Imprinting and Curve Projection

Contents

• 50.1 Introduction
• 50.2 Curve projection and imprinting
  • 50.2.1 Received arguments
  • 50.2.2 Returned arguments
  • 50.2.3 Update control
  • 50.2.4 Project or imprint curves
  • 50.2.5 Summary of options
  • 50.2.6 Choosing the projection method for the curve
    • 50.2.6.1 Normal projection
    • 50.2.6.2 Vector projection
    • 50.2.6.3 Perspective projection
  • 50.2.7 Limiting the distance of the projection
  • 50.2.8 Projecting to hidden faces
  • 50.2.9 Connecting disjoint components
  • 50.2.10 Splitting output curves
  • 50.2.11 Projecting curves to points
  • 50.2.12 Setting precision of imprints
  • 50.2.13 Attaching nominal geometry
  • 50.2.14 Completing imprints
  • 50.2.15 Limiting the distance of imprint completion
  • 50.2.16 Tracking information
  • 50.2.17 Reporting function results
• 50.3 Direct imprinting
• 50.4 Boolean imprinting
  • 50.4.1 Imprinting
    • 50.4.1.1 Completing imprints
    • 50.4.1.2 Adding extra faces to face-imprints
    • 50.4.1.3 Ensuring imprinted edges have consistent direction
  • 50.4.2 Identifying face sets
• 50.5 Legacy curve imprinting
  • 50.5.1 Connecting disjoint components of an imprint
  • 50.5.2 Imprinting in both directions at once
  • 50.5.3 Dealing with faces that obscure the imprint
  • 50.5.4 Dealing with curves that intersect within the view direction
  • 50.5.5 Restricting imprints to nearby faces
  • 50.5.6 Imprint completion
  • 50.5.7 Controlling how curves are imprinted along a vector
  • 50.5.8 Controlling continuity when imprinting along face normals
  • 50.5.9 Tracking information for imprint functions
  • 50.5.10 Imprinting vertices

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50.1 Introduction

You can use Parasolid’s imprinting or projection functionality to imprint or project entities onto a body, sheet, surface or a set of faces. This chapter describes this functionality using:

• PK_CURVE_project, see Section 50.2, “Curve projection and imprinting”, for more information.
• PK_FACE_imprint_curves_2, see Section 50.3, “Direct imprinting”, for more information.
• Boolean tools, see Section 50.4, “Boolean imprinting”, for more information.
• Other imprinting functions, see Section 50.5, “Legacy curve imprinting”, for more information.

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50.2 Curve projection and imprinting

You can use PK_CURVE_project for normal and vector projection or imprinting of a set of curves to a body, surface or a set of faces. A projection down the face normal is performed, unless a vector is supplied, in which case a projection in a vector direction is performed. The resultant projected curves and points are either orphan or construction geometry.

For examples of this functionality, see the code example in the C++\Code Examples\Modelling\Projecting Curves and Imprinting folder, located in example_applications in your Parasolid installation folder.

50.2.1 Received arguments

PK_CURVE_project receives the following arguments:

50.2.2 Returned arguments

PK_CURVE_project returns the following arguments:

50.2.3 Update control

If your application relies on reproducing behaviour when updating models built using earlier versions of Parasolid, you can use the update option to preserve old behaviour and help eliminate differences in rebuild results. This option lets you turn off some of the projecting enhancements that have been added at different Parasolid versions. Doing this ensures that curve projection gives the same results in the latest version of Parasolid as in earlier versions. See PK_proj_update_t in the PK Interface Programming Reference Manual for more information on this update option.

50.2.4 Project or imprint curves

You can choose to only project curves, only imprint curves or to project and imprint curves using the function option. This option takes the following values:

Different options are available depending on what value of the function option you choose. See Section 50.2.5, “Summary of options” for more information.

Figure 50-1 illustrates the results of choosing different values of the function option.

