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.br |
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.B "rcontrib [ options ] \-defaults" |
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.SH DESCRIPTION |
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< |
.I Rtcontrib |
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> |
.I Rcontrib |
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computes ray coefficients |
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for objects whose modifiers are named in one or more |
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.I \-m |
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If the |
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.I \-n |
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option is specified with a value greater than 1, multiple |
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– |
.I rtrace |
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processes will be used to accelerate computation on a shared |
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memory machine. |
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Note that there is no benefit to using more processes |
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option tells |
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.I rcontrib |
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how many rays to accumulate for each record. |
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< |
The default value is 1, meaning a full record will be produced for |
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> |
The default value is one, meaning a full record will be produced for |
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each input ray. |
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< |
For values greater than 1, contributions will be averaged together |
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> |
For values greater than one, contributions will be averaged together |
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over the given number of input rays. |
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If set to zero, only a single record will be produced at the very |
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end, corresponding to the sum of all rays given on the input |
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to sum RGB values together, but is much more efficient. |
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Using this option, it is possible to reverse sampling, sending rays from |
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a parallel source such as the sun to a diffuse surface, for example. |
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< |
Note that output flushing via zero-direction rays is disabled |
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< |
for accumulated evaluations. |
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> |
Note that output flushing via zero-direction rays is disabled with |
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> |
.I \-c |
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> |
set to zero. |
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.PP |
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The output of |
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.I rcontrib |
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can be used to compute arbitrary input-output relationships in optical |
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systems, such as luminaires, light pipes, and shading devices. |
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.PP |
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< |
.I Rtcontrib |
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< |
calls |
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< |
.I rtrace(1) |
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< |
with the \-oTW (or \-oTV) option to calculate the daughter ray |
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< |
contributions for each input ray, and the output tallies |
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< |
are sent to one or more destinations according to the given |
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> |
.I Rcontrib |
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> |
sends the accumulated rays tallies |
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> |
to one or more destinations according to the given |
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.I \-o |
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specification. |
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If a destination begins with an exclamation mark ('!'), then |
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specification if present. |
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The actual bin number is computed at run time based on ray direction |
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and surface intersection, as described below. |
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< |
If the number of bins is known in advance, it should be specified with the |
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> |
The number of bins must be specified in advance with the |
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.I \-bn |
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option, and this is critical for output files containing multiple values |
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per record. |
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or |
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.I \-e |
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option. |
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< |
Since bin numbers start from 0, the bin count is always equal to |
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< |
the last bin plus 1. |
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< |
Set the this value to 0 if the bin count is unknown (the default). |
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> |
Since bin numbers start from zero, the bin count is always equal to |
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> |
the last bin plus one. |
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The most recent |
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.I \-b, |
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.I \-bn |
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.I \-y |
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if the |
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.I \-c |
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< |
is 0, when they control the resolution string |
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> |
is zero, when they control the resolution string |
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produced in the corresponding output. |
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.PP |
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If a |
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.I \-b |
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expression is defined for a particular modifier, |
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the bin number will be evaluated at run time for each |
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< |
ray contribution from |
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< |
.I rtrace. |
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> |
ray contribution. |
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Specifically, each ray's world intersection point will be assigned to |
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the variables Px, Py, and Pz, and the normalized ray direction |
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will be assigned to Dx, Dy, and Dz. |
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option. |
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The computed bin value will be |
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rounded to the nearest whole number. |
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+ |
For a single bin, you may specify |
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+ |
.I "\-b 0", |
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+ |
which is the default. |
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This mechanism allows the user to define precise regions or directions |
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they wish to accumulate, such as the Tregenza sky discretization, |
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which would be otherwise impossible to specify |
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described in the |
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.I rcalc(1) |
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man page. |
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< |
Unlike |
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> |
Like |
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.I rcalc, |
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.I rcontrib |
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will search the RADIANCE library directories for each file given in a |
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.PP |
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To compute an array of illuminance contributions according to a Tregenza sky: |
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.IP "" .2i |
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< |
rcontrib \-I+ \-b tbin \-o sky.dat \-m skyglow \-b 0 \-o ground.dat \-m groundglow |
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< |
@render.opt \-f tregenza.cal scene.oct < test.dat |
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> |
rcontrib \-I+ \-f tregenza.cal \-b tbin \-bn Ntbins \-o sky.dat \-m skyglow |
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> |
\-b 0 \-o ground.dat \-m groundglow @render.opt scene.oct < test.dat |
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.SH ENVIRONMENT |
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RAYPATH path to search for \-f and \-M files |
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.SH AUTHOR |
