Re: [Bf-committers] It's time to get rid of cloth

[Brecht Van Lommel via Bf-committers]

To be clear, cloth simulaton does use an implicit solver, including ideas
from the Baraff paper like filtered CG.

For volumetric soft bodies, there was a summer of code project this year.
It uses an implicit solver. However it's not currently in a state that is
good enough to go into master.
https://wiki.blender.org/wiki/User:Mattoverby/GSoC2020/mattoverby_final_report


On Tue, Nov 3, 2020 at 2:19 AM bjornmose via Bf-committers <
bf-committers@blender.org> wrote:

> Well,
>
> my last contribution was ' old man grumbling'
>
> to be more constructive I'd like point to the issues to be focused on:
>
> We do have stiff PDEs ODEs to solve. We know very well, that common
> forward solvers perform very poor under 'stiff' conditions. David Baraff
> proposed using 'implicit backward solvers' some days (~ 10 * 356) ago.
> Even 'numerical recipes' knows stiff differential equations.
>
> How deal with it?
>
> 1. Implement solvers that can do .. expensive but possible in open source.
>
> 2. Think about volume energy constraints ( see 3. )
>
> 3. Think over the model .. a mesh is a mesh .. blender as grown from
> past knows 2D objects in 3D .. a skin of faces. Works very fine if is
> forward driven. But there is no reliable concept if we want to have
> vertex to vertex interaction deep inside. (Think of the cube having
> springs  from (1,1,1) to (-1,-1-1))   The fist thing on the task list
> IMHO should be to add 'edges' that is vertex to vertex connections that
> do not modify the surface but represent physical interaction.
>
>
>
> On 02.11.20 19:07, Brecht Van Lommel via Bf-committers wrote:
> > The paper shows how to make SDF collision more accurate by using the SDF
> > directly rather than sampling it. We have triangle mesh based collision
> in
> > Blender, which in a state-of-the-art implementation would avoid those
> > problems already.
> >
> > The point of switching to SDFs would be performance, at the cost of
> detail
> > loss compared to triangle mesh based methods.
> >
> > On Mon, Nov 2, 2020 at 5:38 PM Aaron Carlisle via Bf-committers <
> > bf-committers@blender.org> wrote:
> >
> >> Hi looking at this thread I wonder if anyone has looked into
> implementing
> >> SDF
> >> based collision detection in Blender. It seems to be quite a bit more
> >> stable
> >> than sample based detection. Here is a recent paper on the topic [1]
> >> 
> >>
> >> 1. https://mmacklin.com/sdfcontact.pdf <
> >> https://mmacklin.com/sdfcontact.pdf>
> >>
> >> On Wed, Oct 21, 2020, 21:56 bjornmose via Bf-committers <
> >> bf-committers@blender.org> wrote:
> >>
> >>> Might it be, that old experienced coders knowing physics and all the
> >>> other things about stiff differential equations turned their back to
> >>> blender development?
> >>>
> >>> May be because lack of time .. may be an ignored patch proposal .. for
> >>> those do not have the time at hand to provide elaborated solutions?
> >>>
> >>> Well ...
> >>>
> >>> bjornmose
> >>>
> >>>
> >>> On 20.10.20 20:35, Joe Eagar via Bf-committers wrote:
>  Brecht, you can avoid the worst numerical instability issues of CCD by
>  adding a small repulsion force when cloth is in close proximity with
>  geometry.  IIRC most commercial cloth sims do this.
> 
>  Ton, I'm sorry I blew up.  Cloth collision is something of a
>  special nightmare for me.
> 
>  Sergej, that's fair.
>  Sebastian, sounds like you're doing good work, just remember that
> >> robust
>  collisions are important :)
>  ___
>  Bf-committers mailing list
>  Bf-committers@blender.org
>  https://lists.blender.org/mailman/listinfo/bf-committers
> >>> ___
> >>> Bf-committers mailing list
> >>> Bf-committers@blender.org
> >>> https://lists.blender.org/mailman/listinfo/bf-committers
> >>>
> >> ___
> >> Bf-committers mailing list
> >> Bf-committers@blender.org
> >> https://lists.blender.org/mailman/listinfo/bf-committers
> >>
> > ___
> > Bf-committers mailing list
> > Bf-committers@blender.org
> > https://lists.blender.org/mailman/listinfo/bf-committers
> ___
> Bf-committers mailing list
> Bf-committers@blender.org
> https://lists.blender.org/mailman/listinfo/bf-committers
>
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Re: [Bf-committers] It's time to get rid of cloth

[bjornmose via Bf-committers]

Well,

my last contribution was ' old man grumbling'

to be more constructive I'd like point to the issues to be focused on:

We do have stiff PDEs ODEs to solve. We know very well, that common
forward solvers perform very poor under 'stiff' conditions. David Baraff
proposed using 'implicit backward solvers' some days (~ 10 * 356) ago.
Even 'numerical recipes' knows stiff differential equations.

How deal with it?

