[HOpenGL] Re: rendering fonts with OpenGL

[Glynn Clements]

Sebastian Sylvan wrote:

> > So if performance does matter you recommend avoiding framebuffer
> > operations in general? I am thinking about how to display a clickable UI
> > in front of a 3D scene and, naively, I would have drawn pixmaps on top
> > of the scene using the framebuffer. If I try to do the same using texture
> > mapped polygons, what is the best setup/projection to make it look like
> > a flat window like UI? How to avoid perspective and blurring effects?
> 
> Use orthogonal projection with the same width and height as your
> resolution (to make it easier to target a specific position in
> pixel-units) and make sure you draw your polygons so they're the exact
> size of the bitmap of the texture. Remember that in OpenGL (x,y)=(0,0)
> is situated at your lower left and not your upper left (as in, for
> example, windows GDI).

You can set up the projection matrix so that the origin is in the
top-left. However, this will result in a negative determinant, so
polygons will be "inside-out" (e.g. the front/back-facing test will be
inverted).

-- 
Glynn Clements <glynn at gclements.plus.com>