A minimal yet complete implementation of virtual texturing that is cross-platform and provides a reference sample app.

This work is an OpenGLES-specific and modernized fork of LibVT plus a cross-platform sample app. Special thanks to Julian Mayer for his original implementation and thorough documentation.

Goals:

• Provide a minimal example of virtual texturing to help in learning the algorithm and to serve as a building block for other projects.

• Enable cross platform native builds on Mac, Windows, and Linux, and a future WebGL build via Emscripten. To this end, C++ and OpenGLES were chosen from the start.

• Supply a reference sample that demonstrates the LibVT calls necessary to load and render a virtual texture, while utilizing SDL for cross-platform windowing and event handling.

NOTE: This code is work in progress. More code minimization needs to be done, multi-threading is not enabled yet, and an Emscripten build is pending. But at least an interactive demo is now available on Mac, Windows, and Linux.

The sample shows rendering of a test virtual texture to a simple quad. A traditional static texture is also drawn underneath to show how to mix regular rendering with LibVT rendering.

Controls:

Zoom:     Mouse wheel
Pan:      Arrow keys
Orbit:    Left mouse button drag
Reset:    'R' key
Quit:     'ESC' key

Install dependencies for your platform.

Install Homebrew if you don't have it, then SDL2 and SDL2_image:

brew install SDL2
brew install SDL2_image

Build and run:

cd hello-vt
make
cd Sample
./bin-mac-x86_64/vtdemo

or

./bin-mac-arm64/vtdemo

depending on your Mac.

Setup clang compilation on Windows. First, install MSYS from cmd.exe:

winget install MSYS2.MSYS2
setx PATH "%PATH%C:\msys64\clang64\bin"

Then run from MSYS2 CLANG64 shell:

pacman -Syu
pacman -S base-devel mingw-w64-clang-x86_64-toolchain
pacman -S mingw-w64-clang-x86_64-SDL2
pacman -S mingw-w64-clang-x86_64-SDL2_image

Then to build and run:

cd hello-vt
make
cd Sample
./bin-win-x86_64/vtdemo.exe

This was tested on Debian 11.3 and Ubuntu 24.04. Install required build tools and libraries:

sudo apt update
sudo apt install build-essential clang
sudo apt install libsdl2-dev libsdl2-image-dev
sudo apt install chromium
cp /usr/lib/chromium/*.so hello-vt/Dependencies/lib-linux

Then to build and run:

cd hello-vt
make
cd Sample
./bin-linux-x86_64/vtdemo

Many virtual texturing implementations have been available in C, C++ and JS, using OpenGL, Direct3D, and WebGL. However, for the purposes of this project they are either not well-documented, not minimal, not cross-platform, or not straightforward to build due to age (most date from 2010 or earlier).

Of note, OpenSeaDragon is an excellent implementation of virtual texturing but is not a good fit for this project because it is not C++ and not minimal.

Instead, LibVT was chosen for its C++ implementation, OpenGLES code path, and decent documentation. Fixes were made to LibVT to get it running again 15 years later, and to remove code not on the OpenGLES 2 code path. Further, an SDL-based sample app with a pre-processed test image is provided to demonstrate LibVT. (Note: At one time LibVT provided its own pre-built sample, but the link is dead and not saved on archive.org).

• Multi-threading! Virtual texturing must at least have a separate image file loading thread.
• Fix all compiler warnings across all platforms.
• Add OpenGLES 3 native build.
• Minimize LibVT code to OpenGLES 2 and 3 code paths only. So far, only the shaders have been simplified for OpenGLES 2.
• Add WebGL 1 and 2 builds via Emscripten, using the OpenGL ES 2 and 3 code paths, respectively.
• Visualize virtual and physical textures for debugging
• Handle more image formats (currently PNG only)

• Erik Larsen (LibVT fork and sample app)
• Julian Mayer (original LibVT author)