JavaFX 3D Rotation around Scene Fixed Axes - javafx

Question

Creating a Virtual Trackball
Using JavaFX I want to create a virtual trackball device where X and Y mouse drag events rotate my virtual trackball in an intuitive way.
Intuitive (at least to me) means, with my scene axes being:
X increasing left to right
Y increasing top to bottom
Z increasing perpendicular to the screen towards the viewer
I want vertical mouse drag events to cause the trackball to roll around the
scene X axis, and mouse horizontal drag events to cause the trackball to
rotate around the scene Y axis.
Starting with the Oracle JavaFX SmampleApp 3D, I have modified things so my scene
comprises a fixed axis x:red, y:green, z:blue, a camera a PerspectiveCamera
trained on the axis origin, and my trackball (which, for now is a cube so we
can watch how it behaves when rotated).
Mouse dragged movement in the X direction, rotates the
trackball around the trackball's y-axis
Mouse dragged movement
in the Y direction, rotates the trackball around the
trackball's x-axis
First I Rotate the trackball 45 degress around the Y axis (by dragging the
mouse horizontally). Then if I drag the mouse vertically, the trackball
rotates about it's X axis. However, the trackball's X axis has now been
rotated through 45 degrees by the previous rotation, and I do not get the behaviour that I want, which is to rotate the trackball around the fixed X axis (i.e. the fixed red axis as it appears in my scene)
This code is based on original code from:
https://docs.oracle.com/javase/8/javafx/graphics-tutorial/sampleapp3d.htm
The code for XForm is at https://docs.oracle.com/javase/8/javafx/graphics-tutorial/sampleapp3d-code.htm#CJAGGIFG
How do I need to change my code to achieve my aims?
package moleculesampleapp;
import javafx.application.Application;
import javafx.scene.*;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javafx.scene.paint.PhongMaterial;
import javafx.scene.shape.Box;
import javafx.scene.shape.Shape3D;
public class MoleculeSampleApp1 extends Application {
Group root = new Group();
Xform axisXForm = new Xform();
Xform boxXForm = new Xform();
Xform worldXForm = new Xform();
Xform cameraXform = new Xform();
PhongMaterial redMaterial,greenMaterial,blueMaterial;
PerspectiveCamera camera = new PerspectiveCamera(true);
private static double CAMERA_INITIAL_DISTANCE = -450;
private static double CAMERA_INITIAL_X_ANGLE = -10.0;
private static double CAMERA_INITIAL_Y_ANGLE = 0.0;
private static double CAMERA_NEAR_CLIP = 0.1;
private static double CAMERA_FAR_CLIP = 10000.0;
private static double AXIS_LENGTH = 250.0;
private static double MOUSE_SPEED = 0.1;