1. Implement solvers that can do .. expensive but possible in open source.

2. Think about volume energy constraints ( see 3. )

3. Think over the model .. a mesh is a mesh .. blender as grown from
past knows 2D objects in 3D .. a skin of faces. Works very fine if is
forward driven. But there is no reliable concept if we want to have
vertex to vertex interaction deep inside. (Think of the cube having
springs  from (1,1,1) to (-1,-1-1))   The fist thing on the task list
IMHO should be to add 'edges' that is vertex to vertex connections that
do not modify the surface but represent physical interaction.



On 02.11.20 19:07, Brecht Van Lommel via Bf-committers wrote:

The paper shows how to make SDF collision more accurate by using the SDF
directly rather than sampling it. We have triangle mesh based collision in
Blender, which in a state-of-the-art implementation would avoid those
problems already.

The point of switching to SDFs would be performance, at the cost of detail
loss compared to triangle mesh based methods.

On Mon, Nov 2, 2020 at 5:38 PM Aaron Carlisle via Bf-committers <
bf-committers@blender.org> wrote:


Hi looking at this thread I wonder if anyone has looked into implementing
SDF
based collision detection in Blender. It seems to be quite a bit more
stable
than sample based detection. Here is a recent paper on the topic [1]


1. https://mmacklin.com/sdfcontact.pdf <
https://mmacklin.com/sdfcontact.pdf>

On Wed, Oct 21, 2020, 21:56 bjornmose via Bf-committers <
bf-committers@blender.org> wrote:


Might it be, that old experienced coders knowing physics and all the
other things about stiff differential equations turned their back to
blender development?

May be because lack of time .. may be an ignored patch proposal .. for
those do not have the time at hand to provide elaborated solutions?

Well ...

bjornmose


On 20.10.20 20:35, Joe Eagar via Bf-committers wrote:

Brecht, you can avoid the worst numerical instability issues of CCD by
adding a small repulsion force when cloth is in close proximity with
geometry.  IIRC most commercial cloth sims do this.

Ton, I'm sorry I blew up.  Cloth collision is something of a
special nightmare for me.

Sergej, that's fair.
Sebastian, sounds like you're doing good work, just remember that

robust

collisions are important :)
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Re: [Bf-committers] It's time to get rid of cloth

[Brecht Van Lommel via Bf-committers]

The paper shows how to make SDF collision more accurate by using the SDF
directly rather than sampling it. We have triangle mesh based collision in
Blender, which in a state-of-the-art implementation would avoid those
problems already.

The point of switching to SDFs would be performance, at the cost of detail
loss compared to triangle mesh based methods.

On Mon, Nov 2, 2020 at 5:38 PM Aaron Carlisle via Bf-committers <
bf-committers@blender.org> wrote:

> Hi looking at this thread I wonder if anyone has looked into implementing
> SDF
> based collision detection in Blender. It seems to be quite a bit more
> stable
> than sample based detection. Here is a recent paper on the topic [1]
> 
>
> 1. https://mmacklin.com/sdfcontact.pdf <
> https://mmacklin.com/sdfcontact.pdf>
>
> On Wed, Oct 21, 2020, 21:56 bjornmose via Bf-committers <
> bf-committers@blender.org> wrote:
>
> > Might it be, that old experienced coders knowing physics and all the
> > other things about stiff differential equations turned their back to
> > blender development?
> >
> > May be because lack of time .. may be an ignored patch proposal .. for
> > those do not have the time at hand to provide elaborated solutions?
> >
> > Well ...
> >
> > bjornmose
> >
> >
> > On 20.10.20 20:35, Joe Eagar via Bf-committers wrote:
> > > Brecht, you can avoid the worst numerical instability issues of CCD by
> > > adding a small repulsion force when cloth is in close proximity with
> > > geometry.  IIRC most commercial cloth sims do this.
> > >
> > > Ton, I'm sorry I blew up.  Cloth collision is something of a
> > > special nightmare for me.
> > >
> > > Sergej, that's fair.
> > > Sebastian, sounds like you're doing good work, just remember that
> robust
> > > collisions are important :)
> > > ___
> > > Bf-committers mailing list
> > > Bf-committers@blender.org
> > > https://lists.blender.org/mailman/listinfo/bf-committers
> > ___
> > Bf-committers mailing list
> > Bf-committers@blender.org
> > https://lists.blender.org/mailman/listinfo/bf-committers
> >
> ___
> Bf-committers mailing list
> Bf-committers@blender.org
> https://lists.blender.org/mailman/listinfo/bf-committers
>
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Re: [Bf-committers] It's time to get rid of cloth

[Aaron Carlisle via Bf-committers]

Hi looking at this thread I wonder if anyone has looked into implementing
SDF
based collision detection in Blender. It seems to be quite a bit more stable
than sample based detection. Here is a recent paper on the topic [1]


1. https://mmacklin.com/sdfcontact.pdf 

On Wed, Oct 21, 2020, 21:56 bjornmose via Bf-committers <
bf-committers@blender.org> wrote:

