[Radiance-general] Solar penetration

[Bruce Sounes]

When I did 'Building Science' many years ago, we used "solar protractors" to
read off the suns altitude and azimuth at different times of the year. The
solar protractor was a plot of the suns path across a hemisphere for
different times of the day for a given latitude, generally printed on a A4
bit of clear plastic. This was used in assessing orientation of designs in
plan and overhangs/shading in section. Alternatively we could use it to
assess solar penetration from a point inside the building by marking out on
the protractor the area of sky visible through openings.

What I would like to do is step back a bit to the solar protractor idea. I
want to plot the sun's path across the sky from a specified view - say for
the solstices and equinox - annotate the time of day, and overlay on a
previously rendered view. I think this could be a more graphic illustration
of when and for how long the sun will penetrate into a space. It should be
quicker than several animations.

I think this could be quite easily done by rendering sequences of empty
scenes from the required viewpoint and combining them and the fully rendered
scene using pcomb. The sun positions could appear as dots. (Would the 0.5
degree angle subtended by sun be too small?). Can anyone help me with
functions I would need to feed pcomb - to convert "suns" to dots and the
skys to white graphic infomation and how do I automate the annotating? The
final compositing could be done with Photoshop. I have tried the long way
round - plotting the sun paths on cad - but this seemed unneccessarily
fiddly and potentially inaccurate.

Many thanks

Bruce Sounes