private static double ROTATION_SPEED = 2.0;
double mousePosX, mousePosY;
double mouseOldX, mouseOldY;
double mouseDeltaX, mouseDeltaY;
private void handleMouse(Scene scene) {
scene.setOnMousePressed(me -> {
mousePosX = me.getSceneX();
mousePosY = me.getSceneY();
mouseOldX = me.getSceneX();
mouseOldY = me.getSceneY();
});
scene.setOnMouseDragged(me -> {
mouseOldX = mousePosX;
mouseOldY = mousePosY;
mousePosX = me.getSceneX();
mousePosY = me.getSceneY();
mouseDeltaX = (mousePosX - mouseOldX);
mouseDeltaY = (mousePosY - mouseOldY);
if (me.isPrimaryButtonDown()) {
boxXForm.ry.setAngle(boxXForm.ry.getAngle() - mouseDeltaX * MOUSE_SPEED * ROTATION_SPEED); // left right
boxXForm.rx.setAngle(boxXForm.rx.getAngle() + mouseDeltaY * MOUSE_SPEED * ROTATION_SPEED); // up down
}
});
}
private void handleKeyboard(Scene scene) {
scene.setOnKeyPressed(event -> {
switch (event.getCode()) {
case Z:
camera.setTranslateZ(CAMERA_INITIAL_DISTANCE);
cameraXform.ry.setAngle(CAMERA_INITIAL_Y_ANGLE);
cameraXform.rx.setAngle(CAMERA_INITIAL_X_ANGLE);
boxXForm.reset();
break;
}
});
}
PhongMaterial createMaterial(Color diffuseColor, Color specularColor) {
PhongMaterial material = new PhongMaterial(diffuseColor);
material.setSpecularColor(specularColor);
return material;
}
#Override
public void start(Stage primaryStage) {
root.getChildren().add(worldXForm);
root.setDepthTest(DepthTest.ENABLE);
// Create materials
redMaterial = createMaterial(Color.DARKRED,Color.RED);
greenMaterial = createMaterial(Color.DARKGREEN,Color.GREEN);
blueMaterial = createMaterial(Color.DARKBLUE,Color.BLUE);
// Build Camera
root.getChildren().add(camera);
cameraXform.getChildren().add(camera);
camera.setNearClip(CAMERA_NEAR_CLIP);
camera.setFarClip(CAMERA_FAR_CLIP);
camera.setTranslateZ(CAMERA_INITIAL_DISTANCE);
cameraXform.ry.setAngle(CAMERA_INITIAL_Y_ANGLE);
cameraXform.rx.setAngle(CAMERA_INITIAL_X_ANGLE);
// Build Axes
Box xAxis = new Box(AXIS_LENGTH, 1, 1);
Box yAxis = new Box(1, AXIS_LENGTH, 1);
Box zAxis = new Box(1, 1, AXIS_LENGTH);
xAxis.setMaterial(redMaterial);
yAxis.setMaterial(greenMaterial);
zAxis.setMaterial(blueMaterial);
axisXForm.getChildren().addAll(xAxis, yAxis, zAxis);
worldXForm.getChildren().addAll(axisXForm);
// Build shiney red box
Shape3D box = new Box(80, 80, 80);
box.setMaterial(redMaterial);
boxXForm.getChildren().add(box);
worldXForm.getChildren().addAll(boxXForm);
Scene scene = new Scene(root, 1024, 768, true);
scene.setFill(Color.GREY);
handleKeyboard(scene);
handleMouse(scene);
primaryStage.setTitle("Molecule Sample Application");
primaryStage.setScene(scene);
primaryStage.show();
scene.setCamera(camera);
}
public static void main(String[] args) {
launch(args);
}
}

