-\section S1_PADDER The PADDER Algorithm
-
-PADDER is an algorithm that creates a set of particules called a "discrete mesh".
-The particules are characterized by a location in space and a weight that can be considered
-as the radius of a sphere whose center is the location of the particule.
-
-Discrete meshes are typically used to modelize civil components in rapid dynamic
-computation problems (seisms, chocs). These components consists in concrete parts
-embedding steal bares for reinforcement. These parts are input to the algorithm
-as standard finite elements meshes. The cells of theses meshes drive the location
-and sizing of particules.
-
-In the med representation, a discrete mesh is described as MED_BALL elements.
-A MED_BALL element is defined by a location and a radius.
-
-\section S2_PADDER The PADDER SALOME plugin
-
-The PADDER algoritm is integrated in the module SMESH as a SALOME
-plugin. This section illustrates how to use this plugin to create a
-discrete mesh.
-
-In this example, we suppose that two standard meshes (Finite Elements
-Meshes) have been created and publish in the study to modelize the
-concrete part (here with the name "concrete") and the steal bars part
-(here with the name "ferrail"):
-
-\image html SMESH_spadder_start.png
-
-The PADDER plugin can be invoked from the SMESH plugins menu, as
-illustrated on the figure below:
-
-\image html SMESH_spadder_menu.png
-
-When you clic on the "PADDER mesher" item, the graphical interface of
-the PADDER plugin appears:
-
-\image html SMESH_spadder_plugindialog_start.png
-
-This interface invites you to specify input data by pressing the button
-"Input". This command opens the Input dialog box to specify the list
-of meshes and the type of the selected meshes (to be choosen between
-"concrete" or "steelbar" using the combobox on the right side of the
-input line):
-
-\image html SMESH_spadder_inputdialog_start.png
+\section S1_PADDER The SpherePadder Algorithm
+
+SpherePadder is a geometric algorithm that creates a set of rigid
+spherical particles of different sizes called a "discrete element
+mesh". The centroid positions of particles are randomly generated by a
+"disordering" technique described in [1] that provides a polydisperse
+assembly with a particular size distribution. The spheres are
+positioned or “padded” into a tetrahedral mesh, which must be
+generated first. As illustrated below, SpherePadder creates a Discrete
+Element (DE) assembly in seven steps (see [1] for details):
+
+\image html padder_image01.png
+
+In order to increase the density of the whole packing and to fill
+spheres in the gaps close to the mesh boundaries (created by removing
+boundary spheres), SpherePadder detect `void spaces' where new spheres
+could be added by applying a particular geometric procedure, using
+tetrahedra resulting from a tridimensional Delaunay triangulation
+built with the sphere centers. That triangulation is generated by
+using the CGAL library [2].
+
+DE meshes generated by SpherePadder algorithm are used in EUROPLEXUS
+fast dynamics software simulations [3] to model the discontinuous
+behaviour (fractures, fragmentation) of reinforced concrete structures
+under severe dynamic loads such as impacts or explosions. The
+characteristic size of elements does not have to be representative of
+concrete constituents, such as granulars or cement matrix, since the
+aim is to reproduce the dynamic behaviour of the simulated material at
+the macroscopic scale.
+
+To generate DE mesh for a reinforced concrete structure, one should
+supply a single tetrahedral mesh for concrete and as many segment-type
+1D meshes as groups of steel reinforcement bars of different
+diameters. The size (length) of segment-type steel reinforcement
+elements should correspond to the modelled bar’s
+diameter. SpherePadder algorithm will create steel discrete elements
+by using the segment’s length as the DE diameter.
+
+Warning: The User should control that all steel bars of a given
+diameter in a mesh belong to the same mesh group, and that different
+steel bar groups do not use the same diameter.
+
+\image html padder_image02.png
+
+If steel mesh is not provided, a pure concrete DE mesh is generated.
+
+In MED representation, DE meshes are described by using MED_BALL type
+structural elements. Each MED_BALL element is defined by its centroid
+location and a diameter.
+
+Written in C++, SpherePadder is free software licensed under the terms
+of the GNU General Public License.
+
+Bibliography:
+- [1] J.-F.Jerier, V.Richefeu, D.Imbault, F.-V. Donzé, “Packing spherical discrete elements for large scale simulations”, Computer Methods in Applied Mechanics and Engineering 199 (2010) 1668–1676.
+- [2] CGAL, Computational Geometry Algorithms Library. https://gforge.inria.fr.
+- [3] EUROPLEXUS: a computer program for the finite element simulation of fluid–structure systems under transient dynamic loading. http://europlexus.jrc.ec.europa.eu, (User’s Manual).
+
+\section S2_PADDER The SpherePadder SALOME plugin
+
+The SpherePadder algorithm is implemented as an external software
+program. This external program is integrated in the SMESH module as a
+SALOME plugin that manage the execution of the SpherePadder program
+from within the SALOME framework. This section illustrates how to use
+this plugin to create a discrete element mesh.
+
+In this example, we consider a concrete piece with a single
+reinforcement bars group. Thus, two standard (Finite Element type)
+meshes have been created and published in the study, the first one
+named “concrete”, and second one named "ferrail", for the steel bars
+part:
+
+\image html padder_image03.png
+
+The SpherePadder plugin can be activated in the SMESH plugins menu, as
+illustrated on the figure below:
+
+\image html padder_image04.png
+
+When clicking on the "PADDER mesher" item, the graphical interface of
+the SpherePadder plugin appears:
+
+\image html padder_image05.png
+
+This interface invites you to specify input data by pressing the
+button "Input". This command opens the Input dialog box allowing to
+specify the list and the type of selected meshes (to be chosen between
+"concrete" and "steelbar" using the combobox on the right side of the
+input line):
+
+\image html padder_image06.png