Curve frame on surface

Слиты nikitronn запросил слияние curve_frame_on_surface в master

Created by: portnov

Given a surface and a curve in the surface's U/V space, this node calculates a reference frame of a curve for the given value of curve's T parameter. The frame is calculated so that:

  • it's X axis is pointing along surface's normal;
  • it's Z axis is pointing along curve's tangent (in 3D space);
  • it's Y axis is perpendicular to both X and Z.

This node allows one to place some object at the curve on the surface, while aligning it both with curve's tangent and surface's normal.

Usual "curve frame": Screenshot_20200804_141023

Curve frame on surface: Screenshot_20200804_141225

Preflight checklist

Put an x letter in each brackets when you're done this item:

  • Code changes complete.
  • Code documentation complete.
  • Documentation for users complete (or not required, if user never sees these changes).
  • Manual testing done.
  • Unit-tests implemented.
  • Ready for merge.