GLSL functions

• length(x) – length of a float, vec2, vec3 or vec4
• distance(a, b) – distance between a..b
• step(edge, x) – return 0 if x < edge, otherwise 1
• smoothstep(edge0, edge1, x) – like step but interpolatie between edge0 and edge1.
• mix(x, y, a) - interpolate between x..y with a = 0 .. 1
• min(x, y) – return the lesser value
• max(x, y) – return the greater value
• clamp(x, a, b) – clamp the value between [a .. b]
• Trigonometric functions, eg. sin(x), cos(x), atan(x)