Creating Profiles

Contents

• 36.1 Introduction
• 36.2 Imprinting
  • 36.2.1 Creating primitive sheet bodies
  • 36.2.2 Using existing entities
• 36.3 Creating outline curves, perspective outlines, and spun outlines
  • 36.3.1 Received and returned arguments
  • 36.3.2 Specifying options
  • 36.3.3 Shrinking perspective outline curves
  • 36.3.4 Clipping perspective outline curves
  • 36.3.5 Returning wire or sheet bodies
  • 36.3.6 Returning topological entities
  • 36.3.7 Differentiating between several outlines
  • 36.3.8 Update control
  • 36.3.9 Reporting function results

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36.1 Introduction

A profile is a general term for a simple zero-, one- or two-dimensional body that is subsequently used to create new bodies with free-form geometry. Creating profiles is an important technique in solid modeling, and Parasolid provides functionality to make it simple.This chapter describes how you can create profiles from a set of curves, by creating sheet bodies directly or from existing entities.

This chapter contains the following sections:

• Imprinting. See Section 36.2.
• Creating outline curves and spun outlines. See Section 36.3.

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36.2 Imprinting

The most basic way of creating a profile is to build it piecemeal by imprinting a series of curves:

• You can scribe new curves directly onto existing entities. You can create new faces by scribing onto a solid body, or you can extend a wire body by scribing onto the wire body or onto its region.
• Alternatively, you can project existing curves onto a body. Different effects can be achieved, depending on whether you project the curve along the face normal onto which you are imprinting, or whether you project the curve along a specified vector.

Figure 36-1 Imprinting curves by scribing and projecting

36.2.1 Creating primitive sheet bodies

Parasolid provides a range of functionality to let you create primitive sheet bodies such as circles, polygons and rectangles.

36.2.2 Using existing entities

Parasolid provides tools to create a wire profile from a set of existing edges or curves in a single operation, and to turn a closed wire into a sheet body if required.

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36.3 Creating outline curves, perspective outlines, and spun outlines

You can use PK_BODY_make_curves_outline, PK_BODY_make_persp_outline and PK_BODY_make_spun_outline to create a profile from the outline of one or more solid or sheet bodies. PK_BODY_make_curves_outline also allows you to create a profile from the outline of one or more wire or general bodies.

Parasolid supports the following types of outlines:

• An outline curve is the outline created by drawing around the boundary of a set of bodies, as seen from a specified view direction. This is illustrated in Figure 36-2.

Figure 36-2 Creating outline curves for a body

• A perspective outline is created by drawing around the boundary of a body or set of bodies, as seen from a perspective view point as shown in Figure 36-3. Generating a perspective view can be useful in certain applications, for example when generating the shadow of a part under room lighting.

Figure 36-3 Creating a perspective outline for a body

• A spun outline is the rotational equivalent of an outline curve. If you consider spinning a set of bodies around a specified axis, you can think of the spun outline as a cross-section through the resulting spun body. If the spun outline is projected onto a plane that passes through the spin axis, its shape describes the hole that would need to be cut from the plane in order for the bodies to pass through it, as shown in Figure 36-5.

For an example of this functionality, see the code example in the C++\Code Examples\Modelling\Outline And Spun Outline folder, located in example_applications in your Parasolid installation folder.

Figure 36-4 Creating spun outlines for a body

Figure 36-5 Creating spun outlines for two bodies

Both outline curves and spun outlines share a number of properties, as follows:

• They must consist of an ordered set of connected curves
• They must consist of one or more closed loops, each with a non-empty interior. For example, you cannot create an outline of a sheet body if any part of it is edge-on in the specified view direction.
• They can either be projected onto a specified plane, or remain as 3-dimensional curves to retain their 3-D information.
• A shadow curve is basically an outline curve that is projected directly onto a body. Shadow curves are the curves that are projected onto a set of bodies when viewed from a specific direction, splitting the bodies into visible and invisible areas when they are viewed from that direction. They are known as shadow curves because they represent areas of light and dark if you assume that a light source is placed at the view direction. See Chapter 41, “Shadow Curves”, for more information.