Answer 1

Thanks to bronkowitz in this post here: JavaFX 3D rotations for leading me towards this solution!
package moleculesampleapp;
import javafx.application.Application;
import javafx.geometry.Point3D;
import javafx.scene.*;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javafx.scene.paint.PhongMaterial;
import javafx.scene.shape.Box;
import javafx.scene.shape.DrawMode;
import javafx.scene.shape.Shape3D;
import javafx.scene.shape.Sphere;
import javafx.scene.transform.Affine;
import javafx.scene.transform.Rotate;
public class MoleculeSampleApp1 extends Application {
Group root = new Group();
XformBox cameraXform = new XformBox();
XformBox ballXForm = new XformBox();
Shape3D ball;
PhongMaterial redMaterial, greenMaterial, blueMaterial;
PerspectiveCamera camera = new PerspectiveCamera(true);
private static double CAMERA_INITIAL_DISTANCE = -450;
private static double CAMERA_INITIAL_X_ANGLE = -10.0;
private static double CAMERA_INITIAL_Y_ANGLE = 0.0;
private static double CAMERA_NEAR_CLIP = 0.1;
private static double CAMERA_FAR_CLIP = 10000.0;
private static double AXIS_LENGTH = 250.0;
private static double MOUSE_SPEED = 0.1;
private static double ROTATION_SPEED = 2.0;
double mouseStartPosX, mouseStartPosY;
double mousePosX, mousePosY;
double mouseOldX, mouseOldY;
double mouseDeltaX, mouseDeltaY;
private void handleMouse(Scene scene) {
System.out.printf("handleMouse%n");
scene.setOnMousePressed(me -> {
mouseStartPosX = me.getSceneX();
mouseStartPosY = me.getSceneY();
mousePosX = me.getSceneX();
mousePosY = me.getSceneY();
mouseOldX = me.getSceneX();
mouseOldY = me.getSceneY();
});
scene.setOnMouseDragged(me -> {
mouseOldX = mousePosX;
mouseOldY = mousePosY;
mousePosX = me.getSceneX();
mousePosY = me.getSceneY();
mouseDeltaX = (mousePosX - mouseOldX);
mouseDeltaY = (mousePosY - mouseOldY);
if (me.isPrimaryButtonDown()) {
ballXForm.addRotation(-mouseDeltaX * MOUSE_SPEED * ROTATION_SPEED, Rotate.Y_AXIS);
ballXForm.addRotation(mouseDeltaY * MOUSE_SPEED * ROTATION_SPEED, Rotate.X_AXIS);
}
});
}
private void handleKeyboard(Scene scene) {
scene.setOnKeyPressed(event -> ballXForm.reset());
}
PhongMaterial createMaterial(Color diffuseColor, Color specularColor) {
PhongMaterial material = new PhongMaterial(diffuseColor);
material.setSpecularColor(specularColor);
return material;
}
#Override
public void start(Stage primaryStage) {
System.out.printf("start%n");
root.setDepthTest(DepthTest.ENABLE);
// Create materials
redMaterial = createMaterial(Color.DARKRED, Color.RED);
greenMaterial = createMaterial(Color.DARKGREEN, Color.GREEN);
blueMaterial = createMaterial(Color.DARKBLUE, Color.BLUE);
// Build Camera
root.getChildren().add(camera);
cameraXform.getChildren().add(camera);
camera.setNearClip(CAMERA_NEAR_CLIP);
camera.setFarClip(CAMERA_FAR_CLIP);
camera.setTranslateZ(CAMERA_INITIAL_DISTANCE);
camera.setTranslateZ(CAMERA_INITIAL_DISTANCE);
cameraXform.addRotation(CAMERA_INITIAL_X_ANGLE, Rotate.X_AXIS);
cameraXform.addRotation(CAMERA_INITIAL_Y_ANGLE, Rotate.Y_AXIS);
// Build Axes
Box xAxis = new Box(AXIS_LENGTH, 1, 1);
Box yAxis = new Box(1, AXIS_LENGTH, 1);
Box zAxis = new Box(1, 1, AXIS_LENGTH);
xAxis.setMaterial(redMaterial);
yAxis.setMaterial(greenMaterial);
zAxis.setMaterial(blueMaterial);
root.getChildren().addAll(xAxis, yAxis, zAxis);
// Build shiney red ball
ball = new Sphere(50);
ball.setDrawMode(DrawMode.LINE); // draw mesh so we can watch how it rotates
ballXForm.getChildren().add(ball);
root.getChildren().addAll(ballXForm);
Scene scene = new Scene(root, 1024, 768, true);
scene.setFill(Color.GREY);
handleKeyboard(scene);
handleMouse(scene);
primaryStage.setTitle("TrackBall");
primaryStage.setScene(scene);
primaryStage.show();
scene.setCamera(camera);
}
public static void main(String[] args) {
launch(args);
}
}
class XformBox extends Group {
XformBox() {
super();
getTransforms().add(new Affine());
}
/**
* Accumulate rotation about specified axis
*
* #param angle
* #param axis
*/
public void addRotation(double angle, Point3D axis) {
Rotate r = new Rotate(angle, axis);
/**
* This is the important bit and thanks to bronkowitz in this post
* https://stackoverflow.com/questions/31382634/javafx-3d-rotations for
* getting me to the solution that the rotations need accumulated in
* this way
*/
getTransforms().set(0, r.createConcatenation(getTransforms().get(0)));
}
/**
* Reset transform to identity transform
*/
public void reset() {
getTransforms().set(0, new Affine());
}
}

Answer 2

If I understand your question correctly the only thing you have to do is to replace this line.
Xform cameraXform = new Xform(RotateOrder.ZYX);
This changes the rotation order of the single rotations and should give you what you need.