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--- wiki:motionscope_app2 [2022/05/18 13:48]
vizycam [Capturing non-parallel motion (homography to the rescue!)]
+++ wiki:motionscope_app2 [2022/05/18 15:52] (current)
vizycam [MotionScope]
@@ Line 8: / Line 8: @@
 {{wiki:motionscope3.mp4|816x540|loop,autoplay}}
+Check out the above video on [[https://youtu.be/z8bPvyXYJOw|YouTube]].
 ======Quickstart======
@@ Line 193: / Line 195: @@
 These controls are fairly self-explanatory -- adjusting the controls changes the perspective of the live camera view.  The ''Shear'' controls are used less often, which is why they aren't normally displayed.
-Back to the "ball falling from a building" example, or in our case, ball falling from a parking garage: Vizy is pointed up at an angle to capture the motion of the ball as it falls.  Vizy is tilted 90 degrees to capture more of the vertical motion.
+Back to the "ball falling from a building" example, or in our case, ball falling from a parking garage: Vizy is pointed up at an angle to capture the motion of the ball as it falls.  Vizy is rotated 90 degrees to capture more of the vertical motion -- check out the picture of Vizy below (Vizy is on its side looking up).  Note also, it's hooked up to a [[wiki:powering_vizy#powering-vizy-through-the-usb-c-connector|portable charger for power]].
 {{wiki:image_908.jpg?360}}
 {{wiki:image_906.jpg?350}}
-We can adjust the perspective controls during analysis within the ''Analyze'' tab.  Note, how the sides of the parking garage become parallel -- it's as if we're looking at the plane of motion head-on instead of up at an angle.  Note also that we enable the ''Show grid'' overlay so we can line things up more easily (vertical lines should be parallel with respect to each other and the y axis.)
+We can adjust the perspective controls during analysis within the ''Analyze'' tab.  Note, how the sides of the parking garage stairwell become parallel -- it's as if we're looking at the plane of motion head-on instead of up at an angle.  Note also that we enable the ''Show grid'' overlay so we can line things up more easily (vertical lines should be parallel with respect to each other and the y axis.)
 {{wiki:perspective3.mp4|800x450|loop,autoplay}}
-Before we adjust the perspective the ''x velocity'' graph is curved, but after the perspective is corrected, the ''y velocity'' graph becomes a straight line, which is what you'd expect from an object experiencing constant acceleration.  (Not to confuse things, but the ''x velocity'' graph becomes the ''y velocity graph'' after we rotate (roll) the perspective 90 degrees.)
+Before we adjust the perspective the ''x velocity'' graph is curved, but after the perspective is corrected, the ''y velocity'' graph becomes a straight line, which is what you'd expect from an object experiencing constant acceleration.  (Not to confuse things, but the ''x velocity'' graph essentially becomes the ''y velocity'' graph after we rotate (roll) the perspective 90 degrees, hoo boy, this was supposed to be a simple example...)
 {{wiki:image_922.jpg?350}}
@@ Line 209: / Line 211: @@
 By changing the camera perspective in this way, we are able to accurately measure the acceleration of the ball at close to 9.8 m/s<sup>2</sup>
-, although given the nature of acceleration (a derivative of a derivative) we need to average over lots of measurements to reduce the measurement noise -- below, we adjusted the ''Spacing'' so that we averaged over all measurement points to get the overall average acceleration.
+, although given the nature of acceleration (a double time-derivative of position) we need to average over lots of measurements to reduce the noise introduced by differentiation -- below, we adjusted the ''Spacing'' so that we averaged over all measurement points to get the overall average acceleration.
 {{wiki:image_923.jpg?350}}

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