Comprehensive Guide to Babylon.js Game Engine, Animation System

Animation System

Babylon.js provides a powerful animation system that enables smooth transitions and movements for all scene objects. From simple property changes to complex character animations, the framework offers comprehensive tools for bringing your 3D world to life.

Basic Animation

Create animations by defining keyframes for any object property:

// Create a box to animate
const box = BABYLON.MeshBuilder.CreateBox("box", {size: 1}, scene);

// Create an animation for position
const animation = new BABYLON.Animation(
    "positionAnimation",   // Name
    "position.y",          // Property to animate
    30,                     // Frames per second
    BABYLON.Animation.ANIMATIONTYPE_FLOAT, // Type of value
    BABYLON.Animation.ANIMATIONLOOPMODE_CYCLE // Loop mode
);

// Define keyframes
const keyFrames = [];
keyFrames.push({ frame: 0, value: 0 });     // Start at y=0
keyFrames.push({ frame: 30, value: 3 });    // Move to y=3 at frame 30
keyFrames.push({ frame: 60, value: 0 });    // Back to y=0 at frame 60

// Assign keyframes to animation
animation.setKeys(keyFrames);

// Attach animation to the box
box.animations = [animation];

// Start the animation
scene.beginAnimation(box, 0, 60, true); // true = loop

Easing Functions

Add natural motion with easing functions:

// Create an easing function
const easingFunction = new BABYLON.CircleEase();
easingFunction.setEasingMode(BABYLON.EasingFunction.EASINGMODE_EASEINOUT);

// Apply to animation
animation.setEasingFunction(easingFunction);

Available easing types: BABYLON.BackEase, BABYLON.BounceEase, BABYLON.CircleEase, BABYLON.CubicEase, BABYLON.ElasticEase, BABYLON.ExponentialEase, BABYLON.PowerEase, BABYLON.QuadraticEase, BABYLON.QuarticEase, BABYLON.QuinticEase, BABYLON.SineEase

Animation Blending

Smoothly transition between animations:

// Create a second animation
const animation2 = new BABYLON.Animation(
    "scaleAnimation",
    "scaling",
    30,
    BABYLON.Animation.ANIMATIONTYPE_VECTOR3,
    BABYLON.Animation.ANIMATIONLOOPMODE_CYCLE
);

// Define keyframes for scaling
const scaleKeyFrames = [];
scaleKeyFrames.push({ frame: 0, value: new BABYLON.Vector3(1, 1, 1) });
scaleKeyFrames.push({ frame: 30, value: new BABYLON.Vector3(2, 0.5, 2) });
scaleKeyFrames.push({ frame: 60, value: new BABYLON.Vector3(1, 1, 1) });
animation2.setKeys(scaleKeyFrames);

// Start with position animation
const animatable = scene.beginAnimation(box, 0, 60, true);

// Later, blend to scale animation
setTimeout(() => {
    box.animations = [animation2];
    scene.beginAnimation(box, 0, 60, true, 1.0); // 1.0 = blend speed
}, 3000);

Animation Groups

Synchronize multiple animations:

// Create an animation group
const animationGroup = new BABYLON.AnimationGroup("myGroup");

// Add animations to the group
animationGroup.addTargetedAnimation(animation, box);

Adding Multiple Animations

// Create and add rotation animation
const rotationAnimation = new BABYLON.Animation(
    "rotationAnimation",
    "rotation.y",
    30,
    BABYLON.Animation.ANIMATIONTYPE_FLOAT,
    BABYLON.Animation.ANIMATIONLOOPMODE_CYCLE
);

const rotationKeys = [];
rotationKeys.push({ frame: 0, value: 0 });
rotationKeys.push({ frame: 60, value: Math.PI * 2 });
rotationAnimation.setKeys(rotationKeys);

animationGroup.addTargetedAnimation(rotationAnimation, box);

Animation Group Control

// Control the animation group
animationGroup.play(true); // true = loop
// animationGroup.pause();
// animationGroup.stop();
// animationGroup.reset();

// Adjust speed
animationGroup.speedRatio = 0.5; // Half speed

// Animation group events
animationGroup.onAnimationEndObservable.add(() => {
    console.log("Animation group completed");
});

Skeletal Animation

Work with rigged character animations:

// Import a rigged model
BABYLON.SceneLoader.ImportMesh("", "models/", "character.glb", scene, (meshes, particleSystems, skeletons, animationGroups) => {
    const character = meshes[0];
    const skeleton = skeletons[0];
    
    // Play an animation by name
    const idleAnim = animationGroups.find(a => a.name === "Idle");
    const walkAnim = animationGroups.find(a => a.name === "Walking");
    const runAnim = animationGroups.find(a => a.name === "Running");
    
    if (idleAnim) idleAnim.play(true);

Animation Switching

Switch between animations with blending:

