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evolross
04-10-2010, 01:57 AM
I think I've found a fairly simple dynamics-related task that is impossible for Lightwave to achieve with its current dynamics system (using version 9.6).

I have a shot where I need to make about 100 clones of a simple object fall and tumble through the air (rotating) and then come to rest on a curved object in a sticky manner (like velcro) AND the object needs to logically lay flat according to it's shape (see images). The objects fall in spurts, so they don't all collide at the same time with the sticky object.

I've tried using both Particle FX and Hard FX. The problem I'm running into is with Particles, I can't get the objects to stop rotating once their stuck to the sticky object. With Hard FX, the objects will stick and even lay flat (almost) but they don't stop moving around. They continue to fall and slightly rotate. And yes, I tried the enveloping gravity trick. It doesn't work in this case. It stops the objects from continuing to fall, but once the gravity is zero, the objects float up or sideways because the sticky object's surface is curved (see images).

The only solution I've found is really convoluted and uses Hard FX and MDDs. I can almost get the cloned objects to stick to the sticky object using Collision FX set to "Bounce" with a Fix setting to 1. Setting the Collision object to "Sticky" would never actually cause the falling discs to stick, no matter what the settings were. They'd only slide along the surface and then off the ball. Go figure!? :bangwall: I got the discs to almost lay flat, but not quite. The problem is they keep sliding and moving slightly. So to correct this, I bake each object to an MDD and then use DPont's MDD Pointer Node to freeze the MDD of the falling disc right as it hits the sticky object (or right after it has laid down). This achieves the effect I'm going for, but unfortunately the process is way too long because I have like twenty clone objects each with about ten discs in it. I use this method because I need to have staggered drops of several groups of discs. Each group hits the ball at the same time roughly. So tweaking and going through this process of baking, then freezing at the right moment takes way too long. Unless there's some way to script all this. Like a Motion Bake All Objects command.

Over the last seven years, there's at least four or five threads related to the rotational and gravity issues related to particles, cloning objects, and dynamics. What a bummer that Newtek never updated the dynamics all this time. I guess there were bigger fish to fry.

As a sanity check, I wanted to post a sample object and scene, which is a simplified version of my real shot and see if anyone has any ideas. I'm thinking maybe with DPont's Particle Scan node something might be possible, I don't know enough about it yet. Maybe there's a way to use the normals of the ball to lay the falling discs properly.

With the images attached and the scene, imagine that the ball and chips have a velcro surface and as the discs hit the ball, they lay flat and immediately stick. Even on the sides of the ball it would stick and not slide. That's the behavior I'm looking for. On the images attached, I manually animated the second image how I wanted it to look for reference. My real shot has too many objects to do it this way. In the attached scene, I don't have any particles or FX setup. It's just an empty scene with the ball and chips.

It's a bummer, but I may have to take this one over to Maya. Certain people wonder why 3D artists move away from Lightwave. This is the perfect example.

JamesCurtis
04-10-2010, 03:15 PM
There is a setting for the dynamics that's supposed to stop this behavior from happening. Problem is, I can't recall what the solution was. Maybe you can do a search here in the foruim on dynamics and stopping vibration.

erikals
04-11-2010, 10:57 AM
100 coins on that small ball... hm, so what will the end result look like?

hrgiger
04-12-2010, 03:58 AM
Edited. Wrong thread.

damain.bond
10-15-2010, 11:09 AM
Did anyone find a solution to this, as I am trying to acheive the same effect and have been beating my head against the wall for the last week on this.

Dodgy
10-15-2010, 07:45 PM
Have a look at this scene.

prometheus
10-16-2010, 04:41 AM
There is a setting for the dynamics that's supposed to stop this behavior from happening. Problem is, I can't recall what the solution was. Maybe you can do a search here in the foruim on dynamics and stopping vibration.

perhaps stop by stabilizer?

Michael

damain.bond
10-16-2010, 05:24 AM
Thanks for the suggestion prometheus, Dodgy's scene did use Stop by Stabilizer on layer 2 which has a HardFX Dynamic.

This answers the question posed originally by evolross, but it now seems I am attempting something more difficult. I need my spherical object to be rotating and the particles then fall off as the object rotates.

I don't need may to stick - perhapss 20 of of hundreds of other cells, so looks like I will have to keyframe each one individually - shame, I wanted the realistic effects that Dynamics gives.

I am very rusty on Lightwave, so any suggestions how I can link a particle to an object and have it remain fixed are welcome - I guess at the point they meet I look to parent the particle to the object?

Thanks

Damian

Dodgy
10-16-2010, 06:56 AM
You could put the pieces in place, then use Start by event (I think it is of the top of my head?) and have a collison object or a few run over the surface to release the pieces. Very simple to set up.

evolross
10-29-2010, 11:23 PM
This answers the question posed originally by evolross...
Not quite... though I really appreciate your example Dodgy. I had no idea about StopByStabilizer. It's one of those crazy checkboxes in the Dynamics system where you have no idea what it does.

The key to what I was trying to do was to have the "coins" tumbling as they fall, then they hit and instantly stick like velcro. No bounce, they need to just impact, fall over, and stick... as if there's velcro on the broad side of the disc.

I loaded up your example Dodgy but the problem I'm having is that I can't get a single object (like your object of discs) to allow the parts to tumble/rotate as they fall. I tried running them through an Event collision and playing with the Force tab on the discs but they stop instantly when they hit the Event object... I'm thinking because of the StopByStabilizer. I also tried raising them up and dropping them through a funnel to get them rotating. This works, but half the coins stop in the funnel because of StopByStabilizer and the other half don't stick to the ball because they're now rotating (which is good) but the StopByStabilizer doesn't stop them until they settle for quite a bit. If it could just stabilize them much quicker... but since there's no settings for that... :grumpy:

This is what I'm talking about. If I use particles and FX_Linker you can never get them to stop rotating once they impact.

