What does this value do in 'Squash and Stretch'?

[mmmaarten]

When looking in Bone constraints of the lower leg bone at Squash and Stretch (when using a target bone on a leg) there are two textboxes; one after the checkbox to turn squash & stretch on, and the max IK stretching.
The latter is quite clear. But what does the first textbox value do?


Looking in the manual (p147) doesn't help much, as it only says; leave it at 1. It doesn't say anything about why and what this value stands for (at least not that I could find in the manual). When I change its value to 0.5 or 2 (so less or more than 1) it disables the squashing and stretching it seems like. But I completely miss the why and for turning on/off there's already a checkbox, so to me this doesn't make sense so far. There must be a reason this textbox is there other than 'leave it at 1', right?



Another thing that I find weird is that when unchecking the Squash & Strech checkbox, but leaving the maximum stretch at 1.5, it still does squashing & stretching, eventhough it is turned off with the checkbox. This feels like the checkbox is obsolete and it doesn't really matter if it's turned on or not, because it only looks at the maximum ik stretch value?

So I wonder;
- what does the first value stand for?
- why is squashing and streching still working when turning it off? (what's the use of that checkbox? or what am I missing here?)

[Greenlaw]

The easiest way to see the effect of the Squash and Stretch constraint is to add a single bone and bind a rectangle to the bone.

Now move to an animation frame and play with the length of the bone. (Note: You have to be on a non-zero frame to see deformations accurately. Some features will sort of work on the setup frame 0, but many will not. As a general rule, you should always test your rig on a non-zero frame.)

With the Squash and Stretch constraint disabled, as you stretch or shorten the bone length, the box will scale taller or shorter with the bone as expected.

Now enable the Squash and Stretch constraint for the bone and try it again. As the bone 'stretches', the box will get skinnier, and as the bone 'squashes', the box will get fatter. The visual result is that the box tries to maintain its volume as it squashes and stretches.

The number value next to the Squash and Stretch option is a multiplier. For example, if you increase this number to 2, the bone will now squash or stretch the box double the amount.

That's pretty much it.

The next property, Maximium IK Stretching, is fun to use in a character's legs if you have target bones. When this is enabled for legs, the value (also a multiplier) determines how far the bones will stretch before the legs lift off the ground. So if you set this value to 2 and lift the character into the air, the legs will stretch double their length before the legs lift off the ground.

Bonus trick: If you combine Squash and Stretch with Maximum IK Stretching, the leg artwork will get skinnier before the legs lift off. This combination is a lot of fun for very cartoony characters.

Note that you can't really see the squash effect in this particular leg setup because the character's knees will bend with IK, and the leg bones never actually 'squash'. However, you can still keyframe the 'squash' effect into the legs where you want the compression to occur. (I guess if you want, you can get this to work using a Smart Bone Action, but unless you really need to do that all the time, it's probably not a practical use of Smart Bones in a general purpose rig.)

Tip: I would study some of the content that comes with Moho, like the Bunny and Robot. From what I recall, these rigs use these features and I found it very educational to break them apart.

Hope this helps.

[mmmaarten]

{ fine explanation by Greenlaw here }

Ah, okay. Cool! Now I start to get it! And now I see it working!

I knew squash and strech on a simple cube in Moho (to preserve volume like Disney's law), but I was confused because the stretching on the IK (because of the target bone) WAS working on frame zero, but the 'normal' squashing'n'streching wasn't. So now I understand why that first value didn't do anything; I was only testing on frame 0 and thought the 'normal' squash'n'stretch would work there too, just like the IK stretching did. But now I understand that isn't the case and both are treated differently. Kindof confusing, but I should've tried it on a frame higher than 0 indeed. Than I wouldn't have this confusion.

So this also means that the checkbox before the squash and stretch line is only for the 'regular' squash and stretch feature (to preserve volume) and NOT for the IK stretching, right?

Thanks again for your help! It's starting to make sense to me now!

BTW I'm following the 'ANIMATING YOUR PHOTOSHOP CHARACTER IN MOHO' series from the Lost Marble shop now and that one is pretty useful to get started. It doesn't go very deep, but it gives a pretty good overview on some of the most important rigging features of Moho as a starter.

[Greenlaw]

Cool! Glad that info helps.

So this also means that the checkbox before the squash and stretch line is only for the 'regular' squash and stretch feature (to preserve volume) and NOT for the IK stretching, right?

That's correct. Squash And Stretch Scaling and Maximum IK Stretching are two separate constraints. Squash And Stretch Scaling makes bone length affect the 'volume' of the artwork, and Maximum IK Stretching sets how far IK can lengthen a bone.

These constraints can each be used alone for one type of effect, or they can be used together for another. How they're used is up to you.

[mmmaarten]

That's correct. Squash And Stretch Scaling and Maximum IK Stretching are two separate constraints.

Thanks for the confirmation! Appreciated!

[mmmaarten]

Documenting and trying out things for myself I think it's supercool that Moho let's us enter values for squash'n'stretch! It's a lot of fun to see what it does when setting higher values, it instantly feels so exagerated toon Love it!