
# Getting Started - Wheel Animation

## Foundation of Animation

We will start with a wheel and rotate it about its axle. Remember that in order to have the car the upright we rotated it about the x axis and so the axle is along the y axis of the cylinder.

We need to create a new animation object

```javascript
    const animWheel = new BABYLON.Animation("wheelAnimation", "rotation.y", 30, BABYLON.Animation.ANIMATIONTYPE_FLOAT, BABYLON.Animation.ANIMATIONLOOPMODE_CYCLE);
```
which has the parameters - name, property to animate, animation frames per second, property to animate type, loop mode, in this case repeat animation.

We follow this with the key frame array where we set values for the property to animate by frame number
```javascript
const wheelKeys = []; 

//At the animation key 0, the value of rotation.y is 0
wheelKeys.push({
    frame: 0,
    value: 0
});

//At the animation key 30, (after 1 sec since animation fps = 30) the value of rotation.y is 2PI for a complete rotation
wheelKeys.push({
    frame: 30,
    value: 2 * Math.PI
});
```

Finally we link the key frame array to the animation, the animation to the mesh and begin it.
```javascript
//set the keys
animWheel.setKeys(wheelKeys);

//Link this animation to the right back wheel
wheelRB.animations = [];
wheelRB.animations.push(animWheel);

//Begin animation - object to animate, first frame, last frame and loop if true
scene.beginAnimation(wheelRB, 0, 30, true);
```

<Playground id="#KDPAQ9#14" title="Simple Wheel Animation" description="Simple demonstration of animating one of the car's wheels." image="/img/playgroundsAndNMEs/gettingStartedWheelAnimation1.jpg"/>

Since all the wheels rotate the same we can use the same animation for all.

```javascript
scene.beginAnimation(wheelRF, 0, 30, true);
scene.beginAnimation(wheelLB, 0, 30, true);
scene.beginAnimation(wheelLF, 0, 30, true);
```

To ensure that in later playgrounds new code is not overwhelmed by a large amount of previous coding we will save the car as a model and import and animate it as an item.

```javascript
BABYLON.SceneLoader.ImportMeshAsync("", "url to model car", "car.babylon").then(() =>  {
    const wheelRB = scene.getMeshByName("wheelRB");
    const wheelRF = scene.getMeshByName("wheelRF");
    const wheelLB = scene.getMeshByName("wheelLB");
    const wheelLF = scene.getMeshByName("wheelLF");

    scene.beginAnimation(wheelRB, 0, 30, true);
    scene.beginAnimation(wheelRF, 0, 30, true);
    scene.beginAnimation(wheelLB, 0, 30, true);
    scene.beginAnimation(wheelLF, 0, 30, true);
});
```

<Playground id="#KDPAQ9#15" title="Animating All 4 Wheels" description="Adding the wheel animation to all 4 tires." image="/img/playgroundsAndNMEs/gettingStartedWheelAnimation2.jpg"/>

We can now animate the car itself and add it into the village


# Getting Started - Car Animation

## Animate the Car in the Village

In a similar way to how we animated the wheels we now animate the car to travel a straight line over 5 secs., stop for 2 secs. and then repeat.
```javascript
const animCar = new BABYLON.Animation("carAnimation", "position.x", 30, BABYLON.Animation.ANIMATIONTYPE_FLOAT, BABYLON.Animation.ANIMATIONLOOPMODE_CYCLE);

const carKeys = []; 

carKeys.push({
    frame: 0,
    value: -4
});

carKeys.push({
    frame: 150,
    value: 4
});

carKeys.push({
    frame: 210,
    value: 4
});

animCar.setKeys(carKeys);

car.animations = [];
car.animations.push(animCar);

scene.beginAnimation(car, 0, 210, true);
```

<Playground id="#KDPAQ9#16" title="Animated the Car Forward" description="Simple example of how to animate the car's position forward." image="/img/playgroundsAndNMEs/gettingStartedCarAnimation1.jpg"/>

After adjusting the position of the car and its route so that it travels past the village houses we have 

<Playground id="#KDPAQ9#17" title="Add the Car to the Village" description="Add the animating car back into the village." image="/img/playgroundsAndNMEs/gettingStartedCarAnimation2.jpg"/>

In this case we have built the car. Let's now look at a model character that we can import along with its built-in animation.




# Getting Started - Car Materials

## Car Material

Just as we used different images on different faces of a box something similar is available for extruded polygons and cylinders.

For the car body we use this image

![car](/img/getstarted/car.png)

and this one for the wheels

![wheel](/img/getstarted/wheel.png)

For both the extruded polygon and the cylinder face 0, is the bottom, face 2 the top and face 1 the edge joining the bottom and top. Remember that currently the car body and its wheels are built lying down

The top and bottom of the car body use the image in the top left (almost) quarter. The edge part goes across the bottom, round the front, across the top and down the back of the body uses the lower half of the image.

