Chapter 11: Creating Geometry Displays

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11.1 Using the GUI to Display Geometry

A geometry display is a display of your model's geometric features (keypoints, areas, nodes, elements, loads, etc.). This is the kind of display that you might typically produce during the model-generation and load-definition phases of your analysis. Figure 11-1 shows a typical geometry display.

Figure 11-1 Typical geometry display



Many users find that the most convenient way to create and control geometry displays is by using the functions available under Utility Menu>Plot and Utility Menu>PlotCtrls. Alternatively, you can use graphics action and control commands, as described in the following subsections.

11.2 Creating Displays of Solid-Model Entities

The following commands will create displays of solid-model entities:

Table 11-1 The commands for displaying solid-model entities

Command

GUI Menu Paths

Purpose

APLOT

Main Menu>Preprocessor>Operate>Show Degeneracy>Plot Degen Areas

Utility Menu>Plot>Areas

Utility Menu>Plot>Specified
Entities>Areas

Displays a plot of areas

EPLOT

Utility Menu>Plot>Elements

Displays a plot of elements

KPLOT

Utility Menu>Plot>Keypoints

Utility Menu>Plot>Specified Entities>Keypoints

Displays a plot of keypoints

LAYPLOT

Utility Menu>Plot>Layered Elements

Displays the layer stacking sequence and layer angle orientation of layered element types such as SOLID46 and SHELL91

LPLOT

Utility Menu>Plot>Lines

Utility Menu>Plot>Specified Entities>Lines

Displays a plot of lines

NPLOT

Utility Menu>Plot>Nodes

Displays a plot of nodes

/REPLOT

Utility Menu>Plot>Replot

Re-executes the last display action executed

VPLOT

Main Menu>Preprocessor>Operate>Show Degeneracy>Plot Degen Volus

Displays a plot of degenerated volumes

The controls you establish before you invoke these actions can also cause your displays to contain other information, such as lower-order entity numbers (for instance, node numbers associated with selected elements), loads, etc.

11.3 Changing the Specifications for Your Geometry Displays

In addition to the features listed below, also see Chapter 8 for general graphics specifications that apply to any type of display, including geometry displays.

11.3.1 Changing the Style of Your Display

The following sections describe a number of ways to change the way your models are displayed.

11.3.1.1 Displaying Line and Shell Elements as Solids

If your model consists of line elements (such as beams and pipes) or shell elements, you can use the following to display many of them as solids:

Command(s):

GUI:

Utility Menu>PlotCrls>Style>Size and Shape

The ANSYS program uses a rectangular cross section for beams and shells, and uses circular cross sections for pipes. The element real constants are used to proportion the cross section.

You can also use the /ESHAPE command to show the orientation of reinforcing (rebar) in SOLID65 elements (see Figure 11-2). For the rebar to be visible, you must enable vector mode using the /DEVICE command (Utility Menu>PlotCtrls> Device Options). You must also activate a basic plot type using the /TYPE command (Utility Menu>PlotCtrls>Style>Hidden-Line Options). To view the rebar, issue these commands in the following order: 

/ESHAPE,1
/TYPE,,BASIC
/DEVICE,VECTOR.ON
EPLOT
Figure 11-2 Element plot of SOLID65 concrete elements



11.3.1.2 Displaying Only the Edges of an Object

While working with displays, you might want to see only the edges of an object; that is, you might want to remove element outlines from the interior of the object. To see only the edges of non-contour displays (EPLOT), issue /EDGE, ,1 (Utility Menu>PlotCtrls>Style>Edge Options). On contour displays (PLESOL, PLETAB, PLNSOL, PLTRAC), edges are displayed by default (/EDGE, ,0).

11.3.1.3 Displaying the Interior Element Edges of an Object

While working with displays, you might prefer to see the interior element edges, or detail, of an object. If you are working with non-contour displays (EPLOT), the interior element edges are displayed by default (/EDGE, ,0). To see the interior element edges of contour displays (PLESOL, PLETAB, PLNSOL, PLTRAC), issue /EDGE, ,1.

An edge, as used in the above context, is the common line between adjacent faces that are not coplanar. The ANGLE field on the /EDGE command allows you to specify the "degree of coplanarity" at which an edge should be displayed. That is, if ANGLE = 45° (which is the default value), an edge is displayed only if the two adjacent faces deviate from coplanarity by more than 45°. If ANGLE = 0°, even the slightest deviation from coplanarity causes the edge to be displayed. The default value of 45° is particularly helpful in displaying a cylindrical shell model as a smooth cylinder rather than as a "faceted" cylinder.

