A generalization of the engine used in JaredAll/Tetris. This project extends that educational project with versatility in mind. This engine is intended to be able to run any two dimensional game.

This project is another playground in which to make software engineering decisions, good or bad, and leverage C++'s dynamic and static polymorphism. However, the challenge is greater here than in Tetris. Designing a game engine that can run any game requires more thought and care than one that is suited to only a single game.

The Engine class orchestrates the Allengine runtime. It is responsible for creating and maintaining the SDL window, keeping the frame timer, updating game components, handling input, and calling the renderer. The advance function template is used to advance the game for a single frame, and is SFINAE'd away if called with a vector of anything other than GameComponents. The instantiation for that type also includes the instantiation for the private methods render_components and update_components; check out my blog, jaredall.dev, for a deeper explanation of the Engine architecture.

The Allengine incorporates rudimentary two dimensional physics using the PhysicsComponent and PhysicsHandler classes. The details of the physical interactions handled by the PhysicsHandler themselves comprise the Vector2 class. The class uses a magnitude and angle to represent a vector. It is also a template with three different specializations based upon the type traits the template parameter exhibits. The first is the default specialization, which only implements vector addition. The second specialization is for those Qualitys that have been specified as integratable. This specialization includes an integrate(delta_t) method that returns a Vector2 parametrized by the Quality specified in the integrated Quality's definition. This allows the type representations to reflect how the qualities of interpreting an integration are determined in real life. For example, integrating a velocity equation yields a displacement equation. The third specialization simply expands upon that idea with an integrate2 method, allowing one to go directly from an acceleration vector to a displacement vector. By making the Vector2s typed we decrease the chances of using two different qualities in a calculation. It should be noted that these integrate methods assume that the acceleration is constant; however, for small delta_t, repeated integrations should approximate a changing acceleration.

I have added CMake compatibility for the Allengine tests executable. The tests executable will run a small example game using the Allengine. Running the Allengine tests requires PThreads, SDL2, SDL2_Image, and SDL2_TTF. The CMakeLists.txt file is under the /build/cmake/ directory.