JavaFX 3D Rotation around Scene Fixed Axes -

creating virtual trackball

using javafx want create virtual trackball device x , y mouse drag events rotate virtual trackball in intuitive way.

intuitive (at least me) means, scene axes being:

• x increasing left right
• y increasing top bottom
• z increasing perpendicular screen towards viewer

i want vertical mouse drag events cause trackball roll around scene x axis, , mouse horizontal drag events cause trackball rotate around scene y axis.

starting oracle javafx smampleapp 3d, have modified things scene comprises fixed axis x:red, y:green, z:blue, camera perspectivecamera trained on axis origin, , trackball (which, cube can watch how behaves when rotated).

• mouse dragged movement in x direction, rotates trackball around trackball's y-axis
• mouse dragged movement in y direction, rotates trackball around trackball's x-axis

first rotate trackball 45 degress around y axis (by dragging mouse horizontally). if drag mouse vertically, trackball rotates it's x axis. however, trackball's x axis has been rotated through 45 degrees previous rotation, , not behaviour want, rotate trackball around fixed x axis (i.e. fixed red axis appears in scene)

this code based on original code from: https://docs.oracle.com/javase/8/javafx/graphics-tutorial/sampleapp3d.htm

the code xform @ https://docs.oracle.com/javase/8/javafx/graphics-tutorial/sampleapp3d-code.htm#cjaggifg

how need change code achieve 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); // 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);     }  } 

if understand question correctly thing have replace line.

xform cameraxform = new xform(rotateorder.zyx); 

this changes rotation order of single rotations , should give need.