README.md

About

Use the Arcball to allow the user to freely rotate the 3D world using a virtual trackball.

This Arcball library was adapted from code by Simon Greenwold for Yale's Model Based Design class, with additional momentum code cribbed from Cinder and GLUI's C++ Arcballs.

Originally distributed on the Processing wiki, somewhat adapted since then to be less "magic" and hopefully more versatile.

For an alternative camera manipulation interface, try peasycam.

Installation

Download or clone the project.

Unzip, rename the folder to arcball and copy it into the libraries folder of your Processing sketch folder, then restart Processing.

Usage

Create an instance of the Arcball class, initialize it in your setup function and apply it in your draw function, either to the camera (if you don't want it to affect your lighting) or directly to the model if you prefer. Apologies for the mysterious sign issues, at some point I will sit down and derive the correct equations for Processing's default camera so that the angle and axis can be applied directly.

    import com.processinghacks.arcball.*;

    Arcball arcball;
    boolean applyToCamera = true;

    void setup() {
      size(640,480,P3D);
      // for a default Arcball
      // centered on width/2, height/2, -min(width/2,height/2)
      // with radius min(width/2,height/2)
      arcball = new Arcball(this);
    }

    void draw() {
      background(100);

      beginCamera();
      camera();
      if (applyToCamera) {
        translate(width/2,height/2);
        PVector axis = arcball.getAxis();
        rotate( arcball.getAngle(), axis.x, axis.y, -axis.z );
        translate(-width/2,-height/2);
      }
      endCamera();

      lights();
      pushMatrix();
      noStroke();
      fill(#ff9900);
      translate(width/2,height/2);
      if (!applyToCamera) {
        PVector axis = arcball.getAxis();
        rotate( -arcball.getAngle(), -axis.x, -axis.y, axis.z );
      }
      box(200.0);
      popMatrix();

      camera();
      noLights();
      fill(255);
      textAlign(LEFT, TOP);
      text(applyToCamera ? "camera" : "model", 10, 10);
    }

    void keyPressed() {
      if (key == ' ') {
        applyToCamera = !applyToCamera;
      }
    }

Bugs / Requests

Please file an issue on github

Enjoy!