Controlling blendshape envelope using a falloff object like in MASH

[dkrelina]

I'm wondering if it's possible to control the intensity of a blendshape object using another shape (let's say a sphere in this case). As the blendshape object gets closer to the center of the sphere, the blendshape envelope approaches a value of '1'. When the blendshape object is outside the sphere, the envelope will remain at '0'.

Using this approach, I would like to be able to animate the sphere moving across the blendshape object and for the blendshape object to"ripple" from one shape to another in a progressive, wave-like movement, similar to an object passing through a lattice or the behavior of the MASH falloff objects.

Is it possible to do this with blendshapes?

[mspeer]

Hi!

Use Set Driven Key or an Expression.

Please read the Maya Online Help / Documentation for more details.

[dkrelina]

Thanks, an expression or driven key might work.

Have a look at this video. It explains the effect I'm trying to achieve. I'm trying to make the extrusions on the cylinder grow/shrink as the falloff object passes over them in a similar way to how the cubes rise/fall.

https://streamable.com/kseld

I'm using a blendshape to grow the extrusions. The issue I haven't been able to solve is having some parts of the geometry influenced by blendshape, and others not. Ideally I would like to define these areas using a falloff object that can be animated, like in the video.

Any ideas?

[mspeer]

Hi!

"some parts of the geometry influenced by blendshape, and others not"

You can't mask or limit the affected area of one single blend shape (or at least there is no "easy" way to do this).

You may find an other way to get the desired result.

[dkrelina]

There is a way to mask an area of a blendshape using the Paint Blend Shape Weights Tool.

But I would like to animate black and white gradient to achieve the effect in the previous post.

Is it possible to use a ramp as a 3D texture to define the blendshape weights? That way I could animate the ramp to get the desired effect.

[dkrelina]

Also, I notice that on the blendshape node itself, there is an attribute named 'Base Weights' with an array size equal to the number of vertices on the object. It's not totally clear to me what is the function of this attribute, but I wonder whether it is possible to input an animatable ramp and connect it to this attribute to drive the per-vertex weight of the blendshape.

[mspeer]

Hi!

The Paint Blend Shape Weights Tool paints values to Vertices, this is not a texture that uses UV's or can be "easily" replaced by a ramp.

You may use the Base Weights values to create what you want, but it would need a lot effort to do this, there is no direct or easy way.

Again, i suggest to use an other approach.

[NateLikesTea]

I'd really like to see this functionality in Maya.  It seems like a no-brainer.

Here's a thread on CGSociety back from 2011 that achieved the result with a few scripts, although apparently the evaluation of the setup was pretty slow and they couldn't manipulate it in real time:

https://forums.cgsociety.org/t/can-i-use-a-ramp-to-control-a-blendshape-weight/1516297/5

[NateLikesTea · Accepted solution]

Hey actually, Rampweights is exactly the functionality I was looking for, which I'm pretty sure would be a good solution for you too:

http://www.braverabbit.com/rampweights/

Although the video demos the tool on a facial rig, I use it in medical animation to make a blendshape propagate down an object, like a vessel constricting (like blood vessels pumping, or peristalsis, etc).

[misha123]

This sounds like the Mash Blend Deformer