The Uchronia Project Blender Game Engine (UPBGE) is a Blender’s builtin tool for real-time projects, from architectural visualizations and simulations to games.
Originally a fork from the Blender Foundation’s Blender Game Engine, became indepent with the Blender Foundation’s announcement of BGE’s removal and replacement with a new Interactive Engine. With this independency, the UPBGE’s developers have freedom to change and add features that could not be changed before (because the possibility of an official Blender merge, now discarded).
UPBGE have lots of new features, improvements and bugs fixed that BGE haven’t. Some features that UPBGE supports are:
Realtime advanced physics powered by Bullet, including rigid bodies, soft bodies, obstacle simulation and path finding.
Easy and straightforward visual logic system.
Development process entirely inside Blender, without needing to import/export assets.
Execution of game in Blender’s viewport (for fast previewing) or on an standalone executable.
Blender’s Linked Libraries feature, allowing to organize projects in multiple blend files.
OpenGL custom shaders for visual effects and post processing.
Fake or realtime reflections setting directly through the interface.
UPBGE is maintained by a group of developers in their spare time and its community. You can contribute to UPBGE if you code in C++ or Python: just open a pull request, submit your changes and wait for the reviewers. Also, even if you don’t code, you can contribute by submiting bug reports, feature requests and participating discussions on issues.