The app features a flashlight toggle. When aiming the flashlight of the mobile device at the retroreflectors, the light bounces back to the camera sensor. The retroreflective material is modulated by an LCD shutter (placed on top of it). The shutter can be activated by a low potential difference (~1 to 4 Volts), which is generated by human interaction or environmental changes like heat and pressure.
Check out the other version of this app, which performs real-time analysis by plotting light intensities in real-time for high framerate applications: https://github.com/jacobsayono/lightintensityapp
Note: Light intensity thresholds may need better adjustments to prevent tracking bright backgrounds.
Here's a better example (all environments have different lighting conditions):
TODO: create small UI to control the thresholds manually on the app.
Orientation sensing (collaboration with Texas A&M University who uses this app to test their composable 3D printed reflective filaments):
Some personal notes:
lightintensityapp video demo (from https://github.com/jacobsayono/lightintensityapp):
