link3d

Process Help

LINK3D - interactive string editing and wireframe generation

Process Name	Menu Path	Link to Command Table
LINK3D	Command line only	Click here

Introduction
Files, Fields and Parameters
Example
Notes
Errors

Introduction

LINK3D is an interactive graphics process used to define, digitize and edit coordinate strings, and then to link these strings together with triangular facets to form one or more wireframes.

Interactive Graphics

The process uses a single graphics window, within which any view plane may be specified. A view is defined by two rotations: first, an "azimuth" rotation about the Z coordinate axis, followed by a "dip" rotation about the (transformed) X coordinate axis. The view may be specified directly, or interactively by means of a graphical device. Strings and wire frames are visible for a fixed distance in front of and behind this plane. This distance is (by default) set to infinite, so that all objects are visible. However, the front and back "clip distance" may be set to any other value as appropriate.

String Handling

LINK3D allows a large number of strings to be displayed and edited at once. The process incorporates the same string creation and editing facilities as the DIGIT and RDDESN processes.

The process has been written in a way that often requires the user to select a string. This is done by pointing to the string with the pointer device and pressing the left-hand button.

Tag strings

Tags may be assigned to points to control the behavior of the wire frame creation function, typically to ensure that some feature of the object being modeled is correctly represented. This is done by creating a "tag string". In creating a tag string, you are defining triangle edges that are required in the wire frame. Tag strings are saved in the output string and wire frame points file by means of a TAG field: any string in which the TAG value is not a missing value is a tag string.

Linking strings

LINK3D offers two methods of generating the triangles that form the wire frame. The first of these, the LINK-STRINGS command, joins two strings together. The strings to be linked are indicated by means of the pointer, and may be open or closed. Tag strings are honored.

The second command that generates triangles is the END-LINK command, which fills a closed string (i.e. a perimeter) with triangles. The perimeter should be planar, however this is not necessary. The END-LINK command ignores tags.

There are two un-linking commands that may be used. The first of these, the UNDO-LAST-LINK command simply removes the triangles created by the last LINK-STRINGS or END-LINK command. UNDO-LAST-LINK only removes the triangles from the last operation; it cannot be used to successively undo all linking. More generally, the UNLINK-STRING command allows the user to point to any string visible in the display and then removes all triangles which are attached to that string.

When a string becomes part of a wire frame, LINK3D places certain restrictions on the subsequent editing of that string. For example, if a string has been linked, the DELETE-MODE command is prevented from removing points from the string until the string has been unlinked. This is done automatically whenever editing a linked string would cause problems. Note that the MOVEPOINTS command will operate on linked strings, and if a linked point is moved, then the attached triangles move as well.

Files, Fields and Parameters

Input Files

Name	Description	I/O Status	Required	Type
PERIMIN	Input string file. If the file already exists, it must contain the fields XP ,YP, ZP, PTN and PVALUE. If this file does not exist, it will be created with explicit numeric fields XP, YP, ZP, PID, PTN, PVALUE, , and TAG plus any additional attribute fields which are specified (see below). If this file is also to be used as the wireframe points file it must contain an explicit numeric field PID.	Input	Yes	String
WIREPTIN	Input wireframe point file. If the file already exists, it must contain the fields XP ,YP, ZP and PID. If this file does not exist, it will be created with explicit numeric fields XP, YP, ZP, PID, PTN, PVALUE, , and TAG plus any additional attribute fields which are specified (see below). If this file is also to be used as the string file it must contain the explicit numeric fields PTN and PVALUE.	Input	Yes	Wireframe Points
WIRETRIN	Input wireframe triangle file. If this does not exist, it will be created with explicit numeric fields PID1, PID2, PID3, TRIANGLE, SID plus any additional attribute fields which are specified (see below). If the file already exists, it must contain all the five fields mentioned above.	Input	Yes	Wireframe Triangle
SECTION	Overwritten	No	Section Definition	Optional section definition file. If this file does not exist it will be created. This file must contain the fields XCENTRE, YCENTRE, ZCENTRE, SAZI, SDIP, HSIZE, VSIZE, DPLUS, DMINUS and TEXT. All fields are numeric except for TEXT which must be 6 words long. It is advisable to specify a section file as this is used to change views from within LINK3D. Views can be created and stored in the section file from within LINK3D.

