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Thread: to buy or not to buy syflex for Lightwave ?

  1. #361

    thank you for info Greenlaw, i'll read it a second/third time later, it's always a lot to remember when it comes to sims, what works/what doesn't, what to watch out for.

    It's possible to use the actual character mesh for collision in Bullet, but you'll need to scan it to MDD and make it a Deformable Bullet Object.
    i did this without baking, worked alright, though had some jitter.

    so, yep, i too had Bullet jitter problems, with self collision turned off though.

    question > do you still use Syflex? why / why not?  
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  2. #362
    Thank you very much Greenlaw.

    I figure one can use ChronoSculpt to fix any problems self collision would potential fix if one was using it.

  3. #363
    Eat your peas. Greenlaw's Avatar
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    One more thing: I recommend baking the sim to MDD when you're done and removing Bullet. This will speed up your renders and prevent potential errors if Bullet tries to recalc during rendering. This is especially true in network rendering but helps for local renders too.

    What I usually do is I make a separate 'Bullet Calc' scene, containing ONLY the essential elements for the calculations, and then export my MDD from there to use on the final shaded object in my master scene. No sense bogging that scene down with all that overhead.

    Regarding jitter: there are a few causes for that and ways to prevent it. In my experience, jitters occur when a situation has been created where an object is never allowed to rest so Bullet can never deactivate itself. This commonly occurs when you use a single Parts object for a bunch of little pieces, instead of separate individual objects.

    Watch for things like debris falling off the ground plane or table. If those infinitely falling bits and pieces never come to rest, then as far as Bullet is concerned, that singular Parts object is never coming to rest so it keeps calculating for collision (the jitters.) Or maybe there are so many pieces in the Parts object that they keep rolling and bumping into other, causing endless motion, so again the object never comes to rest as a whole for Bullet to deactivate it. (A bowl of marbles, maybe?)

    The way to prevent this is to not use Parts, and to use individual objects so Bullet can evaluate the activity for each piece separately and deactivate them separately.

    Using a Parts object may be convenient for reducing Scene Editor clutter (it really is!) but it can be a pain in the butt when you need the Parts object to completely come to rest. Fortunately, during actual production scenes, we usually cut away from the action long before anybody notices. (Watching a full simulation, from start to finish, can actually gets really boring in a movie or TV show. That's what editing is for.)

    So, I often use Parts objects when I think it won't matter. But when I need to show a full, non-jittery sim, I'll just 'bite the bullet,' so to speak, and break out all the pieces as separate objects. Doing this usually prevents the jitters, even if you have those pesky infinitely falling pieces in the sim. This is another reason I use a separate 'Bullet Calc' scene--this way, I can dedicate all computer resources to one task and not be weighed down by other stuff happening in the scene non-essential to the calculation.

    If I still see problems in the sim, I may just kill the offending pieces during the sim so you never see them, or I'll fix the problem using Chronosculpt. (In VFX work, cheating can be a virtue.)

    And if there are STILL problems, Bullet is fast enough that I can change the conditions slightly and re-do sims multiple times until I get what I want. Most of my sims only take a few minutes, whether it's for hair, destruction or cloth effects. I don't usually have time for anything much longer. IMO, I'm just a generalist and anything beyond my capabilities should go to a dedicated dynamics artist using Houdini.

    Regarding Syflex, I have a license, and played a little with it but I never took the time to properly learn and use it for real work. I keep it on-hand, 'just in case,' and one of these days I will learn how to use it. Fortunately, so far I've been able to do most of what I need with LightWave Bullet.

  4. #364
    Eat your peas. Greenlaw's Avatar
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    Another comment. (Sorry, I'm having an awful headache this weekend so I keep forgetting stuff.)

    If you look at the collision objects and their settings in Bullet, you'll see that I'm only using 'Mesh' for the rounded box shape, and I'm using Sphere and Capsule mode for the, well, spheres and capsules. I'm not completely sure about this but I think Bullet is faster if you use the preset primitives instead of the actual meshes. (Note: there's an option that will overlay a wireframe of the primtive over the mesh so you can see how it aligns.)

    Of course, sometimes you need the actual mesh for accuracy. Even in that case, i'll try to use a lower-res proxy version of that shape.

  5. #365
    Eat your peas. Greenlaw's Avatar
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    Maybe this is my last comment: Most of the time, I think it's better to just build the folding (like in elbows and knees) into the mesh/rig. You can use Joint Morph+ for this. This way, you get exactly the folds you want that look consistent every time, and it doesn't require dealing with dynamics for every scene.

    My feeling is that dynamics is more practical and better suited for flowing fabrics. (Not a firm rule, just a guide. It really depends on the requirements of the project of course.)

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