How to create a simple 3D scene

In this tutorial we will go throught the example example_7_cameraSystem.py where we will build a scene with two cubes and a camera.

The final result looks like this:

../../../_images/cubesExample.png

Create the scene and the camera

The code below creates the scene and adds a camera

# Scenegraph with Entities, Components
rootEntity = scene.world.createEntity(Entity(name="Root"))

# Spawn Camera
mainCamera = SimpleCamera("Simple Camera");

As you see we currently have only a single Entity to our scene. The camera is a system, it traverses the scene to render the content with the code below

scene.world.traverse_visit_pre_camera(camUpdate, mainCamera.camera)

Create the cube

Now lets add some cubes to the scene

cube_bot: GameObjectEntity = CubeSpawn("BOT CUBE")
scene.world.addEntityChild(home1, cube_bot);
cube_top: GameObjectEntity = CubeSpawn()

This code block creates a cube entity and adds it to the scene under the “home1” entity. The CubeSpawn() method initializes the vertices of our cube.

../../../_images/scenegraph.png

As you can see in the image above, this is the scenegraph hierarchy. All the entities and components are visible.

Put it all together

In the main game loop we are doing the following

  1. Traversing all the objects and update their transformations

scene.world.traverse_visit(transUpdate, scene.world.root)

  1. Update our camera. We can also manipulate the camera using real-time GUIs

scene.world.traverse_visit_pre_camera(camUpdate, mainCamera.camera)
scene.world.traverse_visit(camUpdate, scene.world.root)

  1. Call the renderUpdate system to render the scene

scene.world.traverse_visit(renderUpdate, scene.world.root)

Note

Keep in mind that the transUpdate, the camUpdate and the renderUpdate are systems. The traverse_visit method visits all the entities of our scenegraph and applies the given system when applicable.