Figure 50-1 Choosing whether to project, imprint, or project and imprint input curves

50.2.5 Summary of options

You can set a number of options when either projecting curves, imprinting curves or doing both operations simultaneously using the PK_CURVE_project_o_t option structure. All options are available for all values of function unless otherwise stated. This contains the following:

50.2.6 Choosing the projection method for the curve

The method option allows you to choose whether to project a curve using a normal, vector, or perspective projection. All of these options are discussed in this section.

50.2.6.1 Normal projection

To produce a normal projection, where a curve is projected down the normal of a face, the method option must be set to PK_proj_method_normal_c.

Although normal projections are performed down the face normal, they are also implicitly bidirectional. Therefore, if the projection curves are within the normal field of the face but lie behind it, they will project onto the target. Normal projections are best used when projecting curves that are close to and related to the faces that they are being projected onto. When performing a normal projection, we recommend that you limit the maximum distance to avoid unexpected projections on distant faces. See Section 50.2.7, “Limiting the distance of the projection” for more information on maximum distance.

Figure 50-2 Normal projection

50.2.6.2 Vector projection

To produce a vector projection, where a given point on the curve is projected from the curve in the direction specified by direction , the method option must be set to PK_proj_method_vector_c.

For vector projections, bidirectional allows you to project curves in the positive and negative direction . Figure 50-3 shows an upward vector projection of a curve onto a body.

Figure 50-3 Curve projection using the bidirectional option.

50.2.6.3 Perspective projection

To produce a perspective projection, where a curve is projected along a ray away from a given eye point onto a target, the method option must be set to PK_proj_method_perspective_c. The origin of the projection is specified by eye_position . This is illustrated in Figure 50-4.

Figure 50-4 Perspective projection

50.2.7 Limiting the distance of the projection

You can limit the distance of the projection from the input curve using the use_max_dist and max_dist options. The use_max_dist option takes the following values:

If use_max_dist is set to a non-default value, the value of max_dist must be greater than zero.

50.2.8 Projecting to hidden faces

You can control how to project to hidden faces using the hidden option. This option takes the following values:

Figure 50-5 shows three cases of a downward vector projection of a curve onto a body.

• If you supply three faces as input faces and set PK_proj_face_hidden_no_c, all faces are projected to.
• If you supply three faces and set PK_proj_face_hidden_array_c, one face is fully projected to and part of a second face that is not hidden by either of the other two faces is also projected to.
• If you supply three faces and set PK_proj_face_hidden_body_c, one face is fully projected to and part of a second face that is not hidden by any of the faces of the body.

Figure 50-5 Vector projection of a curve using hidden option

50.2.9 Connecting disjoint components

You can control the connection of disjoint components of a curve projection using the connect option. With this option, resultant curves that would otherwise have been disjointed can be connected. This option takes the following values:

Figure 50-6 illustrates this option.

• If you supply the whole body as the input body and use PK_proj_connect_none_c, the curve is projected onto two faces.
• If you supply the whole body as the input body and use PK_proj_connect_side_c, the curve is projected onto all three faces.
• If you supply a single side-on face from the sheet as the input body and use PK_proj_connect_side_all_c, the curve is projected onto the face.

Figure 50-6 Curve projection using the connect option

50.2.10 Splitting output curves

Projected curves are split at G1 discontinuities.You can control how they are further split at clashes and self-intersections with the split_clash option. This option takes the following values:

Figure 50-7 shows a B-curve and a line as the two input curves being projected onto a body. These input curves clash and the resultant projection shows this clash.

• By setting split_clash to PK_proj_split_clash_no_c, the projected curves are not split.
• By setting split_clash to PK_proj_split_clash_self_c, the projected B-curve is split at the point of self-intersection.
• By setting split_clash to PK_proj_split_clash_all_c, the projected B-curve is split at the point of self-intersection and the projected line curve and B-curve are both split where they clash with each other.

Figure 50-7 Curve projection using the split_clash option

If no split occurs, a record of type PK_REPORT_record_3_t will be written to a Parasolid Report with the following status:

See Chapter 11, “Using Reports” for more information about the Parasolid Report mechanism.