The bottom of the car body is as you would expect and is given by the bottom left co-ordinates (0, 0.5) to the top right ones (0.38, 1);

```javascript
faceUV[0] = new BABYLON.Vector4(0, 0.5, 0.38, 1);
```

The top of the car body uses the same image but it needs flipping over to fit the other side of the car.
```javascript
faceUV[2] = new BABYLON.Vector4(0.38, 1, 0, 0.5);
```

The edge runs from (0, 0) to (1, 0.5)
```javascript
faceUV[1] = new BABYLON.Vector4(0, 0, 1, 0.5);
```

<Playground id="#KDPAQ9#12" title="Adding Materials To The Car" description="Simple demonstration of adding a material to the extruded car body." image="/img/playgroundsAndNMEs/gettingStartedCarMaterials1.jpg"/>

A wheel is more straight forward because of its symmetry and it uses the whole image for the top and bottom and just picks up a black pixel for the edges.

```javascript
wheelUV[0] = new BABYLON.Vector4(0, 0, 1, 1);
wheelUV[1] = new BABYLON.Vector4(0, 0.5, 0, 0.5);
wheelUV[2] = new BABYLON.Vector4(0, 0, 1, 1);
```
Putting these together and rotating the finished car upright gives

![car model](/img/getstarted/carmodel.png)

<Playground id="#KDPAQ9#13" title="Adding Materials To The Wheels" description="Simple demonstration of adding a material to the extruded wheels." image="/img/playgroundsAndNMEs/gettingStartedCarMaterials2.jpg"/> 

At last we are ready to think about animating the wheels.


# Getting Started - Character Animation

## A Walking Figure
Sometimes the easiest way to add a model to a scene is to obtain one from elsewhere. This could be one you have created in your favorite model building software or one your have purchased.

The *Dude* model is one that has been built with its own skeleton animation.

![dude walking](/img/getstarted/dude.gif)

Once imported the character and its skeleton are obtained from the meshes and skeletons properties of the results object.

```javascript
BABYLON.SceneLoader.ImportMeshAsync("mesh name", "path to model", "model file", scene).then((result) => {
    var dude = result.meshes[0];
    dude.scaling = new BABYLON.Vector3(0.25, 0.25, 0.25);
                
    scene.beginAnimation(result.skeletons[0], 0, 100, true, 1.0);
});
```

<Playground id="#SFW46K#1" title="Loading an Animated Character" description="Simple example of loading an animated character into your scene." image="/img/playgroundsAndNMEs/getingStartedCharacterAnimation.jpg"/>

Currently the character is set in one position and we would like him to walk around the village. This time instead of creating another animation object for the character we will change its position and orientation before each frame is rendered. 


# Getting Started - Mesh Parents

## Parents and Children

We are going to add a very simple car that moves through the village. 

No matter how simple a car needs wheels and we have to combine the body of the car and the wheels. 

![car model](/img/getstarted/carmodel.png)

Using merge meshes to combine them would result in the wheels not being able to rotate. Instead we set the body of the car as a parent of each wheel.

Before building our simple car let's take a way to set a parent and what this means.

```javascript
messhChild.parent = meshParent
```

Any use of position, scaling and rotation on the parent will also be applied to the child. Setting the position of the child is done in the parent space, setting the rotation and scale of the child takes place in the child's local space.

You can vary the values in the following playground to see the effect on the parent and child.

<Playground id="#GMEI6U" title="Understanding Parenting" description="Simple playground to help demonstrate parenting." image="/img/playgroundsAndNMEs/gettingStartedParents.jpg"/>

Now we are ready to build the car and afterwards to animate it.

You can read more about [parenting](/divingDeeper/mesh/transforms/parent_pivot).



# Getting Started - Extruding Polygons

## Building the Car
The car is going to be a very simple one. The body will be built using the *extrudePolygon* method. This is another shape that can be built using *MeshBuilder*. The outline of the shape is drawn in the XZ plane, with points in counter-clockwise order and the extrusion is in the Y direction. The origin for the polygon is the zero point on the bottom plane.

