# Generate Comparison Results

In the Generate tab, define the following options, which will be used to generate the comparison results.

The options available in this tab will vary depending on the Location you select.
1. Click the Generate tab.
2. From the Location list, specify where the entities you are comparing can be found.
• Choose Auto to generate results for entities positioned at any location, by automatically calculating a transformation matrix between the source and target entities. A maximum of one match for each source entity will be found. This option is only available for CAD-CAD comparison.
• Choose Position to generate results for entities positioned at a location that you specify. For the Source entities and the Target entities collectors, select up to three locations on the source that correspond to the same three locations on the target. This option will use these locations to define the transformation of the source entities to the target entities. A maximum of one match for each source entity can be found.
• Choose Recursive to generate results for entities positioned at any location, by automatically calculating transformation matrices between the source and target entities. Multiple matches can be found for each source entity. A source entity may match more than one target entity positioned at a different location. This option is only available for CAD-CAD comparison.
• Choose Rotate to generate results for entities rotated about a vector. Multiple matches may be found for each source entity, depending:
Axis
Select a collector that defines the rotation axis/vector.
Angle
Specify the rotation angle to search and find target entities.
Steps
Specify the number of times to increment the angle value when searching.
For example, in the image below, assume the red element is the source, the blue elements are the target, and the z-axis is the rotation vector. If the angle = 60 and the steps = 1, then only the first blue element will be found. If the steps = 2, then the first two blue elements will be found. If the steps = 3, then all three blue elements will be found. Similarly, if the angle = 30 and the steps = 1, then no blue elements will be found, but if the steps = 2, then the first blue element will be found.
• Choose Same side to generate results for entities positioned at the same location. A maximum of one match can be found for each entity source.
• Choose Symmetry to generate results for entities positioned symmetrically about a plane. A maximum of one match can be found for each source entity. When you select this option, the Symmetry plane selector becomes active. Use the Symmetry plane selector to select the plane about which the symmetry exists.
• Choose Translate to generate results for the entities translated along a vector. Multiple matches may be found for each source entity, depending on:
Direction
Select a collector that defines the translation vector.
Distance
Specify the translation distance to search and find target entities.
Steps
Specify the number of times to increment the distance value when searching.
For example, in the below image, assume the red element is the source, the blue elements are the target, and the x-axis is the direction vector. If the distance = 2 and the steps = 1, then only the first blue element will be found. If the steps = 2, then the first two blue elements will be found. If the steps = 3, then all three blue elements will be found. Similarly, if the distance = 1 and the steps = 1, then no blue elements will be found, but if the steps = 2, then the first blue element will be found.
3. In the Tolerance field, enter the tolerance to use for comparing entities, in model units.

A smaller value will lead to a more strict interpretation, while a larger value will lead to a looser interpretation.

The tolerance is not used to remove features smaller than the tolerance value. All features for a surface or mesh are considered valid for comparison regardless of their size, and must be within the tolerance of a similar feature on the compared entities for the surfaces or elements to be considered matched or overlapped.

4. For Result type, select the level of detail for the results.
Higher levels of detail require more calculation and processing time. Each level of detail produces different results based on the type of comparison you are performing. For detail description of the result types, refer to Comparison Result Types.
5. Optional: Perform a comparison a shells using their thickness.
1. Select the use thickened shells checkbox.
Restriction: Only available when you are comparing FE-CAD/CAD-FE.
2. To keep the internally calculated fillet distance relatively small, meaning that elements near fillet regions must also be close to the surfaces to prevent them from being marked as intersected, select the Match fillets checkbox.

Fillets are assumed to lie nearby fillet roots, which are located at all t-intersections and bends in the mesh of at least 44 degrees. Any nodes within an internally calculated distance of a fillet root are treated as being inside the fillet, and therefore they cannot cause an element to be marked as intersected. When you clear the Match fillets checkbox, the internally calculated distance will be relatively large, preventing many elements in fillet regions from being marked as intersected if they are not close to the surfaces.

The internally calculated fillet distance is based on the thickness of the elements touching the fillet root and the average thickness in the model. It is not a precise determinant of the actual fillet region and is only intended to prevent elements that are not close to the surfaces due to the presence of fillets from being marked as intersected. As a result, most models with fillets will have elements in the fillet regions marked as overlapped or intersected rather than matched.
Note: Clearing the Match fillets checkbox may cause the internally calculated fillet distance to be rather large for certain models, and may potentially mark elements as overlapped when they would otherwise be marked intersected due to the element's edges not matching surface lines.
3. Use the Ignore holes/slots option to specify which holes and/or slots in the surface data to ignored during the comparison.
If the features are smaller than the specified Holt/slot diameter and/or Slot length criteria, then they will be ignored. Element edges in the region of an ignored hole or slot are not required to be within the tolerance of a surface line. Element nodes over an ignored hole or slot cannot cause the element to be marked as intersected.
6. To use the normal projection of the centroid of an element to help determine with which surface an element should be associated, select the Include element centroids checkbox.

