The geometry of the model is defined by a set of points in the part system. The names of all points begin with a *. The location of the points can be specified with respect to either the part origin, or another point. At least one node in the model, however, must be specified with respect to the part system. Every point belongs to a part, and to allow for specifying fixed positions in space, there is a part which does not belong to any body, GROUND. Therefore, to define fixed locations in space one can specify that the following points will be fixed by issuing &DESCRIBE PART GROUND before the fixed points are defined. The part system of GROUND is the global system.

To define a point, one issues the command:

     *NAM, X, Y, Z, -OPTIONS

and the available options are:

     -DEL, DOF(1), .... DOF(i)

     -REFERENCE, *RPA, *RPB,..

     -RECT

     -CYLINDER

     -SPHERICAL

     -LOCATION, XO, YO, ZO, RX, RY, RZ

     -LOCATION, XO, YO, ZO, *PT(1), *PT(2), *PT(3), *PT(4)

where *NAM is the name of the point defined, and X, Y, Z are the coordinates (feet or meters) in the "current point system" defined by the &DEFAULT command. The option -DEL is used to delete the degrees of freedom of a node specified by DOF(i) which must be either X, Y, Z, RX, RY, or RZ. If no DOFs are specified, then all degrees of freedom will be fixed. If the option -REFERENCE is employed, then the coordinates are relative to the specified points; otherwise, they are with respect to the part origin.

If one reference point is specified, then X, Y, and Z define a vector from this reference point to point *NNAM. If two points are specified, then X specifies the distance from the point *RPA to point *NNAM, along a line from *RPA to *RPB, and Y and Z are ignored. If three points are specified, then they will define a local coordinate system with the origin being at the first point, the x axis being from point 1 to point 2, the z axis being perpendicular to the plane formed by the three points, and the y axis given by the right hand rule. Again, X, Y, and Z are local coordinates in this system. If four points are specified, then a point is first located at the intersection of the two lines which connect *RPA and *RPB, and *RPC and *RPD. The X, Y, and Z coordinates then define the vector from this point to point *NNAM. Remember that if one changes the coordinates of a point being referenced, then the coordinates of the defined point will also change. Some examples of using reference points are shown below:

     *PT3  10 -REFERENCE *PT1 *PT2

This will create a point 10 feet (or meters) from *PT1 along a line formed by *PT1 and *PT2. This example is handy for defining points along a battered jacket leg.

     *PT5 -REFERENCE *PT1 *PT2 *PT3 *PT4

This will create a point at the intersection of the lines formed by points *PT1 and *PT2, and *PT3 and PT4, which is useful for defining points at the middle of X braces.

If one wished to temporarily override the current system, he may do so by specifying any of the options -RECT, -CYLINDER, -SPHERICAL, or -LOCATION which were discussed with the &DEFAULT command.

Points to which one attaches structure have a special name, nodes. Each point which is not a node will have a node associated with it. Any load associated with a point is ultimately applied to the structure at the associated node. The associated node is the node closest to the point which is in the "associated node set." Normally, this set will be the set of all nodes. In some situations, however, one wishes to exclude certain nodes for being "associated" and thus from attracting loads. This is accomplished with the command:

     &DESCRIBE NODE_NAS, PART_NAME(1), :PNT_SEL(1), ...

where PART_NAME(i) is a part name, and :PNT_SEL(i) is a selection criteria which defines the nodes which will not be associated.

Often, it is desirable to obtain information about certain points on the bodies during a simulation. The points at which these reports will be issued are defined by the command

     &DESCRIBE INTEREST  -OPTIONS

and the available options are:

     -DELETE, :PNT_SEL(1) .... :PNT_SEL(i)

     -ASSOCIATE, :PNT_SEL(1) .... :PNT_SEL(i)

Here :PNT_SEL(k) are selectors for points. The option -DELETE deletes the interest points selected by all of the selectors and -ASSOCIATE makes interest points of all points selected by the selectors. Interest points have a bit more information associated with them than the other types of points. In particular, each time the &DESCRIBE INTEREST, is issued, the global location of the interest point is saved. These locations are used for a reference in measuring "motion" in several reports.

The string function for points is one of the most useful, and its form is:

     &POINT(ACTION, DATA,  -OPTION)

Here, ACTION must be either COORDINATES, D_NODE, PART, EULER_ANGLES, N_2NODES, N_BOX, RATIO, DEFLECTION, HOOK_LOC, OFFSET, CLOSE, NEAREST, or REL_MOTION. The details of DATA vary with ACTION, but normally DATA will be one or more point names. If ACTION is COORDINATES, this function returns the location of the point specified with DATA. Here, the location returned will be in the part system, unless one of the options -BODY or -GLOBAL has been specified. If the point has not been defined, a null string will be returned. One can use this function during an INMODEL, to define locations which may be required, provided that the point referenced has been previously defined. If ACTION is D_NODE, the function will return the distance between the two points specified via DATA. If ACTION is PART, the part name of the point specified with DATA is returned.