Output Files

Name	I/O Status	Required	Type	Description
WIREPTOU	Output	No	Wireframe Points	Optional output point file [for wireframe model] This file has all the same fields as the input string file, as well as new PID and TAG fields.
WIRETROU	Output	No	Wireframe Triangle	Output triangle file [for wireframe model].
PERIMOUT	Output	No	String	Optional output string file.

Fields

Name	Description	Source	Required	Type	Default
ATTRIB1	Optional attribute field 1. If specified, this field will appear in the output file with a value specified for each digitised point. Attribute fields may be numeric or alphanumeric. If alphanumeric attributes are used, they MUST already exist in the PERIMIN file. In LINK3D Attributes need only be specified if the PERIMIN file is being created. The process automatically picks up non-standard fields as attributes.	PERIMIN	No	Any	Undefined
ATTRIB2	Optional attribute field 2.	PERIMIN	No	Any	Undefined
ATTRIB3	Optional attribute field 3.	PERIMIN	No	Any	Undefined
ATTRIB4	Optional attribute field 4.	PERIMIN	No	Any	Undefined
ATTRIB5	Optional attribute field 5. LINK3D can handle up to 10 attribute fields at once.	PERIMIN	No	Any	Undefined

Parameters

Name	Description	Required	Default	Range	Values
MAXPTS	Maximum number of points in any one string. The maximum number of strings that can be handled has been set for your installation. This is typically 500 strings (the actual number is displayed by LINK3D at run time). If MAXPTS is absent, a value is calculated that will avoid LINK3D having to page strings to and from a temporary disk file. (500).	No	500	Undefined	Undefined
COPYPER	If set to 1, then all strings will be copied from PERIMIN to PERIMOUT , subject to any retrieval criteria. Default is no copy. If PERIMOUT is not set, COPYPER is ignored.	No	0	0,1	0,1
COPYWF	If set to 1, then all points and triangles will be copied from WIREPTIN to WIREPTOU and from WIRETRIN to WIRETROU , subject to any retrieval criteria. Default is no copy. If WIREPTOU and WIRETROU are not set, COPYPWF is ignored.	No	0	0,1	0,1

Notes

A.		When LINK3D is first started, you are asked how any attribute fields are to be handled. Currently, attribute values at each point may be handled in any of the following ways:
	1.	The attribute value is CONSTANT within the string. The value of each CONSTANT attribute will be the same at each point in the string. It is entered when the string is first defined (with the NEW STRING [/GN] command) and may be changed via the EDIT ATTRIBUTE [/QA] command.
	2.	The attribute value is PROMPTED for as each point is digitized.
	3.	The attribute value is INCREMENTED along the string. Any base and increment values can be used, and these are entered when the string is defined via the NEW STRING [/GN] command. The base/increment values may also be changed via EDIT ATTRIBUTE [/QA]. The values attached to each point are recalculated automatically if points are deleted from the string, or if new points are inserted into the string. Note also that the REVERSE ORDER [/SV] command will also cause the values to be recalculated.
	4.	The attribute field will contain the CUMULATIVE DISTANCE along the string to each point. The value of the attribute at each point is handled entirely by LINK3D, and is re-calculated each time the string is edited in any way.
	5.	The attribute provides INFORMATION and values cannot be changed. The value of the attribute can be displayed with the QUERY POINTS [/QP] command. This type of attribute can also be used to carry miscellaneous fields through to the output file.
B.		The field name is recognized when used as an attribute field. The value contained in the field should correspond to a color number (in the range 1-16), and will be used by LINK3D as the color in which to display the string. Note that the FILTER S [/DF] command (see above) required one of the attribute fields to be .
C.		The digitizer menu used by LINK3D is usually generated by means of a MACRO (usually digimenu.mac). By default, this menu is A4 in size. The menu can, however, be reduced (or enlarged) by using a photocopier if desired. This can be especially useful if using a digitizer smaller than A0.