50.2.11 Projecting curves to points

You can control the projection of lines and linear B-curves to point-like projections using the create_points option. This option takes the following values:

Figure 50-8 illustrates a point-like projection from a line that is vertically projected down onto a body. By setting the option to PK_proj_to_points_no_c, no point-like projections are created. By setting PK_proj_to_points_end_on_c, a point-like projection is created where the input line intersects the target face.

Figure 50-8 Projecting a vertical line down onto a face to create a point-like projection

Figure 50-9 shows three input lines that are projected down onto an input body. With the option set to PK_proj_to_points_no_c, three edges are projected onto the body, one from each input line. With PK_proj_to_points_tol_c, two edges and a point (tolerant vertex) are projected. This is because the projection of the red line is shorter than two times the tolerance passed into PK_CURVE_project and is therefore projected as a point.

Figure 50-9 Creating point and line projections from three lines

50.2.12 Setting precision of imprints

You can control how precision is applied to imprinted edges and vertices using the imprint_precision option. This option takes the following values:

50.2.13 Attaching nominal geometry

You can choose whether to attach the projected curves as nominal geometry using the nominal option. This option takes the following values:

50.2.14 Completing imprints

You can choose whether to complete an imprint such that the end vertices of the imprint lie on an edge of the body or face using the complete option. This option takes the following values:

Figure 50-10 shows the effect of using the complete option for PK_CURVE_project. For PK_proj_complete_edge_c, the edge is extended to the first edge encountered in each direction; for PK_proj_complete_faceset_c, the edge is extended to the first laminar or boundary edge in each direction.

Figure 50-10 Effect of the complete option for PK_CURVE_project

See Section 50.2.15, “Limiting the distance of imprint completion” for information on how to limit the distance of the imprint completion.

50.2.15 Limiting the distance of imprint completion

As described in Section 50.2.14, “Completing imprints”, you can use the complete option to control whether imprint completion can be extended up to an edge, or to the boundary of a supplied faceset. You can also optionally choose to limit the distance of an imprint completion using the complete_bound and complete_bound_distance options. With these options, an imprint will not be extended if the completion distance is greater than the supplied bound distance.

The complete_bound option takes the following values:

The complete_bound_distance option is the distance used to bound the imprint completion. If complete_bound is set to a non-default value, complete_bound_distance must be greater than tolerance .

Figure 50-11 illustrates the result of using these options when complete is set to PK_proj_complete_edge_c. In (a) the completion edge is not within the bound limits and therefore the imprint will not be extended. In (b) the completion edge is within the bound limit set by complete_bound_distance and therefore the imprint will be extended.

Figure 50-11 Limiting the extension of the imprint using complete_bound and complete_bound_distance options

50.2.16 Tracking information

You can track edges produced by imprint completion from projected curves using the tracking option. This option takes the following values:

Figure 50-12 illustrates the tracking information that is returned when a curve A is projected onto a face B creating two new edges, C and D. Two track records are returned, one for each edge created by the imprint:

Figure 50-12 Tracking information returned when projecting curves

50.2.17 Reporting function results

You can use the results_output option to choose whether to output the results of the operation in the return and tracking arguments of PK_CURVE_project, or in the Parasolid Report. This option has the following values:

If you choose to output the results to the Parasolid Report, you can optionally choose to return the originating intervals for each projection in the report using the want_orig_intervals option. When set to PK_LOGICAL_true, the parameter intervals on the input curves that produced the projection or imprint are returned. This is illustrated in Figure 50-13.

Figure 50-13 Returning the originating parameter interval of the input curve

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50.3 Direct imprinting

Parasolid also provides imprinting functionality in the form of direct imprinting. Unlike the more general imprinting functionality provided by PK_CURVE_project (see Section 50.2), direct imprinting requires that the set of curves to be imprinted are coincident with the surface of the face onto which they are imprinted. Direct imprinting is a convenient way, for example, to create a set of profiles by imprinting sets of planar curves on planar sheets.

