Hi,

I'm creating a cloth setup using Vellum in Houdini 17 and had a few questions on how to recreate some of the things I would do in a Maya cloth setup.

1. Relative Motion.
In Maya I can constrain the nucleus solver node between a null constrained to a fast moving character and a non moving null at the origin. By weighting the constraint between the two nulls, I can remove or reduce the affect of extreme motion on a cloth simulation. How can I do this with Vellum?

2. Input Attract.
I have my simulation geometry point deformed to animated geometry pre vellum solver node. In Maya, I can use input attract to goal portions or percentages of the simulation to follow the animation shape during the simulation. How can I do this in Vellum?

3. Constrain points to animated object on moving character.
In Maya, I can create transform constraints on vertices of cloth and then parent that under a null which can be animated to help position parts of cloth. This setup can travel with the character by constraining it to an additional locator traveling with a character. In Houdini, I can create groups and use Attach to Geometry constraints to constrain those grouped points with the corresponding geometry. This works to constrain points to animatable nulls. Now I need it to travel with the character. I think I need some kind of expression to keep the nulls that the cloth points are constrained translating and orienting to a vertex on the character with a position offset.

Thanks,

Adnan

Hey Adnan,

So like all things in Houdini there are multiple ways to solve try and get to those but I'll try to break it down a bit based on how I'm doing it



In terms of mimicking the Input attract one of the easiest ways is to pin the “sim cloth” to the animated cloth. If you are not receiving a “wrapped cloth” from animation you can easily make it yourself by just point deforming the cloth to the animated character. Once you have this “wrapped cloth”, you can pin the cloth to the anim with varying levels of strength to get the desired effect. There should be a example of this in the H17.5 help example files under the name “sop_example_armtarget”. Alternatively, because vellum is basically particles, you can just use the pop attract to have the cloth try to stick to it's corresponding “animated” counterpart. I haven't tested the speed of the two methods but I have made a series of cfx tools that use that as a base.

For the retaliative motion if you are trying to solve at origin you can simply (in a subnet) Pack-> wrangle v@P =set(0,0,0); -> unpack - this will give you a semi motion killed animation to work with. In order to reverse it simply attach an “add” node after the pack and then in another subnet - (resulting anim into first input of a wrangle - obj merge point into second) -> @P += point(@OpInput2, “P”, 0);.

Hopefully that helps and If i have time Ill try to come back and upload a scene file

Thanks so much for this Rhartmann! I created a setup with the wrangles as you suggested and managed to add a blendShape node so that the motion can be partially decreased, as all as all or nothing. I have tested the pinning to create the equivalent of input attract and will continue testing that further, but you gave me an important piece of the puzzle. Thanks!

Adnan

Hi ,

Would it be possible in Houdini to paint input mesh attract, If Yes please explain How?
I highly appreciate if someone can share scene file for my better understanding.