Figure 36-6 Shadow curves on a set of bodies

36.3.1 Received and returned arguments

PK_BODY_make_curves_outline, PK_BODY_make_persp_outline, and PK_BODY_make_spun_outline receive the following arguments:

n_bodies 

bodies 

transfs 

view_direction

eye_position

spin_axis

options 

PK_BODY_make_curves_outline, PK_BODY_make_persp_outline and PK_BODY_make_spun_outline can output results in their returned arguments or in the Parasolid Report. See Section 36.3.9, “Reporting function results” for more information.

PK_BODY_make_curves_outline and PK_BODY_make_spun_outline return the following arguments:

n_curves 

curves 

intervals 

topols 

outlines 

curve_tolerances 

max_separation 

The returned curves , intervals , topols , outlines , and curve_tolerances are all of length n_curves .

PK_BODY_make_persp_outline returns the following arguments:

result

tracking

Any new curves that are created as a result of the function call are attached as construction geometry to the original bodies. Alternatively, you can choose to create a body from the returned curves. See Section 36.3.5, “Returning wire or sheet bodies”, for information on how to do this.

36.3.2 Specifying options

You can set a number of options when creating outline curves, perspective outlines, and spun outlines, using the associated PK_BODY_make_curves_outline_o_t, PK_BODY_make_persp_outline_o_t, and PK_BODY_make_spun_outline_o_t options structure respectively. These options structures contain the following options:

project
 

tolerance
 

want_body

body_dimension

keep_as_facet

results_output

PK_BODY_make_curves_outline_o_t and PK_BODY_make_spun_outline_o_t contain the following options:

project_position
 

want_topols
 

edge_on

update

invisible

n_exclude_faces

exclude_faces

Figure 36-7 Creating an outline of an edge-on sheet body when the edge_on option is set to PK_outline_edge_on_all_c

Figure 36-8 Creating an outline of a non-edge-on sheet and wire inputs when the edge_on option is set to PK_outline_edge_on_both_c_

Figure 36-9 Creating invisible outlines of a body with two blind holes and one through hole using the invisible option in PK_BODY_make_spun_outline

Figure 36-10 Creating invisible outlines of a body and excluding multiple sets of faces using the n_exclude_faces and exclude_faces options in PK_BODY_make_spun_outline

PK_BODY_make_persp_outline_o_t has the following options:

36.3.3 Shrinking perspective outline curves

The project_scale option allows you to shrink outline curves projected onto a plane by a specified value. This functionality can be useful when projecting the outline of large input bodies (that lie within the size box) onto a plane where the result outlines would be projected outside of the size box. By specifying a value in project_scale , you can shrink the resultant outline curves by that value so they will fit within the size box. For example, if you set project_scale to PK_scale_factor_10x_c, a scaling factor of 10 is used and the size of the perspective outline is reduced by a factor of 10.

If project_scale is set to PK_scale_factor_1x_c, no rescaling is applied.

36.3.4 Clipping perspective outline curves

PK_BODY_make_persp_outline has a number of options that enable you to clip the outline curves so that only those curves that fall within a specified range are generated. These options are discussed in this section.

The clipping option specifies the various types of viewing ranges that you can use to clip the outline curves. The types of viewing ranges are defined using various combinations of the view_angle , view_direction , spin_angle , spin_direction , and clipping_body options. These are as follows:

Figure 36-11 Example of clipping outline curves using PK_persp_clipping_cone_c

Figure 36-12 Example of clipping outline curves using PK_persp_clipping_sector_c

Figure 36-13 Example of clipping outline curves using PK_persp_clipping_wedge_c

Figure 36-14 Example of clipping outline curves using PK_persp_clipping_pyramid_c

Figure 36-15 Example of clipping outline curves with a clipping body

36.3.5 Returning wire or sheet bodies

PK_BODY_make_curves_outline and PK_BODY_make_spun_outline both return the curves that form the requested outline, together with tolerance and interval information for those curves.Usually, however, it is more convenient to access those curves via a body. PK_BODY_make_curves_outline, PK_BODY_make_persp_outline, and PK_BODY_make_spun_outline functions have the want_body and body_dimension options that allow you to do this.

If want_body is PK_LOGICAL_false, Parasolid attaches the outline curves to the appropriate input bodies as construction geometry.If want_body is PK_LOGICAL_true, Parasolid creates a single body that contains all the curves that formed the requested outline. The returned curves are attached to this body as principal geometry. Only one body is created per set of outlines; if the generated outline contains multiple loops of curves, then this body may consist of disjoint components.

