1. OpenGL ES 2.0 how to draw a line? 2D, that is just an abstract line.
  2. What does setting the coordinates in x,xf mean? What is f - is cast to float?
  3. Is it possible for a line to change color in runtime?

    1 answer 1

    For the first question, read the OpenGL ES 2.0 Programming Guide (in English only).

    In the second "OpenGL red book" (available in Russian), the secret suffix f denotes a floating point number of 32 bits.

    Thirdly, of course, it is possible because OpenGL is a rather low-level specification, you are limited only to your own imagination.

    PS Books are required to read OpenGL is full of slightly non-obvious approaches.