.. role:: code
   :class: code

MbLineSegment3D Straight-Line Segment
=====================================
.. _MbLineSegment3D_Straight_Line_Segment_:

.. kernel version: 118065

The :code:`MbLineSegment3D` class is declared in the *cur_line_segment_3d.h* file. 

The :code:`MbLineSegment3D` straight-line segment is defined by the start point
:ref:`MbCartPoint3D <MbCartPoint3D_Radius_Vector_of_Point_in_3D_Space_>` **point1** and the end point
:ref:`MbCartPoint3D <MbCartPoint3D_Radius_Vector_of_Point_in_3D_Space_>` **point2**. 

.. figure:: ../../pictures/O.4.3.1.png
   :width: 12cm
   :align: center

In the method

.. code-block:: cpp 
   
   PointOn( double & t, MbCartPoint3D & r ) 

the radius vector **r** of the segment is described by the vector function 

.. math::

   \mathbf{r}(t) = (1 - t) \cdot \mathbf{point1} + t \cdot \mathbf{point2}.

The domain of the segment parameter lies within the range from zero to one. 
The parameter *t*\ :subscript:`min` = 0 corresponds to the start point **point1** of the segment, and the parameter *t*\ :subscript:`max` = 1 corresponds to the end point **point2** of the segment.