diff -r c1cf31b48c1b -r 7e6b4b31a0b7 man/man1/rlux.1
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+++ b/man/man1/rlux.1	Sun Apr 10 14:33:37 2011 +0100
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+.\" RCSid goes here.
+.TH "RLUX" "1" "16/01/2011" "RADIANCE" ""
+.SH "NAME"
+rlux \- compute illuminance from ray origin and direction
+.SH "SYNOPSIS"
+.B rlux
+[
+.B rtrace args
+]
+.B octree
+.SH "DESCRIPTION"
+The
+.I ximage
+command can output certain information about the pixel under the cursor.
+This is configurable with the 
+.I \-o
+command line option. The default setting is \-ood, which outputs
+the ray origin and ray direction. This output can be directly passed to
+.I rtrace
+which, in combination, with the original octree that the image was rendered
+from, can compute the irradiance at this pixel for the red, green and blue channels.
+
+This is essentially what
+.I rlux
+does, but it additionally converts the RGB irradiance output from
+.I rtrace,
+which is in W/m2/sr, into the corresponding illuminance, given in lux.
+.SH "EXAMPLES"
+To calculate the RGB irradiance for a certain pixel in an HDR picture
+.IP "" .2i
+ximage nice.hdr | rtrace \-i+ \-dv \-h\- \-ab 3 scene.oct
+.PP 
+Now left\-click on a pixel and press the 't' key in ximage, or middle\-click.
+
+To do the same, but output the illuminance
+.IP "" .2i
+ximage nice.hdr | rtrace \-i+ \-dv \-h\- \-ab 3 scene.oct | rcalc \-e '$1=47.4*$1+120*$2+11.6*$3' \-u
+.PP 
+To let rlux do all the work. This is equivalent to the previous example.
+.IP "" .2i
+ximage nice.hdr | rlux \-ab 3 scene.oct
+.SH "SEE ALSO"
+ximage(1), rtrace(1), rcalc(1)