Provided by: radiance_4R1+20120125-1.1_amd64 
NAME
gensurf - generate a RADIANCE or Wavefront description of a curved surface
SYNOPSIS
gensurf mat name 'x(s,t)' 'y(s,t)' 'z(s,t)' m n [ -e expr ][ -f file ][ -s ][ -o ]
gensurf mat name 'x(s,t)' 'y(s,t)' dfile m n [ -e expr ][ -f file ][ -s ][ -o ]
gensurf mat name dfile dfile dfile m n [ -s ][ -o ]
DESCRIPTION
Gensurf produces either a RADIANCE scene description or a Wavefront .OBJ file of a functional surface
defined by the parametric equations x(s,t), y(s,t), and z(s,t). The surface normal is defined by the
right hand rule as applied to (s,t). S will vary from 0 to 1 in steps of 1/m, and t will vary from 0 to
1 in steps of 1/n. The surface will be composed of 2*m*n or fewer triangles and quadrilaterals. The
expressions are of the same type used in RADIANCE function files. Auxiliary expressions and/or files may
be specified in any number of -e and -f options. The -s option adds smoothing (surface normal
interpolation) to the surface. The -o option produces a Wavefront .OBJ file rather than a RADIANCE scene
description. This is most useful as input to the obj2mesh(1) program for producing a compiled mesh. A
single "usemtl" statement will appear at the beginning of the .OBJ output, echoing the modifier given on
the command line.
Rough holes may be cut in the mesh by defining a valid(s,t) function. Where this function is positive,
polygon vertices will be produced. Where it is negative, no geometry will be output. Surface normal
interpolation will ignore any invalid vertices.
The second invocation form reads z data values from the file dfile. This file must give either m*n or
(m+1)*(n+1) floating point z values. If m*n values are given, then the values correspond to the centroid
of each quadrilateral region. If (m+1)*(n+1) values are given, then the values correspond to the
vertices of each quadrilateral region. The ordering of the data in the file is such that the s values
are changing faster than the t values. If a minus ('-') is given for dfile, then the values are read
from the standard input.
The third invocation form is used to read coordinate triplets from a file or the standard input. The
three dfile arguments must all be the same, and the corresponding file must contain three floating point
values for each point location. The ordering and other details are the same as those described for z
value files above.
EXAMPLE
To generate a tesselated sphere:
gensurf crystal ball 'sin(PI*s)*cos(2*PI*t)' 'cos(PI*s)' 'sin(PI*s)*sin(2*PI*t)' 7 10
To generate a 10x20 smoothed height field from 12 recorded vertex z values:
gensurf dirt ground '10*s' '20*t' height.dat 2 3 -s
AUTHOR
Greg Ward
BUGS
The smoothing operation requires that functions be defined beyond the [0,1] boundaries of s and t.
SEE ALSO
genrbox(1), genrev(1), genworm(1), icalc(1), obj2mesh(1), obj2rad(1), rpict(1), rvu(1), xform(1)