ADJUSTING TO REALITY

We still have no access to point cloud data for the cathedral.  Fortunately we have the TruView site that was placed into the public domain by Leica shortly after the fire.  Gradually we have figured out how to adjust the “Z” coordinates of picked points to align with our Revit model.  


It’s a little bit tedious, but we can record these values on screenshots and on section/elevation views.  It seemed prudent to create a lightweight file with a copy of the grid and place scaled jpegs in section views,  fade the image with a semi-transparent masking region, and draft over a revised setting out for the major elements.  Within this study file, we have set the shared coordinate system to read out the TruView Z coordinates.  The TruView zero is basically a tripod height above the triforium gallery floor.

Two types of spot elevation can be used to report both the TruView & model coordinates for any given point.

Based on this analysis we have been able to adjust various elements, dropping the sill heights of the clerestory windows running around the chancel at high level. (it seems that they are systematically lower than those of the Nave, by about 750mm)  The adjacent “flat” roof and parapet railing were also dropped, while the sloping roof over the outer aisles has been given a steeper pitch and raised a little.

At the internal corner where the chancel meets the transept there is a round column. This has been represented by a placeholder family, to be elaborated by whoever claims the task.

My role in the team has been to push ahead with this kind of  “roughing out”.  As my original placeholder families are replaced by others, the “technical views “ that Revit updates constantly for us begin to come to life, stimulating our imagination and asking penetrating questions.

Gradually the cathedral becomes more and more familiar to us, like an old friend

For example, the triforium roof alongside the nave was very puzzling some months ago but is now a suitable subject for explanatory diagrams as we start to tell our stories more clearly.

By taking measurements in TruView across groups of buttresses it has been possible to confirm an exercise I carried out some months ago based on a jpeg plan from the point cloud. This implies a number of adjustments to the grid.

Personally I think we should continue our strategy of straightening up the building and keeping all the elements aligned to a regular, orthogonal grid.

Ultimately this is a judgment call based on our mission to create a study model for didactic purposes and to place the results of our explorations in the public domain. Ours is a parallel effort to the model being built by the construction team which necessarily must model each element individually and reflect the minor deviations that occur on site for a variety of reasons.  By contrast, we are creating a somewhat idealised and simplified model of Notre Dame; trying to uncover the underlying rationale.

I think the two efforts are complementary in the struggle to understand what this ancient monument means to France, to students of architecture, to BIM addicts and heritage workers of various kinds, to devout Catholics and to the general public all around the world many of whom have vivid memories of tourist visits to Paris in the years before the fire.

A mobile friendly model would be great. In that vein I tried the Enscape3d Web standalone on my android phone. It may be me but I couldn’t figure out how to walk around.


A quick upgrade next, to arches at the base of the Bell Towers where it connects to the nave and aisles. Adjusting widths and editing the profile to replace the sharp edges with reeding.

The transept ends need a lot of work not least to define the voids inside the thickness of the wall that connect the spiral stairs to various visible doorways. Not surprisingly, the wall joins get in a bit of a tangle when trying to model something of this complexity.   We really need someone to take ownership of this area and build it more systematically.  

But before attempting this, perhaps we need to adapt to the revised grid so that we don’t end up doing everything twice.

Just to complicate things the rose windows needed to be lifted by about a metre, which makes the relationship to the vaults behind much more sensible, but requires multiple adjustments to adjacent elements.

And finally, the gables above. Waiting for Marc to finish the North Rose, so using the South version as a temporary placeholder.  Below that small rose a length of railing above an in-place sweep, and atop it all, a simple coping to “finish” the steep slopes that define the top of the gable.  More to do to elaborate this, but at least it’s starting to catch up with the rest of the model.