U3D is greatly inspired by OGRE (http://www.ogre3d.org/) and Horde3D (http://www.horde3d.org/). Additional inspiration & research used:

• Rectangle packing by Jukka Jylänki (clb) (http://clb.demon.fi/projects/rectangle-bin-packing/)
• Tangent generation from Terathon (http://www.terathon.com/code/tangent.html)
• Fast, Minimum Storage Ray/Triangle Intersection by Möller & Trumbore (http://www.graphics.cornell.edu/pubs/1997/MT97.pdf)
• Linear-Speed Vertex Cache Optimisation by Tom Forsyth (http://home.comcast.net/~tom_forsyth/papers/fast_vert_cache_opt.html)
• Software rasterization of triangles based on Chris Hecker's Perspective Texture Mapping series in the Game Developer magazine (http://chrishecker.com/Miscellaneous_Technical_Articles)
• Networked Physics by Glenn Fiedler (http://gafferongames.com/game-physics/networked-physics/)
• Euler Angle Formulas by David Eberly (https://www.geometrictools.com/Documentation/EulerAngles.pdf)
• Red Black Trees by Julienne Walker (http://eternallyconfuzzled.com/tuts/datastructures/jsw_tut_rbtree.aspx)
• Comparison of several sorting algorithms by Juha Nieminen (http://warp.povusers.org/SortComparison/)

U3D uses the following third-party libraries:

• AngelScript 2.35.1 WIP (http://www.angelcode.com/angelscript)
• Boost 1.64.0 (http://www.boost.org) - only used for AngelScript generic bindings
• Box2D 2.3.2 WIP (http://box2d.org)
• Bullet 3.06+ (http://www.bulletphysics.org)
• Civetweb 1.7 (https://github.com/civetweb/civetweb)
• FreeType 2.8 (https://www.freetype.org)
• GLEW 1.13.0 (http://glew.sourceforge.net)
• SLikeNet (https://github.com/SLikeSoft/SLikeNet)
• libcpuid 0.4.0+ (https://github.com/anrieff/libcpuid)
• Lua 5.1 (https://www.lua.org)
• LuaJIT 2.1.0+ (http://www.luajit.org)
• LZ4 1.7.5 (https://github.com/lz4/lz4)
• MojoShader (https://icculus.org/mojoshader)
• Mustache 1.0 (https://mustache.github.io, https://github.com/kainjow/Mustache)
• nanodbc 2.12.4+ (https://lexicalunit.github.io/nanodbc)
• Open Asset Import Library 4.1.0 (http://assimp.sourceforge.net)
• pugixml 1.10+ (http://pugixml.org)
• rapidjson 1.1.0 (https://github.com/miloyip/rapidjson)
• Recast/Detour (https://github.com/recastnavigation/recastnavigation)
• SDL 2.0.10+ (https://www.libsdl.org)
• SQLite 3.20.1 (https://www.sqlite.org)
• StanHull (https://codesuppository.blogspot.com/2006/03/john-ratcliffs-code-suppository-blog.html)
• stb_image 2.18 (https://nothings.org)
• stb_image_write 1.08 (https://nothings.org)
• stb_rect_pack 0.11 (https://nothings.org)
• stb_vorbis 1.13b (https://nothings.org)
• tolua++ 1.0.93 (defunct - http://www.codenix.com/~tolua)
• WebP (https://chromium.googlesource.com/webm/libwebp)
• ETCPACK (https://github.com/Ericsson/ETCPACK)
• Tracy 0.7.6 (https://github.com/wolfpld/tracy)

DXT / ETC1 / PVRTC decompression code based on the Squish library and the Oolong Engine.
Jack and mushroom models from the realXtend project. (https://www.realxtend.org)
Ninja model and terrain, water, smoke, flare and status bar textures from OGRE.
BlueHighway font from Larabie Fonts.
Anonymous Pro font by Mark Simonson.
NinjaSnowWar sounds by Veli-Pekka Tätilä.
PBR textures from Substance Share. (https://share.allegorithmic.com)
IBL textures from HDRLab's sIBL Archive.
Dieselpunk Moto model by allexandr007.
Mutant & Kachujin models from Mixamo.
License / copyright information included with the assets as necessary. All other assets (including shaders) by U3D authors and licensed similarly as the engine itself.