issue

issue

## introduction

This is a suggestion on how we could make use of preprocessor definitions inside a shadermaterial.

## Why 

I needed a shadermaterial that had more then 16 texture uniforms defined but depending on the configuration of my application only used 16 or less texture uniforms. So I needed the rebuild my shader sourcecode programmatically or I could make a definition system which used preprocessor definitions.

## definition

We add a new property to the object to define the preprocessor