Update README.md - better explaination of features

Author: mcDandy

README.md

@@ -12,8 +12,28 @@ Adds math nodes for numbers and types which do not need it. I got inspired by wa
 
 # Features
 
-- expression parsing with support for functions (sin, cos, tan, asin, acos, atan, atan2, sinh, cosh, tanh, asinh, acosh, atanh, abs, sqrt, ln, log, exp, pow, smin, tmin, smax, tmax, tnorm,snorm (norm not applicable on number math node), floor, ceil, round, gamma,clamp,sigmoid), math operators (binary and unary +,- and ^,*,/,%) and constants (e,pi)
-- run expressions on both components of CONDITIONING (not that I know what they do), LATENT, IMAGE and FLOAT
+- expression parsing with support for functions and variables:
+ - functions:
+  - sin, cos, tan
+  - asin, acos, atan
+  - atan2 (x,y)
+  - sinh, cosh, tanh (can produce NaN outside range -1...1)
+  - asinh, acosh, atanh (can produce NaN outside range -1...1)
+  - abs, sqrt (produces NaN on negative numbers), ln (log with base e), log (base 10), exp, pow
+  - smin, tmin, smax, tmax, tnorm,snorm (norm not applicable on number math node), floor, ceil, round, gamma,clamp,sigm, math operators (binary and unary +,- and ^,*,/,%) and constants (e,pi)
+   - s prefixed return one number
+   - t prefixed work element-wise
+ - variables
+  - a, b, c, d : inputs of type based on node
+  - w, x, y, z : each node allows use of 4 additional floats
+  - W : Width of tensor - does not work on FLOAT and CONDITIONING
+  - H : Height of tensor - does not work on FLOAT and CONDITIONING
+  - C : Channel of tensor - used as color chanel in IMAGE or as information channel in others. does not work on FLOAT and CONDITIONING
+  - B : Batch - does not work on FLOAT and CONDITIONING
+  - X : X position in tensor - does not work on FLOAT and CONDITIONING
+  - Y : Y position in tensor - does not work on FLOAT and CONDITIONING
+  - I : Tensor used to initalise sampler - usually zeroed out and generated by Empty Latent Image node - Exclusive for NOISE
+- run expressions on both components of CONDITIONING (not that I know what they do), LATENT, IMAGE, NOISE and FLOAT
 
 ## Develop