[Sidefx-houdini-list] Fast character cloth sims

Marten Blumen martyb at gmail.com
Wed May 31 14:15:59 EDT 2017


H16 cloth solver has hidden 'unit length/mass' parameters, you can simple
unhide them, that will scale with upon creation based on the 'Hip File
Options' preference.

On 1 June 2017 at 02:26, Vincent Fortin <vfortin at gmail.com> wrote:

> Also FEM is highly dependent on scene scale. Check your units and try
> scaling down your model. Rebuild your setup from scratch and compare
> simulation times.
>
> I'm not a cloth expert either but this has helped me a lot in the past. I'd
> be curious to have a look at your scene if you can share it.
>
> Good luck!
>
>
> On Wed, May 31, 2017 at 7:08 AM, Phil Spicer <PSpicer at bournemouth.ac.uk>
> wrote:
>
> > Hi Steven,
> >
> > I have always found cloth to be fine in Houdini and I also remember a
> > cloth competition a few years back where a wide variety of costumes and
> > material types were developed by Houdini Artists, so great cloth can
> > definitely be achieved.
> >
> > I am no cloth expert by any means, but the key workflow considerations
> > I’ve found to reduce simulation times are:
> >
> > 1. Use a Soft Peak or Peak SOP to slightly inflate your character
> > collision mesh. This inflated mesh is hidden at render time with the
> > original character mesh being used instead.
> > 2. Activate Concave Bullet Collision geometry for the inflated collision
> > mesh.
> > 3. Ensure your cloth geometry is triangulated (for example using a Divide
> > SOP)
> > 4. Have less topology on your cloth geometry, and subdivide it post
> > simulation to create the final cloth aesthetic.
> > 5. Use the Rest Geometry / Target Geometry options to help give more
> > bespoke movement and shape to the cloth (for example animated rippling
> rest
> > geometry).
> > 6. Set the Cloth Thickness appropriately, and check its thickness by
> > activating the cloth thickness guide.
> > 7. Surface Mass Density can be set quite low (for example 0.005)
> > 8. Normal Drag and Tangent Drag can be set to 0.
> > 9. Material Stiffness can initially be set to 1.
> > 10. FEM Solver Minimum Substeps can be channel referenced into Max
> > Collision Passes, Penetration Recovery and Max Fully Implicit Passes, so
> > they can be increased simultaneously whilst still keeping their values
> > relatively low.
> >
> > I would do a basic setup such as this before playing with the more
> bespoke
> > cloth physical parameters such as the ones you mention.
> >
> > I have a simple cape skirt example file I can send you if you want based
> > on the above, and the visual result is a slightly heavy cloth aesthetic
> > with a fast sim. I can be emailed directly at pspicer at bournemouth.ac.uk<
> > mailto:pspicer at bournemouth.ac.uk>
> >
> > Kind regards,
> >
> > Phil.
> >
> >
> >
> > Philip Spicer
> > Programme Leader - MA Digital Effects
> > National Centre for Computer Animation
> > Bournemouth University - UK
> >
> > https://www.youtube.com/user/NCCADigitalFX
> >
> >
> > On 31 May 2017, at 00:12, Steven Quinones Colon <
> steven at stevenquinones.com
> > <mailto:steven at stevenquinones.com>> wrote:
> >
> > Hi Guys,
> >
> > A very simple nooby question. I have a simulation of a character being
> > thrown across the room. He is an alembic animation about 18,000 points
> as a
> > collider, and  has a business suit(just a jacket now for testing) with
> > about 42,000 points, and I'm getting really flimsy looking cloth(more
> like
> > silk) with the soft leather preset,  it's also taking more that half an
> > hour per frame for the simulation. I've played with Stiffness Multiplier
> > and Stretch Stiffness but anything past 2000 slows everything to a crawl,
> > dampening helped. Any tricks from the experienced folks for this kind of
> > sim for both of these problems?
> >
> > Best,
> >
> > Steven
> >
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