The outline for the car consists of an array of vector3 points forming a horizontal base line, a quarter circle for the front, followed by a horizontal base line. The vertical back with be formed by the *extrudePolygon* method as it automatically joins the first and last point.

```javascript
//base
const outline = [
    new BABYLON.Vector3(-0.3, 0, -0.1),
    new BABYLON.Vector3(0.2, 0, -0.1),
]

//curved front
for (let i = 0; i < 20; i++) {
    outline.push(new BABYLON.Vector3(0.2 * Math.cos(i * Math.PI / 40), 0, 0.2 * Math.sin(i * Math.PI / 40) - 0.1));
}

//top
outline.push(new BABYLON.Vector3(0, 0, 0.1));
outline.push(new BABYLON.Vector3(-0.3, 0, 0.1));
```

These and the depth to extrude along Y, give the shape for the car
```javascript
const car = BABYLON.MeshBuilder.ExtrudePolygon("car", {shape: outline, depth: 0.2});
```

> Note: The *extrudePolygon* and [PolygonMeshBuilder](https://doc.babylonjs.com/divingDeeper/mesh/creation/param/polyMeshBuilder) both use a *earcut* slicing algorithm.  
> The playground has earcut defined but if you are following this tutorial on your own file system that you will need to download the earcut algorithm via [cdn](https://unpkg.com/earcut@latest/dist/earcut.min.js) or [npm](https://github.com/mapbox/earcut#install).  
> If you are using TypeScript then you can inject the earcut algorithm as the *earcutInjection* parameter on the [extudePolygon function](https://doc.babylonjs.com/typedoc/classes/babylon.meshbuilder#extrudepolygon).

<Playground id="#KDPAQ9#10" title="Learning to Extrude" description="Simple demonstration showing the basics of extruding meshes." image="/img/playgroundsAndNMEs/gettingStartedExtrude1.jpg"/>

We form the wheel for the right back position from a cylinder and add it as a child to the car. Then make copies for the right front, left back and left front wheels. This time using *clone* rather than *createInstance* since we can clone a clone. When we clone a wheel its parent is made the parent of the clone.

```javascript
const wheelRB = BABYLON.MeshBuilder.CreateCylinder("wheelRB", {diameter: 0.125, height: 0.05})
wheelRB.parent = car;
wheelRB.position.z = -0.1;
wheelRB.position.x = -0.2;
wheelRB.position.y = 0.035;

const wheelRF = wheelRB.clone("wheelRF");
wheelRF.position.x = 0.1;

const wheelLB = wheelRB.clone("wheelLB");
wheelLB.position.y = -0.2 - 0.035;

const wheelLF = wheelRF.clone("wheelLF");
wheelLF.position.y = -0.2 - 0.035;
```

<Playground id="#KDPAQ9#11" title="Extruding Wheels" description="Expanding on the basics of extruding meshes." image="/img/playgroundsAndNMEs/gettingStartedExtrude2.jpg"/>

Now we will make the car look a bit more like a car using some textures.




# Getting Started - Working With Code

## A Walk Around The Village

There is a useful property of a mesh, *movePOV* which allows us to move a mesh relative to its point of view. Generally a newly created mesh will be considered as facing the negative z direction and this is the direction of its point of view. To move a mesh forward 6 units in the direction of its point of view you use

```javascript
mesh.movePOV(0, 0, 6)
```
The parameters are, in order, distance to move to the right, up and forward, generally these are the negative x axis, the positive y axis and the negative z axis in the mesh's local space.

In Babylon.js you can write code that will be executed before the rendering of the next frame using

```javascript
scene.onBeforeRenderObservable.add(() => {
    //code to execute
});
```

In this way properties of objects can be changed render frame by render frame.

Let us take the simple case of a sphere moving around the edges of a triangle. We want the sphere to appear to slide along one side, turn to slide along the next and then turn and slide along the last side and then repeat.

This is also an opportunity to introduce two types of mesh you can create, a sphere and a series of lines. Take a sphere sliding around an isosceles right angled triangle as an example.

```javascript
const sphere = BABYLON.MeshBuilder.CreateSphere("sphere", {diameter: 0.25});

//end points for the line sequence in an array
//y component can be non zero
const points = [];
points.push(new BABYLON.Vector3(2, 0, 2));
points.push(new BABYLON.Vector3(2, 0, -2));
points.push(new BABYLON.Vector3(-2, 0, -2));
points.push(points[0]); //close the triangle;

BABYLON.MeshBuilder.CreateLines("triangle", {points: points})
```

Also you can see an other method, *rotate*, of rotating. This method rotates the mesh about the given axis by the given angle in radians. It adds to the current rotation.
```javascript
mesh.rotate(axis, angle, BABYLON.Space.LOCAL);
```

To produce the animation before each render frame the sphere will move a distance of 0.05. When the distance it has travelled is greater than 4 the sphere will make a turn, greater than 8 it will turn again and when greater than the perimeter it will reset and start again.

