Positional Modifiers are minor words which specify the relative direction of one position and/or object to another. These modifiers are valuable in the definitions of geometric objects where multiple solutions exist. Positional modifiers are based on the Cartesian coordinate system and interpreted with respect to the WCS. Positional modifiers apply to a large number of geometric objects and each modifier is associated with a numerical value which may be used instead of the word.
The use of positional modifiers may fail in certain cases. If this occurs, try a user defined reference point instead. Refer to the specific command being used for the correct implementation of the reference point.
The six positional modifier minor words are:
XSMALL, YSMALL, ZSMALL
XLARGE, YLARGE, ZLARGE
Many of the modifiers such as left, right, in, out, etc., are applicable to a limited number of geometric objects and are covered in the specific section where they apply.
Positional modifiers may be used in GRIP Statements only where the statement format allows. The word PMOD is used to tell you to enter one of the positional modifiers. The X, Y and Z modifiers are classified as two and/or three dimensional. As shown below, the two dimensional modifiers "PMOD2" are a subset of the three dimensional modifiers "PMOD3". "PMOD2" modifiers are used in situations where only the X and Y directions are a factor. An example is where the WCS and the current view must be coincident such as in the construction of dimensions or drafting objects.
XSMALL - 1 - PMOD2/PMOD3
YSMALL - 2 - PMOD2/PMOD3
ZSMALL - 3 - PMOD3
XLARGE - 4 - PMOD2/PMOD3
YLARGE - 5 - PMOD2/PMOD3
ZLARGE - 6 - PMOD3
The first character of each word, X, Y, and Z, represents the corresponding axis of the Cartesian coordinate system. The values SMALL and LARGE represent the negative and positive directions of the Cartesian coordinate system respectively.
This example shows the use of a positional modifier to tell GRIP at which end of a line (LN1) it should create a point (P1).
ENTITY/PT1,LN1
LN1=LINE/-1,3,-2,3,6,-3
PT1=POINT/ENDOF,ZSMALL,LN1
The point PT1 is defined at the coordinates of 3, 6 and -3 which is at the end of the line with the smallest Z value (-3 is smaller than -2).
Positional modifiers are general direction indicators which are used to minimize or eliminate ambiguity. In the example above, for instance, XLARGE or YLARGE would have produced the same point.
Another application of the positional modifier is the creation of an object at a given distance from another. For example, in the definition of a line parallel to an existing line, a positional modifier is required to specify on which side of the existing line the new line is created. See the example below.
This example shows how a positional modifier is used to tell GRIP which side of the existing line (LN(1)) to create another line (LN(2) and LN(3)) parallel to it at a specified distance (.75).
ENTITY/LN(3)
LN(1)=LINE/-1,-1,1,1
LN(2)=LINE/PARLEL,LN(1),YLARGE,.75
LN(3)=LINE/PARLEL,LN(1),YSMALL,.75
Parallel Lines Using Positional Modifiers
This example depicts the use of positional modifiers using numerical values instead of minor words.
ENTITY/LN(4),FLT(4)
LN(1) =LINE/0,0,1,0
LN(2) =LINE/1,0,1,1
LN(3) =LINE/1,1,0,1
LN(4) =LINE/0,1,0,0
FLT(1)=FILLET/4,LN(4),5,LN(1),RADIUS,.25
FLT(2)=FILLET/1,LN(2),5,LN(1),RADIUS,.25
FLT(3)=FILLET/1,LN(2),2,LN(3),RADIUS,.25
FLT(4)=FILLET/4,LN(4),2,LN(3),RADIUS,.25
The FILLET statements above, using numerical values, are equivalent to the following FILLET statements, using the positional modifier words.
FLT(1)=FILLET/XLARGE,LN(4),YLARGE,LN(1),RADIUS,.25
FLT(2)=FILLET/XSMALL,LN(2),YLARGE,LN(1),RADIUS,.25
FLT(3)=FILLET/XSMALL,LN(2),YSMALL,LN(3),RADIUS,.25
FLT(4)=FILLET/XLARGE,LN(4),YSMALL,LN(3),RADIUS,.25
If a numerical value less than one or greater than six is substituted for a positional modifier, the error message INVALID MODIFIER is displayed.
PT4 is defined as a point at the end of a 1.8 inch vector which starts at PT3 and is parallel to LN1 in the ZLARGE direction.
ENTITY/PT1,PT2,LN1,PT3,PT4
PT1=POINT/1,-1,1
PT2=POINT/-1,1,-1
LN1=LINE/PT1,PT2
PT3=POINT/0,0,0
PT4=POINT/PT3,VECT,LN1,ZLARGE,1.8
The definition of PT4 may also be written as follows:
PT4 = POINT/PT3,VECT,LN1,6,1.8
The line LN2 is created parallel to LN1, at an offset distance of 1 in the positive Z direction.
ENTITY/PT1,PT2,LN1,LN2
PT1=POINT/0,0
PT2=POINT/1,1
LN1=LINE/PT1,PT2
LN2=LINE/PARLEL,LN1,6,1