11.3.1.4 Using Dashed Element Outlines

You can switch the style of element outlines from solid line to dashed line by using the /GLINE command (Utility Menu>PlotCtrls>Style>Edge Options). This command allows you to remove element outlines entirely.

11.3.1.5 Shrinking Entities for Clarity

The /SHRINK command (Utility Menu>PlotCtrls>Style>Size and Shape) shrinks displayed elements, lines, areas, and volumes by a specified percentage so that adjacent entities are separated for clarity. ANSYS ignores a request to shrink the display when the edge option is active.

11.3.1.6 Changing the Display Aspect Ratio

You can artificially distort your display's geometry in a particular direction with the /RATIO command (Utility Menu>PlotCtrls>Style>Size and Shape). This can be useful for displaying details within a long, skinny object more clearly.

11.3.1.7 Changing the Number of Facets

Area and volume raster displays are made up of numerous small facets (or polygons). Occasionally, you might want to obtain a more precise representation of your areas or volumes by increasing the number of facets used to create these displays. To switch between two different facet densities, use either of the following:

Command(s):

GUI:

Utility Menu>PlotCtrls>Style>Solid Model Facets

11.3.1.8 Changing Facets for Powergraphics Displays

When PowerGraphics is enabled, you can display varying degrees of curvature in your model by specifying the number of facets per element edge to be used for element display. Facets are piecewise linear approximations of the actual curve represented by the element face or edge. The greater the number of facets, the smoother the representation of the element surface for element plots.

To specify the number of facets per edge, use one of the following:

Command(s):

GUI:

Utility Menu>PlotCtrls>Style>Size and Shape
Utility Menu>List>Results>Options
Main Menu>General Postproc>Options for Outp

11.3.1.9 Changing Light-source Shading

Light-source shading will enhance raster displays on 2-D and 3-D devices having at least eight color planes (28 = 256 colors). To specify the number of color planes necessary for light-source shading, use one of these methods:

Command(s):

GUI:

Utility Menu>PlotCtrls>Device Options

On some 3-D devices, you can adjust the intensity of ambient and directional light, change the light direction, and modify the directional light reflectance factor, using the /LIGHT command (Utility Menu>PlotCtrls>Style>Light Source). You can also change the light direction for 2-D devices with /LIGHT when the Z-buffering hidden-line option is used.

11.3.1.10 Changing Hidden-line Options

By default, raster displays will be created as Z-buffered displays. See the description of the /TYPE command in the ANSYS Commands Reference for other "hidden-line" options. All non-Z-buffered hidden-line options produce the same results in vector displays. For area, volume, and p-element Z-buffered displays, you can further specify the type of surface shading (the "smoothness" of the object) using the /SHADE command (Utility Menu>PlotCtrls>Style> Hidden-Line Options). Also, you can use the /GFILE command to set the resolution of Z-buffered displays that are written to graphics files.

11.3.1.11 Section, Slice, or Capped Displays

To view the interior of a 3-D solid element model, you can use section displays, slice displays, or capped displays. (These are all special versions of hidden-line displays controlled by the /TYPE command.) A section display produces an image of a 2-D planar section that is defined by the intersection between your model and the cutting plane (see below for a discussion of cutting planes). A slice display is similar to a section display except the edge lines of the remaining 3-D model are also shown. A capped display produces an image of a 3-D portion of your model with a portion of the model display "cut off" by the cutting plane.

11.3.1.12 Specifying the Cutting Plane

Three types of graphics displays-section, slice, and capped-require a cutting plane. Specify the cutting plane via the /CPLANE command (Utility Menu> PlotCtrls>Style>Hidden-Line Options), and define the plane as either:

11.3.1.13 Vector Versus Raster Mode

The /DEVICE command (or /SHOW command) allows you to toggle between vector and raster mode. By default, raster mode is active; that is, polygons are filled with color when they are displayed. This affects area, volume, and element displays, as well as the geometry in postprocessing displays. Vector mode produces "wireframe" displays, which show only the outlines of entities, and which usually take less time to form than do raster displays. To display wireframe outlines for solid model entities only (areas and volumes) when your graphics session is otherwise in raster mode, specify the WIRE option of /FACET.