The body is not explicitly returned by either PK_BODY_make_curves_outline or PK_BODY_make_spun_outline. To access it, you should call PK_CURVE_ask_part using any of the returned curves as input.

By default, want_body is PK_LOGICAL_false: you should only set it to PK_LOGICAL_true if project is not PK_outline_project_no_c.

You can also control the type of body created using the body_dimension option, which takes the following values:

Figure 36-16 shows an example where outline curves are created for a disjoint body and attached to a new body. The resulting body is also disjoint, whether a wire body or a sheet body is requested.

Figure 36-16 Creating disjoint outline curves from a disjoint body

By contrast, Figure 36-17 shows an example where outline curves are created for a non-disjoint body. In this case, if a wire body is requested, the result is disjoint.

Figure 36-17 Creating disjoint outline curves from a non-disjoint body

Depending on the nature of the input body and the view_direction used in PK_BODY_make_curves_outline and PK_BODY_make_persp_outline, it is possible, when requesting a wire body ( body_dimension is PK_TOPOL_dimension_1_c) that the body created is general, even if the input body is not general. Figure 36-18 shows an example where the two components of a disjoint body, when viewed from a particular view direction, cause the resultant outline to form a general body.

Figure 36-18 Creating a general outline curves body

36.3.6 Returning topological entities

As well as the outline curves themselves, PK_BODY_make_curves_outline and PK_BODY_make_spun_outline can also return, in topols , the topological entities from the original bodies that were used to create each curve. The entity that is returned for each curve depends on how the curve was derived:

• If a curve in the outline was derived from an edge in the original body, that edge is returned.
• If a curve in the outline was derived from a silhouette curve in the original body, the face on which the silhouette lies is returned.

This is illustrated in Figure 36-19, which shows an outline consisting of 4 curves.

Figure 36-19 Topological entities used to create outline curves

The topological entities that are returned for each curve in the outline are shown below. Note that the face F1 is returned for both C2 and C4, since these curves are created from the silhouette of F1.

If you are using PK_BODY_make_persp_outline, the equivalent information is returned in the tracking argument if want_tracking is PK_LOGICAL_true.

36.3.7 Differentiating between several outlines

The curves returned by PK_BODY_make_curves_outline, PK_BODY_make_persp_outline, and PK_BODY_make_spun_outline often make up more than one outline, as shown in Figure 36-20. This may happen when you create outlines of several overlapping bodies, as shown in the figure, or when you create outlines of a body containing holes. When several outlines are returned, use the value of outlines to find which curves make up each outline.

Figure 36-20 Returning several outlines from PK_BODY_make_curves_outline or PK_BODY_make_spun_outline

Suppose, for example, that three outlines were returned, consisting of 2, 7, and 2 curves respectively (as in Figure 36-20). In this case, the value of outlines would be

(0 0 1 1 1 1 1 1 1 2 2 )

This indicates that the first 2 curves returned form one outline, the next 7 form another outline, and the last 2 form a third outline.

If you are using PK_BODY_make_persp_outline, outlines information is returned in the result structure.

36.3.8 Update control

If your application relies on reproducing behaviour when updating models built using earlier versions of Parasolid, you should use the update option to preserve old behaviour and help eliminate differences in rebuild results. This option lets you disable some curves and spun outline enhancements that have been added at different Parasolid versions. Doing this ensures that PK_BODY_make_curves_outline and PK_BODY_make_spun_outline give the same results in the latest version of Parasolid as in earlier versions. See PK_outline_update_t in the PK Interface Programming Reference Manual for more information on this update option.

36.3.9 Reporting function results

You can use the results_output option to choose whether to output the results of the operation in the returned arguments of PK_BODY_make_curves_outline, PK_BODY_make_persp_outline and PK_BODY_make_spun_outline, or in the Parasolid Report.

Outputting results as a report allows Parasolid to provide more information than is available through the function’s returned arguments. For a successful operation, the report provides a richer set of tracking information. For a failing operation, the details in the report allow you to return enhanced diagnostic information on the failure.

This option has the following values:

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