# Projection Algorithms¶

Projection algorithms allow to define the mesh of a geometrical object by the projection of another already meshed geometrical object.

Note

Source and target geometrical objects mush be topologically equal, i.e. they must have same number of sub-shapes, connected to corresponding counterparts.

Topologically equal faces suitable for 2D projection.

## Projection 1D¶

Projection 1D algorithm allows to define the mesh of an edge (or group of edges) by the projection of another already meshed edge (or group of edges).

To apply this algorithm select the edge to be meshed (indicated in the field Geometry of Create mesh dialog box), Projection1D in the list of 1D algorithms and click the “Add Hypothesis” button. The following dialog box will appear:

In this dialog you can define

• the Name of the algorithm,

• the already meshed Source Edge and

• the Source Mesh (It can be omitted only when projecting a sub-mesh on another one of the same Mesh).

• It could also be necessary to define the orientation of edges, which is done by indicating the Source Vertex being the first point of the Source Edge and the Target Vertex being the first point of the edge being meshed.

For a group of edges, Source and Target vertices should be shared by only one edge of the group. If Source and Target vertices are specified, the edges in the group must be connected. The source and target groups must contain equal number of edges and they must form topologically equal structures.

## Projection 2D¶

Projection 2D algorithm allows to define the mesh of a face (or group of faces) by the projection of another already meshed face (or group of faces). This algorithm works only if all edges of the target face have been discretized into the same number of segments as corresponding edges of the source face.

To apply this algorithm select the face to be meshed (indicated in the field Geometry of Create mesh dialog box), Projection 2D in the list of 2D algorithms and click the “Add Hypothesis” button. The following dialog box will appear:

In this dialog you can define

• the Name of the algorithm,

• the already meshed Source Face and

• the Source Mesh (It can be omitted only when projecting a submesh on another one of the same Mesh).

• It could also be necessary to define the orientation of mesh on the face, which is done by indicating two Source Vertices, which belong to the same edge of the Source Face, and two Target Vertices, which belong to the same edge of the face being meshed.

The groups of faces are suitable for this algorithm only if they contain an equal number of faces and form topologically equal structures.

## Projection 1D-2D¶

Projection 1D-2D algorithm differs from Projection 2D algorithm in one aspect: it generates mesh segments on edges of the face according to the projected 2D elements; thus it does not require the edges to be meshed by any other 1D algorithm; moreover it does not allow to mesh edges of the face using another algorithm via definition of sub-meshes.

## Projection 3D¶

Projection 3D algorithm allows to define the mesh of a shape by the projection of another already meshed shape. This algorithm works only if all faces and edges of the target shape have been meshed as 1D-2D Projections of the faces and edges of the source shape. Another limitation is that this algorithm currently works only on boxes.

To apply this algorithm select the solid to be meshed (indicated in the field Geometry of Create mesh dialog box), Projection 3D in the list of 3D algorithms and click the button. The following dialog box will appear:

In this menu you can define the Name of the algorithm, the already meshed source 3D shape and the Mesh (It can be omitted only when projecting a submesh on another one from the same global Mesh). It could also be necessary to define the orientation of mesh on the shape, which is done by indicating two Source Vertices, which belong to the same edge of the source 3D Shape, and two Target Vertices, which belong to the same edge of the source 3D Shape.