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 Subject: Addition to cloth simulations

weiesnbach opened this issue on Sep 22, 2020 · 10 posts

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  weiesnbach    ( ) ( posted at 11:06PM Tue, 22 September 2020 

I've been wanting this for a while now, and it should be pretty simple, but it would be nice to have a way of making areas of the cloth shrink, so that they fit like spandex or elastic, while other areas are allowed to move freely. Maybe allow it to go slightly lower than the collision detection and then letting the collision stop it from going further. This would allow for more realistic cloth with a lot less work:

image.png


  FVerbaas    ( ) ( posted at 2:41PM Wed, 23 September 2020  · @4400150

What you are asking here presumes that what you see (the outside of the waistband) is positioned such that the inner side of the waistband connects to the skin. Unless in some way the material that fills the waistband is defined, that is not possible. There is no way you can expect a program to dream this up by itself.

Solution for this has been in the cloth room since the beginning with Poser 5. Shrink the waistband until it connects to the skin and make it constrained (or cheorographed if the garment is a conformer).


  FVerbaas    ( ) ( posted at 1:17AM Thu, 24 September 2020 · edited on 1:18AM Thu, 24 September 2020 · @4400166

There could be a solution via displacement maps. Cloth simulation works on mid-plane. The vertices are located in the middle of the fabric. Displacement maps can bring the offset to simulate thickness. Then however you still do not have the edges. Making the edges could be a post- process growing edge facets on free edges of the garment. Also Superfly sadly does not support microfacet displacement.

Growing the edges would be doable but it would require garments are specially prepared for this, come with dedicated scripts, and users need to know what to do. The same script could move the vertices of the collision object a little inward to simulate the reaction of the skin to the pressure of the garment.

This however would require greater control and access than offered by the present script interface. Let's hope the updated Python implementation in Poser12 allows to do this sort of things.


  weiesnbach    ( ) ( posted at 2:24AM Thu, 24 September 2020 · edited on 2:34AM Thu, 24 September 2020 · @4400167

FVerbaas posted at 2:10AM Thu, 24 September 2020 - #4400150

What you are asking here presumes that what you see (the outside of the waistband) is positioned such that the inner side of the waistband connects to the skin. Unless in some way the material that fills the waistband is defined, that is not possible. There is no way you can expect a program to dream this up by itself.

Solution for this has been in the cloth room since the beginning with Poser 5. Shrink the waistband until it connects to the skin and make it constrained (or cheorographed if the garment is a conformer).

The point is to make it shrink to fit the skin, Blender does it, so it's possible.

What your suggesting(constrained) isn't the same and does not allow for natural movement. It just sits there glued on, but by shrinking it it can now move with the underlying mesh and if the hip moves up, the cloth can slide a bit vertically, like clothes naturally do. If it's it's constrained it sit in the exact same place and bends, rather than sliding to accommodate motion.

I generally shrink my models waist(chest, legs, etc., whatever is beneath the fabric) and then scale them back up in the first few frames(generally 3 or 5), and that accomplishes nearly the same thing, but after about 30 frames it loses the effect, because everything has equalized, but by having a continuous shrinking factor applied to the cloth that is constantly interacting with the boundary of the mesh(there's already collision detection happening all the time) it works more naturally, and also looks more natural. Again Blender does this, so it's not even close to being impossible.

...and the inner waist band does in fact connect directly to the skin, it was made in Blender, using their shrinking tool so that it sits exactly at 0.001m off of the skin at 10xs Poser scale in Blender, and is exactly 0.002m thick at 10xs Poser scale in Blender.

...as far as what fills the waist band is concerned, cloth self collision will take care of that, or better yet just give it some internal pressure, Bullet Physics already does that.


  weiesnbach    ( ) ( posted at 2:47AM Thu, 24 September 2020  · @4400168

FVerbaas posted at 2:42AM Thu, 24 September 2020 - #4400166

There could be a solution via displacement maps. Cloth simulation works on mid-plane. The vertices are located in the middle of the fabric. Displacement maps can bring the offset to simulate thickness. Then however you still do not have the edges. Making the edges could be a post- process growing edge facets on free edges of the garment. Also Superfly sadly does not support microfacet displacement.

Growing the edges would be doable but it would require garments are specially prepared for this, come with dedicated scripts, and users need to know what to do. The same script could move the vertices of the collision object a little inward to simulate the reaction of the skin to the pressure of the garment.

This however would require greater control and access than offered by the present script interface. Let's hope the updated Python implementation in Poser12 allows to do this sort of things.

