What is the intended usage case for Shear?

amcleod

So, maybe this is a silly question, but... how do people usually use the Shear tool? I've been having a bit of trouble understanding its intended use.

Originally I was thinking it was to make the rotation of a bone to appear to rotate in perspective, but that can't be right, because Shear adjusts the rotation equally on both "sides" of the x-axis. Rotation in perspective requires something a bit different.

So, how do people usually use this tool?

amcleod

Xelnath

I think it was initially a poor-man's FFD.

Erika

Hwadock used shear to do this, which wasn't possible as easily before thanks to shear.
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Pharan

@Erikari That's not really "shear". At least, shear wasn't necessary to achieve that.
It's just nonuniform/matrix scale (which does involve a bit of shearing in the math sense).
So... you wouldn't be totally wrong. :p

@amcleod. Shearing was added because it was easy to achieve given the new transform-inheritance-via-matrix introduced in 3.0.
Xelnath is correct. It adds a bit of deformation so things don't look too stiff, without the need for deform keys or weights. And you don't need Spine Pro for it. It also means that type of deformation can be done to a whole hierarchy of bones/parts, instead of just one image (for deform keys)

So no, it's not for achieving perspective. It's more useful for accentuating motion and making organic things look and move in a more squishy manner. I think it's best when used in the context of motion and in small enough amounts that it doesn't LOOK like shear is happening but you FEEL the wavy/squishy/jiggly movement.

amcleod

Pharan, thanks for the explanation; that's quite helpful. Would you happen to have/know of an example animation that uses Shear in motion in the way that you're describing? Just so I can see it in context? It's always easier to understand art stuff with visuals.

Mario

The Spineboy example has shear on a couple of animations. See the dopesheet for which bones have shearing applied to them.

Pharan

What? Spineboy doesn't have shear keys. He was animated before 3.2.

Mario

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See shear on head. Welp, looks like that animation actually didn't make it into the Spineboy sample that comes with Spine. Oh no, we both suck again!

Søren

Shear is especially useful on very cartoony characters. For example on a jump that is moving forward you can use it to squash (along with scale in some cases) when the character lands and stretch when he jumps. Using shear gives a slightly better result than just using scale.

amcleod

Thanks guys, this all helps. In the Spineboy example badlogic posted, shear is used to create that smearing look when he's spinning around, right?

Mario

Exactly.