Menu Commands

AO	OPEN ALL [/GO]
	Make all strings open strings. This is the opposite of the CLOSE ALL [/GL] command. Certain processes require that input perimeter files contain perimeters in which are not closed. This command allows this to be done easily.
AP	CLOSE ALL [/GL]
	Make all strings perimeters. A perimeter is defined here as being a string whose first and last points are at the same coordinate location. This command is equivalent to executing the CLOSE [/SC] command (q.v.) on all current strings, thus turning them all into perimeters.
BF	FLUSH FILES [/CI]
	Rationalizes the wire frame points and triangle files. This command removes unwanted and absent records from the wire frame files and ensures the files are up to date on disk.
BR	BREAK [/SB]
	Break a string. This command allows any string to be broken at any point. The point at which the break is made is chosen by pointing to the required location with the cursor. If there is no currently "selected string", any point on any string may be selected as the break location. If there is a selected string, the break location must be chosen on that string. In order to break a string at a previously defined point, it may be selected by clicking button two in snap-to-point mode.
CL	CLOSE [/SC]
	Close a string. This turns a string into a closed perimeter. If there is no selected string the required string is first selected by the cursor. Once closed, the QUERY STRING [/QQ] command may be used to calculate the area enclosed by the perimeter. If a string is already closed, this command has no effect. Closing a string ensures that the first point is repeated at the end of the string.
CU	CURSOR [/CU]
	Switch between cursor and keyboard mode, and vice-versa.
DE	DELETE MODEL [/GD]
	Delete vertices (points on the string). If a string has been selected by use of the SELECT STRING [/QS] command, then only vertices on this string will be deleted; otherwise any point on any string may be deleted. A message is displayed indicating which of these two modes will be used. Once this command has been selected, a delete mode is entered. In this mode, the nearest point to the cursor is deleted when a button is pressed. The delete mode is turned off when any other command is chosen.
DF	DEFAULTS [/QF]
	The DEFAULTS command allows you to examine and change such values as the size and type of symbols used in the screen display. A menu of choices is displayed: WIREFRAME DISPLAY [/QFW] Allows you to specify whether the wire frames stored in the input [/QFWI], or output [/QFWO] file, or both the input and output files [/QFWB] are to be displayed each time the graphics display is redrawn. Select "neither" [/QFWN] to disable automatic wireframe display. SLICE WIREFRAME [/QFF] Allows you to specify whether the intersection of the wire frames and the screen plane is automatically displayed each time the display is redrawn. You may choose to slice the input, output or both wireframe files. TAG [QFT] Prompts for the color number to be used when displaying tag strings. The default color for tag strings is color 2. REDUCE POINTS [/QFR] Prompts for the number of points to be removed from a string by the REDUCE POINTS [/SP] command. If a missing value is entered ("-"), (the default) the REDUCE POINTS command removes a "reasonable number" of points. CHARACTER SIZE [/QFH] Prompts for the default size (in millimeters) and aspect ratio (width/height) of characters used in the graphics display. SYMBOL SIZE [/QFS] Prompts for the size and type of symbols used to mark points. PLOT [/QFP] Prompts for the default color used in the graphics display for borders, annotation, etc. GRID TYPE [/QFG] Prompts for the style of grid to be drawn. The number corresponds to the @GRID parameter used in the PLOTFR process. RESOLUTION [/QFE] Prompts for six parameters: a scaling factor and resolution for the X, Y and Z directions. The scaling factors allow you to exaggerate any coordinate direction; the resolution factors allow digitized points to be rounded off to any accuracy. For example, if Z coordinates are meters, enter 0.01 to round all Z values to the nearest centimeter. Similarly, enter 5 to round all Z values to the nearest 5 meter interval. CONTINUE [/QFC] Select CONTINUE to exit the DEFAULTS menu.
DI	DIGITISER [/CD]
