More details on alignment of various elements in the classic #IonicCapital in https://pixelfed.social/p/Splines/800161382832200305

Here, we zoom in on the two #braids assemblies — the straight vertical one on the side of the #capital and the curved one around the neck of the #scroll.

In this diagram, the magenta curve for the curved braids is extended on both sides to show the full original #modulatingSpiral for the rear end of the scroll.

The diagram also shows the lines tangential to the full modulating spiral. As previously mentioned, the top tangent is coincident with the magenta line for the top of the #ovolo. Additionally, the bottom tangent is tangential to the bottom of the #eye of the #volute.

The right tangent of the modulating spiral bisects the curved braid assembly with 4 units on either side of the tangent, and the magenta #tectonic surface further bisects the gap between that tangent and the "underside" of the braids assembly on the right.

The top gap between magenta and blue arcs is split into 6 units and 2 units — same as the proportion of the braids channel above and below the tectonic surface.

Moving on to the bottom of the vertical braids assembly, follow the lines that divide the depth of the assembly (8 units) into 4 portions. The leftmost 2 units are, of course, sub-surface, buried inside the vertical wall of the capital.

The middle line is tangential to the left side of the eye of the volute. The next line, moving right, is tangential to the left side of the modulating spiral. The rightmost line is tangential to the outer surfaces of both braids assemblies, as already mentioned in the previous post.

Note the symmetry of 2 units and 4 units near the left side of the eye.

These meticulous details are what I call pure #poetryInGeometry.

In https://pixelfed.social/p/Splines/792499765146596723, I wrote that Dürer's approximation of #logarithmicSpirals comes close, but still doesn't fit the measurements of the #IonicCapital. This is why.

#3StrandBraids

#Braids are the last of the #decorative elements on the #IonicScroll, but like #EggsAndDarts, they are not specific to the #IonicOrder.

Braids are a popular design motif that find wide currency in modern #hairstyle, #fashion, and fashion accessories like #belts and #bracelets.

Braids come in infinite varieties with varying number of strands, thickness of strands, roundness or flatness of strands, and how tightly or loosely they are wound together. Here, I focus on the 3-strand variant mentioned in #Vignola's book and previewed in https://pixelfed.social/p/Splines/792015485979791089. The image here is brightly colored to draw attention to the 3 strands.

The geometry of braid strands is not at all obvious despite how familiar they look. Also, a braid strand is the only feature in the entire iconic order whose geometry cannot be captured with straight lines and circular arcs. Instead, a strand geometry must be defined in a series of steps starting with a basic #sinusoidal curve.

A sinusoidal curve or #sinusoid is a wave form whose function belongs to a family of functions known as #transcendentalFunctions that also include #logarithmic and #exponential functions. I mentioned #logarithmicSpirals in https://pixelfed.social/p/Splines/792499765146596723, and in a future post I will show how to construct one and compare it with the #spiral used in our implementation of #IonicVolute.

They are called transcendental functions because they transcend the math of finite algebraic polynomials and go beyond geometry into trigonometry. Fortunately, we don't have to go there.

Few #CAD tools have a direct primitive for a sinusoid, but almost all have a primitive for a 3-dimensional round coil shape called a #helix which we can use to create the sinusoids we need for a braid strand. To create a sinusoid, all we need to do is #project a helix on a flat surface to convert it into a 2D waveform.

The #volute is the most striking element of the #IonicOrder, even more than the #scrolls, for there would be no scrolls without volutes.

The #IonicVolute is constructed as a spiral, of which there's a bewildering array of types that have fascinated artists, philosophers, and mathematicians alike for millennia. Most #CAD tools have a built-in primitive for spirals, but you will only waste your time with them because they strive for #continuous curvature changes, when only a #discrete spiral made from circular arcs will work in this design. I spent years trying different kinds and learned a lot in the process.

Even within the family of discrete spirals, there's only one that fits. Dürer's approximation of #logarithmicSpirals with 90° arcs comes close, but still doesn't fit. The only one that works is contrived to fit the measurements of the #IonicCapital, and it's not a general spiral. It's specifically designed for 3 turns, and you can only proceed in one direction — toward the eye. You cannot start at the eye and diverge outward.

The process is not complicated. I purposely left out the measurements in the sketch because they cluttered the area near the eye, but I describe them here.

When µ = 144, you will need to start with a square that is exactly 1 part (8 units) wide and divide it into smaller portions — initially 6, but eventually 24. This is the first time you might regret choosing µ = 144. If you had chosen a value 3x larger, then one part would be 24 units instead of 8. That would certainly have made understanding the volute a little easier but the other measurements would also be 3x and too unwieldy to work with.

There is a happy compromise: Temporarily scale everything up by 3x just for the volute, and once it has been constructed, scale it down to 1/3 to fit with the rest of the design.

So, the first step is to divide the square into a 24x24 grid. Then make 3 concentric squares 4 units apart and mark their ends with points 1 through 12 as shown here.