Designing the optimum and minimal shape and size of a sun shade?


Can Sketchup track a ray from the sun to a person in a model through a window so as to mark that spot on the window, throughout the day and year, thus marking out on the window the places needed to block the sun for that one position in the room.

I’d like to find the minimum size and shape of an opaque shade that when applied to a couple of high windows would perfectly block my view of the sun during an hour or two in the summer. The windows shape makes traditional blinds difficult and I do not want a treatment that is dark all the time, let alone opaque. So I am considering using PLC (polymer liquid crystals, a plastic sheet that is (very nearly) transparent when powered up, but opaque (translucent) when powered off) but its hideously expensive (like $70/sqft). Thus the motivation for just the right shape and coverage. (i’ve of course done the low tech, paper taped to the window, prototype but that’s so low tech…).


It seems to me that long ago someone wrote a plugin that will draw a line from a point in the model to the sun. This would probably do the trick. I’ll search for it and see what I can find. Or maybe one of the other old timers will remember.


Camera face sun. If I remember correctly.


Here are a couple of options.

Jim’s Map Sun and his Attach Camera To Sun could be used with a plugin to draw a line between the camera and a point in the model which of course I can’t find now.

Edit: I think Camera Lines by Rick W might do the trick.


Thanks for the suggestions!


I have concern the approach you are on will not give the results you want. Typically when one looks at the azimuth and elevation of the sun the sun rises over a relative small azimuth angle. During the couse of a summer day which may extend form early in morning to late in the after noon the azimuth changes but elevation stays relative constant. In addition the suns ray trace is just the direction of the electromagnetic wave and so one gets solar heating many hours of the day and not a few as implied in your post.
So my question: Are you worried only about the point you mentioned or is heating a concern.?
BTW I used one of the programs NREL has to plot the sun for Boulder Colorado so you can see the artifact I noted. Boulder sun pos.txt (3.2 KB)


Solar heating is not a concern. Its that I am looking into the sun for just a couple of hours in the summer from where I sit at my desk. There are screens on these windows that were intended to block some sun and I do plan on removing them so heating might become an issue, but I don’t think so. There is major tree coverage, but enough gaps that you still don’t want to be looking at the sun. The ray trace (as the sun moves daily and seasonally) from my eye though the window to the sun, outlines the area I have to shade to not be squinting. I can approximate it (and have done so just with paper to get temp relief) but thought it would be cool to have it exactly plotted.


I think you should explore this idea of tracing rays from the sun but then you should compare what you get to real world results.

And one question comes to mind. Wouldn’t it be easier to wear a visor like accountants and copy editors used to wear? :smiley:


Following on from Dave, make dots every hour on the window for the centre of the sun until lunchtime, then use your model to predict the afternoon dots. If you get it right you can plot the whole year.


You not thought of moving your desk?


Plotting it on the window is not that easy as of course it depends on where you are sitting, so it takes two people (no more to the left, and up a little, too far …). No I can not move my desk (nor want to, I have a fantastic view, most of the time). Yes I was wearing a baseball cap for a while, but it doesn’t really work that well for this case :-).


The file I attached was for every 10 minutes and based on Boulder geo-location and for Dec 17 2015. You can input other time periods of course. You use that data to plot in SU or Open office/ EXCEL spread sheets… There are several programs to obtain the info you want, are probably much better vetted than some of the plugins. NREL even includes in their extensive program ( Energy Plus) a fenestration electrochromic analysis capability but , IMHO it is much too complex for what you need. The department of energy issued a white paper which was not very supportive of that technology from a cost benefit analysis stand point.
Have you considered using SU to just do a shadow plot?You should be able to geo locate you site, a simple wall model with partial opacity of widow with desk location and may be home in on what you want quickly. If you rely on vegetation that maybe questionable since it grows very year.
Can you post the geo location of your site and a simple model of wall, desk location, picture of window(s). If your site is far from a NGS marker there are SU plugins that covert the xy SU reports to geo info so you can locate the house very accurately. Some analysis I have done using what SU reports for Boulder shows it is off 45 meters in long which would not be good enough for your use, (Lat is close enough). The USGS data sheet info has more precision that what SU loads but, you can input to SU manually with required precision and it is the dead on then. The program I used above would not allow me to input to accuracy I wanted so would not recommend using that for any thing final.


Thanks, I don’t have the model yet, I wanted to check out if the end result was going to work before I got into how to use SU to do so! i.e. it will take me a bit, but maybe I can get to this next week.


Suggest you should focus on getting info for good geo-location, desk size and location in room and window info, house location and orientation and location of widows in house. If you do not have widow opening & basic dimension ( Not straight on=> take a picture) but from some what a iso view showing the edges etc so it can be photo matched. The actual model will take a few minutes. Attached is really crude … model I made while posting, its located at Boulder Colorado. Accurate geo loc is important ! shadow study.skp (211.1 KB).
Note I blocked one of the widows to prevent sun shine