Making the Pantheon in Grasshopper

Hey there,

This is a model of the Pantheon. I followed this youtube tutorial from TU Darmstadt: “Model the Pantheon in Grasshopper - YouTube”. Then I added an extra step to the coffers.

I want to make the coffer at the top of this arc shorter than the coffers towards the base.

That is, taller coffers at the base and shorter ones on top.

But this curve is being divided into equal lengths. If i could edit the “parimeters as a list” visible in the Panel in my screenshot I could control the height of each coffer.

That’s my goal but I’m not sure how to achieve it. If anyone could show me how to manually edit those parameters that would be great! also, any other advice to achieve the aim is appreciated.


Pantheon (18.3 KB)

I found this paper where they discuss the geometry of the coffers:
I think that you need to decide first of all what is the geometric relation between the coffers, depending on this there are quite a few ways to approach this.

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The geometry of the Pantheon is a little more complex than it first appears to be. While I don’t want to get into a discussion about that in particular as we’d be here all day, I have had a got at creating squarer coffers:

There are three ways of dividing the arc in the attached file. The first is your original method which splits the arc into evenly sized segments. The second, I’ve simply scaled the lower coffers up and higher coffers down. The third works out exactly how long the vertical division should be based on how long the bottom edge of the coffer is. This creates a coffer where the two sides and bottom edge are equal, and only the top edge is shorter, which gives is a very square appearance. If you wanted it even squarer, you could simply find the average of the top and bottom edge of each coffer and set the side length to that.

The maths for this coffer height is a little complex. I was hoping to not use a loop, but the maths gets unwieldy after a few iterations, so I went for the simper approach of just looping it!

As I said, there are loads of little details about the pantheon geometry. For one, the coffers themselves don’t point to the centre of the dome, but to a position directly beneath the centre of the dome where the viewer would be stood. In that regard, the coffers aren’t symmetric about their horizontal plane, but are skewed so that their bottom side is much steeper than the top side:

Anyways, hope this helps!

Pantheon (35.5 KB)


Wow! Great, thanks for that Matt. You’ve fixed the coffers and made them more accurate. It looks much closer to the original building. Any chance you could bake the grasshopper into a polysurface and upload the .3dm file?

My grasshopper wouldn’t open the file because of a problem with the anemone plug in

This is the current document:

I’ve internalised the anemone section so should work for you without. It would be worth installing anemone either way though, very useful for stuff like this!

Pantheon (33.0 KB)

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Looks great, thanks!

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Nice render! Can you send me the 3dm file you made of this? My rendering skills are pretty low so would be keen to see how you did this.

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I used v-ray in rhino 6 with concrete material from under “Free Concrete Vray Materials”. The “sun” command in rhino opens a menu to control where the sun is. Then I made the sun color a bit yellow in the v ray settings.

I dont have the file open right now. You can edit this yourself in the GH definition pretty easily.