Figure 50-14 Creating profiles on a face using direct imprinting

You can perform direct imprinting using PK_FACE_imprint_curves_2. This function receives a face and a set of curves and intervals, and creates new edges and faces.

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50.4 Boolean imprinting

Parasolid provides several imprinting tools that you can use for your own purposes. These tools can be used to implement your own manual boolean functionality, should you want to include unique features in your application that could not be done conveniently using the standard Parasolid boolean functionality. For example, using these tools you could add features such as a higher degree of user interaction, or some kind of preview functionality.

Two boolean tools are provided:

• Imprint edges on a target and tool body to show where the two bodies intersect. See Section 50.4.1.
• Divide faces on a body (usually those created as a result of the imprinting operation) into distinct face sets so that you can decide which parts of the body to keep, and which to throw away. See Section 50.4.2.

To implement your own manual boolean functionality, you could imprint edges on a target and tool, identify the distinct face sets on the target and tool, and then use PK_FACE_delete_2 to remove the ones you don’t want. Finally, you could use PK_BODY_apply_knit_pattern to fuse the remaining face sets into a single body.

Boolean tools could also be used for a range of other operations. For example, you could use them in conjunction with other Parasolid tools to remove unwanted areas of overlapping sheet bodies before sewing them.

50.4.1 Imprinting

The initial stage of a boolean operation is to intersect the target and tool entities and imprint edges and vertices on them where they intersect. These imprinted edges and vertices form the boundaries of intersection between target and tool entities.

You can create sets of imprinted edges and vertices on a target and tool entity using PK_BODY_imprint_body, PK_BODY_imprint_faces_2, and PK_FACE_imprint_faces_2. These functions create imprinted edges and vertices on the supplied entities and return these edges and vertices as paired sets.

Figure 50-15 Imprinting a cylindrical tool on a target cube resulting in four pairs of imprinted edges

These functions receive option structures to control the imprinting process. These contain the following options:

imprint_tool

imprint_overlapping

extend_face_list

matched_region

imprint_complete_targ

imprint_complete_tool

imprint_extend_targ

imprint_extend_tool

update

have_tolerance

tolerance

In addition, PK_BODY_imprint_faces_2 and PK_FACE_imprint_faces_2 contain the following option:

imprint_dir

50.4.1.1 Completing imprints

You can complete an imprint on the target or tool - that is, extend the imprinted edge to another nearby edge on the body so as to create a closed loop of edges - from any vertex of an imprinted edge that has been created by an intersection with a laminar edge on the other body. Four options in PK_BODY_imprint_o_t, PK_BODY_imprint_faces_o_t, and PK_FACE_imprint_faces_o_t are used to control how this behaviour can be used.

The effect of these options is illustrated in Figure 50-16.

Figure 50-16 Completing imprinted edges on target bodies

The corresponding imprinted (or original) edges and vertices are returned in matching arrays contained within the results structure. In the case of PK_FACE_imprint_faces_2, where an entity has been created because of imprint completion, the matched element in the other list will be PK_ENTITY_null.

50.4.1.2 Adding extra faces to face-imprints

When using PK_FACE_imprint_faces_2, PK_BODY_imprint_faces_2, PK_FACE_boolean_2, or PK_FACE_instance_tools, you may also be able to prevent open loops of edges by adding neighboring faces from either the target or tool (or both) into the imprint. This is done using the following option:

extend_face_list

Careful use of this option allows an effect similar to blend propagation. For example, you can pass a single tool face, and request that the tool faces are extended, and Parasolid creates a complete closed imprint on the target automatically.

The behaviour of extend_face_list is explained in Figure 50-17, which shows how an imprint on a target and tool may be extended. All four values for extend_face_list are illustrated.

Figure 50-17 Extending the list of faces in a face imprint on the target and the tool

The extend_face_list options take effect before any imprint_complete options (see Section 50.5.6, “Imprint completion”) that have been specified.

