From BlenderWiki
[edit] In Blender: Squash and Stretch
Collected in this page are resources that can be used to apply Squash and Stretch effects.
[edit] Object non uniform scaling
Using only scaling in X, Y and Z, plus translations and rotations, users can apply Squash and Stretch in stills and keyframed animations of very basic models, like the available mesh primitives. The bouncing ball, which is the best known exercise for traditional animation apprentices is a classic example of what can be done. <LINK object transformations>
This is as simple as it gets, but it can be a basis for good introductory exercises, where most if not all principles can be applied, ranging from raw moves and collisions to acting.
[edit] Motion blur
If the only need for Squash and Stretch were to simulate fast motion and to fight strobing, this principle would be a thing of the past (and the world would be a much less interesting place, if we may add).
This because specific tools available in Blender can do a better job:
Old and simple, but good enough for the least demanding situations, specially being so easy to use.
For more ambitious projects, but it requires basic knowledge of compositing in the program.
These two functionalities require a fraction of the work we'd have to mimic the effect with actual deformations, considering how complex some sequences can be.
Tutorial
Strobing (includes motion blur at the end).
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[edit] Lattices and other indirect deformations
Applying Squash and Stretch to anything but the most trivial shapes requires control over the deformations. An indirect way to get this, without having to change the actual model, is by using one of the “geometry deforming” tools:
General advice
there are situations where one of these tools can offer a very good solution, so getting acquainted with them is not a bad idea.
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[edit] Blend shapes
Here we reach maximum control for vertex deformations. This functionality might even be a little overkill for basic cartoon squash and stretch of the head and body, where a good armature setup can work very well.
But it shines where point by point control is needed, facial expressions being a notable example.
If good squashing and stretching for a model cannot be achieved by object scaling, adding one blend shape for each is a good, easy to animate alternative. To create each shape, an artist could start with non uniform scaling and then edit the new mesh key to correct the parts that still don't look well.
Blend shapes can also be used to correct thinning of surfaces near bending joints, e.g. for muscle bulging.
But at this point, let's invert the situation. More important then how to use blend shapes to apply Squash and Stretch is how to use the latter to create realistic blend shapes.
This principle of animation is a vital component behind facial expressions. Any movement in our faces involves areas that bulge and areas that crease – and this is all about squashing and stretching. Just look at yourself in a mirror and smile, frown, sneer, squint, etc. until you're convinced!
To learn more:
- From the Manual: Shape Keys
- Blender Summer of Documentation: Character Animation: Shapes
[edit] Armatures
As we mentioned in the section devoted to joints, a fundamental application of this principle is in bending and stretching the character's armature, where stretching translates to straightening and squashing, to bending.
There are many tools to help posing characters. This is at the heart of a 3D animator's work, right there with facial expressions and lip synchronization. Blender has very good support for rigging and posing already and continues to be improved. The rest is up to aspiring animators, there is a lot to learn about the related concepts, methods and tools. Learning them (IK chains, FK, constraints, actions, etc.) is the fundamental pre-requisite to be able to apply the principles discussed in this text. First we learn how to do, then how to do better.
[edit] Rubber bones
It's also possible, in good toon tradition, to compress and extend bones beyond their “rest lengths”, using the “stretch” parameter for bones that are part of IK chains and the “stretch to” constraint.
Tutorial
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Another way, that works without changing bone sizes, is to disconnect a bone from its parent. After that the bone is free to be moved, pulling with it the vertices under its influence. The “Connected” toggle button is in the “Armature Bones” at the Edit Buttons window while in armature edit mode.
[edit] Soft bodies
Blender's collection of effects includes support for soft bodies, a kind of object data deformation that simulates the behavior of soft materials using calculations based on the their physics. It can work particularly well for animating jellylike or rubbery things, but is also useful for cloths.
Most of all, soft bodies can be a great help for Squash and Stretch, specially the more subtle and frequent use of it. With them we can have jiggly “flesh” that will be animated automatically as the character moves.
The workflow to create such animations is basically twofold: on one side we prepare the object for soft body, setting the right parameters and probably painting vertex weights to define how flexible each part of the model (cheeks, abdomen, etc.) should be. On the other we simply animate the character's main moves: walking, talking, etc. When we turn softbody support on, Blender should make the softer parts as we defined for the character behave as expected, as long as the parameters and vertex weights are set correctly.
Note, though, that this simulated effect may not be adequate or desirable for a given character, but it's surely worth learning and experimenting with.
Summer of documentation 2006 -- Willian 02:06, 29 June 2006 (CEST)
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