	Switch between cursor and digitizer input mode, and vice-versa. The first time the digitizer is used, you will be prompted to digitize a set of reference points from which the digitizer to "world" coordinates (e.g. meters) transformation is calculated. At least three points whose world coordinates are known must be digitized to do this. Note that it is always possible to compute an exact transformation if only three reference points are used. This means that if you make an error in digitizing the reference points, you may not know that a poor transformation is being used. The likelihood of an error decreases as more reference points are used. We recommend that you always use four reference points for this purpose. Once you have entered the coordinates of all the reference points to be used, you will be prompted to digitize the corresponding locations IN THE SAME ORDER. When this has been done, the transformation coefficients are calculated and you are asked to digitize a Check Point. The calculated world coordinates of this point are then displayed and you are asked to CONFIRM that the accuracy is acceptable before proceeding. Finally, you will then be asked to define the location of the digitizer menu by digitizing the left-hand, then the right-hand registration marks. You should fix the menu securely to the digitizer before doing this. The digitizer menu may be relocated at any time the digitizer is being used. There is a small fixed "menu", usually in the lower left-hand corner of the digitizer with boxes marked "LOCATE DATAMINE MENU"; "ERASE DATAMINE MENU" and "RESTORE DATAMINE MENU". Select the first of these and you will be prompted to digitize the left-hand and right-hand menu registration points again. You may do this as often as required. Select the second of these boxes to erase temporarily the large DATAMINE menu (for example to digitize a string that runs behind the menu). Select the third of these boxes to restore the menu again.
EA	ERASE ALL [/GE]
	command does NOT erase strings from either the input or output string files; strings are only erased from memory. If you choose to erase wireframes, these are erased from the output wire frame files. Selective deletion of wireframes may be done by using the unlink string command. The user is required to confirm the type of erase required: ERASE STRINGS [/GES] ERASE WIREFRAMES [/GEW] ERASE BOTH [/GEB] CANCEL [/GEC]
ED	EDIT ATTRIBUTE [/QA]
	Edit attribute values. This command allows you to select any previously defined points with the cursor or digitizer, and edit any attribute values attached to them. If the attribute is CONSTANT for the string; or is INCREMENTAL along the string, you may edit the value(s) for the entire string by picking ANY point on the string. If the attribute is PROMPTED, each edit affects only the picked point. You cannot edit CUMULATIVE-DISTANCE or INFORMATIONAL attributes. Note that for numeric fields, the default response (in square brackets) is the current value of the attribute, which is selected by pressing <RETURN> alone. The default response for alphanumeric fields is blanks.
EL	END-LINK [/WE]
	Triangulate end face on any string. You will always be prompted to select a string for end linking.
ER	ERASE STRING [/SE]
	Erase a string. If there is no selected string, the string to be erased is first selected by cursor. The selection must be confirmed before the string is deleted: [/SEY] to erase the string; [/SEN] to cancel the command.
EX	EXIT [/X]
	Exit from LINK3D. You will be asked to confirm that you indeed want to exit. Before exit, the wire frame files are automatically "rationalized", to remove all redundant and unnecessary records.
FA	FILTER ATTRIBUTES
	Filter attributes. This command allows you to filter out certain strings (and colors) by specifying values for each attribute NOT to be displayed.
GA	GET ALL STRINGS [/FA]
	Get all strings from either the input or output file into the internal arrays for editing. String from the file will be added into memory; existing ones will not be lost. Use the ERASE ALL [/GE] command to erase all strings first if you wish. If the maximum number of strings that can be handled is about to be exceeded, the command is terminated with a message. You may use the this command in conjunction with the RETRIEVAL CRITERIA [/CT] command to set temporary retrieval criteria on those strings to be read from file.
GS	GET STRING [/FG]
	Get single string from file. This command allows you to load any single string from either the input or output file. You will be asked to give the PVALUE of the string in the file. The string will be added into the internal arrays; existing ones will not be lost.
HE	HELP [/H]
	Provide help on commands. The help command will prompt you to select the command for which you require help. It then displays a description of the operation of that command.
IN	INSERT [/GI]
