For some reason I started watching YouTube videos of Notre Dame again. I came across one (in French) that deals with renovation activities from six or seven years ago. There is a great sequence that shows the casting of a set of new bells. It also deals with improvements to the organ, including the new console which Ryan did such a good job of modelling.

I started to notice fleeting glimpses of areas that have intrigued me, so I kept hitting the pause button and taking screen shots. There are steps where the aisles of the choir hit the curve of the apse. It’s very difficult to get a clear view, because the flying buttresses get in the way. I was aware of this step, but I hadn’t realized that it contained little rows of windows. Something similar happens along the nave, but at a higher level. That was a mystery at first until we realized that the clerestory windows had been enlarged at a later date. Maybe the step in level where the choir meets the apse tells a similar story.

The next one was really exciting to me. Some guys are threading a big flexible pipe out of one door and into another. This is at the NW corner of the transepts. I’ve been looking for a view of this area for a few weeks now, to confirm my idea that the door above the short flight of triangular steps leads to the bridge across the North transept, (below the rose window) by going outside and back in again.
1 = the door at the top of the steps.
2 = a small door I was unaware of that seems to lead into a square “chimney” which remains somewhat mysterious to me.
3 = the door leading to the bridge, and
4 = an arch that seems to be propping up that chimney. This is also completely new and unexpected to me, even though I’ve been working on this model for almost a year.

So there are some changes here that need to be made when time permits. The arch is fairly straightforward. (1) but the roof needs to be raised and converted into the “flat-stone-slab” type. I’m not quite sure how that works and what the knock-on effects are for the windows below and the vaults over the chapels, which relate to the windows on one side and to arches into the outer aisle on the other side. I had assumed that you would have to go down some steps to get to the roof surface and back up again to access the door to the bridge. An interesting puzzle to tackle there.

So what about the title? The literal meaning refers to the distortions in the floor plan. Could we actually reflect this in our Revit model? A bit of drafting to explore this. Looking at floor plans, sometimes they have been straightened up. Sometimes they seem to bent at the crossing, like a broken backbone. Lying in bed one night I got the idea of creating the choir as a separate link and rotating the whole link by a degree or two. But it doesn’t work. The distortions are more complex than that.

I drafted out a skewed grid that seems to work quite well. But decided against trying to implement it. It’s still a simplification of reality, so we might as well use a simplification that makes modelling a lot easier (an orthogonal grid)

Another thing I’ve been doing while lying in bed is to practice inventing ornament (leaves and scrolls) by drawing on my phone. I was inspired by some YouTube videos that I watched, but rather than copy something, I just adopted the general idea and improvised.

Back to vaults. The sexapartite (sexa/hexa whatever) vaults that I made long back are a bit of a mess. I have a much better cross vault family based on spherical geometry, so I can use this for the man span. Then I can construct the two side arches, plus the big arch across the middle. Took a while to figure out the geometry and convert it into formulas, but I got there

That’s as far as I could get with the traditional family editor. The side vaults are kind of like the zigzag vaults around the apse. So I decided to use the 9 point adaptives that I had used there.

That worked fairly well, but I had to repeat the same sequence 8 times, and they tend to click onto the wrong edge … because the ribs have lots of parallel edges. But at least you end up with a family that adapts to different widths and depths

That as long as it remains regular. Ie the two side arches have to be the same size and everything must be orthogonal. That won’t work for the transepts because the aisles to the west are different widths compared to the ones on the east side. Basically, we need to “fake” the skewed grid in some way. My solution (for now) is to rotate the centre rib slightly. So I have a second version of the family that handles the transition across the transepts caused be the different aisle widths. It’s a cheat of course, but it works quite well.

While I was working on this, Nader popped up on Slack talking about a book by Andrew Tallon that he had acquired. He’s the guy who scanned the cathedral about 12 years ago. He was a Belgian/ American academic who died somewhat tragically in 2018 and scanned many gothic cathedrals.

In this book there is a colour coded diagram that indicates when different parts of Notre Dame was built. I think this must have been created by a graphic artist because, although it picks up the skewed grid quite well, other aspects of the drawing are quite inaccurate. It’s fine for the purpose intended though. It’s quite interesting to compare it to a much older drawing that I found on the internet when I first started working on Notre Dame.

More interesting are some images taken from the point cloud. At the moment I only have some slightly distorted images taken with a smart phone, but they still provide useful insights.

It’s quite interesting to reflect on the various activities that combine to form the experience of Project Notre Dame. There are days of intense modeling activity. Periods of sifting through source material and comparing it to the model. Times when the information coming in seems to undermine all the progress to date. Weekends when I can’t resist going off at a tangent.

The cumulative effect is a very rich tapestry of background familiarity. Looking at new photos I quickly realise just where I am in the building and what I expect to see. New insights pop out from the background and tap me on the shoulder ... "hey look, you didn't notice me before!"

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