We set up a track array of objects with the properties turn and distance. After travelling the given total distance the sphere will rotate by the given turn value.

```javascript
const slide = function (turn, dist) { //after covering dist apply turn
    this.turn = turn;
    this.dist = dist;
}
const track = [];
track.push(new slide(Math.PI / 2, 4));  //first side length 4
track.push(new slide(3 * Math.PI / 4, 8)); //at finish of second side distance covered is 4 + 4
track.push(new slide(3 * Math.PI / 4, 8 + 4 * Math.sqrt(2))); //all three sides cover the distance 4 + 4 + 4 * sqrt(2)
```

Whenever the required distance is reached a turn is made and the array index pointer, p, is increased by 1. The modulo operator *%* is used to reset the pointer to zero at the end of the array.

```javascript
if (distance > track[p].dist) {        
    sphere.rotate(BABYLON.Axis.Y, track[p].turn, BABYLON.Space.LOCAL);
    p +=1;
    p %= track.length;
}
```

To prevent floating point errors accumulating, whenever the index pointer is reset to 0 the position and rotation of the sphere is also reset

```javascript
if (p === 0) {
    distance = 0;
    sphere.position = new BABYLON.Vector3(2, 0, 2); //reset to initial conditions
    sphere.rotation = BABYLON.Vector3.Zero();//prevents error accumulation 
}
```

<Playground id="#N9IZ8M#1" title="Animating To a Path" description="Simple example of animating an object along a path." image="/img/playgroundsAndNMEs/gettingStartedVillageWalk1.jpg"/>

A little trickier and using a bit of trial and error for the turns and distance we can achieve a more complicated walk for the character around the village. One reason for using degrees and converting them to radians for the *rotate* method is that it is easier to adjust by adding one or two degrees.

Since the character, dude, imported from the *.babylon* file has had its rotation set using a *rotationQuaternion* rather than rotation we use the rotate method to reset the characters orientation.

```javascript
dude.position = new BABYLON.Vector3(-6, 0, 0);
dude.rotate(BABYLON.Axis.Y, BABYLON.Tools.ToRadians(-95), BABYLON.Space.LOCAL);
const startRotation = dude.rotationQuaternion.clone(); //use clone so that variables are independent not linked copies
```

```javascript
if (p === 0) {
    distance = 0;
    dude.position = new BABYLON.Vector3(-6, 0, 0);
    dude.rotationQuaternion = startRotation.clone();
}
```

<Playground id="#KBS9I5#81" title="Character Walking Through Town" description="Animate a character walking through the village." image="/img/playgroundsAndNMEs/gettingStartedVillageWalk2.jpg"/>

We now have two things moving around the village a car and a character. How can we avoid them colliding?


## Animating the Village

Our village is not very lively at the moment so let's add some animation. We are still in the early stages of learning Babylon.js and nowhere near adding a Simms family. The parents and children you are about to be introduced to are the silent type and a way of linking together meshes so that changes to a parent mesh are also applied to their children meshes. We are going to animate a very simple car with wheels that are children to the parent car body. Unlike a real car it is the car body that takes the wheels with it. There is one way that our mesh parents and children behave like a real family, the children can act independently of the parent. Good job too as we do not want the car to rotate with the wheels.

Of course you do not have to build an animation of your own, you can import a ready made one and we will show you the basis of importing an animated character and have it move around the village.

# Getting Started - Web App Layout

## Varying Web App Layout
Whilst you probably want your game or app to take up most of the page you might want some space for instructions as an example. Just place your *&lt;canvas&gt;* element in a *&lt;div&gt;* and arrange the elements as you need.

```html
<div id = "holder">
        <canvas id="renderCanvas" touch-action="none"></canvas> 
</div>
<div id = "instructions">
    <br/>
    <h2>Instructions</h2>
    <br/>
    Instructions Instructions Instructions Instructions Instructions 
    Instructions Instructions Instructions Instructions Instructions 
</div>
```
with additional styles
```html
<style>
    #holder {
        width: 80%;
        height: 100%;
        float: left;
    }

    #instructions {
        width: 20%;
        height: 100%;
        float: left;
        background-color: grey;
    }
</style>
```

[Example App and Instructions](/webpages/app3.html) importing the model village

You could of course still build your scene completely from code

[Example App and Instructions](/webpages/app4.html) building the village from code

During the next stage in developing the world we are going to add movement by animating a very basic car. A car needs wheels that turn independently of the car body. To see how this is achieved we need to look at parenting the wheels to the body.

Getting Started - Chapter 3 - Village Animation

Animating the Village

Coming next

Getting Started - Chapter 3 - Mesh Parents

Learn the basics of parenting objects in your scene.

Getting Started - Chapter 3 - Extruding Polygons

Learn to create your own meshes by extruding mesh faces.

Getting Started - Chapter 3 - Car Materials

Learn to add materials to extruded meshes.

Getting Started - Chapter 3 - Wheel Animation

Learn to the basics of animations in Babylon.js.

Getting Started - Chapter 3 - Car Animation

Continue learning about animations in Babylon.js.

Getting Started - Chapter 3 - Character Animation

Learn to load objects with animation, into your scene.

Getting Started - Chapter 3 - A Walk Around The Village

Learn to move an animating object through your scene.