Reduction parameters

Using the data reduction, the number of surface triangles can be reduced, or the triangles can be pairwise united in quadrilaterals. Data reduction is applicable to any surfaces generated by Tosca Structure.smooth; it also affects the original surface, but does not modify loaded nodes. By default, data reduction is turned off.

Following parameters guide the data reduction:

Data reduction parameters of Tosca Structure.smooth

Parameter

Value

Description

Supported by

TAe

GUI

TExt

TS.pre

TS.smooth

REDUCTION_RATE

Real value between 0 and 100

Default: 0.3

Defines the percent of faces that should be removed during the data reduction; if set to 0, no data reduction occurs. If set to 100, the data reduction stops when no faces can be removed (that is checked using REDUCTION_ANGLE parameter).

x

x

x

x

REDUCTION_ANGLE

Real value in degrees between 0 and 90

Default: 15

Defines the maximal angle between adjacent faces at a node such that the node may be removed during the data reduction.

x

x

x

x

MIXED_MESH

yes (unite triangles to quadrilaterals)

no (no change)

default: no

If set to YES, then the quadrilaterals are formed from adjacent triangles; applies to VTFX, ONF, IGES and WRL output formats only.

-

x

x

x

SELF_

INTER- SECTION_

CHECK

off (no checks)

check (check once)

runtime (check always)

iterative (first run without check, rerun if needed)

Default: iterative

Defines if the self-intersection checks are to be performed during the isocut, smoothing and data reduction. See below.

x

x

x

-

MIN_ANGLE

Real value between 0 and 90

Default: 15

Defines the minimal angle of the triangles that result from the smoothing and data reduction; triangles with smaller angles may be present if they are created during the isocut. Too large value may prevent the smoothing; too small value may lead to degenerated triangles.

x

-

x

-
Important:

Note that SELF_INTERSECTION_CHECK and MIN_ANGLE parameters are also used during isosurface generation and smoothing.

The data reduction consists in decreasing the number of surface triangles; it might be needed in case that the surface is produced from a very fine FE model or simply has too many faces. The data reduction can be applied to isosurfaces as well as surfaces of models with or without optimization displacements. During the data reduction, the adjacent triangles with nearly coinciding planes get united and subsequently subdivided so that a triangular surface with smaller number of faces is obtained. This process is repeated until the decrease of the number of triangles reaches a certain percentage of the starting number of triangles; this percentage is the value of the parameter REDUCTION_RATE. If set to 0 (default), no data reduction is performed; if set to 100, the data reduction is repeated until the number of triangles cannot be decreased further. The conditions that define if a local data reduction can be made are as follows:

  • the angle between the normals of adjacent triangles is less than the value of REDUCTION_ANGLE parameter (default value is 15°);
  • the angles of triangles after the reduction are larger than the value of MIN_ANGLE parameter;
  • no self-intersection occurs after the reduction (only checked if SELF_INTERSECTION_CHECK parameter is set to iterative or runtime).

As seen from the example shown below, in order to achieve maximal data reduction, REDUCTION_RATE parameter should be set to 100 and REDUCTION_ANGLE parameter to a large value (e.g. 45). However, the surface then becomes coarse. By changing the REDUCTION_ANGLE parameter, the surface with sufficient smoothness and reasonably small number of triangles can be obtained.

The parameters MIN_ANGLE and SELF_INTERSECTION_CHECK usually do not influence the number of triangles remaining after the data reduction, unless MIN_ANGLE is set to a large value (30 or more; default value is 15). Note that these parameters are also used in the surface smoothing.

REDUCTION_RATE = 0 (default) REDUCTION_ANGLE = 15 (default) 4842 faces (100%)

REDUCTION_RATE=100 REDUCTION_ANGLE =15 (default)




REDUCTION_RATE = 50 REDUCTION_ANGLE = 15 (default) 2420 faces (50.0%)

REDUCTION_RATE = 100 REDUCTION_ANGLE = 45 480 faces (9.9%)

Data reduction can also achieved by generating the mixed triangular-quadrilateral surface. If the parameter MIXED_MESH is set to yes, then the quadrilaterals are formed from adjacent triangles. The triangles can only be united when the resulting quadrilateral is convex and non-degenerated, and the angle between the normals of the triangles is smaller than a certain constant value (currently 15°). An example of using the MIXED_MESH parameter is presented in the following figure.

Important:

The output of a mixed surface is only available for certain output formats (namely VTFX, ONF, IGES and WRL).

In case of other formats, the triangular surface is always saved, thus the parameter MIXED_MESH has no influence on the result. Also, the triangular surface is always used for the generation of the slices and the border.

MIXED_MESH = no (default): 4842 triangles


MIXED_MESH = yes: 2642 triangles, 1100 quadrilaterals

The generation of the mixed mesh can be combined with the data reduction described above; it is performed after the data reduction is finished.