| VVUDMV(3NCARG) | NCAR GRAPHICS | VVUDMV(3NCARG) |
VVUDMV - This routine is the user-definable external subroutine used to draw masked vectors. The default version of the routine draws any polyline all of whose area identifiers are greater than or equal to zero.
CALL VVUDMV (XCS,YCS,NCS,IAI,IAG,NAI)
´VVUDMV´ is the name given to the default version of
the masked vector drawing routine, and it is also the name given to the
argument through which the external subroutine is passed to VVECTR. However,
you may choose any acceptable FORTRAN identifier as the name of a
user-defined version of the routine. The substitute routine must have an
argument list equivalent to the default version of VVUDMV. Also, whether or
not the default version is used, the subroutine that calls VVECTR should
contain an external declaration of the routine similar to the following:
EXTERNAL VVUDMV
If the MSK parameter is set to the value 1, specifying high
precision masking, Vectors sends one set of X and Y polyline coordinate
arrays to the area masking routine, ARDRLN, for each vector arrow. ARDRLN
subdivides the polyline into pieces such that each smaller polyline has a
single area identifier with respect to each area identifier group, then
makes a call to VVUDMV for each polyline piece. While the default version of
VVUDMV only checks to see that none of the area identifiers are negative, a
user-defined version could perform more complicated decision processing
based on knowledge of the meaning of specific area identifier groups and/or
area identifier values. Note that, before invoking VVUDMV, ARDRLN modifies
the user coordinate space by making the following calls:
CALL GETSET(VPL,VPR,VPB,VPT,WDL,WDR,WDB,WDT,LLG) CALL
SET(VPL,VPR,VPB,VPT,VPL,VPR,VPB,VPT,1)
These calls temporarily turn the user to NDC mapping into an identity, allowing the user to call any of the routines, CURVE, CURVED, or the GKS routine GPL, to render the polygon piece , without worrying about a possible non-identity mapping between user and world coordinates.
If MSK has a value greater than 1, specifying low precision masking, Vectors calls the routine ARGTAI to get the area identifiers with respect to the area identifier groups for a single point that locates the base position of the vector. Vectors then calls the VVUDMV routine itself, passing the coordinate arrays for a complete vector arrow. Thus, a vector arrow whose base position is within an area to be masked can be eliminated, but an arrow whose base position is nearby, but outside, a masked area may intrude into the area. Also, in this case, since faster rendering is the goal, Vectors does not convert the coordinate arrays into normalized device coordinates and do the identity SET call. Therefore, the user should use only CURVE or CURVED to render the polyline, unless there is no possibility of a non-identity user to world coordinate mapping.
The current version of Vectors supports masked drawing with up to 64 area groups. Vectors will exit with an error message if an area map with more than 64 groups is passed to it.
Use the ncargex command to see the following relevant examples: ffex05, vvex01.
To use VVUDMV, load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in that order.
Online: vectors, vectors_params, vvectr, vvgetc, vvgeti, vvgetr, vvinit, vvrset, vvsetc, vvseti, vvsetr, vvumxy, ncarg_cbind.
Hardcopy: NCAR Graphics Fundamentals, UNIX Version
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University Corporation for Atmospheric Research
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| April 1993 | UNIX |