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https://github.com/mjakeman/zig-animate

Animation, interpolation, and sequencing library for zig.
https://github.com/mjakeman/zig-animate

animation animation-library interpolation zig zig-library

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Animation, interpolation, and sequencing library for zig.

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README 

        
# zig-animate

A property animation library in Zig.



## Demo 1: Property Interpolation

Full demo code in [`animator.zig`](src/animator.zig).



```zig

const start = Vec2{ .x = 0, .y = 0 };

const end = Vec2{ .x = 1, .y = 1 };



const anim = Animator(Vec2).init(start, end, EaseInCubicVec2);



// 2D Cubic Easing

try std.testing.expectEqual(Vec2{ .x = 0.015625, .y = 0.015625 }, anim.eval(0.25));

try std.testing.expectEqual(Vec2{ .x = 0.125, .y = 0.125 }, anim.eval(0.5));

try std.testing.expectEqual(Vec2{ .x = 0.421875, .y = 0.421875 }, anim.eval(0.75));

try std.testing.expectEqual(Vec2{ .x = 1, .y = 1 }, anim.eval(1));

```



## Demo 2: Sequencing

Full demo code in [`sequencer.zig`](src/sequencer.zig).



We can animate a complex object:

```zig

const TestObject = struct {

    value: f32,

    other_value: Vec2,



    const Self = @This();



    fn update(self: *Self, value: f32) void { ... }

    fn update_other(self: *Self, other_value: Vec2) void { ... }

}

```



Sequencing multiple property animations:

```zig

var testObj: TestObject = undefined;

testObj.value = 30;

testObj.other_value = Vec2{ .x = 10, .y = 10 };



// Go from 30 to 50 over 80 frames

const valueAnim = animator.Animator(f32).init(30, 50, curves.EaseInCubic);

const valueEvent = Event.create_transition(TestObject, f32, &testObj, &valueAnim, 80, TestObject.update);



// Go from (10, 10) to (6, 4) over 65 frames

const otherValueAnim = animator.Animator(Vec2).init(Vec2{ .x = 10, .y = 10 }, Vec2{ .x = 6, .y = 4 }, EaseInCubicVec2);

const otherValueEvent = Event.create_transition(TestObject, Vec2, &testObj, &otherValueAnim, 65, TestObject.update_other);



// Create a sequencer

var sequencer = Sequencer.init(TestAllocator);

sequencer.add_event(0, valueEvent);

sequencer.add_event(0, otherValueEvent);



// Move the sequencer forward

sequencer.tick(10);



// Check the values

const expectedVal = curves.EaseInCubic(30, 50, 10.0 / 80.0);

try std.testing.expectEqual(expectedVal, testObj.value);



const expectedVector = EaseInCubicVec2(Vec2{ .x = 10, .y = 10 }, Vec2{ .x = 6, .y = 4 }, 10.0 / 65.0);

try std.testing.expectEqual(expectedVector, testObj.other_value);

```



## Key Concepts

The three files in this library are:

 * `animator.zig`: Contains Animators, which are objects that animate over a given property. You have one animator per property, so a location/rotation/scale animation might have `locationAnim: Animator(Vec3)`, `rotationAnim: Animator(Quat)`, `scaleAnim: Animator(Vec3)` (respectively).

 * `sequencer.zig`: Allows for Actions (one-off event) and Transitions (ongoing event) to be scheduled and run. You have one sequencer per project/module/grouping of animations.

 * `curves.zig`: A collection of interpolation functions for f32. See the `animator.zig` class for an easy example of how to create higher dimension interpolation functions (e.g. for Vector2/3/4/etc).



## Examples

In each source file, there are fully-commented tests demonstrating some key patterns.



For example, see [sequencer.zig](/src/sequencer.zig).



## Building

Standard Zig library:

```

zig build

zig build test --summary all

```



## About

This repo is a mirror of the in-tree animation library from my personal game engine project. As such, this library is actively (albeit infrequently) maintained.



### Contributions

Contributions are welcome, although keep in mind the library scope is intentionally small.



### Licence

MIT Licensed - do what you want!