Splines<a href="https://pixelfed.social/discover/tags/IonicVolutes?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#IonicVolutes</a> are the sinews of <a href="https://pixelfed.social/discover/tags/IonicScrolls?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#IonicScrolls</a>. Without <a href="https://pixelfed.social/discover/tags/volutes?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#volutes</a>, there would be scrolls, but not <a href="https://pixelfed.social/discover/tags/Ionic?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#Ionic</a> Scrolls. Each scroll starts with a volute in front, modulates through as many as six volutes of different shapes and sizes as it reached the back, with the scroll surface closely hugging the volutes at each contact point in ALL 3 dimensions. This is a key point to remember before we start <a href="https://pixelfed.social/discover/tags/reverseEngineering?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#reverseEngineering</a> the first <a href="https://pixelfed.social/discover/tags/primaryProfileCurves?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#primaryProfileCurves</a> from old image scans.<br>
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This diagram shows the <a href="https://pixelfed.social/discover/tags/scaffolding?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#scaffolding</a> we will construct using straight lines and rectangles, first in 2 dimensions, then place them front-to-back in 3 dimensions using precise markers, and finally scale and superimpose the volutes on this scaffolding.<br>
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All of this will be done before we derive the primary profile curves from the image scans.<br>
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How did I know about this scaffolding? I didn't. It is not documented anywhere that I'm aware of. I developed this after years of striving to derive the correct shape, and I hope that there are people who can still "see" things I might have missed and help improve the design.<br>
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So, the actual process went like this: I drew outlines from 2D image scans in the top view, getting close to <a href="https://pixelfed.social/discover/tags/Vignola?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#Vignola</a>'s detailed sketches. Then, I did the same thing with image scans in the side view, and I found that the designs didn't line up.<br>
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After several iterations, I got the designs to line up in both views, and it was obvious that the bell shape of the scroll would follow the large volute in the front.<br>
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So, I used the large volute as a "rail" and tried to sweep the primary profile curves on one rail. Big mistake! The undulating shapes of the primary profile curves wobbled wildly on the single rail and the middle, 3/4, and back of the scroll were twisted out of shape!<br>
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Instead of trying to <a href="https://pixelfed.social/discover/tags/sweepOneRail?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#sweepOneRail</a>, I decided to clamp down wobbling with another operation called <a href="https://pixelfed.social/discover/tags/sweepTwoRails?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#sweepTwoRails</a>, using volutes at both front and back ends as rails with less wobbling.<br>
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You will need a <a href="https://pixelfed.social/discover/tags/CAD?src=hash" class="u-url hashtag" rel="nofollow noopener" target="_blank">#CAD</a> tool to practice.