# How to 3D-Model the Ambulatory (Back Part) of a Byzantine Church

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## What is an Ambulatory?

The Ambulatory is the back part of a medieval church. They usually had a very distinct form, and consisted mostly of octagonal walls, covered with domes. In Gothic cathedrals the octagonal shape would be often surrounded by buttresses, while in Byzantine architecture it featured imposing, large windows, with columns made of marble.

## First Step in Modeling an Ambulatory

In a previous tutorial we had looked at how to create an octagonal dome. The same form will be used for the main shape of the Ambulatory. To be brief, you can create a cylinder as a primitive, set it (for example in Blender) to have eight sides, and then create a roof on its top, by extruding the point in the center of the octagon and then linking it to all vertices in the top surface of the octagon. The shape you should end up with is similar to the one shown in Figure A.

You then move to position your shape as depicted in Figure B (provided you have created the Byzantine Chapel shown in previous parts of the tutorials; don’t worry if you have not, you can just use this as a guide to position the Ambulatory in your own models).

## Second Step in Modeling an Ambulatory

This is the most elaborate of the steps; you first position a window-shaped closed volume, which you will subtract from the walls of your church model. You then create (using that window-shaped volume) three more objects, which are miniature versions of the same shape. The central one has to reach a little higher than the two peripheral ones. These three will be subtracted from the result of the subtraction of the main window-shaped volume from the church’s walls. A final, fourth form, to be subtracted along with the three smaller window-like shapes from that same result, is a cube, positioned below them.

The specific locations of all those forms are shown in Figure C; remember that you must first subtract the large window shape in the back, from the walls of the church, and then subtract the group of the other four forms from your result!

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What you will be left with is presented in Figure D.

In Figure E the only thing added was two white columns.

## Third Step in Modeling an Ambulatory

You can create a dome, to make the top of your ambulatory more interesting. The dome will typically have the diameter of the corresponding circle inscribed to the octagon of your ambulatory walls. Remember to erase some of the surfaces of your sphere (used to make the dome) so that they won’t show beneath! Figure F presents the placement and final form of the sphere, once you have edited out the areas which aren’t needed.

Lastly, you copy the ambulatory form you created, and place it – scaling it down – on either side of the main Ambulatory. Figure G shows the final result...

## Possible other steps

You can experiment by using different set-ups for the Ambulatory. Some cathedrals have Ambulatories that feature a number of smaller parts, surrounding a large, central form, while others use either a single formation, or a triad of formations, of which the central formation is either larger or they all retain the same size.