCenter(pane);

        Scene scene = new Scene(root, 800, 600);
        primaryStage.setScene(scene);
        primaryStage.show();

    }

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

Switch x = 144 with x = 145 for testing. The console shows whether there's an intersection or not.

The problem you have is that you're comparing different bounds.

See the documentation of Node, section "Bounding Rectangles" about how the various bounds are calculated.

you are right, collision works fine. I found out that my bug was in the duplication of Path object. Path tempPath = new Path(player.getPath().getElements());) The properties of the old path, like Stroke and Color, did not get transferred to the new one. therefore it is needed to reassign properties. — Egidijus Bartušis, Jun 08 '15 at 19:00

javafx collision issue between path(line) with thick stroke and circle

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