3D Rendering with raylib
gymECS, rendering is ensured by a system like any other ones, which will parse the
World and execute rendering commands based on the entities and components. From the user point of view, rendering is thus controlled just by manipulating data that are in the world.
In a general way, ECS makes easy the implementation of different rendering engines on top of similar game logics. In the following, I show how we can use the RayLib librairy, and its Python binding to make 3D rendering.
Note about speed: Raylib is a library that uses function calls to execute rendering operations, which may be slow in python due to the generation of too many calls (and python is bad when calling functions). We could make use of better 3D rendering librairies (like Panda3D) to speed-up our rendering. For instance Panda3D is using python to define a rendering structure (scene graph) which is then executed directly in C, avoiding to make too many python calls at each frame.
Implementation is available in:
gymecs/raylib.pyfor the core components, entities and systems
gymecs_examples/raylibmazefor the multi agent maze
In order to use raylib as a rendering library, the simplest way is to define new components dedicated to rendering. When these components will be attached to particular entities, then the rendering will be automatically executed.
The first step is to define the RayLibDrawComponent that is the component in charge of drawing. This component is the basic class for any rendering component.
The drawing component
This component contains two fields:
activatedthat will tell the system to draw or not (allowing us to desactivate the drawing whenever we want)
draw_layerthat is used to define in which order the components will be drawn. Indeed, the components with low values of
draw_layerwill be executed first, allowing to manage the drawing priorities (for instane, the camera has to be drawn at the beginning of each frame rendering)
This component also contains a
_draw method that will be executed by the drawing system at execution. (Note that, since we have updated the
Entity classes, by conventions, components methods have to be prefixed by
_ to avoid to be considered as data)
Now, we can define different components corresponding to different assets to draw. For instance, if one want to draw a rectangle, we can define the RayLibRectangle component as:
The rectangle component
In this case, the rectangle will be drawn at a fixed position. If we want to attach this rectangle to a moving object, we can define another component:
The rectangle component attached to an entity position
This RayLibRectangle_EntityPosition component is reading the drawing position directly into the entity it is attached to (instead of a fixed position), and will thus follow the entity movements.
A similar effort can be put to define components to draw the walls or the ground of the maze (see
Background and Camera
To configure the 3D scene, we also need to define the background and camera into the scene. This is done by defining two other components:
The background and camera components
In order to render the scene, we need to define a new system called RayLibSystem that will be in charge of executing the drawing. This sytem is generic to any game using raylib rendering. Note that by choosing not to execute this system in a game, you will have a game running ‘headless’ while executing this system at each step will execute the rendering. It is thus easy to execute the game a super speed by desactivating the rendering.
The RayLibSystem proceeds in three steps:
- first, it identifies the entities that have rendering components. (For that, we have implemented a new method get_components_by_type in World)
- second, it orders the components by
- last, it executes the components in the right order, only if they are
The resulting code is the following:
The rendering system
*And that’s it !!!! As you can see, adding a 3D rendering layer is very simple !!
Important: Since the 3D rendering has to be made at a given framerate, the RayLibSystem needs the use of a
_game_dt arguments at execution time.
The 3D Multiagent Maze game
To illustrate our new components and systems, we have updated the very simple maze game presented during the first post. To make it 3D, the modifications are the following (see
- We have added rendering components to the
Mazein the game
- We have added the
Gameclass and we execute this system at each step
- In addition, we have added a
ControlCamerasystem to control the camera
The modifications are very few lines to make our maze 3D. Of course, the rendering made here is quite simple, but can be easily modified to reach a good level.
The Maze Game in 3D
I have illustrated the basic principles to use ECS for 3D rendering. Making more complex and beautiful games is now just a matter of coding and deploying the right components. Again, the clear advantage of ECS is the seperation between the game data (the World) and the systems, rendering being just a system like the others. Disconnecting rendering can be made by just not executing this system, while activating rendering can be made by just adding some components in the game data. Next step will be to implement realistic 3D physics… See you in a next post.