StarrySky

A WIP platformer game, written in C++17, using GLFW.

Prior to December 15th 2020, Starry Sky was licensed under the GPLv3. After December 15th 2020, Starry Sky is licensed under the MIT license.

It uses sprite-batching and texture atlases to recreate the experience of games from the 16-bit and 32-bit eras, but with a maintainable, modern code-base.

Design Philosophy:

• Inspired by the Suckless project's minimalist design philosophy
• Data-oriented design in the backend, hidden behind object-oriented abstraction layers in an API
• Focus on balancing performance and easy-to-read code
• Performance goals:
  • To run at 60fps on a Raspberry Pi Zero
  • To keep the total binary size less than 100 MB

Building:

git clone --recursive https://github.com/Kieran-Weaver/StarrySky
cd StarrySky
make

To run the tests:

make test

External Dependencies:

• GLFW
• GLM

External Test Dependencies:

• Catch2

Building on Windows:

Git, at least in msys2, does not handle symlinks properly on Windows. Before running make on Windows, run ./symlinks.sh to restore the symlinks.

Usage:

./Platformer

Features:

• Pixel-perfect collision
• DDS/DXT5 Textures
• Custom sprite-batching algorithm
• RAII classes:
  • Sprite and Texture
  • Window and Camera
  • Map and MovingEntity
  • SpriteBatch and TextureAtlas

Todo:

• Add proper unit tests - In Progress
• Implement editor functionality
• Add documentation for APIs
• Add plugin system
• Add python bindings for the collision and graphics libraries
• Replace imgui example files with custom implementations
  • Render through the sprite-batching API - Done
  • Handle input through the Window class
• Improve graphics backend:
  • Add 3D functionality
• Add game features:
  • Sprites
  • Enemy AI
  • Dynamically load resources

Project Layout:

• src/GL contains the graphics backend, which is currently based on OpenGL 3.x and GLFW
• src/util contains common code that everything else uses.
• src/file contains APIs to read and write text, memory mapped, and JSON files
• src/core contains the physics and map system and any helper files.
• src/game contains the game's AI and higher-level game concepts such as game mechanics.
• src/test contains Catch2 tests for the other components

Using Starry Sky as a Library

The GL portion of Starry Sky can be used as a standalone rendering library. The lib target in the Makefile creates build/libSSGL.a, which contains the implementation of the GL, util, and file folders, as well as code required to use ImGui. The rendering library can draw 3 different types of objects: Sprites, Tilemaps, and ImGui windows. Both Sprites and Tilemaps are drawn using the SpriteBatch object, while ImGui windows are drawn automatically when ImGui is used. See include/GL/Sprite.hpp, include/GL/Tilemap.hpp, and https://github.com/ocornut/imgui for information on Sprites, Tilemaps, and ImGui respectively.

Example code:

#include <GL/TextureAtlas.hpp>
#include <GL/SpriteBatch.hpp>
#include <GL/Camera.hpp>
#include <GL/Window.hpp>
#include <GL/Sprite.hpp>
#include <GLFW/glfw3.h>
int main(int, char const**) {
	float x1=0.0, y1=360.0;
	Window window(1280, 720, 3, 3, "data/fonts/boxfont_round.ttf", "Example");
	window.getWindowState() = { new Camera(Rect<float>(-2000.f,-2000.f,4000.f,4000.f),Rect<float>(0.f,0.f,800.f,400.f), window) };
	TextureAtlas atlas("resources/data/atlas.json");
	SpriteBatch batch(atlas, "resources/data/shaders.json");
	Texture t = atlas.findSubTexture("test1");
	Sprite s;
	s.setTexture(t);
	while (window.isOpen()){
		s.setPosition(x1,y1);
		x1 += 1.0f;
		s.rotate(0.1f);
		window.startFrame();
		batch.Draw(s);
		batch.Draw(window);
		window.endFrame();
	}
	return 0;
}

Acknowledgements and Links:

include/GL/Sprite.h, include/GL/SpriteBatch.h, include/GL/Texture.h, include/GL/TextureAtlas.h, and src/GL/TextureAtlas.cpp are originally from https://github.com/ricanteja/Moony-SpriteBatch, but were rewritten for Starry Sky.

The original engine for Starry Sky was based off of https://github.com/pixelpicosean/PlatformerEngine, but it was also rewritten.

The engine uses texture atlases which are generated by https://github.com/Kieran-Weaver/crunch

References

Collision:

R. R. Ciferri, A. C. Salgado, M. A. Nascimento and G. C. Magalhaes, "A performance comparison among the traditional R-trees, the Hilbert R-tree and the SR-tree," 23rd International Conference of the Chilean Computer Science Society, 2003. SCCC 2003. Proceedings., Chillan, Chile, 2003, pp. 3-12, doi: 10.1109/SCCC.2003.1245440.

T. Lee, S. Lee, "OMT: Overlap Minimizing Top-down Bulk Loading Algorithm for R-tree," CAiSE Short Paper Proceedings 2003.

Norbert Beckmann, Hans-Peter Kriegel, Ralf Schneider, and Bernhard Seeger. 1990. The R*-tree: an efficient and robust access method for points and rectangles. SIGMOD Rec. 19, 2 (Jun. 1990), 322–331. DOI:https://doi.org/10.1145/93605.98741