===== Transformation: Stretching in 3D space =====
**Definition**: x'=x0+(x-x0)/scale (inverse mapping)

**Call**: hfSTretch3D(xt,x0,sx,sy,sz);

**Parameters**:

xt - point coordinates array to be changed

x0 - reference point for stretching

sx,sy,sz - scaling factors along axes

**Test file**: [[http://hyperfun.org/stretch.hf|stretch.hf]]