Ubuntu Manpage: vwrays - compute rays for a given picture or view

Provided by: radiance_4R1+20120125-1.1_amd64

NAME

       vwrays - compute rays for a given picture or view

SYNOPSIS

       vwrays [ -i -u -f{a|f|d} | -d ] { view opts ..  | picture [zbuf] }

DESCRIPTION

Vwrays takes a picture or view specification and computes the ray origin and direction corresponding to
each pixel in the image. This information may then be passed to rtrace(1) to perform other calculations.
If a given pixel has no corresponding ray (because it is outside the legal view boundaries), then six
zero values are sent instead.

The -i option may be used to specify desired pixel positions on the standard input rather than generating
all the pixels for a given view. If the -u option is also given, output will be unbuffered.

The -f option may be used to set the record format to something other than the default ASCII. Using raw
float or double records for example can reduce the time requirements of transferring and interpreting
information in rtrace.

View options may be any combination of standard view parameters described in the rpict(1) manual page,
including input from a view file with the -vf option. Additionally, the target X and Y dimensions may be
specified with -x and -y options, and the pixel aspect ratio may be given with -pa. The default
dimensions are 512x512, with a pixel aspect ratio of 1.0. Just as in rpict, the X or the Y dimension
will be reduced if necessary to best match the specified pixel aspect ratio, unless this ratio is set to
zero. The -pj option may be used to jitter samples. The default value of 0 turns off ray jittering.

If the -d option is given, then vwrays just prints the computed image dimensions, which are based on the
view aspect and the pixel aspect ratio just described. The -ld switch will also be printed, with -ld+ if
the view file has an aft clipping plane, and -ld- otherwise. This is useful for passing options to the
rtrace command line. (See below.)

If the view contains an aft clipping plane (-va option), then the magnitudes of the ray directions will
equal the maximum distance for each pixel, which will be interpreted correctly by rtrace with the -ld+
option. Note that this option should not be given unless there is an aft clipping plane, since the ray
direction vectors will be normalized otherwise, which would produce a uniform clipping distance of 1.

If a picture is given on the command line rather than a set of view options, then the view and image
dimensions are taken from the picture file, and the reported ray origins and directions will match the
center of each pixel in the picture (plus optional jitter).

If a depth buffer file is given as well, then vwrays computes the intersection point of each pixel ray
(equal to the ray origin plus the depth times the ray direction), and reports this instead of the ray
origin. The reported ray direction will also be reversed. The interpretation of this data is an image
of origins and directions for light rays leaving the scene surfaces to strike each pixel.

EXAMPLES

       To  compute  the ray intersection points and returned directions corresponding to a picture and its depth
       buffer:

         vwrays scene_v2.hdr scene_v2.zbf > scene_v2.pts

       To determine what the dimensions of a given view would be:

         vwrays -d -vf myview.vf -x 2048 -y 2048

       To generate a RADIANCE picture using rtrace instead of rpict:

         vwrays -ff -vf view1.vf -x 1024 -y 1024 | rtrace  `vwrays  -d  -vf  view1.vf  -x  1024  -y  1024`  -ffc
         scene.oct > view1.hdr

AUTHOR

       Greg Ward Larson

ACKNOWLEDGMENT

       This work was supported by Silicon Graphics, Inc.

BUGS

       Although  vwrays  can  reproduce  any  pixel ordering (i.e., any image orientation) when given a rendered
       picture, it will only produce standard scanline-ordered rays when given a set of view parameters.