I have found this great tutorial in gen patch a day5

https://cycling74.com/tutorials/gen-patch-a-day/.

The problem is that I can not clearly understand what actually happens.

OK, if I have a 2 dim 3 plane matrix, length will give me sqrt(r^2+b^2+g^2) for every pixel.

So I am new to isosurf and I can not imagine why [matrix 1 float32 32 32 32] -> [length] gives sphere???

I have found this great tutorial in gen patch a day5
https://cycling74.com/tutorials/gen-patch-a-day/.
The problem is that I can not clearly understand what actually happens. 

distance functions?