Working with Polyhedral Entities in Civil Engineering 3D Design

You can manage polyhedral features and Exact entities in different infrastructures thanks to data conversion.

This task shows you how to:

 

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Convert a Mesh/Scan/Cloud of Points into a Polyhedral Feature

You can convert a Mesh/Scan/Cloud of Points into the target geometric representation, i.e. a polyhedral feature.

  1. To convert the terrain (mesh) into a polyhedral feature, select the terrain in the Terrain Preparation app.
  2. Click the Enable for Engineering 3D Design contextual command.

    This command is available in both Terrain Preparation and Civil Engineering 3D Design apps.

    The terrain's PartBody contains:

    • The terrain which is colored gray in the 3D area.
    • A new polyhedral feature Body from (name of the terrain) , with the polyhedral mask displayed on it, is created in the active set and displayed in gray.

    As a mesh can be composite, i.e. composed of several cells, the resulting will be composite also. Here is the mapping between initial and resulting objects:

    Initial data type Conversion result
    Cloud of points -
    Grid of points Grid of points
    Set of grids Set of grids
    Mesh Mesh and sub mesh are converted as a mesh. If a mesh is split into several disconnected zones, each zone will be converted.
    Scan

    is converted as a polyline. The conversion command will generate a very basic feature from the geometry: A scan is converted in a wire of one edge if open or in a wire of two edges if closed.

    Vectors -
    Set of scans is converted as much polylines it contains scans.

    If there is an update of the terrain data, you must convert this new terrain and use the Replace command.

    After conversion, you can launch Civil Engineering 3D Design commands such as Trim, Intersection, Split, Transformation (rotation, translation, symmetry...), Join, Point, Line and Plane.

  3. Select the terrain to trim the two surface elements (the terrain and the new polyhedral feature) by cutting each other mutually.
  4. From the Wireframe and Surface section of the action bar, click Trim .
  5. Select the volume that has been converted into a polyhedral feature.
    The Trim feature appears under the Polyhedral node. Then you can cut the terrain with the volume.

Convert an Exact Feature into a Polyhedral Feature

You can convert an exact entity into a polyhedral feature with the Tessellate command, available in the Civil Engineering 3D Design app.

If you tessellate a surface, you obtain a mesh with a faceted geometry. If you tessellate a curve (wire), you obtain a polyline.

This command is associative and contains only one parameter: the SAG representing the chordal error between original surface and mesh triangles.

  1. To convert an exact volume (or surface) into a polyhedral entity with a given accuracy, click Tessellate from the Wireframe and Surface section of the action bar.

    When you have hybrid inputs for an operator supporting only identical types, just tessellate the exact input to get two identical type operands.

  2. Select the feature to tessellate: the volume (or a surface/exact wire).

    The entity Tessellate is created under the node Geometrical Set. As the volume has been tessellated, it is compatible with the new polyhedral feature Body from (name of the terrain) .

    After conversion, you can select both polyhedral entities and use the Civil Engineering 3D Design commands such as Trim, Intersection, Split, Transformation (rotation, translation, symmetry...), Join, Point, Line and Plane.

    If you choose the Split functionality for example, a Split feature with the polyhedral mask appears under Geometrical Set.

  3. Select one of these sag modes (tolerance) that measures the maximum deviation between the initial surface/wire and the tessellated surface:
    • Fine: already defined parameters for a minimum and accurate tesselation.
    • Optimized: already defined parameters for an optimized tesselation.
    • Coarse: already defined parameters for a rough tesselation.
    • Manual: you can define a sag value manually. When a tessellation feature is created for the first time, the default value in the 3DPart can be defined in a specific preference. This preference, Tesselation of polyhedral features, available in Me > Preferences > Infrastructure > 3D Shape Infrastucture in the 3D Shape tab, can be locked by an administrator.

    You can tessellate surfaces or wires automatically: It is possible in some cases to tessellate automatically the exact input when needed. This will create an internal Tessellate feature.

    You can choose the tesselation Type and sage value in Me > Preferences > Infrastructure > 3D Shape Infrastucture in the 3D Shape tab.

    If an automatic tessellation has been created by an exact feature for the first time, the sag value is the one stored in the Me > Preferences and this value is then stored on the 3Dpart for further reuse. Once an automatic tessellation feature has been created, the value used for the next automatic tessellation features is the one stored on the 3D part (no more fetched in the preferences).

    The value used for an automatic tessellation feature and stored on the 3D part is accessible either through (x) or by displaying the properties on the 3DPart.

