Updated readme with topics and usage guide

Author: jtomori

README.md

@@ -1,2 +1,32 @@
-# vex_tutorial
-Extensive tutorial showing possibilities of VEX scripting language inside Houdini
+# VEX TUTORIAL
+## Extensive tutorial showing examples of usage of VEX scripting language inside SideFX Houdini
+<p align="right">by Juraj Tomori</p>
+
+### How to use
+You can clone, or [directly download](https://github.com/jtomori/vex_tutorial/archive/master.zip) this repository.<br>
+It contains **examples.hipnc** and **vex/include/myLib.h** files which are full of various examples with explanations in comments.<br>
+Alternatively you can use this page for quick looking at the topics covered and some of the code that I include here as well. I am not including here all of the code since sometimes it might not make a lot of sense outside of Houdini.
+
+### Topics
+* debugging, utputing text with printf()
+* hand editing of values in Geometry Spreadsheet, lock, delta lock
+* external vex files/libraries referencing
+* void functions
+* variable casting
+* function casting
+* accessing parameters from myself, another node, easy creation
+* accessing attributes from myself, another inputs
+* accessing volumes, from another inputs as well
+* function overloading
+* vector swizzling
+* accessing values in vectors, matrices, arrays
+* arrays: slicing, reversing, saving into attribs, changing file path example
+* escaping strings
+* checking for existence of attributes, auto attribute creation
+* optransform usage
+* accessing / changing prim intrinsics - vdb, prims, packed, abc
+* writing vex snippets, inlines in vops
+* structs, struct functions - limited OOP
+* functions returning an array, array of structs
+* including *math.h* - useful constants, xform orders
+* DOPs - accessing geometry, volumes, bindings, gas field vop, gas field wrangle, sop solver