	Insert vertices (points on the string). If a string has been selected by use of the SELECT STRING [/SS] command, then new vertices will be inserted into this string only; otherwise points may be inserted into any string. A message is displayed showing which of these two modes of operation will be used. Once this command has been selected, LINK3D enters insert mode. In this mode, a point is inserted following the nearest point to the cursor when a button is pressed. The insert mode is turned off when any other command is chosen.
JO	JOIN STRINGS [/SJ]
	Join two strings end to end. If there is a selected string, it is used as the first string to be joined; otherwise you will be requested to pick the first of the two strings. You will then be requested to pick the second string: this is the string to be joined onto the end of the first. All CONSTANT, INCREMENTAL, and CUMULATIVE-DISTANCE attributes on the second string will be replaced with values from the first string.
LK	LINK STRINGS [/WL]
	Link two strings by triangulation, honoring any TAG values which match. If there is no selected string, you will be prompted for the first string to link. Then, you will be prompted for additional strings to extend the wireframe. Select any other command to cancel.
ML	MULTIPLE SLICE [/WM]
	Create wire frame slices in a set of planes which are parallel to the current view plane. The first slice is in the current view plane. You will be prompted for the increment between slice planes. You will also be prompted to specify whether the slices are to be converted to strings (and added to the current set of strings), or just displayed.
MO	MOVE POINTS [/GM]
	Move points. This command allows you to pick any currently defined vertex and move it to a new location. You will be asked repeatedly to pick a point to be moved and then to point to its new location. If there is a current "selected string", then only points in that string will be moved. You can terminate this command by selecting another command. Only CUMULATIVE-DISTANCE attributes are updated during the MOVE command.
NF	SET CLIPPING [/DC]
	Set Near and Far clipping limits. This command allows you to specify how far in front of and behind the current view plane data should be displayed. Useful values to specify are NEAR = 0, FAR = +. This will hide objects in front of the current view plane.
NL	NON-STOP LINKING [/WN]
	"Non-stop" linking. This command links strings together in the order in which they were defined. This command is provided for compatibility with LINKPE, to enable strings to be linked from macro operation.
NS	NEW STRING [/SN]
	Define a New String. You will be prompted to supply values for any CONSTANT attributes, and the starting and increment values for INCREMENTAL type attributes. Points are then added by using the F1 or F2 buttons. Duplicate points will not be accepted. You will be asked for any PROMPTED attributes as each point is digitized. The New string command is exited by selecting another command.
NV	GET VIEW [/DG]
	This command allows the user to select a view from the section definition file &SECTION. Views can be saved to the section definition file with the SAVE VIEW [/DV] command.
OK	Used to confirm operations, such as after the ER (Erase) command (macro operation only).
PA	REDRAW [/DR]
	Refresh screen display. This command is implemented at a low level and will not interrupt any other modal command (such as DELETE MODE [/GD]).
PL	MAKE PLOT FILE [/CM]
	Make a plot file of the screen display. You will be asked to supply the name for the DATAMINE plot file that will be created.
PN	PAN [/DP]
	Pan the current display sideways. This command allows you to move the window visible on the display. You will be prompted to pick two points: these correspond to the location of any point in the window before and after it is shifted.
PS	SMOOTH [/SM]
	"Parabolic Smoothing". This command smooths a string by inserting new points between each existing pair of points.
QL	QUERY LINES [/QL]
	Query line mode. This command requests you to define the end-points of a line, and then calculates and displays various statistics about the line. The displayed values include: X, Y and Z coordinates of each end-point and the difference between the X, Y and Z coordinates of each end; the slope, horizontal and vertical distance between the two points; and the azimuth, dip and gradient of the line joining the two points. Note that if the end-points are defined using button 2, then they will be snapped onto previously-defined coordinate points.
QP	QUERY POINTS [/QP]
	Query point mode (Display coordinates). The point to be queried must be chosen by the cursor (mouse) or the digitizer. If you select a point using button 1, the coordinates of the point picked are displayed. If you use button 2, the nearest defined point is selected and its coordinates and any attribute values are displayed.