Convert a Polyhedral Polyline into an Exact Polyline

You can convert a polyhedral polyline into a GSD exact polyline composed of as many edges and wires as there are bars and domains in the initial polyhedral polyline. The main advantage of this command is to open the Shape and Part design commands for a polyline coming from the polyhedral world. As all the commands (for example, Sweep) are not compatible with polyhedral entities, you can use Create Polyline to convert a discrete polyline into a GSD polyline.

  1. To convert a polyhedral polyline into an exact polyline, click Create Polyline from the Wireframe and Surface section of the action bar.
  2. Select a polyhedral edge (Polyhedral Wire polyline).

Once a surface or a terrain has been converted into a polyhedral feature, you can use some Civil Engineering 3D Design commands that are not supported by this conversion, such as intersection, projection, ...

Use Miscellaneous Commands

There is a series of miscellaneous Civil Engineering 3D Design commands that are supported by this conversion.

  1. You can use the following commands in the context of polyhedral feature.

    The following table exposes what are the compatible commands with the conversion command:

    Command Conversion result

    Export

    Export a polyhedral feature in a standard STL format from the Export menu.

    Export a polyhedral feature in a standard mesh format through the Terrain File Export menu.

    Solids

    Considering the automatic Boolean operations which occur for solids in bodies, the behavior is different from wireframe & surfaces.

    In a solid body, it is not possible to mix exact and polyhedral solids. A solid tessellate command is added.

    If you want to make a Boolean operation (Add / Remove / Intersect or Assemble) between two solid bodies of different kinds, you need first to add a tessellate feature at the end of the exact solid body, and then do the boolean operation between both polyhedral inputs. This tessellate can be automatically created.

    You can also split a polyhedral solid body by a polyhedral surface. If you need to split by an exact surface, a tessellate needs to be added first.

    And you can split an exact solid body by a mesh. This will require the tessellation of the solid.

    Assembly Cut

    It is also possible to create an Assembly Cut from the Assembly Design app. You can select polyhedral mesh as cutting element. As a result, the impacted solid will be automatically tessellated when needed and split by the cutting element.

    Support associative design on topological feature using sub-elements

    It is possible to access the sub-elements of a polyhedral feature, wherever it comes from a tessellation or when it has been natively generated. You can use or extract internal faces, edges or vertices on a polyhedral feature. For example:

    • Extract internal edge to make a projection.
    • Compute boundary between two tangency discontinuities.

    Conversion from Terrain to polyhedral feature generates only a simplified feature, therefore it does not give access to what can look as internal faces, edges or vertices.

    Hybrid Operations (*)

    In some particular cases, it is possible to directly make operations involving objects of different nature: polyhedral and exact (CATBody) features without explicitly converting the objects. The conversion remains mandatory but is done automatically by the command.

    The tessellation feature is automatically created and stored under the (exact) feature involved in the operation. This allows to reuse this tessellated view of the feature when needed later. The value used for the tessellation parameter is the one stored as the default value in the current 3D Part, except the first time when the value is fetched from the Preferences.

    Only three options of the Tesselation of polyhedral features in Me > Preferences > Infrastructure > 3D Shape Infrastucture in the 3D Shape tab are available for automatic tessellation: Fine / Optimized / Coarse. Note that a fine tessellation, even though more precise, takes more memory and disk space than a coarse one.

    Properties

    Right-click on a polyhedral feature to display mesh information.

    Drafting

    You can create a drawing containing any of the three kinds of geometric representations (mesh/scans/clouds of points).

    Road Design

    		The Road Surface and Road Preliminary Design commands are based on the polyhedral modeler.

    (*) For example: the trim of an exact surface by a polyhedral surface. You can directly pick both objects and press OK. Internally, the exact surface is tessellated and the trim between the selected polyhedral surface and the one created on the fly is performed. The result is a mesh. The commands supporting this behavior are:

    Command Result

    Intersect exact surface/polyhedral surface or polyhedral surface/exact surface

    A polyhedral surface

    Split an exact surface by polyhedral surface or polyhedral surface by an exact surface

    A polyhedral surface

    Trim an exact surface by polyhedral surface or polyhedral surface by exact surface

    A polyhedral surface

    Projection (directional) of an exact curve on a polyhedral surface

    A polyhedral curve

  2. You can use some other hybrid operations that do not require conversion. Therefore no need to convert the input data in the same representation to be able to use the command. It concerns a limited set of operators in which the result can be well defined:
  3. The Contour Map and Deviation Analysis commands from Terrain Preparation are also available in the Civil Engineering 3D Design app, in the Review section of the action bar for the first one, in the Tools section for the second one. These commands work on a polyhedral feature.