+ mipmap-control - controls how the mipmap levels are computed.
+ Each color channel can be computed with different functions
+ among average, sum, product, min and max. For example :
+ <function-r>average</function-r>
+ <function-a>min</function-a>
+ function-r - function for red
+ function-g - function for green
+ function-b - function for blue
+ function-a - function for alpha