Will eventually become a two player 2D submarine game with some fluid dynamics. BattleSub is using Magnum Graphics, Box2D, EnTT, and ImGUI:
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Well, let me just spend some words on the commit messages. I wanted to use Lua for scripting and configuration purposes, which I did in other projects before. But then TravisCI errored, because of missing Lua. So I added Lua, changed its version for CI, changed Ubuntu version in CI, added missing headers and everything was fine, eventually, apart from - git.
Ofcourse, there is a backup, but given BattleSubs current state and popularity, I do not see any reason to further fiddle around with git, trying to merge the backup including history with current changes.
So now, since the history is gone, lets just add a little changelog here, beginning today (2022-05-13):
Upcoming: Let's go fishing...
Teaser
Update 2022-11-12: Boids implementation is going well. All rules have been implemented in a first version. The boids branch has been added to the github repo today. Final work on parameterisation and exposing parameters to Lua and the debug GUI are being done.
2022-09-12: Colorful densities
The density implementation was changed from 1 to 3 channels (RGB32 float textures) to enable color selection for densities. The configuration was partly (proof of concept) exported to Lua following a more flexible binding structure.
2022-09-06: Long live the particles, show the beauty
Physical particles and their lifetime have been reconfigured. New screenshots and explanations were added.
2022-05-13: Lua love:
Lua has been added to enable configuration via scripts
To build and install after cloning run
cd scripts
./build_dependencies && ./buildfrom BattleSub directory.
If successful, run BattleSub using ./run or /<path>/<to>/scripts/run if in another directory.
You can always have a look at .travis.yml for a configuration that should work. In general, dependencies are:
- SDL2
- Lua
Other dependencies will be installed and compiled when running "build_dependencies" (see above).
While I tried to stay portable with all code and libraries, BattleSub currently only supports Linux, since I don't exactly know, how to develop for Windows. Every support is welcome, ofcourse.
Since other libraries are what drives a great part of this project, I think they should go first. I appreciate all the hard work done by publicy available libraries, such as Magnum Graphics, Box2D, EnTT, and Dear ImGUI, as well as other contributions I maybe forgot.
Special thanks go to Vladimír Vondruš and supporters, not only for the aforementioned Magnum Graphics middleware, but also the fast response time on gitter.im on my questions. Not only have the dev(s) been answering my API-related questions, but have also been giving valuable hints on concepts for implementation of different aspects.
Final buffer composition with debug GUI:
Physical objects generate velocity sources as well as density sources in each frame. They can also be just generated without a physical object. While the velocity sources modify the vector field which will influence physical objects and fluid densities, the density sources themself will increase the density of the fluid grid cells. The following images show these two sources (velocity and density):
The velocity field a vector field. Here, direction is color coded while intensity displays the velocity magnitude. The velocity field is used to move itsself (self advection), to move the density field (advection), and to move the physical objects. Since physical objects are calculated on the CPU, the velocity field is subsampled and read back to CPU. A double buffered, threaded pixelbuffer is used via DMA to avoid blocking. Sub-sampling is done spatially as well as temporally. In each frame, a lower resolution stripe of the velocity field is read back. There are no visible artifacts on physics objects, since sudden changes do only appear for force/acceleration. Influence on objects velocities and positions is implicitely smoothened by integration of accelerations.
The densities, generated by density sources, are influenced by the vector field. Here, they are a purely visual representation (which might be smoke for gases, water bubbles in fluids or different coloured fluids in other cases) only which refers to a particle density.
The pressure field is calculated with a numeric optimisation, i.e. iteratively. It originates from divergence and ensures, that grid cells are mass preserving. This finally leads to vortices.
The heightmap is a background image that is procedurally generated by mainly using several octaves of different noise functions.
The velocity field distorts the heightmap based on velocity direction and magnitude to simulate a visual waterflow. This is pure cosmetics, kind of the "rule of cool".
The velocity field may also be displayed by vectors. It is based on the subsampled field that was read back to CPU. It is further subsampled for reduced density and thus, better visualisation.
Physical objects are influenced by the subsampled velocity field that was read back to CPU. Velocity probes measure the field in several points and include normal vectors of the objects edges to finally calculate the velocities/forces acting on objects. The probes show the current relative velocity (radius) and field direction (radial line).
