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.\" RCSid "$Id" |
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.TH GENSURF 1 11/15/93 RADIANCE |
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.SH NAME |
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gensurf - generate a RADIANCE description of a curved surface |
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.SH SYNOPSIS |
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.B "gensurf mat name 'x(s,t)' 'y(s,t)' 'z(s,t)' m n" |
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[ |
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.B "\-e expr" |
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][ |
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.B "\-f file" |
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][ |
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.B \-s |
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] |
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.br |
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.B "gensurf mat name 'x(s,t)' 'y(s,t)' dfile m n" |
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[ |
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.B "\-e expr" |
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][ |
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.B "\-f file" |
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][ |
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.B \-s |
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] |
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.br |
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.B "gensurf mat name dfile dfile dfile m n" |
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[ |
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.B \-s |
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] |
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.SH DESCRIPTION |
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.I Gensurf |
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produces a RADIANCE scene description of a |
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functional surface defined by the parametric equations |
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.I x(s,t), |
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.I y(s,t), |
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and |
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.I z(s,t). |
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The surface normal is defined by the right hand rule as |
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applied to |
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.I (s,t). |
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.I S |
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will vary from 0 to 1 in steps of |
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.I 1/m, |
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and |
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.I t |
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will vary from 0 to 1 in steps of |
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.I 1/n. |
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The surface will be composed of |
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.I 2*m*n |
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or fewer triangles and quadrilaterals. |
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The expressions are of the same type used in RADIANCE |
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function files. |
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Auxiliary expressions and/or files may be specified |
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in any number of |
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.I \-e |
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and |
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.I \-f |
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options. |
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The |
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.I \-s |
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option adds smoothing (surface normal interpolation) to the surface. |
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.PP |
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Rough holes may be cut in the mesh by defining a valid(s,t) function. |
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Where this function is positive, polygon vertices will be produced. |
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Where it is negative, no geometry will be output. |
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Surface normal interpolation will ignore any invalid vertices. |
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.PP |
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The second invocation form reads z data values from the file |
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.I dfile. |
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This file must give either m*n or (m+1)*(n+1) floating point z |
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values. |
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If m*n values are given, then the values correspond to the centroid |
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of each quadrilateral region. |
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If (m+1)*(n+1) values are given, then the values correspond to the |
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vertices of each quadrilateral region. |
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The ordering of the data in the file is such that the s values are |
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changing faster than the t values. |
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If a minus ('-') is given for |
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.I dfile, |
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then the values are read from the standard input. |
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.PP |
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The third invocation form is used to read coordinate triplets from a |
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file or the standard input. |
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The three |
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.I dfile |
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arguments must all be the same, and the corresponding file must |
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contain three floating point values for each point location. |
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The ordering and other details are the same as those described |
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for z value files above. |
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.SH EXAMPLE |
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To generate a tesselated sphere: |
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.IP "" .2i |
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gensurf crystal ball 'sin(PI*s)*cos(2*PI*t)' 'cos(PI*s)' 'sin(PI*s)*sin(2*PI*t)' 7 10 |
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.PP |
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To generate a 10x20 smoothed height field from 12 recorded vertex |
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z values: |
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.IP "" .2i |
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gensurf dirt ground '10*s' '20*t' height.dat 2 3 -s |
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.SH AUTHOR |
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Greg Ward |
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.SH BUGS |
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The smoothing operation requires that functions be defined |
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beyond the [0,1] boundaries of s and t. |
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.SH "SEE ALSO" |
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calc(1), genbox(1), genrev(1), genworm(1), rpict(1), rview(1), xform(1) |