Simple Simulation Engine

a minimalistic engine for:

• Physical simulations
• Numerical math
• Game development
• Computer graphics
• Educational purposes

Table Of Contents

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• Simple Simulation Engine
  • Table Of Contents
  • Structure and Dependecies
  • Compilation - quickstart - remarks
  • Content
    • C++ part - C++ Planned or Preliminary or ToDo
    • Python
    • Web
  • Aim and Philosophy

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Structure and Dependecies

• Computational core is written in C/C++11. It should have no dependencies on external libraries. Even C++STL is avoided where possible. Attempt is made to optimize simultanously run-time speed, code length, compilation time, and interal interdependece of modules. In that respect especially tradeoffs for using templates and class hierarchies are considered.
• C/C++ part is compiled using CMake 2.8 and tested with gcc 5.4.0 on Ubunt 16.04. Code::Blocks project is generated by cmake .. -G "CodeBlocks - Unix Makefiles". There are several CMake projects for different parts which differ in dependencies
• Standalone apps, games and demos use SDL2 and OpenGL 1.2 and 4.0 for Graphical user interface. Some other dependencies (e.g. SDL2-net, SDL2-image, SDL2-ttf) may be added to particular build target but are not required globaly.
• There is stand allone set GPU accelerated simulations using OpenCL
• Some apps use embeded Lua3.2 for scripting, but it is not globally required.
• Python 2.7 + numpy + matplotlib is used to make convenient science/engineering packeges partialy wrappaing the C/C++ core libraries.
• In addition there are some documents using iPython (Jupyter) and javascript+WebGL for rendering interactive 3D graphics and editors of glsl shaders on web. These are independent on the rest.

Compilation

• tested on Ubunu 16.04 64bit)

quickstart

1. make sure you have installed gcc >=5.4.0, CMake >2.8, libglew-dev, SDL2-dev
2. got to cpp/Builds/sketches_SDL/ create subdirectory Build
3. from cpp/Builds/sketches_SDL/Build generate makefiles by cmake .. -G "CodeBlocks - Unix Makefiles"
4. in the same directory compile the project make. The compiled binaris are stored in cpp/Build

remarks

• you may also load Code::Blocks project cpp/Builds/sketches_SDL/SimpleSimulationEngine.cbp and compile particular build target from Code::Blocks
• If cmake or make fails due to some dependencies, you may try compile just part of the project (e.g. cpp/Build/libs) which has less dependencies
• you may also remove problematic build targets by commenting out particular parts of CMakeFile.txt

optional

6. If you were able to compile sketches_SDL you may try compile applications and games in cpp/Builds/apps/ or the whole project in the same way just in cpp/Builds/all/ (you will need liblua5.2-dev and libtolua5.2-dev)
7. You may try compile OpenCL demos in cpp/Build/sketches_OCL in the same way. This will require properly installed GPU drivers and opencl libraris. These are platform dependent. Personally I tested with nvidia-opencl-dev.
   • Note: be very carefull when installing GPU drivers on linux, ou can easily brak the system (I did 3 times). In my case nvidia-opencl-dev installed dependecies libcuda-378 nvidia-378 nvidia-opencl-icd-378 nvidia-prime nvidia-settings opencl-headers. I also added nvidia-modprobe. When you break your system this make help:

     sudo apt-get autoremove --purge nvidia-*
     sudo stop lightdm
     sudo apt-get install xserver-xorg-video-nouveau
     

     there are many guides for installing GPU drivers on linux. I found particularily helpfull and working this one

Content

<font color="green"> This is work in progress. Often particular modules of the engine are functional, but they are not put together to build an unified system and work together. </font>

C++ part

• Math

  • 2d vector, 3d vector, 3x3 matrix, 4x4 matrix, Quaternions
  • Fast math rutines with approximations of some functions ( e.g. goniometry, Error function ... )
  • Functions with derivatives ( like tresholds and sigmoides, and Lorenzieans etc. )
  • Composing of complicated 1D,2D,3D functions from simple primitives with analytic gradients
  • Splines in 1D, 2D 3D, e.g. cubic hermite spline <font color="green" size=2> (other splines needs to be systematized) </font>
  • [Simplex noise] (cpp/common/math/Noise.h)
  • Basic linear algebra ( matrix multiplication, transpose, GaussJordan solver, Biconjugate gradinet iterative solver, Fitting, Jacobi matrix diagonalization), and N-dimensional vectors
  • Minimalistic Fourier transform, with FFT for $2^N$ elemetns

• Math solvers

  • Brent line search
  • Stochastic optimization
  • iterative non-linear gradient based optimization using FIRE (faster and more robust CG, comparable and sometimes better than BFGS)
  • Variable step ODE integrator by Runge–Kutta–Fehlberg

• Computational Geometry

  • Basic 2d and 3d shapes computational geometry, ray tracing, Covex polygons, polygon Mesh and regular polyhedra

• Spatial datastructures - <font color="green" size=2> This needs cleanup, there is too many duplicite methods/versions. Especially, Rulers should be splited from data. </font>

  • Various methos for acceleration of local interactions and nearest neighbor search e.g. HashMap, nD BoundigSphere hierarchy, and grids.
  • Various grids (trinagular, rectangular, cubic, and triclinc )
  • Some maps suport raymarching/rasterization e.g. trinagular and cubic

• Physical simulations

  • Rigid-Body dynamics in 2D and 3D - with application in RigidBody molecular dynamics, Flight dynamics and vehicle on tarrain, and Sailing
  • SoftBody dynamics with Truss simulation (e.g. for something like BridgeBuilder)
  • Molecular mechanics used there
  • simulation of hydraulic errosion for terrain generation

• GUI and interfaces

  • basic SDL2 application prefabricates in 2D and 3D
  • Basic lightweight GUI components (buttons, sliders, input box ... ) for SDL2
  • basic plotting utilities for 1D,2D and 3D data (inspired by matplolib)

• Graphics

  • OpenGL 1.2/2
    • drawing many basic primitives and more complex shapes in 2D and 3D
  • OpenGL 3+
    • Examples of Rendering meshes, rendering to texture, instances, bilboards
    • ScreenSpace ambient occlusion
    • Ray-Traced analytic primitives e.g. Spherical atoms
    • Ray-Marching of analytical functions e.g. molecular orbitals.
    • <font color="green" size=2>TODO: (in-shader Constructive solid geometry CGS)</font>
    • Terrain rendering from heightmap texture with logaritmic depth buffer for large scenes
    • Angularly sensitive bilboards (impostors) for rendering Vegetation and clouds

• Apps and Games

  • Molecular editors with Rigid Body Molecular dynamics (coarse grained=>faster, no need for intramoleculer forcefiel) with python interface, and normal Soft Body Molecular mechanics
  • 3D subsonic aircraft combat simulator
  • 2D Sail-ships simulator with multiplayer and battleship simulator
  • [Land-Combat tactical simulator](cp