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Oct 20, 2020

rlottie

Build Status Build status Gitter

rlottie is a platform independent standalone c++ library for rendering vector based animations and art in realtime.

Lottie loads and renders animations and vectors exported in the bodymovin JSON format. Bodymovin JSON can be created and exported from After Effects with bodymovin, Sketch with Lottie Sketch Export, and from Haiku.

For the first time, designers can create and ship beautiful animations without an engineer painstakingly recreating it by hand. Since the animation is backed by JSON they are extremely small in size but can be large in complexity!

Here are small samples of the power of Lottie.

Contents

Building Lottie

rlottie supports meson and cmake build system. rlottie is written in C++14. and has a public header dependency of C++11

Meson Build

install meson and ninja if not already installed.

Run meson to configure rlottie

meson build

Run ninja to build rlottie

ninja -C build

Cmake Build

Install cmake if not already installed

Create a build directory for out of source build

mkdir build

Run cmake command inside build directory to configure rlottie.

cd build
cmake ..

# install in a different path. eg ~/test/usr/lib
cmake -DCMAKE_INSTALL_PREFIX=~/test ..

# static build
cmake -DBUILD_SHARED_LIBS=OFF ..

Run make to build rlottie

make -j 2

To install rlottie library

make install

Test

Configure to build test

meson configure -Dtest=true

Build test suit

ninja

Run test suit

ninja test

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Demo

If you want to see rlottie library in action without building it please visit rlottie online viewer

While building rlottie library it generates a simple lottie to GIF converter which can be used to convert lottie json file to GIF file.

Run Demo

lottie2gif [lottie file name]

Previewing Lottie JSON Files

Please visit rlottie online viewer

rlottie online viewer uses rlottie wasm library to render the resource locally in your browser. To test your JSON resource drag and drop it to the browser window.

Quick Start

Lottie loads and renders animations and vectors exported in the bodymovin JSON format. Bodymovin JSON can be created and exported from After Effects with bodymovin, Sketch with Lottie Sketch Export, and from Haiku.

You can quickly load a Lottie animation with:

auto animation = rlottie::Animation::loadFromFile("absolute_path/test.json");

You can load a lottie animation from raw data with:

auto animation = rlottie::Animation::loadFromData(std::string(rawData), std::string(cacheKey));

Properties like frameRate , totalFrame , duration can be queried with:

# get the frame rate of the resource.
double frameRate = animation->frameRate();

#get total frame that exists in the resource
size_t totalFrame = animation->totalFrame();

#get total animation duration in sec for the resource
double duration = animation->duration();

Render a particular frame in a surface buffer immediately with:

rlottie::Surface surface(buffer, width , height , stride);
animation->renderSync(frameNo, surface);

Render a particular frame in a surface buffer asyncronousely with:

rlottie::Surface surface(buffer, width , height , stride);
# give a render request
std::future<rlottie::Surface> handle = animation->render(frameNo, surface);
...
#when the render data is needed
rlottie::Surface surface = handle.get();

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Dynamic Property

You can update properties dynamically at runtime. This can be used for a variety of purposes such as:

  • Theming (day and night or arbitrary themes).
  • Responding to events such as an error or a success.
  • Animating a single part of an animation in response to an event.
  • Responding to view sizes or other values not known at design time.

Understanding After Effects

To understand how to change animation properties in Lottie, you should first understand how animation properties are stored in Lottie. Animation properties are stored in a data tree that mimics the information hierarchy of After Effects. In After Effects a Composition is a collection of Layers that each have their own timelines. Layer objects have string names, and their contents can be an image, shape layers, fills, strokes, or just about anything that is drawable. Each object in After Effects has a name. Lottie can find these objects and properties by their name using a KeyPath.

Usage

To update a property at runtime, you need 3 things:

  1. KeyPath
  2. rLottie::Property
  3. setValue()

KeyPath

A KeyPath is used to target a specific content or a set of contents that will be updated. A KeyPath is specified by a list of strings that correspond to the hierarchy of After Effects contents in the original animation. KeyPaths can include the specific name of the contents or wildcards:

  • Wildcard *
    • Wildcards match any single content name in its position in the keypath.
  • Globstar **
    • Globstars match zero or more layers.

