this is a tool I have developed for making sundials and I thought it would be nice to share it in case somebody wants to make a sundial of his/her own.
It is basically a dynamic component with what I call ‘shadow planes’: the planes that are defined for any given fraction of time by the mean sun (point) and the style (straight line) which you can intersect with a surface and create the hourlines for your sundial.
The component is called ‘sunplanes’ and you can download it here:
sunplanes.skp (2.4 MB)
the only thing you have to do, is place the component on the surface of your sundial, and input the following:
a quick explanation:
- GnomonWidth: the thickness that your gnomon is going to have. If it is going to be very thin, or if you chose not to take it into account, you just put zero
- Hours evening: how many hours you want to display for the evening (due to the longitude correction, the sundial might be very asymmetric, so you might want to add an hourline even if it is after sunset just for aesthetic reasons.)
- Hours morning: same as above but for morning.
- Latitude: By far, the most important input. this is the latitude for which your sundial is intended.
- Longitude correction: this is the distance (in degrees) between your sundial and the central meridian of your time zone. Positive values if you’re west of the meridian and negative if you’re east of the meridian.
- Sunplanes Depth and Length: these are just the dimensions of the planes, You should make them big enough to fully cover your sundial’s face so as to produce the sections.
ATTENTION: SKETCHUP ACCEPTS ONLY DECIMAL DEGREES, SO YOU MUST ENTER YOUR ANGLES IN DECIMAL FORM (YOU CAN EASILY FIND ONLINE PAGES TO CONVERT THEM)
Once you have placed the ‘sunplanes’ correctly and set all the adjustments, you should see a few layers appearing in the layer tab:
From A to F you have the subdivisions of time (Hours/HalfHours/QuarterHours/TenMinutes/FiveMinutes/Minutes)
The way you do it from now on is very simple:
- you select the sundial’s face (or part of the face),
- you leave visible only the the layer of the time division you want to imprint (e.g. “A— Hours”),
- select “intersect faces with: model”
Finally, you can create your Gnomon by copying the ‘style’ face and creating a solid that sits on your sundial’s face.
this is a tool that I’ve used to make a few sundials so far and compared to professional programs it has given me accurate results. I cannot guarantee however that there is no miscalculation whatsoever (although I doubt it).I am not responsible if you pay a few handred euros/dollars to make a marble sundial and realize something is off
also, once you’ve made it, it will not display the same time as your cellphone -no sundial does- because of the difference between the mean and actual sun. this is given by the ‘equation of time’ and you can also find it online.Usually it’s a difference of up to +/- 15 mins and you can display it as a graph on your sundial’s face)
Good luck and post photos if you actually make one!