Thank you, Charles! Actually, you found a bug in the code. I substituted in the line...
I propose another algorithm to define normal vectors to path3 at any its points....
I propose another algorithm to define normal vectors to path3 at any its points....
I propose another algorithm to define normal vectors to path3 at any its points....
I propose another algorithm to define normal vectors to path3 at any its points....
I propose another algorithm to define normal vectors to path3 at any its points....
I propose another algorithm to define normal vectors to path3 at any its points....
I propose another algorithm to define normal vectors to path3 at any its points....