Make A Belly Bounce?

[Atom]

Hi All,

 

How would I make a character's belly bounce as he walks? He is kind of a big guy.

[Rainroom]

Using FEM or PBD is ideal for this kind of situation. You can have procedurally animated target geometry to drive the simulation for absolute artistic control over it.

[Atom]

Thanks for the tips, FEM looks promising but I don't see how grains can help?

 

So let's proceed with a FEM based solution. I watched the GoProcedural H13 video on FEM and he mentions you can affect part of a mesh but does not show how?

 

As an example I have a sphere and I have selected half the faces. Those are the only ones I want to be affected by the FEM simulation. However, I can't find a way to make only part of a mesh work with FEM. The entire mesh gets tessellated. I want the sphere to move up and down and have only half of it be a softbody. I want to have a mix of keyframes and simulation, for instance I need gravity but If I turn it on the entire sphere falls and my keyframes are ignored.

ap_half_sphere_FEM.hipnc

[MrScienceOfficer]

http://www.sidefx.com/docs/houdini15.0/dyno/solids#target

 

Its somewhat simple, all you need to do is animate the point attribute values like "targetP" and "targetstiffness", usually in a SOP Solver DOP.  

 

For example bind the sphere to your rig the way you want it, then paint the targetstiffness multiplier value to 0 where the belly is and 1 where it should attach to the rig, then set the targetP of all the points to their current position for each frame in a SOP Solver DOP.  

 

It will probably take a bit of time to get it going, but that's all the major stuff you would need to do.

Edited November 29, 2015 by MrScienceOfficer

[mestela]

The keyframedgrains example shows how to use pbd/grain for softbodies.

 

http://www.sidefx.com/docs/houdini15.0/examples/nodes/dop/popgrains/KeyframedGrains

[Atom]

Thanks Matt, I looked at the example and it has the same limitations as the FEM. It affects the entire objects. I just want part of the sphere/belly to be a softbody, not the entire objects.

 

I don't think I need a full blown simulation, just a way to add a little bounce or jiggle.

 

In Blender I would select the points on the belly, make a vertex group and then use that group in the softbody feature.

 

Is there anything that simple in Houdini?

[Rainroom]

One way would be to extract the belly region and pin the boundary points (unshared edges) to their animated positions. The rest of the points can simulate as grains using targetP, targetstiffness attributes. After the sim you can merge the animated geo and the simulated geo with points fused together.

[michael]

just use bones...(or wires)

 

 

jiggle.0.hip

[Tridae]

Why has nobody mentioned CHOPS?

 

You can easily do this little bit of wobble with the jiggle op. Used this for a lot for adding a little bit of extra motion to characters. 

 

Simple and easy without the overheads of a sim. 

 

Hip attached. 

belly wobble_CHOPS.hip

[Atom]

Thank you Marco, that looks promising.

 

I must admit I have not investigated CHOPs enough.

[akelian]

For a simple FEM setup

I think you are looking for the pintoanimation parameter.

Add it to the points you want to stick to your rig (invert of the belly) in SOP.

 

Source:

http://www.sidefx.com/docs/houdini15.0/nodes/dop/solidobject  

#attributes

Edited February 22, 2016 by akelian