A Multi-spectrum signed distance field font sample for monogame
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README.md

MSDF

A signed distance field font sample for monogame.

Sample

This sample shows how you can integrate msdfgen into your content pipeline to generated signed distance field fonts, and how to correctly render these fonts. Including correct kerning courtesy of my TrueType library.

For more info visit my blog.

The content pipeline project

This sample includes a content pipeline project compatible with Monogame 3.0+. The content processor requires you set the path to the msdfgen binary. I recommend you generate it from this fork as it fixes many issues with complicated fonts.

The game project

The game project contains a simple utility class and shader to draw 3D moving text.

Why (multi-channel) signed distance fields?

Signed distance fields are a technique first described by Valve in this paper. In short a signed distance field is a sort-of height map. Where sea-level are the actually boundaries of the glyph. Everything above sea level is outside the glyph, and everything below sea level is inside the glyph. When a height map is upscaled the GPU fills in the gaps using linear interpolation. The linear interpolation of the height map introduces less noise/faults than interpolating a sharp boundary would do, but we still get the same information.

Traditional signed distance fields only use one channel, but they sometimes have trouble representing sharp corners. Multi-channel signed distance fields solve this problem by using three color channels to store slope information.

Advantages

  • High quality text rendering
  • Low memory usage
  • Fast rendering (the shader is very simple)

Drawbacks

  • No automatic mechanism to determine the right signed distance field size to capture all details
  • No multi-color glyphs (like emoji)
  • Straight lines might look slightly wavery sometimes

Alternatives

  • SpriteFonts, the standard in XNA and MonoGame, look good when rendered at the same size as the sprites were saved, but upscaling and downscaling quickly leads to a serious degradation in quality.
  • A library like slug which renders text directly from the outline data in the font. So no details are missed and no manual configuration is required.