textures and fonts

[sandyrepope]

In the help file for the TBGL module it says that the texture mapping should be disabled before using TBGL_PrintFont.

Why?

Thanks
Sandy

[Petr Schreiber]

Hi Sandy,

it is recommendation, not a must. But good to get rid of side effects.

How does TTF font rendering work in TBGL?

First you create font handle like:


TBGL_BuildFont TBGL_FontHandle("Arial", 16)


This command is the key - it takes the classic Windows font, analyses its characters and internally converts them to little bitmaps, which OpenGL can manipulate.

So if you would not disable texturing before drawing them, TBGL/OpenGL would try to texture them. And as those little character primitives do not have texturing coordinates specified, it provides odd results.

OpenGL works as state machine - you enable texturing, and all following commands are affected by it, until you disable it.
Font you operate using TBGL_PrintFont is no longer GDI object, but OpenGL one.

Microsoft claims mixing OpenGL and GDI drawing a sin :), it is possible, but means dancing on the edge ad bad practise for future.


Hope I made the situation clear now :),
thanks for the question,
Petr

P.S. Will add this info to the help file