Updated

Documentation/doc/biblio/geom.bib

@@ -145397,6 +145397,17 @@ of geometric optics."
 		 any other by flips."
 }
 
+@article{w-sf-76
+, author =	{Neal R. Wagner}
+, title =       {The Sofa Problem}
+, year =        {1976}
+, journal =     {The American Mathematical Monthly}
+, volume =      {83}
+, number =         {3}
+, pages =       {188--189}
+, doi =         {10.2307/2977022}
+}
+
 @inproceedings{ww-oedca-00
 , author =	"Uli Wagner and Emo Welzl"
 , title =	"Origin-Embracing Distributions, or A Continuous Analogue of the Upper Bound Theorem"

Set_movable_separability_2/doc/Set_movable_separability_2/Set_movable_separability_2.txt

@@ -9,18 +9,39 @@ namespace CGAL {
 
 \section sms_sec_intro Introduction
 
+Problems of moving sets of objects, such as polygons in the plane and
+polyhedra in three dimensions, without allowing collisions between the
+objects are ubiquitous in many fields including motion planning,
+computer graphics, VLSI layout, and manufacturing. One class of such
+problems, referred to as <em>Movable Separability of Sets</em>
+\cgalCite{t-mss-85}, considers the separability of sets of objects
+under different kinds of motions and various definitions of
+separation. The <em>moving sofa problem</em> or <em>sofa problem</em>
+(see <a
+href="https://en.wikipedia.org/wiki/Moving_sofa_problem">Moving sofa
+problem</a> is a classic member of this class. It is a two-dimensional
+idealisation of real-life furniture-moving problems; it asks for the
+rigid two-dimensional shape of largest area \f$A\f$ that can be
+maneuvered through an L-shaped planar region with legs of unit width
+\cgalCite{w-sf-76}. The area \f$A\f$ thus obtained is referred to as
+the sofa constant. The exact value of the sofa constant is an open
+problem.  These problems become progressively more challenging as the
+allowable separation motions becomes more complex (have more degrees
+of freedom), the number of objects involved grows, or the shape of the
+objects becomes more complicated.
+
+\cgalFigureBegin{sms_2_fig_sofa_problem,sofa_problem.png} The
+Hammersley sofa has area 2.2074 but is not the largest solution.
+\cgalFigureEnd
+
+\section sms_sec_casting Casting
+
 Casting is a manufacturing process where liquid material is poured
 into a cavity inside a mold, which has the shape of a desired
 product. After the material solidifies, the product is pulled out of
 the mold. Typically a mold is used to manufacture numerous copies of a
-product, in which case we need to make sure that the solidified
-product can be separated from its mold without breaking it.  The
-challenge of designing a proper mold belongs to a larger topic termed
-<em>Movable Separability of Sets</em>; see \cgalCite{t-mss-85}
-These problems become progressively more challenging as the allowable
-separation motions becomes more complex (have more degrees of
-freedom), the number of objects involved grows, or the shape of the
-objects becomes more complicated.
+product. The challenge is design a proper mold, such that the solidified
+product can be separated from its mold without breaking it.
 
 This package provides a function called
 `single_mold_translational_casting_2()` that given a simple closed