    // Later, switch animations with blending
    document.getElementById("walk").addEventListener("click", () => {
        idleAnim.stop();
        walkAnim.play(true);
        walkAnim.speedRatio = 1.0;
    });
    
    document.getElementById("run").addEventListener("click", () => {
        walkAnim.stop();
        runAnim.play(true);
        runAnim.speedRatio = 1.5;
    });

Bone Manipulation

Access skeleton bones for fine control:

    // Access skeleton bones for fine control
    const rightArm = skeleton.bones.find(b => b.name === "RightArm");
    if (rightArm) {
        // Override bone rotation
        rightArm.rotation.z += Math.PI / 8;
    }
});

Morph Targets

Animate between different mesh shapes:

// Import a model with morph targets
BABYLON.SceneLoader.ImportMesh("", "models/", "face.glb", scene, (meshes) => {
    const face = meshes[0];
    
    // Access morph targets
    const morphTargetManager = face.morphTargetManager;
    
    if (morphTargetManager) {
        // Get specific morph targets
        const smileTarget = morphTargetManager.getTarget(0);
        const frownTarget = morphTargetManager.getTarget(1);
        const blinkTarget = morphTargetManager.getTarget(2);

Animating Morph Targets

        // Animate morph target influences
        let time = 0;
        scene.onBeforeRenderObservable.add(() => {
            time += scene.getEngine().getDeltaTime() / 1000;
            
            // Smile-frown cycle
            smileTarget.influence = Math.sin(time * 0.5) * 0.5 + 0.5;
            frownTarget.influence = Math.sin(time * 0.5 + Math.PI) * 0.5 + 0.5;
            
            // Occasional blink
            blinkTarget.influence = Math.pow(Math.sin(time * 3), 16);
        });
    }
});

Animation Events

Trigger events at specific points in animations:

// Create an animation with events
const jumpAnimation = new BABYLON.Animation(
    "jumpAnimation",
    "position.y",
    60,
    BABYLON.Animation.ANIMATIONTYPE_FLOAT,
    BABYLON.Animation.ANIMATIONLOOPMODE_CYCLE
);

const jumpKeys = [];
jumpKeys.push({ frame: 0, value: 0 });
jumpKeys.push({ frame: 30, value: 5 });
jumpKeys.push({ frame: 60, value: 0 });
jumpAnimation.setKeys(jumpKeys);

Adding Animation Events

// Add events at specific frames
jumpAnimation.addEvent(new BABYLON.AnimationEvent(
    10, // Frame number
    function() { 
        // Event callback
        console.log("Starting to jump"); 
        // Play sound
        const jumpSound = new BABYLON.Sound("jump", "sounds/jump.mp3", scene);
        jumpSound.play();
    }
));

jumpAnimation.addEvent(new BABYLON.AnimationEvent(
    50, // Frame number
    function() { 
        console.log("Landing"); 
        // Play landing sound
        const landSound = new BABYLON.Sound("land", "sounds/land.mp3", scene);
        landSound.play();
    }
));

// Apply and play
box.animations = [jumpAnimation];
scene.beginAnimation(box, 0, 60, true);

Procedural Animation

Create animations directly in code:

// Animate in the render loop
let time = 0;
scene.onBeforeRenderObservable.add(() => {
    time += scene.getEngine().getDeltaTime() / 1000;
    
    // Circular motion
    sphere.position.x = Math.cos(time) * 5;
    sphere.position.z = Math.sin(time) * 5;
    
    // Bobbing motion
    sphere.position.y = 2 + Math.sin(time * 2) * 0.5;
    
    // Continuous rotation
    box.rotation.y += 0.01;
    box.rotation.x = Math.sin(time) * 0.2;
});

Babylon.js 7 Animation Improvements

Babylon.js 7 includes enhanced animation capabilities:

Animation Curve Editor

// Animation curve editor integration
const curveEditor = new BABYLON.AnimationCurveEditor();
curveEditor.addAnimation(animation);

Animation State Machine

// Animation state machine
const stateMachine = new BABYLON.AnimationStateMachine("characterStates", scene);

// Define states
const idleState = new BABYLON.AnimationState("idle", idleAnim);
const walkState = new BABYLON.AnimationState("walk", walkAnim);
const runState = new BABYLON.AnimationState("run", runAnim);

// Add states to state machine
stateMachine.addState(idleState);
stateMachine.addState(walkState);
stateMachine.addState(runState);

State Transitions

// Define transitions between states
stateMachine.addTransition(idleState, walkState, "startWalking");
stateMachine.addTransition(walkState, runState, "startRunning");
stateMachine.addTransition(runState, walkState, "slowDown");
stateMachine.addTransition(walkState, idleState, "stop");

// Start with idle state
stateMachine.setCurrentState("idle");

// Later, trigger transitions
document.getElementById("walkButton").addEventListener("click", () => {
    stateMachine.trigger("startWalking");
});

document.getElementById("runButton").addEventListener("click", () => {
    stateMachine.trigger("startRunning");
});