Wednesday, May 1, 2019


I’ve been to Paris once in my life, and that was 40 years ago. Notre Dame doesn’t have any special symbolic meaning to me, but it’s an interesting example of French Gothic and an opportunity for me to explore a different period of architectural history after so long on Project Soane. But of course “my spirit is moved.”  This is a breathtaking space, even in crudely modelled, virtual form.  So I guess she is my lady from one point of view, and yours from a slightly different point of view.  The more we engage with her, the more she becomes "our lady."  Maybe that's an argument for a collaborative modelling effort.

My second weekend on this adventure began with a rethink of the Gothic cross vault that I made at the end of the previous session. I had failed to figure out the formulas needed to make it fully parametric, and resorted to manual adjustments to get the same rise over two different spans (W & B). Coming back fresh, it turned out to be fairly trivial. First set the rise you want (H), then calculate the two radii using basic Pythagoras. (RW & RB)

The vault itself is just a rectangular extrusion cut by two voids. During the week I had come across the Leica site (laser scan data) which has been made public. You can access 360 panoramas from each of the scan locations. This made me realise that there were flat roofs over most of the aisles around the East end.  Photos of a very nice wooden model also helped me to understand this area.

I came to realise that the triforium Gallery turns the corner where it meets the crossing. This allows a connection to the spiral stairs that rise from the ends of the transepts. Some of the impressively detailed models you see on the Web have missed this subtlety.  There are some benefits to using a BIM authoring tool.  It forces you to think in holistic terms about a real building made from buildable elements.

I also realised that the flying buttresses around the East end have a different shape from those along the nave. The angle is somewhat steeper, for example.

I had been wondering why the bays next to the crossing had a different glazing pattern, with a round window sitting below a shorter version of the usual pointed one … like an exclamation mark ! Suddenly it came to me. This serves to disguise the extra width required to accommodate the spiral stairs. When you have a row of identical bays, but one is wider, your brain picks this up in a flash.  But if that bay is different in some more obvious way, the difference in width tends to be overlooked.

To help blend this new pattern into the overall composition it is continued around the corner along the transept elevations.

The sexapartite vaults of the nave were always going to be a challenge. After a couple of abortive attempts, I came up with a dual strategy. The main portion is a formed by two instances of a nested component (a solid cut by a void). The four smaller side branches are surfaces, made in the Conceptual Massing Environment (Point World) and exported to SAT format. This is inserted into the parent family and mirrored to create the 4 instances needed. The various ribs are created as sweeps, using “pick edge” mostly. 

I need to rebuild the surfaces for the side vaults really but they look OK from a distance so let’s crack on. I’m leaving the difficult geometry of the vaults that curve around the apse for another weekend also.

Checking against the internal elevations given by Bannister Fletcher, I made some adjustments in heights and levels of the families I placed last week. Took the opportunity to add a little extra detail also, including the vertical ribs running down from the vaults to the round columns at ground level. 


With the main vaults in place I was able to fire up Enscape3d, place a few people for scale and generate an impressive view of the soaring internal space.  It’s interesting to compare this atmospheric perspective with a Revit 3d view, using a section box and flipping the building on it’s back like a stranded turtle.  Still quite a few vault missing, but I find it very helpful to have these two representations of the same space, generated from a common model, and viewable together.

Time to add some tracery to the glazing then. I wanted to try making this parametric. This will come in handy if I decide to tackle a few more Gothic buildings. 

One approach to controlling this level of complexity is to have a series of parameters all related back to width and height by formulas. I often prefer to use a series of reference planes and equality constraints.

I set up two different tracery patterns like this. They will repay further refinement when I have time, but first I wanted to go for some more test renders using Enscape3d

The space looked too empty so I added some chairs and people, plus the floor tiling material. This resulted in the images at the beginning of this post, and the panorama at the link below.  By now, the West Front was looking underdeveloped in comparison to the rest of the model, so I invested a bit of time upgrading families: splayed reveals to the entrance doors, arched recesses embracing the pairs of windows on either side of the central rose.  All these are still simplified placeholders of course.  I always enjoy the challenge of finding the right balance across the whole model.

Seems like half the world wants to jump on this project in some way. Realistically speaking, my model is not going to be used for the remedial work. (not sure why the press likes to call it "reconstruction".  Our Lady is still largely intact, as far as I know.)   The rose windows are a good example.  The geometry is much more complex than I have shown at present, but it's a good step forward from an empty circle.  Possible the only thing I like about the LOD concept is the idea that models develop by a series of evolutionary steps, gradually adding complexity as our understanding grows.

It’s a learning exercise for me, and potentially for others who may wish to join in. In a sense, Notre Dame belongs to the whole world and for many of us, the best way to express our concern is by making something.

If there are schools of architecture or building that would like to use this as a learning opportunity I am happy to share my model or perhaps to set up some kind of collaboration. 
Anyway, I felt the need to add some very schematic urban context for the exterior shots, now that it's looking more like a real building.  Some people for scale again.

Maybe it’s a bit like world Cup fever, when kids all around get out into the streets and create their own “mini-tournaments.”  I was watching videos of George Lakoff while working this weekend: embodied cognition, thinking with our bodies.  Humans have amazing cognitive abilities, but it’s all built off the “learning by doing” machinery we inherit from distant ancestors.  Drawing and making are incredibly powerful ways of understanding the world.  

Turning to the apse (I’m not really turning.  That’s an example of a metaphor, based on embodied cognition.  We apply the experience of moving our bodies in the real world to the “journeys” we take in our mental worlds)  But “turning to the apse” I decided to try making curved and tapered vaults without resorting to Point World.  This took a fair amount of trial and error, using a swept blend that “shoots past” its target (more metaphors) and is cut back by a void. 

I may go back to the sexapartite vault and try this approach there.  Interesting comparison.

Time was running out.  Quickly back to the West End.  I forgot to tell you about the doors.  I made them as pairs, not sure why.  Above the central entrance there is an organ loft.  I’ve made this too deep at present, but my parametric family couldn’t handle the shallower depth for some reason.  Anyway it was good enough to justify another “screenshot to file” from Enscape.  I’ve added a bit of dapple and pencil shading using PIXLR, just to soften the image.  The placement of the people turned out quite well, I think, helping to emphasise the drama of the space.

I generated a panorama also, so take a look at that.  Probably one more weekend to bring everything up to a similar level of development.  Then we shall have to see.  Back to classicism?  Allow Notre Dame to dominate my life for the next 3 years?  Bit of both?  Make similar models of several other Gothic Cathedrals for a comparative study? 

Who knows?


  1. thank for the wonderful post , lots of information gained , visit us Revit Modeling in India

    CoBie adaptation in USA


I've been getting a lot of spam so had to tighten up comments permissions. Sorry for any inconvenience. I do like to hear from real people