If, when using extend_face_list , you want to ensure that the results of imprint completion during a local boolean operation are limited to the target or tool faces specified in the function call, you should set imprint_complete_targ or imprint_complete_tool (as appropriate) to PK_imprint_complete_faceset_c. If you do not do this, extend_face_list adds neighboring faces up to the laminar edges of the body, as shown in Figure 50-18.

Figure 50-18 Combining imprint_complete_targ and extend_face_list options

50.4.1.3 Ensuring imprinted edges have consistent direction

You can use the imprint_dir option in PK_BODY_imprint_faces_o_t and PK_FACE_imprint_faces_o_t to control whether the directions of any imprinted edges are consistent with the original topology that created them. This option takes the following values:

When identifying whether the edge direction is consistent, it is compared to various test directions derived from the edge's originating topology:

• Face-pair direction: the cross product of the normal of a target face with the normal of a tool face (in that order). Faces from face pairs that have parallel or anti-parallel normals are only used in the calculation of a consistent direction where needed.
• Laminar edge fin direction: the direction of the (only) fin of a laminar edge.
• Original edge direction: the direction of an originating non-laminar edge.
• Imprint edge direction: the direction of a newly imprinted edge.

A consistent direction for an imprinted edge is produced by applying the following tests:

• Considering all face-pair directions at the imprint edge, if there is a unique direction, the edge is made consistent with that direction. In Figure 50-19, this test is used to determine the direction of the purple edge created as a result of imprinting the L-shaped body consisting of red and blue faces onto the yellow body.
• If there is no consistent face-pair direction, but the imprint arose from a laminar edge, the imprint edge is made consistent with the laminar edge fin direction. Figure 50-19, this test would be used for the three edges (between the red and the yellow faces) not shown in purple.
• If there is no consistent face-pair or laminar edge fin direction, but there is an originating target or tool edge, the imprint edge is made consistent with the original edge direction (choosing the target edge in cases where there were both target and tool edges). These imprint edges will be included in the Parasolid report.
• If the edge arose from imprint completion, then it will be made consistent with the direction of the imprint edge it completed from. If that edge was included in the Parasolid report, then so too will be the imprint completion edge.
• All other imprint edges do not have a defined consistent direction, and so will be included in the Parasolid report. Figure 50-20 shows the result of imprinting two cylindrical faces, each of which have coincident edges representing the respective seam lines of the cylindrical surface.

Figure 50-19 Imprinted edges arising from original edges

Figure 50-20 Imprinted edges due to touching cylinders

50.4.2 Identifying face sets

Once edges and vertices has been imprinted on a target and tool body, you need to identify which face sets (on both the target and tool) would survive a boolean operation.

PK_BODY_identify_facesets receives loops of coincident edges, points of contact and a boolean operation (unite, subtract and intersect) and then calculates which face sets would survive the operation and which face sets would be deleted. The loops of coincident edges and points of contact would typically be obtained via calls to the imprinting functions described in Section 50.4.1: PK_BODY_imprint_body and PK_FACE_imprint_faces_2.

Figure 50-21 Simulating a subtract operation based on imprinted edges from Figure 46-11.

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50.5 Legacy curve imprinting

You can use Parasolid’s imprinting functionality to imprint curves, faces, or planes onto a sheet body.

In each of the methods described, edges created by the imprint operation are returned, including those existing edges along which the intersection occurred.

To solve any precision problems, a tolerance is supplied; this value may also be used in the creation of SP-curves on the imprinted edges.

50.5.1 Connecting disjoint components of an imprint

PK_BODY_imprint_cus_vec and PK_FACE_imprint_cus_vec support a connect option that you can use to connect together disjoint components that are created during a single call to those functions. This option lets you control the extent to which imprinted curves are connected together, giving you control over the creation of imprints on both side faces and back-facing faces. It takes the following values, which are illustrated in Figure 50-22:

Figure 50-22 Connecting disjoint components of an imprint

50.5.2 Imprinting in both directions at once

When creating vector imprints, you often want to imprint in both directions along the specified vector. Using the default options, you can only do this with two function calls, which as well as being a performance overhead may also introduce unwanted vertices into the imprint that you then have to remove.

