Merge branch 'release-candidate' into stable
tree: 2072f16b25b034326bf5178471715ca817e1178d
  1. examples/
  2. src/
  3. tests/
  4. .clang-format
  5. .codecov.yml
  6. .gitignore
  7. .kokoro
  8. .travis.yml
  10. BUILD
  14. MotionInterchange.podspec
  15. Podfile
  16. Podfile.lock

Motion Interchange

A standard format for representing motion specifications in Objective-C and Swift.

Build Status codecov CocoaPods Compatible Platform Docs


Installation with CocoaPods

CocoaPods is a dependency manager for Objective-C and Swift libraries. CocoaPods automates the process of using third-party libraries in your projects. See the Getting Started guide for more information. You can install it with the following command:

gem install cocoapods

Add MotionInterchange to your Podfile:

pod 'MotionInterchange'

Then run the following command:

pod install


Import the framework:

@import MotionInterchange;

You will now have access to all of the APIs.

Example apps/unit tests

Check out a local copy of the repo to access the Catalog application by running the following commands:

git clone
cd motion-interchange-objc
pod install
open MotionInterchange.xcworkspace


  1. Architecture
  2. How to define a cubic bezier animation
  3. How to define a spring animation
  4. How to define a motion spec


This library defines a format for representing motion in Objective-C and Swift applications. The primary data type, MotionTiming, allows you to describe the duration, delay, timing curve, and repetition for an animation.

How to define a cubic bezier animation

In Objective-C:

MDMMotionTiming timing = (MDMMotionTiming){
  .delay = 0.150,
  .duration = 0.225,
  .curve = _MDMBezier(0.4f, 0.0f, 0.2f, 1.0f)

How to define a spring animation

In Objective-C:

MDMMotionTiming timing = (MDMMotionTiming){
  .curve = _MDMSpring(1, 100, 10)

How to define a motion spec

Motion timing structs can be used to represent complex multi-element and multi-property motion specifications. An example of a common complex motion spec is a transition which has both an expansion and a collapse variant. If we wanted to represent such a transition we might create a set of structures like this:

struct MDCMaskedTransitionMotionTiming {
  MDMMotionTiming contentFade;
  MDMMotionTiming floodBackgroundColor;
  MDMMotionTiming maskTransformation;
  MDMMotionTiming horizontalMovement;
  MDMMotionTiming verticalMovement;
  MDMMotionTiming scrimFade;
typedef struct MDCMaskedTransitionMotionTiming MDCMaskedTransitionMotionTiming;

struct MDCMaskedTransitionMotionSpec {
  MDCMaskedTransitionMotionTiming expansion;
  MDCMaskedTransitionMotionTiming collapse;
  BOOL shouldSlideWhenCollapsed;
  BOOL isCentered;
typedef struct MDCMaskedTransitionMotionSpec MDCMaskedTransitionMotionSpec;

We can then implement a spec like so:

#define MDMEightyForty _MDMBezier(0.4f, 0.0f, 0.2f, 1.0f)
#define MDMFortyOut _MDMBezier(0.4f, 0.0f, 1.0f, 1.0f)

struct MDCMaskedTransitionMotionSpec fullscreen = {
  .expansion = {
    .contentFade = {
      .delay = 0.150, .duration = 0.225, .curve = MDMEightyForty,
    .floodBackgroundColor = {
      .delay = 0.000, .duration = 0.075, .curve = MDMEightyForty,
    .maskTransformation = {
      .delay = 0.000, .duration = 0.105, .curve = MDMFortyOut,
    .horizontalMovement = {.curve = { .type = MDMMotionCurveTypeInstant }},
    .verticalMovement = {
      .delay = 0.045, .duration = 0.330, .curve = MDMEightyForty,
    .scrimFade = {
      .delay = 0.000, .duration = 0.150, .curve = MDMEightyForty,
  .shouldSlideWhenCollapsed = true,
  .isCentered = false

We can then use this motion spec to implement our animations in a transition like so:

MDCMaskedTransitionMotionTiming timing = isExpanding ? fullscreen.expansion : fullscreen.collapse;

// Can now use timing's properties to associate animations with views.


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Licensed under the Apache 2.0 license. See LICENSE for details.