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.\" RCSid $Id: genBSDF.1,v 1.2 2010/09/04 15:19:28 greg Exp $ |
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.TH GENBSDF 1 9/3/2010 RADIANCE |
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.SH NAME |
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genBSDF - generate BSDF description from Radiance or MGF input |
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.SH SYNOPSIS |
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.B genBSDF |
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[ |
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.B "\-c Nsamp" |
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][ |
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.B "\-n Nproc" |
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][ |
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.B "{+|-}forward" |
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][ |
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.B "{+|-}backward" |
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][ |
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.B "{+|-}mgf" |
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][ |
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.B "{+|-}geom |
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][ |
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.B "\-dim Xmin Xmax Ymin Ymax Zmin Zmax" |
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] |
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[ |
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.B "geom .." |
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] |
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.SH DESCRIPTION |
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.I GenBSDF |
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computes a bidirectional scattering distribution function from |
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a Radiance or MGF scene description given on the input. |
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The program assumes the input is in Radiance format unless the |
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.I \+mgf |
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option is specified. |
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The output conforms to the LBNL Window 6 XML standard for BSDF data, |
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and will include an MGF representation of the input geometry if the |
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.I \+geom |
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option is given. |
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(This is the default, and may be switched off using |
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.I \-geom.)\0 |
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.PP |
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Normally, |
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.I genBSDF |
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computes components needed by a backwards ray-tracing process, |
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.I \+backward. |
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If both forward and backward (front and back) distributions are needed, the |
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.I \+forward |
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option may be given. |
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To turn off backward components, use the |
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.I \-backward |
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option. |
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Computing both components takes about twice as long as one component. |
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.PP |
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The geometry must fit a rectangular profile, whose width is along the X-axis, |
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height is in the Y-axis, and depth is in the Z-axis. |
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The positive Z-axis points into the room, and the input geometry should |
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not extend into the room. |
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(I.e., it should not contain any positive Z values, since the putative |
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emitting surface is assumed to lie at Z=0.)\0 |
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The entire window system should be modeled, including sills and |
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edge geometry anticipated in the final installation, otherwise |
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accuracy will be impaired. |
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Similarly, materials in the description should be carefully measured. |
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.PP |
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Normally, the input geometry will be positioned according to its actual |
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bounding box, but this may be overridden with the |
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.I \-dim |
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option. |
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Use this in cases where the fenestration system is designed to fit a |
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smaller (or larger) opening or is offset somehow. |
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.PP |
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The variance in the results may be reduced by increasing the number of |
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samples per incident direction using the |
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.I \-c |
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option. |
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This value defaults to 1000 samples distributed over the incoming plane |
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for each of the 145 Klems hemisphere directions. |
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.PP |
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In some cases, the processing time may be reduced by the |
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.I \-n |
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option, which specifies the number of simultaneous |
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.I rtrace(1) |
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processes to run in |
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.I rtcontrib(1). |
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.SH EXAMPLE |
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To create a BSDF description including geometry from a set of venetian blinds: |
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.IP "" .2i |
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genblinds blind_white blind1 .07 3 1.5 30 40 | xform -rz -90 -rx 90 > blind1.rad |
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.br |
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genBSDF blind_white.mat glazing.rad blind1.rad > blind1.xml |
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.SH NOTES |
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Currently, |
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.I genBSDF |
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computes only the forward visible transmitted component, |
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though the XML specification provides for front and back |
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transmission and reflection as well. |
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.SH AUTHOR |
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Greg Ward |
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.SH "SEE ALSO" |
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dctimestep(1), genklemsamp(1), genskyvec(1), mkillum(1), rtcontrib(1), rtrace(1) |
