I'm implementing a GUI built on top of OpenGL. I came to the problem that each GUI will have -- text rendering. I know of several methods of rendering text in OpenGL, however, I'm wonderin which of them would be best suited for a GUI.
Generally in a GUI we have two types of text -- static and live. Static is easy enough -- we can render a TTF to a texture and forget about it. It's the "live" text that is more bothering me -- imagine console, or a live chat in a multi-player game.
I thought of several options:
The question hence is -- how to render text in OpenGL efficiently?
If this helps, I'm coding in STL/Boost-heavy C++ and aiming at GForce 6 and later graphics cards.
optimizeLegibility is when the browser emphasizes legibility over rendering speed and geometric precision. This enables the use of special kerning and optional ligature information that may be contained in the font file for certain fonts.
EDIT2: Sean Barrett just released Bitmap fonts for C/C++ 3D programmers.
EDIT: another code gem that's worth a look is Font Stash which leverages Sean Barrett's stb_truetype.h.
You can create a texture in which you render all the characters of your font. Then you just draw textured quads with orthographic projection and proper texture coordinates: this approach works when your text is in a language that doesn't contain much symbols: like english. The font texture is created once at the beginning of the application and then rendering quads is really fast.
That's what I'm using and I believe it's the fastest way to render text in OpenGL. At first, I used Angelcode's Bitmap Font Generator tool and then I integrated FreeType directly and built a big texture containing all the glyphs at application launch. As for tips to improve the quads rendering speed, I just used VBO as for the rest of the geometry in my application.
I'm surprised you have doubts about quad rendering while you don't seem to worry about the performance of generating a texture on the cpu, then uploading it, then binding it to finally render a rectangle with it, that for each frame. Changing OpenGL states is the bottleneck, not the 500 - 1000 quads you'll use for text.
Also, have a look at libraries like the FTGL library who converts the whole font into polygons (geometric fonts).
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