Assignment - Extrude 2D Shape to 3D Shape and manipulate the Vertices and move around the ground.

Index:
    1. Requirements
    2. How to use
    3. Detailed logic of Implementation

Requirements:
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- [earcut](https://github.com/mapbox/earcut) for polygon triangulation.
- [Babylon.js](https://github.com/BabylonJS/Babylon.js) for 3D rendering and interactions.

1. You need to have node, and npm installed.
2. The zip file i provided contains earcut and babylon.js inside node_modules.
3. If it is not there you can install it by 

    npm install babylonjs
    npm install earcut


Below are the functionalities that is offered:
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1. Creating the Object: 

    To Create an object click on the DRAW button on the screen. Now you will be able to draw some points on the ground.
    After you draw a point a marker/dot will appear on the ground.

    Create some points on the ground.

    After you create some points, hopefully more than 2 points, RIGHT CLICK. After doing RIGHT CLICK the points will get joined
    and you will get a closed shaped polygon.

2. Extruding the Object:

    Now After you have done this the EXTRUDE button will be activated. If you click on the EXTRUDE button, the polygon you drew on the ground
    will get extruded to certain height.

3. Moving the Object:

    First you need to go to MOVE mode. To go to MOVE model click on the MOVE Button.
    To move the object Left click on the extruded object, and drag the object to some place. 

    NOte: YOu will only be able to drag the object inside the ground.

4. Draging the Vertices:

    To go to Vertex Edit mode, Click on the Vertex Edit button. Now you will be able to see the vertices that you can edit are highlighted.
    Now click on some vertex and try to move around.



Detailed logic of Implementation
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1. Draw:

    This is simple. I am picking the point. If the point hits the ground then i am getting its coordinates.
    After picking the coordinates i am making a simple dot in the place of it.

    the dot is made by making a small sphere.

    Now when the user does the right click: 
        I am calling the babylonjs CreatePolygon function to create a polygon with given points.

    After the User clicks i am activating the Extrude Button.

2. Extrude:

    To do the extrude i am calling the babylonjs ExtrudePolygon Function. This function will extrude the shape in the negative of the y axis.
    to make it to the above ground i am giving the height to the extruded polygon, so that it will appear above the ground.

    Also the Extrude will remove the 2D polygon and all the dots/Sphere those were marked previously.
    To remove the meshes i am using the mesh.dispose();

3. Move:

    To move around a object, i am having a starting point, which is the current location of the mesh.
    Now when the mouse is dragged i am getting its position by picking.

    Now whereever i hit with picking i am getting its location. Now i am calculating the delta required to go to that position.
    Now after calculating the delta i am adding that delta to the current position of the mesh.

    Note: i am also marking if the next positon is going beyond the ground or not. If it is going beyond the ground i am restricting it.

4. Vertex edit:

    First i am highlighting the vertices we can edit. These are the vertices which are above the ground.
    So, i am first getting the coordinates of its vertices.

    Now i have also worldtransform matrix. This transform matrix stores what transformations have been gone through on that mesh.
    There can be many transformation because of our MOVE Operation.

    Now for each of the coordinates of the vertices i am applying this transformation to get the current coordinates of the verticds.

    Now i am highlighting the vertices by dots for which the y value is more that 0. This is because i want to highlight the vertices which are above ground.


    Second, when user clicks on the marker which is the sphere/dot, which is above the verices, i am getting the vertices which is close to this sphere.
    This will be obviously the vertex which is below the sphere.

    Now when a user drags the sphere to a certain point, i am updating the sphere position as well as the position of the vertices.
    To update the position of the vertex i am getting the inverse of the worldtransform matrix. And then transforming the location of the new position of the sphere.
    The inversed transformed sphere location is being assigned to the vertex.