The GLSL specification says that the guidelines for precision
established by the OpenGL 1.4 specification must be met (page 16).
The OpenGL 1.4 specification requires that “individual results of
floating-point computations are accurate to about one part in 100000”
Does this apply to functions like sin(), pow(), etc?
It seems to me to 1/10000 is a maximum relative error, which means that
sin(0) has to be exactly 0, etc. I suppose this requirement would be
very difficult to meet at cos(nearest float to pi/2), since the result
would be very small.