I have a texture font, which is based on Brad Fish’s GlFont, but I’d put it in a class so that it wiggles along a given line.
The characters in the font are black, and transparent using GL_LUMINANCE_ALPHA, so the the line they’re drawn on top of shows through as you would expect. However, the other lines underneath get obscured by the (no longer transparent) white box containing the font character, and if two lines of text cross, then only one of them is visible, and the other gets obscured by the same white boxes. It’s as if the text characters are only transparent over the nearest item (the line), not over anything else. This seems very strange to me, and is no good as I need everything underneath the text (including other text) to appear through.
To achieve the depth effect I’ve enabled GL_DEPTH_TEST, and have given the various lines different z values up to 0.99, and the text is drawn at 0.1.