Text

You may need to read the articles about textures and transparency before this one.

Text rendering is an extremely complex topic that I can only barely scratch the surface of. As such, I will only be covering the most basic of scenarios in this article. If you'd like to learn more about why text rendering is so difficult, consider reading "Text Rendering Hates You." If you want to do more complex text rendering within a 3D environment, it is typical to use software like Slug to do the heavy lifting for you.

Simply put, text is typically rendered in OpenGL by rendering a transparent textured quad, with the texture being a representation of the desired text. For applications that only need to render a small set of predefined strings, it is trivial to create corresponding textures ahead of time. Otherwise, some effort is required to enable developers to generate textures on the fly.

Glyph Textures

If you only need to render text using a bitmap font with a small set of characters, one approach to rendering text is to use a glyph texture, which is a texture atlas of glyphs (character symbols). By assigning each glyph to a predefined location and size, representations of strings can be generated by calculating the corresponding texture coordinates of the glyphs that it comprises.

The next article is about general-purpose GPU.