Labels

1. Labels
2. Signed Distance Field

Labels deals with displaying text strings in a 3D application. Labels can be used to display information as a 2D overlay on top of the rendered 3D scene, or as 3D strings on 3D surfaces. Strings are displayed as a sequence of bitmapped character images. The vu engine helps by generating a displayable image from string characters.

Labels

Labels are created in the vu engine using font TTF files and the Entity.AddLabel method. AddLabel is a helper method that associates a normal string shader with a bitmapped font image and a text font layout file. For example:

    // load the font shader and font TTF file, indicating the font size.
    eng.ImportAssets("label.shd", "20:lucon.ttf")
    // "fnt:lucon20"       - font mapping asset generated from 20:lucon.ttf
    // "tex:color:lucon20" - texture atlas asset generated from 20:lucon.ttf

    // create the model
    scene2D := eng.AddScene(vu.Scene2D)
    name = scene2D.AddLabel("name", 0, "shd:label", "fnt:lucon20", "tex:color:lucon20")
                              ^              ^         ^                 ^
                              |               |        |                 └ font texture atlas. 
                              |               |        └ bitmap font file. 
                              |               └ label shader 
                              └ the label string.

The string in this case is being displayed as part of a 2D scene so the z position is always 0.

Signed Distance Field

Signed distance fields help to display 3D strings, like lettering on walls. Signed distance fields is a Shader based algorithm combined with specially generated font bit-mapped Texture Atlas. SDF mitigates the effects of pixelization when 3D fonts are viewed close-up.

Dealing with SDF strings instead of regular strings means:

• Using a a SDF aware shader.
• Creating and using corresponding SDF bitmapped font texture atlases.

FUTURE: have vu generate SDF fonts from true type font files.