===============================
Tutorial 2: Rendering in Scenes
===============================

Last tutorial we covered some basic concepts
on GameObjects and Transforms, and this time
we'll be looking at how to render things in
a window.

Scenes
======
A Scene is like a page to draw on: you can
add things, remove things and change things.
To create a scene, you can call
``SceneManager.AddScene``:

   >>> scene = SceneManager.AddScene("Scene")

In your newly created scene, you have 2 GameObjects:
a Main Camera, and a Light. These two things can be
moved around like normal GameObjects.

Next, let's move the camera back 10 units:

   >>> scene.mainCamera.transform.localPosition = Vector3(0, 0, -10)

``scene.mainCamera`` references the Camera Component
on the Main Camera, so we can access the Transform
by using its ``transform`` attribute.

Meshes
======
To render anything, we need a model of it. Let's say
we want to create a cube. Then we need a model of a
cube, or what's called a mesh. Meshes have 3 pieces
of data: the vertices (or points), the faces and the
normals. Normals are just vectors saying which way
the face is pointing.

For this, we don't want to have to create our own
mesh. Fortunately there is a method called
``Mesh.cube`` which creates a cube for us. Here it
is:

   >>> cubeMesh = Mesh.cube(2)

The ``2`` means to create a cube with side lengths of
2. Then, to render this mesh, we need a new Component.

The MeshRenderer
================
The MeshRenderer is a Component that can render a mesh
in the scene. To add a new Component, we can use
a method called ``AddComponent``:

   >>> cube = GameObject("cube")
   >>> renderer = cube.AddComponent(MeshRenderer)

Now we can give our renderer the cube mesh from before.

   >>> renderer.mesh = cubeMesh

Finally, we need a Material to use. To create a Material,
we need to specify a colour in RGB.

   >>> renderer.mat = Material((255, 0, 0))

Here I used a red material. Finally we need to add the cube
to our scene, otherwise we can't see it in the window:

   >>> scene.Add(cube)

The full code:

   >>> from pyunity import *
   Loaded config
   Trying GLFW as a window provider
   GLFW doesn't work, trying Pygame
   Trying Pygame as a window provider
   Using window provider Pygame
   Loaded PyUnity version 0.3.1
   >>> scene = SceneManager.AddScene("Scene")
   >>> scene.mainCamera.transform.localPosition = Vector3(0, 0, -10)
   >>> cubeMesh = Mesh.cube(2)
   >>> cube = GameObject("Cube")
   >>> renderer = cube.AddComponent(MeshRenderer)
   >>> renderer.mesh = cubeMesh
   >>> renderer.mat = Material((255, 0, 0))
   >>> scene.Add(cube)

Then, to run our scene, we use ``scene.Run()``. And now we have
a cube:

.. image:: _static/cube.png

To see it better, let's move the camera up a bit and tilt it
downwards. Replace the third line with this:

   >>> scene.mainCamera.transform.localPosition = Vector3(0, 3, -10)
   >>> scene.mainCamera.transform.localEulerAngles = Vector3(15, 0, 0)

Now we can see it better:

.. image:: _static/cube2.png

Debugging
=========
If you want to see what you've done already, then you can use
a number of debugging methods. The first is to call `scene.List()`:

   >>> scene.List()
   /Main Camera
   /Light
   /Cube

This lists all the Gameobjects in the scene. Then, let's check
the cube's components:

   >>> cube.components
   [<Transform position=Vector3(0, 0, 0) rotation=Quaternion(1, 0, 0, 0) scale=Vector3(1, 1, 1) path="/Cube">, <pyunity.core.MeshRenderer object at 0x0B170CA0>]

Finally, let's check the Main Camera's transform.

   >>> scene.mainCamera.transform
   <Transform position=Vector3(0, 3, -10) rotation=Quaternion(0.9914448613738104, 0.13052619222005157, 0.0, 0.0) scale=Vector3(1, 1, 1) path="/Main Camera">

Next tutorial, we'll be covering scripts and Behaviours.