NAME

       dctimestep - compute annual simulation time-step via matrix multiplication

SYNOPSIS

       dctimestep DCspec [ skyvec ]
       dctimestep Vspec Tbsdf.xml Dmat.dat [ skyvec ]

DESCRIPTION

       Dctimestep  has  two  invocation forms.  In the first form, dctimestep is given a daylight
       coefficient specification and an optional sky vector, which may be read from the  standard
       input  if  unspecified.   The daylight coefficients are multiplied against this vector and
       the results are written to the standard output.  This may be a list of color values  or  a
       combined Radiance image, as explained below.

       In  the  second form, dctimestep takes four input files, forming a matrix expression.  The
       first argument is the View matrix file that specifies how  window  output  directions  are
       related  to some set of measured values, such as an array of illuminance points or images.
       This matrix is usually computed by  rtcontrib(1)  for  a  particular  set  of  windows  or
       skylight  openings.  The second argument is the window transmission matrix, or BSDF, given
       as a standard XML description.  The third  argument  is  the  Daylight  matrix  file  that
       defines  how  sky patches relate to input directions on the same opening.  This is usually
       computed using genklemsamp(1) with rtcontrib in a separate run for each window or skylight
       orientation.   The  final  input  is  the  sky  contribution  vector,  usually computed by
       genskyvec(1), which may be passed on the standard input.   This  data  must  be  in  ASCII
       format,  whereas the View and Daylight matrices are more efficiently represented as binary
       float data if machine byte-order is not an issue.

       Sent to the standard output of dctimestep is either an ASCII color vector with as many RGB
       triplets  as  there  are  rows  in the View matrix, or a combined Radiance picture.  Which
       output is produced depends on the first argument.  A regular file name will be loaded  and
       interpreted  as  a  matrix  to  generate  a  color  results  vector.  A file specification
       containing a '%d' format string will be  interpreted  as  a  list  of  Radiance  component
       pictures, which will be summed according to the computed vector.

EXAMPLES

       To compute workplane illuminances at 3:30pm on Feb 10th:

         gensky 2 10 15:30 | genskyvec | dctimestep workplaneDC.dmx > Ill_02-10-1530.dat

       To compute an image at 10am on the equinox from a set of component images:

         gensky 3 21 10 | genskyvec | dctimestep viewc%03d.hdr > view_03-21-10.hdr

       To compute a set of illuminance contributions for Window 1 on the Winter solstice at 2pm:

         gensky  12  21  14  |  genskyvec  |  dctimestep  IllPts.vmx  Blinds20.xml  Window1.dmx >
         Ill_12-21-14.dat

       To compute Window2's contribution to an interior view at 12 noon on the Summer solstice:

         gensky 6 21  12  |  genskyvec  |  dctimestep  view%03d.hdr  Blinds30.xml  Window2.dmx  >
         view_6-21-12.hdr

AUTHOR

       Greg Ward

SEE ALSO

       genklemsamp(1), genskyvec(1), mkillum(1), rtcontrib(1), rtrace(1), vwrays(1)