PK_BODY_imprint_cus_vec and PK_FACE_imprint_cus_vec support a bidirectional option that let you imprint in both directions using a single function call. This improves performance, and also automatically removes any mergeable vertices that are created as a result of the imprint.

Figure 50-23 shows a simple example in which a curve is imprinted onto a sheet. Because the curve intersects the sheet, imprints in both directions need to be created in order to imprint the entire extent of the curve onto the sheet. Figure 50-23 shows the difference in the results obtained by making two function calls compared to using the bidirectional option.

Figure 50-23 Imprinting in both directions at once

50.5.3 Dealing with faces that obscure the imprint

When imprinting curves on faces using the local function PK_FACE_imprint_cus_vec, Parasolid provides additional control over the imprint operation with the hidden option. This option lets you control the effect of other faces that obscure the faces being imprinted. The hidden option can take any of the following values:

The effect of these values is shown in Figure 50-24, which shows the effect, in cross-section, of imprinting a subset of the faces of a body.

Figure 50-24 Allowing for faces that obscure the imprint

50.5.4 Dealing with curves that intersect within the view direction

Sometimes, when projecting curves onto a face along a vector using PK_FACE_imprint_cus_vec or PK_BODY_imprint_cus_vec, one or more curves will appear to intersect when viewed along the projection vector. This can be problematic: to produce a valid body, additional vertices need to be imprinted at the points where the intersections occur. If you do not wish these vertices to be imprinted, there is no way for the imprint operation to complete successfully. Parasolid lets you control the behaviour in such circumstances using the process_intersections option, which can take the following values:

Figure 50-25 shows a simple example in which a single helical curve is imprinted onto a face. Because the helical curve appears to intersect itself when viewed in the direction of the project vector, a successful imprint is only possible if process_intersections is set to PK_imprint_intersect_fix_c.

Figure 50-25 Imprinting a helical curve onto a face

Figure 50-26 shows an example in which two curves that only appear to intersect when viewed along the projection vector can be successfully imprinted onto a body by setting process_intersections to PK_imprint_intersect_fix_c.

Figure 50-26 Imprinting several curves that only intersect along the projection vector

50.5.5 Restricting imprints to nearby faces

You can control which faces in a body receive imprints when imprinting down the face normal of the body using either PK_BODY_imprint_cus_normal or PK_FACE_imprint_cus_normal.

One way to do this is simply to pass in a specific subset of faces in a body to PK_FACE_imprint_cus_normal. However, in some circumstances this might not be possible or desirable. In such cases, you can restrict imprinting so that only faces that are within a specified distance of the imprinting curves receive imprints, using the following options:

use_max_projection_dist

max_projection_dist

Figure 50-27 illustrates a simple case where a curve is imprinted onto a block. By default, edges are imprinted on both the front and back faces of the block (A). By specifying a max_projection_dist , you can restrict the imprint so that only the nearest face is imprinted (B).

However, for an edge to be imprinted, max_projection_dist must be large enough such that the part of the curve that is imprinted is close enough to the nearest face:

• If only part of the curve is close enough, then no edge is imprinted (C).
• If only part of the curve would be imprinted, and that part is close enough, then an edge is imprinted (D).

Figure 50-27 Restricting imprints to nearby faces

50.5.6 Imprint completion

The functions PK_BODY_imprint_cus_normal, PK_FACE_imprint_cus_normal, PK_BODY_imprint_cus_vec and PK_FACE_imprint_cus_vec allow you to specify whether an edge imprinted on a body should be extended to meet an existing edge. This is done with the imprint_complete option, which takes the following values:

Figure 50-28 and Figure 50-29 show the effect of the imprint_complete option for PK_BODY_imprint_cus_vec and PK_FACE_imprint_cus_vec, respectively. For PK_imprint_complete_edge_c, the edge is extended to the nearest existing edge in each direction; for PK_imprint_complete_laminar_c, the edge is extended to the nearest laminar edge in each direction. In all cases, the extension is tangential to the imprinted edge (i.e. in the direction of the imprinted edge). The difference in the two functions is only evident for PK_imprint_complete_laminar_c, where those edges that are considered laminar edges by PK_FACE_imprint_cus_vec are not laminar edges for PK_BODY_imprint_cus_vec.

