PDA

View Full Version : Bullet Cloth Help Please



SAHiN
03-18-2013, 08:08 AM
Hi,
Does anyone know if there is a way to tell bullet a range to calculate.?
I have mocap sessions which run thousands of frames and all I need calculated is say 300 frame in between those frames, yet Bullet insists on calculating from 0 taking days to reach where I want calculated.


Thanks in advance

prometheus
03-18-2013, 09:06 AM
not sure, try in objects bullet/activation tab and set activation to last key, if you set a keyframe right there at 300.

Michael

Greenlaw
03-18-2013, 10:39 AM
Lately, I've been running Bullet sims to generate secondary animation for mocap CA and some of the motions can run 1400 frames or more. Here are some tips.

Try offsetting the animation that you want to calculate closer zero and make note of that offset. I usually pick a round value that's easy to remember, like 100, 150, 200, etc. If you're using 'new' scene editor, you can select the whole scene and use the Numeric Offset command. I also suggest temporarily switching to Bounding Box mode, especially if you have rigged characters--moving multiple keys around is many, MANY times faster this way. Then, after you run your Bullet sim, bake the motion for affected objects using MD Multi-Baker or DP's BDD Scan. Save your scene as a 'Calc' scene. (Tip: If it's a really long sim (like over 1000 frames,) disable the Enable Bullet button before saving the scene--this should speed up re-loading the scene.)

Now, load your .mdd(s) into your 'final' scene and apply to your objects and apply the offset to the .mdd to set the animation back to where it should be. (Be sure Bullet is not in use in this scene--there's no point re-calculating a baked sim.) If you're using the new MD Multi-Loader, you can quickly apply many .mdds and do the offsets from a single window.

Typically, my 'Calc' scenes contain only the necessary elements for the calculation and they go pretty quickly. An example can be seen in this Sister mocap test I posted a couple of weeks ago: 'Sister' Motion Test (http://www.youtube.com/watch?v=jASC8IOsIqY)

Note here that in this example, the 'Calc' scene contains only the Deformable hair guides and five Collision objects, (Head and four arm sections)--the full mesh was replaced with a null because it was not needed for the simulation. For most shots, I will also remove the lower sections of the arms from the calculation.

In searching for my initial Bullet settings, if calculations are too slow, I may use a half res object to speed things up (in this case, the full res hair object is about 1600 guides so my half res 'starting' object is about 800 guides,) and if that's still too slow, I may also dial down Solver Iterations. Then, when I have something I like, I'll replace the half res object with the full res object, turn up my Solver Iteration to something more appropriate for final, click the Last Frame button (it's much faster than using Play) and take a break.

Even though the above example specifically demonstrates Bullet Deformable for hair, these workflow tips can be adapted and applied to any lengthy or complex Bullet sim.

G.

SAHiN
03-18-2013, 12:30 PM
I tried it but it did jack.. I have no idea what that actually does..
But thank you nevertheless.. I appreciate the help Michael..

SAHiN
03-18-2013, 12:36 PM
Lately, I've been running Bullet sims to generate secondary animation for mocap CA and some of the motions can run 1400 frames or more. Here are some tips.

Try offsetting the animation that you want to calculate closer zero and make note of that offset. I usually pick a round value that's easy to remember, like 100, 150, 200, etc. If you're using 'new' scene editor, you can select the whole scene and use the Numeric Offset command. I also suggest temporarily switching to Bounding Box mode, especially if you have rigged characters--moving multiple keys around is many, MANY times faster this way. Then, after you run your Bullet sim, bake the motion for affected objects using MD Multi-Baker or DP's BDD Scan. Save your scene as a 'Calc' scene. (Tip: If it's a really long sim (like over 1000 frames,) disable the Enable Bullet button before saving the scene--this should speed up re-loading the scene.)

Now, load your .mdd(s) into your 'final' scene and apply to your objects and apply the offset to the .mdd to set the animation back to where it should be. (Be sure Bullet is not in use in this scene--there's no point re-calculating a baked sim.) If you're using the new MD Multi-Loader, you can quickly apply many .mdds and do the offsets from a single window.

