1 .\" RCSid goes here.

     2 .TH "RLUX" "1" "16/01/2011" "RADIANCE" ""

     3 .SH "NAME"

     4 rlux \- compute illuminance from ray origin and direction

     5 .SH "SYNOPSIS"

     6 .B rlux

     7 [

     8 .B rtrace args

     9 ]

    10 .B octree

    11 .SH "DESCRIPTION"

    12 The

    13 .I ximage

    14 command can output certain information about the pixel under the cursor.

    15 This is configurable with the 

    16 .I \-o

    17 command line option. The default setting is \-ood, which outputs

    18 the ray origin and ray direction. This output can be directly passed to

    19 .I rtrace

    20 which, in combination, with the original octree that the image was rendered

    21 from, can compute the irradiance at this pixel for the red, green and blue channels.

    22 

    23 This is essentially what

    24 .I rlux

    25 does, but it additionally converts the RGB irradiance output from

    26 .I rtrace,

    27 which is in W/m2/sr, into the corresponding illuminance, given in lux.

    28 .SH "EXAMPLES"

    29 To calculate the RGB irradiance for a certain pixel in an HDR picture

    30 .IP "" .2i

    31 ximage nice.hdr | rtrace \-i+ \-dv \-h\- \-ab 3 scene.oct

    32 .PP 

    33 Now left\-click on a pixel and press the 't' key in ximage, or middle\-click.

    34 

    35 To do the same, but output the illuminance

    36 .IP "" .2i

    37 ximage nice.hdr | rtrace \-i+ \-dv \-h\- \-ab 3 scene.oct | rcalc \-e '$1=47.4*$1+120*$2+11.6*$3' \-u

    38 .PP 

    39 To let rlux do all the work. This is equivalent to the previous example.

    40 .IP "" .2i

    41 ximage nice.hdr | rlux \-ab 3 scene.oct

    42 .SH "SEE ALSO"

    43 ximage(1), rtrace(1), rcalc(1)