11.3.1.14 Perspective Displays

By default, ANSYS creates a non-perspective display of your model. To cause a perspective display to be formed, use the /VCONE command (Utility Menu> PlotCtrls>View Settings>Perspective View) to define a view cone angle. (The larger the view cone angle, the more pronounced the perspective effect will be.)

11.3.2 Turning Numbers and Colors On and Off

In the ANSYS program, item numbers and colors are usually related. By default, entities will not be numbered. Numbering (and associated coloring, on appropriate devices) can be turned on and off with the following commands:

11.3.2.1 Turning Item Numbers On and Off

You can use the /PNUM command (Utility Menu>PlotCtrls>Numbering) to turn numbering on and off for these items:

Numbers will not be shown in face hidden-line or precise hidden-line displays.

11.3.2.2 Choosing a Format for the Graphical Display of Numbers

You can select the format in which you want floating point numbers to be displayed by issuing the /GFORMAT command. This command lets you indicate the width of the fields in which numbers are displayed and the number of digits that are displayed for a FORTRAN format type. Other commands that let you tailor the appearance of the display to your liking include /PNUM, /PBC, /PBF, and /PSF.

11.3.2.3 Controlling Number and Color Options

Once you have turned numbering on for an item, you can then use the /NUMBER command (which uses the same GUI path as /PNUM) to choose among the four possible "on-off" combinations of numbering and coloring (for instance, show colors and numbers (default); show colors, but not numbers; do not show colors, but show numbers; show neither colors nor numbers).

11.3.2.4 "Hands-on" Control of Color Values

You control the correspondence between specific items or numbers and their associated colors using the /COLOR command (Utility Menu>PlotCtrls> Style>Colors>color option). You can also change the overall color map using the external CMAP program, which enables you to edit and store a new color map on a file. (See Chapter 17 for details on the CMAP program.) Within the ANSYS program, this color map file can then be read using either of the following:

Command(s):

GUI:

Utility Menu>PlotCtrls>Style>Colors>Load Color Map

11.3.3 Displaying Loads and Other Special Symbols

The following sections describe how to manipulate loads and other special symbols.

11.3.3.1 Turning Load Symbols and Contours On and Off

To turn load symbols on or off for degree of freedom constraints and concentrated loads, use the /PBC command (Utility Menu>PlotCtrls>Symbols). /PBC controls both solid-model and finite-element load symbols.

For surface loads symbols or contours, use the /PSF command (Utility Menu>PlotCtrls>Symbols). /PSF activates "immediate" display of surface loads on finite elements, but does not activate "immediate" surface load display on solid model entities.)

For body force load contours, use /PBF (Utility Menu>PlotCtrls>Symbols). /PBF applies to finite-element loads only; body force symbols do not appear in solid model displays. /PBF does not produce an "immediate" display.

You will typically use the above commands to turn load symbols on for visual verification when you apply the loads in SOLUTION (or PREP7). The ANSYS program automatically turns these symbols off when you enter POST1. See Chapter 12 for more information on controlling postprocessing displays.

11.3.3.2 Displaying Boundary Condition Values Next to a Symbol

You can display load symbols by using the /PBC command. (See Section 11.3.3.4 for information on turning other symbols on and off.) This command also provides an option that lets you display the boundary condition values next to the symbols. Some of the boundary condition values that are associated with this command include reaction force (RFOR), reaction moment (RMOM), displacement (U), and current flow (AMPS). See the ANSYS Commands Reference for more information about the various boundary values that are supported.

11.3.3.3 Scaling Vector Load Symbols

/VSCALE (Utility Menu>PlotCtrls>Style>Vector Arrow Scaling) allows you to adjust the scale of vector item symbols (such as the arrows representing concentrated forces, etc.). This same command also allows you to choose a "uniform scaling" option, in which all items' vector symbols have the same length, regardless of their relative magnitudes.

11.3.3.4 Turning Other Symbols On and Off

You can turn symbols for master degrees of freedom, coupled nodes, and nodes in constraint equations on and off with the /PBC command. Use the /PSYMB command (Utility Menu>PlotCtrls>Symbols) to turn symbols on and off for local, nodal, and element coordinate systems, line directions, keypoints/nodes, and layer orientation (for layered elements).

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