Typically, my 'Calc' scenes contain only the necessary elements for the calculation and they go pretty quickly. An example can be seen in this Sister mocap test I posted a couple of weeks ago: 'Sister' Motion Test (http://www.youtube.com/watch?v=jASC8IOsIqY)

Note here that in this example, the 'Calc' scene contains only the Deformable hair guides and five Collision objects, (Head and four arm sections)--the full mesh was replaced with a null because it was not needed for the simulation. For most shots, I will also remove the lower sections of the arms from the calculation.

In searching for my initial Bullet settings, if calculations are too slow, I may use a half res object to speed things up (in this case, the full res hair object is about 1600 guides so my half res 'starting' object is about 800 guides,) and if that's still too slow, I may also dial down Solver Iterations. Then, when I have something I like, I'll replace the half res object with the full res object, turn up my Solver Iteration to something more appropriate for final, click the Last Frame button (it's much faster than using Play) and take a break.

Even though the above example specifically demonstrates Bullet Deformable for hair, these workflow tips can be adapted and applied to any lengthy or complex Bullet sim.

G.

Damn Greenlaw, offsetting the animation is a great idea.. Why didn't I think of that... Thank you.
Half ressing the objects don't really work for me. It's do or die with 270,000 frames of animation waiting to be done for this movie, between my time and machine's time - I'll take the machine time.!
Once I get a proper setting for each character I'll let them roll while we continue Mocap shooting sessions.

Thank you so much Greenlaw. It;s most appreciated .

Mick

Greenlaw
03-18-2013, 01:36 PM
A 270,000 frame Bullet simulation??? Seriously? :)

SAHiN
03-18-2013, 02:04 PM
A 270,000 frame Bullet simulation??? Seriously? :)

No way !! I would jump the damn bridge..:) Right now I'm even moving away from bullet soft all together for the cloth simulations. It's too slow for something that lacks micro fiber animations. This thing needs add ons like "initial position" so after T-pose we can tell bullet what the cloth should sit like and the rest of the animation should start from there etc.. Anyways I have a list of things in my mind for LW but I'm sure beta group will discover what's missing and eventually get them added on.

Greenlaw
03-18-2013, 03:11 PM
LOL...I misunderstood obviously. Anyway, good luck with your project. ;)

G.

SAHiN
03-18-2013, 03:39 PM
LOL...I misunderstood obviously. Anyway, good luck with your project. ;)

G.

Thank you.. :)

Surrealist.
03-18-2013, 03:55 PM
No way !! I would jump the damn bridge..:) Right now I'm even moving away from bullet soft all together for the cloth simulations. It's too slow for something that lacks micro fiber animations. This thing needs add ons like "initial position" so after T-pose we can tell bullet what the cloth should sit like and the rest of the animation should start from there etc.. Anyways I have a list of things in my mind for LW but I'm sure beta group will discover what's missing and eventually get them added on.

Yeah that'd be a useful feature. One thing that might work - maybe - is so save trans object and then use that for the sim. But you'd probably have to reset the collision distance to below that position or you'd get an explosion.

SAHiN
03-18-2013, 03:59 PM
Yeah that'd be a useful feature. One thing that might work - maybe - is so save trans object and then use that for the sim. But you'd probably have to reset the collision distance to below that position or you'd get an explosion.

Yay.. I am getting explosions here.. Care to expand on that collision distance issue ? I think that may be whats slowing bullet down so much..

SAHiN
03-18-2013, 04:35 PM
LOL...I misunderstood obviously. Anyway, good luck with your project. ;)

G.

Can you identify what causes this problem? I think getting these results are slowing down my bullet like mad..

SAHiN
03-18-2013, 05:56 PM
I did sort out my problems. Here is my findings for all those who may try this in the future.

If you need to move your character somewhere else in your scene after applying bullet cloth effects, make sure to move it at frame 0. If you have your T-Pose say at the center of the universe, but you want your character to walk down the corridor of a set you built before, and move the character to walking spot say at frame 1 (just cause you want to keep your frame 0 at T-pose) it will mess up your dynamics as Bullet doesn't like that.
In my case my problem was our Mocap system. We use Inertial mocap system (Xsens). As some of you may know, Inertial systems work on rotation and not translation so, system doesn't actually know where it is. So after T-pose in 1 frame your character moves to somewhere else in the universe. And that messes Bullet soft big time.
I finally figured it out by actually moving the character with skirt in LW content directory..And guess what happened ? It looked as messy as mine. So I moved my starting position to frame 0 and bob was my uncle too (finally).. I hope it helps someone..

Regards
Mick