ncl_isosrf - Man Page

CALL ISOSRF (F,LU,MU,LV,MV,MW,EYE,MUVWP2,SLAB,FISO,IFLAG)

#include <ncarg/ncargC.h>

void c_isosrf (float *f, int lu, int mu, int lv, int mv,
int mw, float eye[3], int muvwp2, float *slab, float fiso,
int iflag)

This routine is part of the Isosurface utility in NCAR Graphics.  To see the overview man page for this utility, type "man isosurface".

F

(an input array of type REAL, dimensioned LU x LV x m,  where "m" is greater than or equal to MW) is a three-dimensional array of data defining the function f(u,v,w). Only the portion of the array consisting of elements  F(IU,IV,IW), for IU = 1 to MU, IV = 1 to MV, and IW = 1 to  MW, is to be used. This may or may not be the entire array.  The data are considered to lie in a box in 3-space with  opposite corners (in the UVW coordinate system) (1.,1.,1.)  and (REAL(MU),REAL(MV),REAL(MW)). The element F(IU,IV,IW)  is considered to be the value of the function f at the  point (REAL(IU),REAL(IV),REAL(IW)).

LU

(an input expression of type INTEGER) is the first  dimension of the array F.

MU

(an input expression of type INTEGER) defines the range  to be used for the first subscript of the array F.

LV

(an input expression of type INTEGER) is the second  dimension of the array F.

MV

(an input expression of type INTEGER) defines the range  to be used for the second subscript of the array F.

MW

(an input expression of type INTEGER) defines the range  to be used for the third subscript of the array F.

EYE

(an input array of type REAL, dimensioned 3) is the  position of the eye in the UVW coordinate system. The eye  position, at (EYE(1),EYE(2),EYE(3)), must be outside the  box containing the data. The point being looked at is at  the center of the data box and the projection plane is  perpendicular to the line of sight. While gaining  experience with the routine, a good choice for EYE is  (5.*REAL(MU),3.5*REAL(MV),2.*REAL(MW)).

MUVWP2

(an input expression of type INTEGER) has the value  MAX(MU,MV,MW)+2.

SLAB

(a scratch array of type REAL, dimensioned at least  MUVWP2 x MUVWP2) is a workspace for ISOSRF.

FISO

(an input expression of type REAL) is the value of  fiso in the equation f(u,v,w)=fiso, which defines the  isosurface to be drawn.

IFLAG

(an input expression of type INTEGER) serves two  purposes:

• The absolute value of IFLAG determines which type of lines  are drawn to approximate the isosurface. Three types of  lines are considered: lines of constant U, lines of  constant V, and lines of constant W. The following table  lists the types of lines drawn for various values of  ABS(IFLAG):

  ABS(IFLAG)	Constant U	Constant V	Constant W
  1	no	no	yes
  2	no	yes	no
  3	no	yes	yes
  4	yes	no	no
  5	yes	no	yes
  6	yes	yes	no
  7	yes	yes	yes

• The sign of IFLAG determines what is inside and what is outside the solid bounded by the isosurface and thus which lines are visible and what is done at the boundary of the box containing the data. If IFLAG is positive, values greater than FISO are considered to be inside the solid formed by the isosurface. If IFLAG is negative, values less than FISO are considered to be inside the solid formed by the isosurface. If the algorithm draws a cube, reverse the sign of IFLAG.

The C-binding argument descriptions are the same as the Fortran  argument descriptions, with the following exceptions:

f

t is dimensioned mw by mv by mu

mu

The third dimension of the array f

mw

The first dimension of the array f

Transformations can be achieved by adjusting scaling statement functions in ISOSRF, SET3D, and TR32.

The hidden-line algorithm is not exact, so visibility errors can occur.

Three-dimensional perspective character labeling of isosurfaces is possible by calling the routine PWRZI.

Use the ncargex command to see the following relevant examples:  tisosr, tpwrzi, fisissrf, fispwrzi.

To use ISOSRF or c_isosrf load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in that order.  

Online: isosurface, isosurface_params, ezisos,  isgeti, isgetr, isseti, issetr, pwrzi,  ncarg_cbind

Hardcopy: NCAR Graphics Fundamentals, UNIX Version

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University Corporation for Atmospheric Research
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