The OpenGL SC 2.0 API addresses the unique and stringent requirements of high reliability display system markets, including FAA DO-178C and EASA ED-12C Level A for avionics, and ISO 26262 safety standards for automotive systems. For text that only changes slowly (so you aren’t continually reloading the texture) that can be blindingly efficient.The Safety Critical Profile for OpenGL ES 2.0 is designed to be deterministic and testable to minimize implementation and safety certification costs – while bringing GLSL shader programmability to safety critical graphics for enhanced graphics functionality with increased performance and reduced power. On systems with decent shader support, I’ve been experimenting with a technique where I send the strings I need down to the GPU as a texture map with one texel per character (containing the ASCII code) and use fragment shader code to convert use that value as the coordinate for looking up the font texture - amazingly, it actually works pretty well. Another approach (if your text is relatively fixed) is to store entire words, phrases or even sentences as texture and draw the whole thing with one textured quad.Ī very long time ago, I wrote a FAQ about this (that was back in the era of OpenGL 1.2!) ()
If you have a lot of text - that might mean drawing a LOT of polygons. One simple way to do that is to make up a short/wide texture map with all of the ASCII characters in it - then write code to draw each letter as a textured quadrilateral using the appropriate texture coordinates to extract the right letter out of the texture map. You either do that outside of the API (maybe using some other operating-system commands) - or you write your own font rendering stuff. There is no API in OpenGL (or OpenGLES) for drawing text.
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