QS	QUERY STRING [/QQ]
	Query (provide statistics on) a string. The required string is first selected. The information shown always includes the range of the X, Y and Z co-ordinates. If the string is closed (a perimeter) the enclosed area is also given, and if the perimeter is anti-clockwise this is indicated.
RD	REDUCE POINTS [/SP]
	Reduces the number of points in a string by a given percentage. This percentage is set using the DEFAULTS [/CF] command.
RE	REVERSE ORDER [/SV]
	Reverse current string direction
RF	REFERENCE POINTS [/CC]
	Define a new set of digitizer reference points (and recalculate the transformation coefficients). This command may be used at any time to redefine the location of the drawing on the digitizer; for example to move on to a new sheet. Details of the operation of this command are given with the description of the DIGITISER [/CD] command. Note that this command allows for new drawings or movements in the plane of the drawing. If you are positioning a drawing from another (or parallel) plane, you MUST indicate the change of view by selecting the RESET LIMITS [/DL] command first.
RO	ROTATE [/DO]
	Rotate the current view to another azimuth and/or dip. This command creates a pop-up "gadget" to allow you to select a new viewing azimuth and/or dip. The current azimuth and dip are displayed. The AZIMUTH is the direction of a line from your eye to the centre of the display. The DIP is the dip of the display plane; remember that -90 degrees is vertically downwards, +90 degrees is vertically upwards. The gadget contains "+" and "-" symbols to allow the current values to be adjusted. These are scaled so clicking BETWEEN the symbols changes the value by 1 degree, clicking ON the symbol changes the value by 5 degrees, and clicking OUTSIDE the symbols adjusts by +/- 10 degrees. The REFRESH box allows you to preview the specified view; ACCEPT accepts the displayed azimuth and dip; and CANCEL resets the view that was current before the command was selected. Selecting any new command (except CANCEL) does the same as selecting the ACCEPT box.
RU	MACRO [/CA]
	Run a macro from a system file containing a set of applicable commands. command macros may not be nested, but one macro may chain to another if the final command in the file is MACRO (RU). Otherwise, the macro file must only contain valid commands and their data.
SC	CONDITION [/SO]
	String stabilization control. Adjusts a string according to supplied maximum and minimum chord lengths and a minimum angle. This command will insert and delete points to satisfy the maximum and minimum chord lengths. The points at any vertex which has an angle of less than the minimum angle is then removed.
SD	SLICE WIREFRAME [/WF]
	Display a wire frame section, where it intersects the current view plane. This is often helpful in identifying where the view plane is, especially when used in conjunction with the SET CLIPPING [/DC] command.
SL	CONVERT SLICE [/WC]
	Perform a wire frame slice where the wire frame intersects the current view plane, and add any resulting strings to those already in memory. Use the SLICE WIREFRAME [/WF] command to preview the wire frame slice.
SM	SNAP MODEL [/CP]
	Set snap mode. Button F2 can operate in one of two modes: point or line. This command toggles between these two modes. In point mode, F2 will find the nearest point to the cursor and make this the accepted point. In line mode, the nearest line is chosen. On entry, Point mode is set. Note that button F2 will ALWAYS snap onto a point or line. This greatly enhances the power of such commands as NEW STRING [/SN], EXTEND [/GX], MOVE POINTS [/GM], QUERY POINTS [/QP], etc. This command is implemented at a low level and will not interrupt any other modal command (such as INSERT [/GI] (insert points)).
SS	SELECT STRING [/GS]
	Select string for editing. Instead of selecting a string for each operation (such as ERASE STRING [/GE], QUERY STRING [/QQ] etc.) this command may be used to define a string for all subsequent operations. The string is selected with the cursor by pointing to it. Once a string has been selected in this way, then subsequent commands needing a selected string will use the one chosen without requesting selection. To cancel a selection, this command is also used, followed immediately by another command.
SU	SUPERIMPOSE PLOT [/CS]