Thank God Bullet is on the way. I'm still going to setup an example in Maya, I just haven't had the time, but I know how to do it.

OnlineRender
10-30-2010, 06:18 AM
use blender physics and import .

Dodgy
10-30-2010, 07:25 PM
Thank God Bullet is on the way. I'm still going to setup an example in Maya, I just haven't had the time, but I know how to do it.

S'funny, after you said that, I thought I'd have a go in maya 8.5 ple. And it was just as much as a pain in the bum as I always have when I venture into maya territory.

Here was my experience, so you can see why I get frustrated.

Make a ball and one coin, easy enough.
Apply passive Rigid body to the sphere, and active to the coin. Add a gravity object and test the effect, twiddle with the settings till it stops pretty much dead. Easy enough.
Duplicate the coin as an instance. Hit play. Only the first coin falls. Why don't the rest fall? They're instances of the first coin after all. Try to apply active dynamics to the other coins. Error, already applied. Select the gravity and set it to affect the instances. Success! Coins fall. But when they start to hit the ball, everything gets very chuggy as they figure out the collision, every time the animation plays. Okay, enable the Dynamics cache to speed up playback. Now all the instances disappear after the first frame.... If I drag the slider backwards, they appear in flashes and seem to be doing what they're supposed to, but playing forwards is broken in a big way.
Delete the cache seems to do nothing. Disable the cache and we're back to everything working, but virtually stopping when the coins start to touch the ball.
Okay, I delete the coins and decide to start from scratch. Make a new coin and duplicate it BEFORE applying the active rigid body. Except Maya says rigid bodies already applied to coins... How exactly? I deleted them from the scene and rebuilt them? Did the rigid body solver latch onto the again because they have the same names?
So I clear the scene to start again from scratch. Build the ball and coins. Apply rigid body to coins... error, they already have rigid bodies connected. What?

So I go back and restart maya. Duplicate the coins as copies, not instances. Things seem to go well this time, as long as I don't want to change my coins, otherwise I'm going to have to duplicate them all again.
Try to replicate that positive result, and it's broken again...

This really doesn't seem as easy or quick as people would have me believe maya is. And that is what frustrates me. People keep saying how superior it is, but then I keep hitting problems like this. And I'm fairly technically minded.

evolross
01-11-2011, 08:55 PM
I guess this is a lot harder than I thought. I finally got back to this and I just burned about four hours screwing with wretched Maya trying everything from nCloth dynamics, to particle/geometry instancing, to Maya's older rigid body dynamics and I still couldn't get it to work right.

I was close with particle instancing, but I'm not talented enough in Maya to write the MEL needed to orient the coins to the sphere's poly normals when they rest. I got them to impact, stop, but not ultimately rest at the correct orientation. Close but no cigar.

nCloth always left a little cloth-like bounce in the coins and rigid bodies as separate meshes took too long to calculate and has one combined mesh of coins would not separate on impact (a la piece into parts). I also couldn't get them to spin/tumble on the way down.

Just when I thought Lightwave's dynamics were hard to use and their documentation sucked... go check out Maya and get ready to hack away forever trying to get something to work. All with no help from the docs and Googling a million random forum pages to figure it out one step at a time. I really, really dislike Maya. :mad:

erikals
01-11-2011, 09:02 PM
use blender physics and import .

nope, because Blender can't export an MDD that will scan multiple objects.
so you will have to save one MDD for each coin...

evolross
01-11-2011, 09:09 PM
Would Blender be able to do a "Piece into Parts" and treat all the coins as one object, breaking apart as they fall and/or collide?

Dexter2999
01-11-2011, 09:49 PM
Do it in reverse? Start in place on the curved position the float away tumbling up through the air.
Reverse the footage in your editor? Or use a batch renamer to rename the image sequence?

erikals
01-11-2011, 10:13 PM
Would Blender be able to do a "Piece into Parts" and treat all the coins as one object, breaking apart as they fall and/or collide?

it might, but it will still have the MDD problem afaik...

Dodgy
01-11-2011, 10:21 PM
I guess this is a lot harder than I thought.

Not to say I told you so but..... :D

I'm really of the opinion that while ALL packages are all better in some areas than others, they're never really as easy as people would have me believe :)

jeric_synergy
01-12-2011, 01:58 AM
Just when I thought Lightwave's dynamics were hard to use and their documentation sucked... go check out Maya and get ready to hack away forever trying to get something to work. All with no help from the docs and Googling a million random forum pages to figure it out one step at a time. I really, really dislike Maya. :mad:

Ahhhh, the ol' "Grass is Always Greener Syndrome".

jeric_synergy
01-12-2011, 02:04 AM
nope, because Blender can't export an MDD that will scan multiple objects.
so you will have to save one MDD for each coin...
But the coins in LW are all one object (I'm surprised to say).

Does that make a difference?

Will Blender not simulate in the same fashion, "Parts-wise", as LW?

++++++++++++++++
I was able to get the sphere to spin the coins off, but a lot of them stayed fixed in space as the sphere rotated below them. So close!


(And Dodgy: you da man.) :thumbsup:

++++++++++++++++
EDIT: If I turn off "Stop By Stabilizer", I can get all the coins to fly off the rotating sphere. Cool!!!