When changing frames of reference, the ACTION EULER_ANGLES may be useful. This action returns a set of Euler angles from three points specified via DATA. These angles will establish the new x axis along the line from first point to second, a new Z axis perpendicular to the plane formed by the three points, and a new Y axis given by the right-hand rule. The Z axis is defined by the cross product of the X axis and the vector from the first to the third point.

The ACTION N_2NODES returns all points along the line segment between the first point specified via DATA and the second one. These points will be in order with the first point specified being the first point returned and the second one specified as the last one returned.

The remaining values ACTION are different than those above in that the DATA are not strictly point names. The ACTION N_BOX is different from the others in that the data here is a set of global coordinates: X1, X2, Y1, Y2, Z1, and Z2. The function will return all points which are in the "box" defined by the six planes defined by these coordinates. The ACTION RATIO will return the last value of joint unity ratio computed for the specified point, and an ACTION of DISPLACEMENT will return the three components of the last computed deflection of the point.

The ACTION HOOK_LOC has a form for DATA of: *NN1, LEN1, *NN2, LEN2, ....., *NN4, LEN4, and is used to find the global position of a hook which is connected to points *NN1, *NN2, etc. It assumes that the harness lengths are LEN1, LEN2, ... respectively. This function is useful primarily in setting up a lifting problem when one models the sling as a collection of flexible connectors.

The values of ACTION OFFSET and CLOSE are used to find offsets. Normally, they are used in the definition of connectors. The form of DATA for OFFSET is: *POIN, :SEL, X, Y, Z and for CLOSE PART_NAME, :SEL, X, Y, Z. Here, X, Y, and Z are locations (feet or meters). For both values of ACTION, MOSES finds the point closest to a specified location but they differ in detail. For an ACTION of OFFSET, the specified point is the location of *POIN plus the X, Y, and Z specified, and any point which matches :SEL in a part different than that of *POINT is a candidate. The string returned is -GO1, the x, y and z values of the offset from specified point to the "close" point, and the string *POIN itself. For CLOSE, the specified point is simply the location in the part PART_NAME defined by X, Y, and Z, and all points which match :SEL are considered for being "close". In either case, the vector returned is represented in the part system of the "close" point. As an example, consider:

     CONNECTOR ~CC &POINT(OFFSET *1 @ 0 0 10)

This will define a connector of class ~CC. End 1 of the connector is at a physical location of *1 plus 0 0 10 in the part system of *1 and end two is at *1. This connection is actually defined via the closest point and an offset and the command set to MOSES will look like

     CONNECTOR ~CC -GO1  XX YY ZZ *B22 *1

where XX, YY, ZZ, and *B22 will be values computed so that the end of the connector is at the correct location.

The ACTION of NEAREST takes a point name and a selector and returns the point which matches the selector closest to the given point. In particular:

     &POINT(NEAREST *R *R@)

will return the name of the point which begins with *R (and which is not *R itself) that is closest the point *R.

Another useful ACTION is REL_MOTION. Here, data is two point names *P1, *P2, and six numbers: X-, X+, Y-, Y+, Z-, and Z+. What the function returns is the minimum and maxima of the relative location between the two points and the values input, i.e. the output is part of the input which has been modified. This is best seen by example. Suppose that one issues:

     &SET ENVEL =
     &SET ENVEL = &POINT(REL_MOT *1 *2 %ENVEL )

You will find that at this point X- = X+, Y- = Y+, and Z- = Z+, and X-, Y-, Z- is the vector from *1 to *2 in the *1 body system. If you issue the second of these commands several times, the result will be that ENVEL will contain the extremes of the relative position between the two points. From the above example, if this ACTION is used with null data, the accumulation is initialized. Also, the values returned are in feet or meters.

Often, one wants to transform vectors from body to global coordinates and conversely. This is easily accomplished with the string function:

     &V_TRANSF(ACTION, BODY_NAME, DATA)

Here, ACTION must be either V_B2G, V_G2B, V_P2B, V_B2P, L_B2G, L_G2B, L_P2B, L_B2P, F_B2G, F_G2B, F_P2B, or F_B2P and DATA is either three or six coordinates (feet or meters) or six force components (bforce, bforce-feet or meters). The function takes the input and transforms it, returning the same number of components as DATA input. If ACTION begins with: a V then a simple vector rotation will be performed, with an L a rotation and a translation will be performed, and with an F a force transformation will be performed. The remainder of ACTION defines the direction of the transformation. The action B2G transforms a body representation into a global one, and G2B the inverse. The action P2B transforms a part representation into a body one, and B2P the inverse.

Once a set of points for a part have been defined, they can be exported to a file for later use with the command:

     &EXPORT POINTS