	Superimpose a DATAMINE plot file. When selected, this command will prompt for a DATAMINE filename. Enter the name of any valid plot file. The contents of the selected file will be displayed on the screen "beneath" all current strings whenever the display is re-drawn. The plot will only be superimposed if the current view is orthogonal, i.e. a plan, X-Z or Y-Z section. It will be re-scaled to match the limits of the display. If no plot appears, it is likely that the coordinate limits in the plot file no not overlap with those of the current display, or the view is oblique. To cancel a superimposed plot, just press <RETURN> instead of entering a plot file name. You are given the option of allowing the snap-to-point and snap-to-line functions to snap to points or lines in the superimposed plot. Note that if the plot file is large, this may greatly increase the time required to find the point to snap to.
SV	SAVE VIEW [/DV]
	Save View. Allows the user to save a view in the section definition file &SECTION. This can be retrieved with the GET VIEW [/DG] command.
TA	TAG STRING [/WT]
	Tag specific perimeter points to be joined. TAG codes are stored in a "TAG" field in the output wire frame point or string file. This command works in much the same way as the NEW STRING command, except that points in a tag string always snap onto existing points.
TR	RETRIEVAL CRITERIA [/CT]
	Set temporary additional retrieval criteria. This command is used to allow LINK3D to read data from the input or output files under various retrieval criteria. Any retrieval criteria that are set by this command are additional to any that were set when LINK3D was started. To un-set additional retrieval criteria, select RETRIEVAL CRITERIA [/CT] and enter just a blank line.
UL	UNDO LAST LINK [/WU]
	Undo last linking operation. This command erases all triangles attached to the string most recently linked using either the LINK STRINGS [/WL] or END-LINK [/WE] commands.
UN	UNLINK STRING [/WI]
	Unlink string. This command erases all triangles attached to a string. If there is no selected string, you will be asked to select the string to be unlinked.
VD	MOVE PLANE [DM]
	Move plane. This command allows you to move the current view plane forwards or backwards.
WA	WRITE ALL STRINGS [/FL]
	Write all strings to the output file. strings in the output file with the same PVALUE as one being written out will be replaced. If a string has no current PVALUE, one is generated for it. This will be one (1) greater than the highest PVALUE found in the file. It will therefore be unique.
WD	DISPLAY WIREFRAME [/WW]
	Wire frame model display. Displays the wire frame models held in the input or output files.
WS	WRITE STRING [/FW]
	Write a single selected string to the output file. The required string is selected by cursor, unless there is a selected string (see SELECT STRING [/GS]).
XS	EXTEND [/GX]
	Extend a string by adding new points to the end. If there is no selected string you will be asked to select the string to be extended with the cursor. Points are then added by using either button F1 or button F2. (Refer to the SNAP MODE [/GP] command for details of how the F1 and F2 buttons differ in operation). Duplicate points will not be accepted. This command is exited by choosing any new command.
XY	RESET LIMITS [/DL]
	Set section plane orientation for current window.
ZA	PLANE BY TWO POINTS [D2]
	Select a new view plane by defining two points. The two points may be obtained by snapping. When the two points have been picked you are asked to choose if you want a vertical or horizontal section.
ZB	PLANE BY THREE POINTS [/D3]
	Select a new view plane by defining three points. The three points may be obtained by snapping. The three points will form a triangle on the new view plane.
ZO	ZOOM IN/OUT [/DZ]
	Zoom in or out. To zoom in, use the cursor to pick the lower left, then the upper right corners of the area to be displayed next. The rectangle thus defined is used to re-define the XY display limits. You may adjust the display in this manner any number of times. To zoom out to the previous view select the ZOOM IN/OUT command twice. If there is no previous view the display will zoom out by a factor of 1.8.

Example

!LINK3D &PERIMIN(OREPERS),&WIREPTIN(OREPERS),&WIRETRIN(ORETRS)

Error and Warning Messages

Message	Description	Solution
>>> ERROR: MORE THAN 10 WORDS IN ATTRIBUTE FIELDS.	One of the attribute fields is more than 10 words (40 characters) in length. Fatal; the process is exited.

>>> ERROR COPYING PERIMETERS <<<	An error occurred while reading in perimeters from the input file and copying them across the output file. Fatal; the process is exited.

>>> ERROR READING INPUT FILE STRING <<<	An error occurred while reading in the strings in the input file. Fatal; the process is exited.