Properties

rLottie::Property is an enumeration of properties that can be set. They correspond to the animatable value in After Effects and the available properties are listed below.

enum class Property {
    FillColor,     /*!< Color property of Fill object , value type is rlottie::Color */
    FillOpacity,   /*!< Opacity property of Fill object , value type is float [ 0 .. 100] */
    StrokeColor,   /*!< Color property of Stroke object , value type is rlottie::Color */
    StrokeOpacity, /*!< Opacity property of Stroke object , value type is float [ 0 .. 100] */
    StrokeWidth,   /*!< stroke with property of Stroke object , value type is float */
    ...
};

setValue()

setValue() requires a keypath of string and value. The value can be Color, Size and Point structure or a function that returns them. Color, Size, and Point vary depending on the type of rLottie::Property. This value or function(callback) is called and applied to every frame. This value can be set differently for each frame by using the FrameInfo argument passed to the function.

Usage

animation->setValue<rlottie::Property::FillColor>("**",rlottie::Color(0, 1, 0));
animation->setValue<rlottie::Property::FillColor>("Layer1.Box 1.Fill1",
    [](const rlottie::FrameInfo& info) {
         if (info.curFrame() < 15 )
             return rlottie::Color(0, 1, 0);
         else {
             return rlottie::Color(1, 0, 0);
         }
     });

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Supported After Effects Features

Shapes Supported
Shape 👍
Ellipse 👍
Rectangle 👍
Rounded Rectangle 👍
Polystar 👍
Group 👍
Trim Path (individually) 👍
Trim Path (simultaneously) 👍
Renderable Supported
Fill 👍
Stroke 👍
Radial Gradient 👍
Linear Gradient 👍
Gradient Stroke 👍
Transforms Supported
Position 👍
Position (separated X/Y) 👍
Scale 👍
Skew ⛔️
Rotation 👍
Anchor Point 👍
Opacity 👍
Parenting 👍
Auto Orient 👍
Interpolation Supported
Linear Interpolation 👍
Bezier Interpolation 👍
Hold Interpolation 👍
Spatial Bezier Interpolation 👍
Rove Across Time 👍
Masks Supported
Mask Path 👍
Mask Opacity 👍
Add 👍
Subtract 👍
Intersect 👍
Lighten ⛔️
Darken ⛔️
Difference ⛔️
Expansion ⛔️
Feather ⛔️
Mattes Supported
Alpha Matte 👍
Alpha Inverted Matte 👍
Luma Matte 👍
Luma Inverted Matte 👍
Merge Paths Supported
Merge ⛔️
Add ⛔️
Subtract ⛔️
Intersect ⛔️
Exclude Intersection ⛔️
Layer Effects Supported
Fill ⛔️
Stroke ⛔️
Tint ⛔️
Tritone ⛔️
Levels Individual Controls ⛔️
Text Supported
Glyphs ⛔️
Fonts ⛔️
Transform ⛔️
Fill ⛔️
Stroke ⛔️
Tracking ⛔️
Anchor point grouping ⛔️
Text Path ⛔️
Per-character 3D ⛔️
Range selector (Units) ⛔️
Range selector (Based on) ⛔️
Range selector (Amount) ⛔️
Range selector (Shape) ⛔️
Range selector (Ease High) ⛔️
Range selector (Ease Low) ⛔️
Range selector (Randomize order) ⛔️
expression selector ⛔️
Other Supported
Expressions ⛔️
Images 👍
Precomps 👍
Time Stretch 👍
Time remap 👍
Markers 👍

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Issues or Feature Requests?

File github issues for anything that is broken. Be sure to check the list of supported features before submitting. If an animation is not working, please attach the After Effects file to your issue. Debugging without the original can be very difficult. For immidiate assistant or support please reach us in Gitter