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 4 pieces of data: the vertices (or points), the faces, the normals and the texture coordinates. Normals are just vectors saying which way the face is pointing, and texture coordinates are coordinates to represent how an image is displayed on the surface of a mesh.
For a simple object like a cube, we don’t need 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(Color(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 PySDL2
Trying PySDL2 as a window provider
Using window provider PySDL2
Loaded PyUnity version 0.4.0
>>> 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(Color(255, 0, 0))
>>> scene.Add(cube)
Then, to run our scene, we use scene.Run()
. And now we have
a cube:
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:
Let’s say we want to place an image onto the cube. To do this, we need to change the Material and add a Texture.
>>> renderer.mat = Material(Color(255, 255, 255), Texture2D("python.png"))
Place python.png
in the same folder as your script and run
the code. Here is the image for reference:
And here is the complete code:
from pyunity import *
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(Color(255, 0, 0), Texture2D("python.png"))
scene.Add(cube)
scene.Run()
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.