stabilized (makes sure font, model or texture loads before using)
modernized includes (#include statements specify irrlicht directory instead of assuming it)
double-click if this program is associated with the file types (mime types are installed by install.sh to allow this on GNU+Linux Systems --see Compile and Install)
hotkeys to cycle through textures and reload model OR texture (see Usage below).
see also CHANGELOG.md

Compile

If you are using GCC to compile, you may need gcc 8.2.1 or higher (C++14 experimental/filesystem works on 8.2.1 for sure, but C++17's filesystem has not been tested and requires minor changes to #include and using statements in UserInterface.cpp)
Make sure you have the Irrlicht and Qt development packages (such as via sudo dnf -y install qt-devel qt-creator irrlicht-devel on Fedora 29)
- Qt is not actually used, only Qt creator (the CONFIG -= qt setting is used in the .pro file).
Open Qt Creator, click File, Open, then choose this project's .pro file.
Build & Run (if you have trouble compiling, see filehandoff#compiling-issues)
Copy all of the files from ./build to your actual build directory, if your build directory is not ./build
(optional) Copy your favorite public-licensed font over ./build/ClearSansRegular.tff or to current working directory of program

Install

If you are not using a release version, compile the program (see above) then copy install.bat to your build directory.
double-click install.bat (read any messages that appear then press a key to continue when prompted).
Associate the B3D file extension (and possibly other Irrlicht- compatible 3D mesh formats--X and OBJ are tested) with %USERPROFILE%\Applications\b3view\b3view.exe (right-click a b3d file, then Open With, show additional programs, then either paste that path or choose This PC, C:, Users, your username, Applications, b3view, b3view.exe)

copy install.sh to your build directory if you are not using a release version and your build directory is not ./build
run install.sh as root, such by running sudo bash install.sh in Terminal from the project directory (if you are not root, the install will install to $USER/Applications after giving an opportunity to cancel with Ctrl C during a countdown). (the script will install the "Blitz3D Model File" (model/b3d) mime type, which will be used for all files with the b3d extension-- this allows associating the file type with a program).
Associate the b3d file extension (and possibly other Irrlicht- compatible 3D mesh formats) with b3view: Right-click any B3D file, "Open With...", find or type b3view, then check "Remember application..." or "Set as default..." or something similar depending on your desktop environment (an option to always use the same program will only be available if the mime type was successfully installed for the user profile or system such as via install.sh).

You can click "File," "Open.", then choose an Irrlicht-compatible B3D file. However, the program is much easier to use if you associate the format with b3view (see "Installation" above) so you can just double- click the file to open b3view automatically.
- / +: To change animation frame rate in increments of 5 fps, click "Faster" or "Slower," or use - key or +/= key. By default, the scene refreshes at 60fps and the animation runs as 30 fps (Irrlicht does interpolation automatically).
t / e: cycle through textures in ../textures using t key (e to go back) such as for Minetest mods, where model must be in modname/models/ and texture must be in modname/textures/. If ../textures doesn't exist relative to the model file's directory, the model file's own directory will be used.
F5: Reload last model file
r: Reload last texture file

ClearSansRegular.ttf (Apache 2.0 License) by Intel https://01.org/clear-sans via https://www.fontsquirrel.com/fonts/clear-sans
ninja.b3d, nskin*.jpg by Psionic (psionic3d.co.uk) http://www.psionic3d.co.uk/downloads/ninja.zip (I've seen this file ripped and in several repos, but finally found the original site above, which has additional skins not found elsewhere, via included "ninja animation ranges.txt" from https://sledjhamr.org/source/media/Irrlicht/) "Feel free to use however you like, commercial etc, credits are Appreciated..." -Psionic
Until original author egrath responds, all files not mentioned above are licensed under the GitHub ToS (GitHub has rights to distribute the files).