Sail Cloth sim fails after about 300 frames

Posted by:seren
Data created:26 December 2016

I'm trying to simulate a sail on a ship.  The ship is moving forward, with a wind modifier bound to the sail. 

All is well up until about frame 300 of the sim.  The fixed points on the sail continue moving forward with the ship, the rest of the sail fails and smears behind the ship as if locked to the frame 300 position. 

Seems to be approx 5000cm / 50m distance.

A simple translating flag sim can be made with a plane with the front edge verts selected, parented to a dummy moving slightly more than 5000cm over 1000 frames.  At this slower speed the problem occurs much later, around frame 980.  At faster speeds the problem occurs earlier, related to distance the cloth is moved? 3dsmax 2016 with and without service packs, lucid 1.3.6 and 1.2.0. 

All drivers up to date, and latest CUDA 8.0 installed

Hi Seren,

I haven't had luck reproducing this issue, sorry. Let's wait for some of the guys with more experience with Lucid.

Jeordanis Figuereo (Product Designer. EPHERE Inc.)

Testing again with different scales unit=1m 1unit=1cm, creating new simple scenes the problem persists. 

If does seem to be 50m distance that is the factor, rather than time or number of frames. 

A sail or flag will not move further than 50m real distance at any scale.  It's as if the simulated cloth hits an invisible brick wall at 50m, but the selected verts carry on through the wall stretching the attachments to the cloth behind them. 

Further testing.  A piece of cloth formed from a plane will hit the same invisible brick wall after falling 50m.  No external propulsion from an animated object, just free falling under simulation. 

50m seems to be some sort of limit to how far a simulated cloth can travel. Note max units set to cm so this is actually 5000cm

Hi Seren,

This is what I find in the docs:

"To preserve the stability of simulation every scene has a default global "sandbox" volume. If any of the simulated particles try to venture beyond its limits they will be stopped by this volume. The default size of this object is 10,000 scene units.

If you create a sandbox collider object described below, it will override the default sandbox volume. Therefore, you can increase or decrease the size of the overall simulation scene by defining your own sandbox collider. "

This may help you to increase the limit of 5000cm. I don't have too much experience with Lucid so I have passed this on to Marsel, he should be able to help you better. :)

Jeordanis Figuereo (Product Designer. EPHERE Inc.)

That is it! You've solved the mystery for me, it is the sandbox that the cloth was hitting.  I will try defing my own.  Smile

Thanks Jeordanis