This project is meant as a reference implementation of MSDF generation, all
code relevant for it can be found in src/font/msdf.c and src/font/msdf.h.
Any other primitives that are used can be found in src/base. The Windows
backend was hacked together rather quickly, but will be improved later.
MSDFs are generated using the direct multi-channel distance field construction method described in Viktor Chlumskys master's thesis. I haven't implemented the collision correction they describe yet, and so there are still some artifacts.
The approach described in the thesis makes three assumptions that TTF-files do not satisfy:
- Contours do not overlap each other.
- Contours do not self-intersect.
- A contours winding number in isolation determines if it is adds or removes area to the shape.
These constraints turn out to be useful when generating MSDFs, but are annoying when designing fonts, so we have to convert between the two forms. This is done by first taking the TTF-encoded contours and loading them in to a uniform format without any implied control points. Then we take any contours that overlap, cut then up and shuffle around their pieces so that any contour only ever intersects with itself. After that, we make sure that contours that intersect themselves are split into multiple non-self-intersecting contours.
At this point we have contours that represents the exact same thing as the original one, just without any overlap or self-intersections. TrueType allows winding numbers of contours to combine in order to cut out holes and combine shapes (non 0 fill rule). The MSDF algorithm considers contours in isolation and thus we need to correct the winding numbers. After this pre-processing, the contours can be sent of for MSDF generation.
Search for x64 Native Tools Command Prompt for VS <year> in the Windows Start
Menu. Navigate to the project root and run scripts\build_msvc.bat. You can
now run the program with build\msdf-gen <TTF-file>.
Make sure you have SDL2 installed.
Open a terminal and navigate to the project root. From there, run
scripts/build_clang.sh. You can now run the program with build/msdf-gen <TTF-file>.
Not supported for now.
You start the program from the command line and provide it with a TTF-file to load. From there, it will generate an MSDF atlas with all ASCII characters from the font and display it. You can drag around the atlas with the left mouse button, and zoom in and out using the scroll wheel. Press tab to switch between displaying the raw texture and the MSDF render.
They are the result of texture bleeding. At the edges and corners of entries in the atlas, we will sample information from up to 4 different glyphs. Due to the way that MSDFs are rendered, the sudden jumps in the samples will produce these artefacts. If the glyphs are rendered one by one, the artefacts won't show up.