Text rendering in OpenGL

[User137]

I don't have yet experience with that, but as far as I image, I should render a character map (atlas) at runtime, using the OS's built in text rendering functions. The character map would be a single channel texture (alpha map). Then each quad's tex-coordinates should map an exact character from the texture. Then I can combine the character alpha map with a custom texture or color to fill the character in the fragment shader. Would that work? How do you do it in your implementations?

No. You can pre-generate a texture, and save the character pixel widths in file. Texture is usually a 24-bit RGBA image. You can even pre-generate one and then add effects in photoshop/gimp.

But wouldn't be a problem for the mipmapping if I use a single texture for font atlas? Is it a better solution to store each character in different texture?

Mipmapping is done per texture basis, fonts shouldn't need any. Mipmapping technique is used to smoothen repeating textures like terrain that fade into distance. Font neither repeats nor has varying depth. And true, you don't want to include fonts in global single texture. You can't mipmap a texture atlas either, it will simply mess up clamping.