Without this option, elements are associated with a given surface based on the largest number of their nodes which are within the given tolerance of that surface. If an element has the same number of nodes within the given tolerance of more than one surface the association will be made arbitrarily. This option uses the projection of the element centroid to remove any ambiguity as to which surface is the best fit.

Additionally, elements that lie partially or completely off the edge of a surface will be marked as unmatched instead of intersected if the projection of the centroid does not lie on any surface. This option is particularly useful when comparing coarse meshes to highly curved surfaces.

This option is turned off by default because it can substantially increase the time spent comparing meshes if there are a large number of ambiguous elements.
Restriction: Only available for CAD-FE/FE-CAD comparisons.
7. To refacet all the surfaces in the model so that their facet size will be roughly equal to that of the compared elements, select the Refined facets checkbox.

This option is particularly useful when comparing highly curved geometries to FE meshes with a tight tolerance.

The Comparison tool uses surface facets, rather than the surfaces themselves, to quickly compare elements to surfaces or surfaces to surfaces. Often the default facets can be long, thin triangles which only roughly capture the surface curvature in highly curved areas. While the default facets can often be “close enough” to the surfaces they represent, nodes of an element which lie exactly on the surface may actually lie outside the given tolerance of the nearest surface facet. If this happens, the elements attached to that node will be marked as intersected or unmatched instead of overlapped or matched.

One solution to this problem is to increase the tolerance, but there are times when using a large tolerance will be undesirable. For those times you can select this option which will recalculate the facets for the surfaces such that they more closely adhere to the actual surfaces. The result will be more accurate results with more elements marked as matched or overlapped instead of intersected or unmatched.

This option is turned off by default because it can substantially increase the time spent making the comparison.
Restriction: Only available for CAD-FE/FE-CAD comparisons.
8. Click Run.

## Comparison Result Types

Overview of the different result types you can select when working with the Comparison tool.

### Standard Comparison

Table 1. Overview of Standard Comparison Result Type
CAD-CAD CAD-FE/FE-CAD FE-FE
Basic Matched (paired)

Unmatched

Matched (paired)

Unmatched

Matched

Unmatched

Full Matched (paired)

Overlapped

Intersected

Unmatched

Matched (paired)

Overlapped

Intersected

Unmatched

Matched

Overlapped

Intersected

Unmatched

Detailed Matched (paired)

Overlapped (paired)

Intersected (paired)

Unmatched

Matched (paired)

Overlapped (paired)

Intersected (paired)

