kf-player

Keyframe style data replay, used for dynamic eye tracking but can keyframe any data set.

Installation

npm install kf-player

Usage

const player = require('kf-player')();
 
player.data({
    1000: {entity1: [100,200], entity2: true},
    2000: {entity1: [200,300], entity2: false}	
});
 
let state = player.at(1.2);
 
console.log(state.entity1);    // [120,220]
console.log(state.entity2);    // true

Multiple data sets can be given by multiple calls to .data(). Any number of entities can be used, and don't need to be specified for each key frame. Each entity can be of primitive, object or array data types.

By default linear interpolation is performed on numeric values, this can be changed to "none" or a custom function (more to be added...):

player.data({
    entities: {
        entity1: {
            interpolation: function(previous,next,percent) { ... }
        }
    },
    1000: {entity1: [100,200], entity2: true},
    2000: {entity1: [200,300], entity2: false}	
});

Alternative data formats can also be used, for example a format compatible with loading csv or similar data (see csvtojson):

player.data({
    timestamp: "TIME",    // Property name
    data: [
        {TIME: 100, x1: 200, y1: 200, x2: 300, y2: 200},
        {TIME: 200, x1: 240, y1: 320, x2: 300, y2: 210}
    ]
});

API

.at(t)

Get the state of all entities at the time t, where t is in seconds. It returns an object with a property for each entity and where the values for each entity have been appropriately (as specified) interpolated.

.duration()

Return total animation duration in seconds.

console.log(player.duration());    // 5.4

.entities()

Return a list of all entities in the animation.

.frameCount()

Return the number of keyframes.

.begin([time])

Start a new animation sequence. Optional: give a time in seconds to start at.

.end()

Finish an animation.

.frame()

Get the state of the animation at the current frame. The frame to return is calculated from the system clock and animation speed. To get a specific point in the animation, use the .at(t) function.

.speed(s)

Set the speed as a multiplier. eg. 2 runs the animation at 2x natural speed. Using no arguments, this function returns the current speed.