About QuaternionLatLong Example

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Learning Objectives

This openFrameworks example utilizes quaternions to plot latitude and longitude onto a sphere.

In the code, pay attention to:

• cities which is a Vector to hold City objects for the data to plot onto the sphere
• ofTranslate(ofGetWidth()/2, ofGetHeight()/2, 40); to make 0,0 the center of the screen
• ofRotate(ofGetFrameNum(), 0, 1, 0); to spin at the rate of 1 degree per frame
• ofDrawSphere to draw the sphere
• latRot.makeRotate(cities[i].latitude, 1, 0, 0); to create a quaternion which will perform a rotation of an angle
• longRot.makeRotate(cities[i].longitude, 0, 1, 0); to create a quaternion which will perform a rotation of an angle
• spinQuat.makeRotate(ofGetFrameNum(), 0, 1, 0); to create another quaternion to ensure it spins on the y axis
• glm::vec3 worldPoint = latRot * longRot * spinQuat * center; to generate the point to map the city by multiplying all of the quaternions and then multipying the center vector to apply the rotation to the center vector

Expected Behavior

When launching this app, you should see

• A white mesh sphere centered in the middle of the screen with a black background
• The sphere will have the cities latitude and longitude mapped and labeled on the sphere
• The sphere will be constantly rotating