About Quaternion Arc Ball Example

--

Learning Objectives

This openFrameworks example illustrates how to rotate a sphere as an arcball by dragging it, utilizing quaternions.

In the code, pay attention to:

• ofTranslate(ofGetWidth()/2, ofGetHeight()/2, 40); to make 0,0 the center of the screen
• curRot.getRotate(angle,axis) which gets the current rotation
• ofDrawSphere to draw the sphere
• ofRotate which applies the rotation from the quaternion to the viewport
• ofApp::mousePressedto capture the last position of the mouse when pressed
• void ofApp::mouseDragged to capture the mouse drag movement change and apply those changes in terms of rotation to be applied in the draw function

Expected Behavior

When launching this app, you should see

• A white mesh sphere centered in the middle of the screen with a black background

Instructions for use:

• Drag the mouse across the sphere to rotate it.