#745 – The Basics of Inertia

Inertia is the idea that an object will resist a change in motion.  For touch manipulation in WPF, inertia means that objects can continue moving a little bit after you lift your finger from the screen.

Inertial behavior depends on two things–the initial velocity of the object a specified deceleration value.

The initial velocity is the speed at which the object is moving across the screen when you let go of it.  The deceleration is the rate at which the initial velocity should be decreased, until it eventually reaches zero.  In other words–how quickly does the object slow down?

The deceleration value has units that are DIPs (device independent pixels) per ms^2 (millisecond squared, or “per millisecond per millisecond”).  I.e. DIPs/ms^2.  In other words, if the object’s initial velocity is expressed in DIPs/ms, how much should that velocity decrease every millisecond?


About Sean
Software developer in the Twin Cities area, passionate about software development and sailing.

2 Responses to #745 – The Basics of Inertia

  1. Pingback: Dew Drop – January 30, 2013 (#1,490) | Alvin Ashcraft's Morning Dew

  2. Pingback: #746 – Specifying Inertial Deceleration « 2,000 Things You Should Know About WPF

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