How to draw a 3D line in Javafx

Question

I am creating a JavaFx project and would like to be able to draw connecting lines in a 3D model. I see simple shapes offered like cylinder, sphere, and rectangles, but no 3D lines. Is there a simple way to add lines in three dimensions instead of two dimensions in JavaFX without using a 3rd party API?

I came across this answer while researching this issue and you don't need any additional 3rd party APIs. The object passed into the method contains two Point3D objects used for the start and end points of your line. This method creates cylinders and then rotates them to the correct orientation in 3D and is based on trigonometry:

    static public Cylinder createCylinder(Segment segment) {
        // x axis vector is <1,0,0>
        // y axis vector is <0,1,0>
        // z axis vector is <0,0,1>
        // angle = arccos((P*Q)/(|P|*|Q|))
        // define a point representing the Y axis
        Point3D yAxis = new Point3D(0,1,0);
        // define a point based on the difference of our end point from the start point of our segment
        Point3D seg = segment.getEnd().subtract(segment.getStart());
        // determine the length of our line or the height of our cylinder object
        double height = seg.magnitude();
        // get the midpoint of our line segment
        Point3D midpoint = segment.getEnd().midpoint(segment.getStart());
        // set up a translate transform to move to our cylinder to the midpoint
        Translate moveToMidpoint = new Translate(midpoint.getX(), midpoint.getY(), midpoint.getZ());
        // get the axis about which we want to rotate our object
        Point3D axisOfRotation = seg.crossProduct(yAxis);
        // get the angle we want to rotate our cylinder
        double angle = Math.acos(seg.normalize().dotProduct(yAxis));
        // create our rotating transform for our cylinder object
        Rotate rotateAroundCenter = new Rotate(-Math.toDegrees(angle), axisOfRotation);
        // create our cylinder object representing our line
        Cylinder line = new Cylinder(1, height);
        // add our two transfroms to our cylinder object
        line.getTransforms().addAll(moveToMidpoint, rotateAroundCenter);
        // return our cylinder for use      
        return line;
    } // end of the createCylinder method

Answer 1

You can mess around with cylinders and stuff but you're going to be constantly scaling/rotating while adding a lot of nodes to the scene. Fine for small lines with only a few steps but for non-trivial problems you'll hit performance issues. Plus its a pain in the butt.

That's why we implemented a Polyline3D object in Fxyz3D which takes a list of points and wraps one contiguous mesh throughout the point space.

https://github.com/FXyz/FXyz/blob/master/FXyz-Core/src/main/java/org/fxyz3d/shapes/composites/PolyLine3D.java

This results in a single node added to your scene regardless of the number of points.

Example using it here: https://github.com/FXyz/FXyz/blob/master/FXyz-Samples/src/main/java/org/fxyz3d/samples/shapes/compound/PolyLines3D.java