Understanding the Meshing Parameters

The following page helps you understand how to set the parameters to generate a meshing on a geometry.

Meshing parameters are the same wherever you decide to set them (Local Meshing or Simulation Meshing).

To define a meshing, there are three meshing settings and three meshing modes.

Meshing Modes

Note: From 2022R2, the new default value is Proportional to Face size. Selecting between Proportional to Face size and Proportional to Body size may slightly affect the result according to the elements meshed.
Note: When setting the meshing to Proportional to Face size, the results may return more faces than Proportional to Body size. These additional faces should be really small and they should not influence the ray propagation.
Note: When running a simulation for the first time, Speos caches meshing information if the Meshing mode is Fixed or Proportional to Body size. This way, when you run a subsequent simulation and you have not modified the Meshing mode, the initialization time may be a bit faster than the first simulation run.

Proportional to Face Size

Proportional to Face size means that the tolerance adapts and adjusts to the size of each face of the object. The Sag and the Step will therefore depend on the bounding box size of each face.

CAUTION: The meshing mode Proportional to Face size is not watertight, leading to potential simulation errors. For more information, refer to Watertight Meshing.

Proportional to Body Size

Proportional to Body size means that the tolerance adapts and adjusts to the size of the body. The Sag and the Step will therefore depend on the bounding box size of the body.

Fixed

Fixed means that the tolerance remains unchanged no matter the size or the shape of the object. The mesh of triangles are forced on the object.

Meshing Setting: Sag

The Sag setting corresponds to a surface deviation. In other words, this is the distance maximum between the geometry (edge and/or face) and a meshing segment.

The Sag applies when the face or edge is curved. When the face/edge is planar the Sag does not apply.

According to the mode selected, the Sag value that you define has a different meaning:

  • When the mode is Fixed: the Sag is expressed in millimeters

    The value entered corresponds to the maximum distance possible.

  • When the mode is Proportional (Face or Body): the Sag has no unit.

    The value entered is a division value. The calculation to find the maximum distance possible corresponds to Face or Body Bounding Box / Sag division value

Fixed Proportional
According to the Sag value, the distance between the meshing and the surface changes.
  • A small Fixed Sag value or a large Proportional Sag value creates triangles that are smaller in size and generated closer to the surface. This will increase the number of triangles and potentially computation time.
  • A large Fixed Sag value or a small Proportional Sag value will generate looser triangles that are placed farther from the surface. A looser meshing can be used on objects that do not require a great level of detail.
Note: In case of a thin body, make sure to apply a fixed meshing sag mode and a meshing sag value smaller than the thickness of the body. Otherwise you may generate incorrect results.
Small Fixed Sag value (or large Proportional Sag value) Large Fixed Sag value (or small Proportional Sag value)

Meshing Setting: Step

The Step parameter corresponds to the maximum edge length of a meshing segment.

A small Meshing Step value generates triangles with smaller edge lengths. This usually increases the accuracy of the results.

According to the mode selected, the Step value that you define has a different meaning:

  • When the mode is Fixed: the Step is expressed in millimeters

    The value entered corresponds to the maximum distance possible.

  • When the mode is Proportional (Face or Body): the Step has no unit.

    The value entered is a division value. The calculation to find the maximum distance possible corresponds to Face or Body Bounding Box / Step division value

Fixed Proportional
According to the Step value, the size of the meshing segments changes.
  • A small Fixed Step value or a large Proportional Step value creates triangles that are smaller in size. This will increase the number of triangles and potentially computation time.
  • A large Fixed Step value or a small Proportional Step value will generate bigger triangles. A bigger meshing can be used on objects that do not require a great level of detail.
Note: For a Heavyweight body, the Meshing step value precision decreases when applying a value below 0.01mm.
Small Fixed Step value (or large Proportional Step value) Large Fixed Step value (or small Proportional Step value)

Meshing Setting: Angle

The Angle setting corresponds to the angle deviation. In other words, this is the maximum angular variation in degrees allowed for all normals to the surface represented by a specific mesh triangle.

The Angle applies when the face is curved. When the face is planar the Angle does not apply because all normals are parallel, meaning the angular variation = 0.

According to the Angle value, the number of triangles can change to respect the constraint:
  • A small Angle value creates triangles that are smaller in size. This will increase the number of triangles and potentially computation time.
  • A large Angle value will generate bigger triangles. A bigger meshing can be used on objects that do not require a great level of detail.
Large Angle Small Angle