I don't even use displacement maps anymore because there's no consistency between superfly and firefly on how they work, and both make sense, but they don't play well together at all. In Superfly you'll have to add so many subdivisions that it just becomes unworkable in any real sense, but in Firefly it assumes those subdivision levels no matter what the underlying mesh has, either way I'm not sure sure collision detection in Poser takes into account displacement(it might but I don't see it happening), and that's the whole point here, is to balance friction, collision, and shrinking to make the cloth fit more naturally, especially while animating.


  thoennes    ( ) ( posted at 12:22AM Sat, 31 October 2020  · @4402559

The cloth simulator does not have cloth elasticity. Wish it did. I've tried heaps of ways to get this using all sorts of hacks over the years. It's just not possible.

The points of a mesh can resist being pulled apart. It would seem the points have inertia (mass) but no internal energy to the mesh points. They're affected by external forces only.

The simulator is almost 20 years old, right?

Another thing I've wanted is thickness and edges. It's a 1 dimensional mesh. To truly get a good image, I simulate the cloth, export to Blender, sculpt (the new cloth sim sculpt is way cool), bring it back into Poser to finish fit-sculpt (for tight things, since Poser's morph tool for this sort of simple stuff has really gotten better). Finally, I export to Blender again, use an edge tool that gives me thickness and rounding at the edges, then back into poser.

I'd actually make more clothing for La Femme but the creation tools in Poser for something as complex as La Femme are crude and anemic.


  weiesnbach    ( ) ( posted at 6:05AM Sat, 31 October 2020  · @4402579

thoennes posted at 5:48AM Sat, 31 October 2020 - #4402559

The cloth simulator does not have cloth elasticity. Wish it did. I've tried heaps of ways to get this using all sorts of hacks over the years. It's just not possible.

The points of a mesh can resist being pulled apart. It would seem the points have inertia (mass) but no internal energy to the mesh points. They're affected by external forces only.

The simulator is almost 20 years old, right?

Another thing I've wanted is thickness and edges. It's a 1 dimensional mesh. To truly get a good image, I simulate the cloth, export to Blender, sculpt (the new cloth sim sculpt is way cool), bring it back into Poser to finish fit-sculpt (for tight things, since Poser's morph tool for this sort of simple stuff has really gotten better). Finally, I export to Blender again, use an edge tool that gives me thickness and rounding at the edges, then back into poser.

I'd actually make more clothing for La Femme but the creation tools in Poser for something as complex as La Femme are crude and anemic.

The best way I've found for posing(it won't work for animating, as I said above, it evens out too quickly), is to scale the underlying model down on the first frame, and then scale it back up while the pose is taking effect. If you have the scale hitting back to 100% at frame 5, and the pose taking effect at frame 15, it will look natural at frame 15, but by the time you hit frame 30 things look saggy....

...and I've been using double sided clothes for a while now, you just have to pay close attention to the thickness(too thick it won't hit soon enough, too thin, and it hits too soon--bad things happen) and turn on self collision, it would be nice to be able to set a distance for self-collision as well, or as I said above have internal pressure--again bullet physics does that but cloth physics does not....

...and yeah I feel you on the 20 year old applications. I've been having that thought a lot lately, and not just with Poser.


  thoennes    ( ) ( posted at 12:46AM Sun, 01 November 2020  · @4402639

weiesnbach posted at 4:39PM Sun, 01 November 2020 - #4402579

The best way I've found for posing(it won't work for animating, as I said above, it evens out too quickly), is to scale the underlying model down on the first frame, and then scale it back up while the pose is taking effect. If you have the scale hitting back to 100% at frame 5, and the pose taking effect at frame 15, it will look natural at frame 15, but by the time you hit frame 30 things look saggy....

...and I've been using double sided clothes for a while now, you just have to pay close attention to the thickness(too thick it won't hit soon enough, too thin, and it hits too soon--bad things happen) and turn on self collision, it would be nice to be able to set a distance for self-collision as well, or as I said above have internal pressure--again bullet physics does that but cloth physics does not....

I've tried double sided as well. For instance, a belt over top of cloth that constricts about the waist. The belt starts as larger scale then shrinks in during the sim. Reason being is I want the cloth to constrict towards the body, not away. To do that, I need the normal to be the other direction. Hmmm. I wonder if it would work with one face with the normals inward, then after the sim, flip the normals back out. Imma try it :)

...and yeah I feel you on the 20 year old applications. I've been having that thought a lot lately, and not just with Poser.


  FVerbaas    ( ) ( posted at 1:26AM Sun, 01 November 2020  · @4402641

When applying scale to tighten clothing up do it subtly and gradually. Use the length of your simulation. The faster the growth, the more momentum is put into the garment and the more frames it takes to let that momentum die away. The 'shaggy' you see may well be the garment at a far end of the 'pendulum swing' the sudden energy burst pushed it in. The garment is a mass&spring system. Morphs act more local than scales, and therfore produce less momentum.

The cloth room is pretty good at solving poke-thru. If you want for example to let a shirt strain over breasts, you can use a start setting with the breast points poking thru slightly.


  FVerbaas    ( ) ( posted at 2:26AM Sun, 01 November 2020  · @4402643

This poke-thru will usually be solved while draping.


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