Unmatched

Matched

Overlapped

Intersected

Unmatched

CAD-CAD
Result Type Description
Basic
Matched
Occurs when a source or target surface is within the given tolerance of a compared surface using a direct surface to surface comparison. All points and lines comprising each surface must match between the surfaces. Each matched surface is placed in a separate match type group with the surface it matches.
Unmatched
Occurs when a source or target surface differs from the closest compared surface to a degree larger than the tolerance.
Full
Matched
Occurs when a source or target surface is within the given tolerance of a compared surface using a direct surface to surface comparison. All points and lines comprising each surface must match between the surfaces. Each matched surface is placed in a separate match type group with the surface it matches.
Overlapped
Occurs when all facet nodes of a source or target surface are within the given tolerance of the compared surfaces and all of the facet nodes on the nearest compared surfaces' exterior edges are within the given tolerance of the source or target surface's exterior edges. All of the overlapped surfaces are placed in a single match type group.
Intersected
Occurs when at least one but not all facet nodes on a source or target surface are within the given tolerance of the compared surfaces or at least one of the facet nodes on the nearest compared surfaces' exterior edges is outside the given tolerance of the source or target surface's exterior edges. All of the intersected surfaces are placed in a single match type group
Unmatched
Occurs when there are no facet nodes on a source or target surface that are within the given tolerance of the compared surfaces, or all the criteria for the intersected match type are met and no interior facet nodes for the surface are within the tolerance of the compared surfaces.
Detailed Behaves the same as Full, except overlapped and intersected match types are separated out into pairs, or contiguous groups which share the same match type.
CAD-FE/FE-CAD
Result Type Description
Basic
Matched
Occurs when a group of elements are found having all nodes within the given tolerance of a surface, the areas defined by the surface and the elements are within 3%, and all of the nodes on the elements' exterior edges are within the given tolerance of the surface's exterior edges. Each matched surface is placed in a separate match type group with the elements it matches.
Unmatched
Occurs for surfaces and elements when the matched criteria are not met.
Full
Matched
Occurs when a group of elements are found having all nodes within the given tolerance of a surface, the areas defined by the surface and the elements are within 3%, and all of the nodes on the elements' exterior edges are within the given tolerance of the surface's exterior edges. Each matched surface is placed in a separate match type group with the elements it matches.
Overlapped
Occurs for a surface when all facet nodes on the surface are within the given tolerance of the elements and all nodes along the nearest FE mesh's exterior edges are within the given tolerance of the surface's exterior edges. It occurs for an element when all of the nodes of the element are within the given tolerance of the surfaces and all of the nodes of the element which touch the FE mesh’s exterior edges are within the given tolerance of the surfaces’ exterior edges. All overlapped surfaces and elements are placed in a single match type group.
Intersected
Occurs for a surface when at least one of the facet nodes on the surface is within the given tolerance of the elements and at least one point along the nearest FE mesh's exterior edges is outside the given tolerance of the surface's exterior edges. It occurs for an element when at least one node of the element is outside the given tolerance of the surfaces, or when at least one of its nodes which touch the FE mesh’s exterior edges is outside the given tolerance of the surfaces’ exterior edges. All of the intersected surfaces and elements are placed in a single match type group.
The options Include Element Centroids and Refine Facets can improve the accuracy of the results in both Full and Detailed results modes. Without these options, some elements will be marked as intersected if one of their nodes lies outside of the tolerance of a coarse facet approximating a curved surface. Other elements may get marked as intersected if it is ambiguous to which surface they belong or if they have one or two nodes within the tolerance of any surface but do not overlap it at all. By including element centroids in the calculations and using refined facets, intersected elements and surfaces may be more accurately marked as overlapped or unmatched.
Unmatched
Occurs for a surface when there are no facet nodes on the surface that are within the given tolerance of the elements. It occurs for an element when no nodes of the element are within the given tolerance of the surfaces.
Detailed Behaves the same as Full, except that each surface will be placed in a separate match type group with the elements it overlaps or intersects with. Due to the grouping process, surfaces that are not grouped with any elements are marked as unmatched. In Full results, such surfaces may be marked as intersected if a surface edge is within the given tolerance of an element but there is no overlap in the interior of either. A given surface may be in two match type groups: one with overlapped elements and another with intersected elements.
FE-FE
Result Type Description
Basic
Matched
Occurs when an element is within the given tolerance of another element using a direct node to node comparison. All matched elements are placed in a single match type group.
Unmatched
Occurs if at least one node for the element lies outside the given tolerance of the nodes of the compared FE mesh.
Full
Matched
Occurs when an element is within the given tolerance of another element using a direct node to node comparison. All matched elements are placed in a single match type group.
Overlapped
Occurs when all nodes of a source or target element are within the given tolerance of the compared elements and all of the element’s nodes which touch the FE mesh’s exterior edges are within the given tolerance of compared FE mesh’s exterior edges. All of the overlapped elements are placed in a single match type group.
Intersected
Occurs when at least one node of a source or target element is outside the given tolerance of the compared elements or at least one of the element’s nodes which touches the FE mesh’s exterior edges is outside the given tolerance of the compared FE mesh’s exterior edges. All of the intersected elements are placed in a single match type group.
Unmatched
Occurs when there are no nodes of a source or target element that are within the given tolerance of the compared elements.
Detailed Behaves the same as Full.

### Thickened Shell Comparison

When you are performing a thickened shell comparison, Basic, Full, and Detailed all produce the same answer.
CAD
Matched
There is no criteria for matched surfaces in a thickened shell comparison. However, a value is provided by dividing the matched FE area by two. Surfaces are set to 100% matched if the FE is also 100% matched. Surfaces are never categorized as matched, though, as the overlapped match type is the maximum category.
Overlapped
Occurs when all points of a surface are within the tolerance of the elements (when offset is projected by thickness). The element edge nodes that are not within the tolerance of a surface edge may be projected on to the surface. This is calculated by dividing the overlapped FE area by two.
Intersected
Occurs when at least one point of a surface is within the tolerance of the elements (when offset is projected by thickness). This value is adjusted to make sure the percentages add up to 100%.
FE
Matched
Occurs when all of an element's nodes (when offset is projected by thickness) are within the tolerance of a surface on both sides. If a node is lying along the edge of a mesh, it must also be within the tolerance of a surface line on at least one side.
Overlapped
Occurs when all of an element's nodes (when offset is projected by thickness) are within the tolerance of a surface on both sides, located over an ignored hole or slot, or within the internally calculated distance of the root of a fillet (any t-intersection or bend in the mesh of at least 44 degrees). If a node is lying along an edge, it must also be within the tolerance of a surface line on at least one side, located over an ignored hole or slot, or within the internally calculated distance of the root of a fillet.
Intersected
Occurs when at least one of an element's nodes (when offset is projected by thickness) are within the tolerance of a surface on at least one side, located over an ignored hole or slot, within an internally calculated distance of the root of a fillet (any t-intersection or bend in the mesh of at least 44 degrees), or within the tolerance of any surface edge.