Here's unsheared spineboy:
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Here's Spine's shear:
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Here's what normal shear/skew (described above) looks like:
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To better see what happens, here is Spine's shear at the top, then unsheared, then normal shear at the bottom.
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The red lines make it easy to see how normal shear doesn't affect the width of spineboy's head, while Spine's shear makes it less wide. The green line appears 3 times and all are the same length. This shows that Spine's shear keeps the head's dimensions.
You can get the normal shear by scaling on the axis being sheared. Conversely, had we gone with normal shear, a little scale would give you the same results.
We tried out different approaches to shear and the way we decided on in the end seemed to be the most useful. I'm open to reasons why it's a bad idea. It's not to late to change if we had to, but speak now! 🙂