Figure 50-28 Effect of the imprint_complete option for PK_BODY_imprint_cus_vec and PK_BODY_imprint_cus_normal

Figure 50-29 Effect of the imprint_complete option for PK_FACE_imprint_cus_vec and PK_FACE_imprint_cus_normal

50.5.7 Controlling how curves are imprinted along a vector

By default, the positions on a body of edges and vertices that are imprinted from curves along a vector are calculated by projecting the curves along that vector.

Sometimes, for example if curves are close to or coincident with the model, this can introduce unnecessary tolerance information into the model. To avoid this, you can use the following options to ensure that the edges and vertices imprinted on a model are exact.

These options are available to both PK_FACE_imprint_cus_vec and PK_BODY_imprint_cus_vec:

imprint_coi_exactly

imprint_exactly

50.5.8 Controlling continuity when imprinting along face normals

You can specify the continuity of projection curves that are imprinted using either of the normal imprinting functions PK_BODY_imprint_cus_normal and PK_FACE_imprint_cus_normal. You do this using the preferred_continuity option, which can take the following values:

50.5.9 Tracking information for imprint functions

All four of the curve imprinting functions - PK_BODY_imprint_cus_normal, PK_FACE_imprint_cus_normal, PK_BODY_imprint_cus_vec, and PK_FACE_imprint_cus_vec - can return detailed tracking information that relates the curves used for the imprinting function to both the edges imprinted and the topology on which those edges were imprinted.

Figure 50-30 shows the tracking information returned in the track_records sub-structure when imprinting two curves onto the sheet body shown. One curve creates an imprinted edge on a face in the body, and the other curve creates an imprinted edge on an existing edge. Two track records are returned, as follows:

• One contains the curve used for the imprint (A), the face that received the imprint (B), and the imprinted edge (C).
• The other contains the curve used for the imprint (D), the edge that received the imprint (E), and the newly created edge (F).

Figure 50-30 Tracking the results of imprint operations

If you use the imprint_complete option (as described in Section 50.5.6, “Imprint completion”), then any edges that are created as a result of the completion are also returned in product_topols . The corresponding original_topols contains the topology on which the completion has been imprinted, but it does not contain a corresponding originating curve, since no such curve exists. Figure 50-31 illustrates the tracking information that is returned when a curve A is imprinted onto a face B and imprint completion is turned on, creating two new edges, C and D. Two track records are returned, one for each edge created by the imprint:

• The record for edge C includes the new edge (C), the face used for the imprint (B), and the originating curve (A).
• The record for edge D includes the new edge (D), the face used for the imprint (B), but does not include an originating curve, since no such curve exists.

Figure 50-31 Tracking information returned when using imprint completion

This tracking information is available by default in PK_BODY_imprint_cus_vec and PK_FACE_imprint_cus_vec. In PK_BODY_imprint_cus_normal and PK_FACE_imprint_cus_normal, it needs to be enabled using the following option:

tracking_type

50.5.10 Imprinting vertices

PK_EDGE_imprint_point adds a vertex to an edge at specified coordinates, providing that a vertex does not already exist at that position. The added vertex splits all edges, except for a ring edge, into two.

PK_FACE_imprint_point adds a vertex to a face on a sheet, solid or general body. The new vertex is an isolated vertex, and a new loop is created to contain it.

PK_REGION_imprint_point adds a vertex to a region of a general body. The new vertex is an acorn vertex in the region, and a corresponding acorn shell is created to contain it.

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