Presentation
This is a toy/experimental project showing off how to get started rendering glyphs with Eric Lengyel's Slug algorithm on both CPUs and GPUs.
I recommend reading at least the slides linked in the reference section before any of the code.
Requirements
- Windows x64
- Visual C++ 2013 or later for compiling
- OpenGL 3.2 for the hardware renderer
Project breakdown
| Sub-project | Purpose |
|---|---|
| Font generator | Reads a .ttf TrueType font file and outputs a .sluggish file |
| Software renderer | Reads a .sluggish file and outputs a .tga image per specified code point |
| Hardware renderer | Reads a .sluggish file and renders up to 6 specified glyphs using OpenGL |
| Feature | Support |
|---|---|
| Curves texture (FP32) | YES |
| Bands texture (U16) | YES |
| Cutting glyphs into bands (performance) | YES |
| Sorting curves (performance) | YES |
| High-quality implementation of anything | NO |
| High performance | NO |
| 16-bit floating point encoding | NO |
| Data de-duplication and compression | NO |
| Text layouting | NO |
| Colored shapes | NO |
| Adaptive super-sampling | NO |
| Gamma correction | NO |
| Bounding polygons | NO |
The goal was to keep things pretty simple while still not having awful performance. For instance, cutting the glyphs into bands has been implemented because it's simple and improves performance massively.
Debugging
By default, the debugger's target executable isn't in the output directory but a directory path specified by the SLUGGISH_APP_DIR environment variable.
The .exe and .pdb files are copied over to that directory after every build.
To make this process easy, you can launch Visual Studio through a simple batch script:
:: This file would sit next to the Sluggish directory
cd Sluggish\makefiles\vs2013
set SLUGGISH_APP_DIR=C:\important_stuff\sluggish
Sluggish.sln
References
To learn more about how the Slug algorithm works, refer to:
GPU-Centered Font Rendering Directly from Glyph Outlines by Eric Lengyel
Journal of Computer Graphics Techniques (JCGT), vol. 6, no. 2, 31-47, 2017
Paper: http://jcgt.org/published/0006/02/02
Slides: http://terathon.com/i3d2018_lengyel.pdf
Licenses
| Project/File | License(s) | License File(s) |
|---|---|---|
| This project | Unlicense (public domain) | UNLICENSE.MD |
| SDL 2 | zlib | libs/SDL2/COPYING.txt |
| GLEW | Modified BSD License Mesa 3-D License (MIT) Khronos License (MIT) |
libs/GLEW/LICENSE.txt |
| premake 5 | premake 5 | makefiles/PREMAKE_LICENSE.txt |
| stb_truetype.h | Pick-a-license: Unlicense (public domain) MIT |
code/generator/stb_truetype.h |
| stb_image_write.h | Pick-a-license: Unlicense (public domain) MIT |
code/renderer_sw/stb_image_write.h |
Patent
While there is no patent on the Slug algorithm as of the time of writing, Eric Lengyel has made an application for one and the process is still on-going...