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Kwesikwaa Hayford
Kwesikwaa Hayford

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Houdini: Keep A Chaotic Character Vellum Cloth Under Control

Does the cloth on your animated character look chaotic and out of your control?

default chaos vs velocity blended calm

Vellum has a "one toggle switch and a slider" solution for this problem. The slider allows you to control how chaotic/tamed the cloth can get. Let's get started!

Below is my setup. I basically used a cube as the main character in this case and transformed it with a trig function to make it oscillate on the y axis. A point velocity node ends the cube's node chain. Getting the character's velocity is very important for the setup and needed for the fix to work. The cloth is a grid with an initial vellum cloth setup to get an already draped cloth for as initial state. Simple network

The entire network

First, the cloth is attached to the cube via a Vellum Constraint Attach To Geometry node. A primitive group I made on the cube and named "att" is fed into the group slot of the constraint. The point velocity node from the cube is piped into the collision geometry input of the constraint node. A vellum solver is then dropped to demo how it goes. Attached but definitely chaotic. This is where the solution comes in.

The first Attach Constraint is indicated in green and the second is indicated in blue

A second Attach to Geo Constraint is added after the first one(mind you we are keeping both). This time all the group slot will be left empty and the stretch stiffness set to 0. The Velocity Blend property under the Stretch tab is then activated. The amount is now based on what feedback you get and what you are going after. In my case I settled with 0.3. Keep in mind that without the point velocity node from the cube, this will not work.

the first Attach Constraint is on the left and the second is on the right. Take note of the differences in the marked areas

That is it. The hip file is in a github repo Houdini-Vellum-Blend-HipFile

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