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.\" RCSid "$Id$" |
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.TH RTCONTRIB 1 5/25/05 RADIANCE |
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.TH RCONTRIB 1 5/25/05 RADIANCE |
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.SH NAME |
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rcontrib - compute contribution coefficients in a RADIANCE scene |
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.SH SYNOPSIS |
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][ |
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.B \-V |
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][ |
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.B "\-t secs" |
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][ |
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.B "\-c count" |
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][ |
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.B \-fo |
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][ |
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.B "\-o ospec" |
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][ |
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.B "\-p p1=V1,p2=V2" |
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][ |
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.B "\-b binv" |
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][ |
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.B "\-bn nbins" |
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.B octree |
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.br |
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.B "rcontrib [ options ] \-defaults" |
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.br |
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.B "rcontrib \-features [feat1 ..]" |
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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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Output flushing at fixed intervals may be enabled with the |
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.I \-x |
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option, which specifies the number of records |
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(-c accumulations) before each flush. |
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If the |
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.I \-y |
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option is also set, then periodic flushing is disabled and the |
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output size for an RGB image is the taken from the x and y dimensions. |
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In lieu of periodic flushing, a flush may be forced as mentioned above |
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by sending a sample with a zero direction vector, although you |
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must still send a full record of rays before output occurs. |
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.PP |
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If progress reports are desired, the |
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.I \-t |
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option specifies a time interval in seconds for reports sent to |
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standard error. |
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This requires that the number of input samples is known, meaning a |
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.I \-y |
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parameter has been specified. |
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.PP |
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The output of |
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.I rcontrib |
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has many potential uses. |
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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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option may be used to further define |
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a "bin number" within each object if finer resolution is needed, and |
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this will be applied to a "%d" format in the output file |
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specification if present. |
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specification if present. |
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(The final integer will be offset incrementally |
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if the output is a RADIANCE picture and more than one modifier has |
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the same format specification.)\0 |
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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 \-p, |
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.I \-b, |
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.I \-bn |
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and |
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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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arguments and files read using the |
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.I \-f |
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option. |
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Additional parameter values that apply only to this modifier may be specified |
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with a |
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.I \-p |
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option, which contains a list of variable names and assigned values, separated |
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by commas, colons, or semicolons. |
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The computed bin value will be |
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rounded to the nearest whole number. |
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(Negative bin values will be silently ignored.)\0 |
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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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replaced by the contents of the given environment variable. |
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A command argument beginning with an at sign ('@') is immediately |
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replaced by the contents of the given file. |
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.PP |
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.I Rcontrib |
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supports light source contributions from photon maps generated by |
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.I mkpmap(1) |
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with its |
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.I -apC |
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option. Enabling photon mapping is described in the |
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.I rtrace |
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man page along with its relevant settings. In photon mapping mode, |
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.I rcontrib |
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only supports contributions from light sources, not arbitrary modifiers. |
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The |
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.I -b |
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option is supported along with its associated ray variables, as |
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discussed above. Ray coefficients are also supported via the |
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.I \-V- |
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option. Using fewer photons than there are light sources for the photon |
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density estimates results in omitted contributions, thus the bandwidth |
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is clamped accordingly and a warning is issued. |
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.SH EXAMPLES |
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To compute the proportional contributions from sources modified |
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by "light1" vs. "light2" on a set of illuminance values: |
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by "light1" vs. "light2" on a set of irradiance values: |
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.IP "" .2i |
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rcontrib \-I+ @render.opt \-o c_%s.dat \-m light1 \-m light2 scene.oct < test.dat |
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.PP |
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.IP "" .2i |
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pcomb \-c 100 90 75 c_light1.hdr \-c 50 55 57 c_light2.hdr > combined.hdr |
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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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To compute an array of irradiance 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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.PP |
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To perform an annual simulation of 365 daily sun positions in photon mapping |
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mode: |
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.IP "" .2i |
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rcontrib \-I+ \-h \-V \-fo \-o c_%s.dat \-M lights \-ap contrib.pm 365 |
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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 BUGS |
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We do not currently compute contributions or coefficients properly |
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in scenes with participating media. |
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A single warning will be issued if a scattering or absorbing medium |
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is detected. |
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.SH AUTHOR |
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Greg Ward |
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.SH "SEE ALSO" |
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cnt(1), genklemsamp(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1), |
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rcalc(1), rpict(1), rsensor(1), rtrace(1), total(1), vwrays(1), ximage(1) |
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cnt(1), genklemsamp(1), getinfo(1), mkpmap(1), pcomb(1), pfilt(1), |
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ra_rgbe(1), rcalc(1), rfluxmtx(1), rmtxop(1), rpict(1), rsensor(1), |
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rtrace(1), total(1), vwrays(1), ximage(1) |
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