> Might it be, that old experienced coders knowing physics and all the
> other things about stiff differential equations turned their back to
> blender development?
>
> May be because lack of time .. may be an ignored patch proposal .. for
> those do not have the time at hand to provide elaborated solutions?
>
> Well ...
>
> bjornmose
>
>
> On 20.10.20 20:35, Joe Eagar via Bf-committers wrote:
> > Brecht, you can avoid the worst numerical instability issues of CCD by
> > adding a small repulsion force when cloth is in close proximity with
> > geometry.  IIRC most commercial cloth sims do this.
> >
> > Ton, I'm sorry I blew up.  Cloth collision is something of a
> > special nightmare for me.
> >
> > Sergej, that's fair.
> > Sebastian, sounds like you're doing good work, just remember that robust
> > collisions are important :)
> > ___
> > Bf-committers mailing list
> > Bf-committers@blender.org
> > https://lists.blender.org/mailman/listinfo/bf-committers
> ___
> Bf-committers mailing list
> Bf-committers@blender.org
> https://lists.blender.org/mailman/listinfo/bf-committers
>
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Re: [Bf-committers] It's time to get rid of cloth

[bjornmose via Bf-committers]

Might it be, that old experienced coders knowing physics and all the
other things about stiff differential equations turned their back to
blender development?

May be because lack of time .. may be an ignored patch proposal .. for
those do not have the time at hand to provide elaborated solutions?

Well ...

bjornmose


On 20.10.20 20:35, Joe Eagar via Bf-committers wrote:

Brecht, you can avoid the worst numerical instability issues of CCD by
adding a small repulsion force when cloth is in close proximity with
geometry.  IIRC most commercial cloth sims do this.

Ton, I'm sorry I blew up.  Cloth collision is something of a
special nightmare for me.

Sergej, that's fair.
Sebastian, sounds like you're doing good work, just remember that robust
collisions are important :)
___
Bf-committers mailing list
Bf-committers@blender.org
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Re: [Bf-committers] It's time to get rid of cloth

[Joe Eagar via Bf-committers]

Brecht, you can avoid the worst numerical instability issues of CCD by
adding a small repulsion force when cloth is in close proximity with
geometry.  IIRC most commercial cloth sims do this.

Ton, I'm sorry I blew up.  Cloth collision is something of a
special nightmare for me.

Sergej, that's fair.
Sebastian, sounds like you're doing good work, just remember that robust
collisions are important :)
___
Bf-committers mailing list
Bf-committers@blender.org
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Re: [Bf-committers] It's time to get rid of cloth

[Daniel Seita via Bf-committers]

Hi all,

I haven't emailed on this email list before, but I'm happy to see
discussion about the cloth simulator in Blender. It is the main reason why
I started using Blender, and I know a fair amount of folks in my community
(AI and robotics researchers) who would love to explore cloth capabilities.

I have used (Py)Bullet recently, and have collaborated with the folks
working on cloth simulation as part of my Google internship. While they are
working on it (see https://github.com/bulletphysics/bullet3/pull/2872) from
my experience, for more physically realistic cloth, I honestly go with
Blender. The main reason why I have used (Py)Bullet has less to do with the
simulator quality and more to do with issues I ran into with vertex pinning
/ unpinning in Blender. For reference, I am the person who wrote this:
https://devtalk.blender.org/t/pinning-and-moving-vertices-of-cloth-at-arbitrary-frame-sequences-with-updated-physics/13542

Daniel


On Tue, Oct 20, 2020 at 8:24 AM darkdefende--- via Bf-committers <
bf-committers@blender.org> wrote:

> I see that my name isn't with my email address.
> So just so clarify, I'm Sebastian Parborg.
>
> On Tue, Oct 20, 2020 at 02:20:46PM +0200, darkdefe...@gmail.com wrote:
> > To fix the cloth tunneling though the cube, activate "Single sided" in
> > the cube's collision settings and it should work much better.
> >
> > Anyways, during my recent work with Bullet, I tested some things that
> > are currently not integrated into blender.
> >
> > Mainly Bullet softbodies and cloth.
> >
> > Both have their use cases, but as Brecht pointed out, the Bullet cloth
> > physics is way more unstable and doesn't have no where near as many
> > features as our current cloth sim. So outright replacing our current
> > system with that would just be a downgrade on so many levels (except
> > speed).
> >
> > I would say that all of our physics simulations currently needs a lot of
> > work to be faster, more stable, and nicer to use. The majority of them
> > feels half baked at the moment I my opinion. (And it shows as it seems a
> > lot of people does not use them in production because they are simply not
> > good enough yet)
> >
> > My current plan was to first make Bullet integration in Blender better.
> > As I deem this to be the easier task. However I have a lot of other work
> > I need to do, so progress is slow.
> > This is also because I want the Bullet refactor to align nicely with our
> > new node system. (So we don't have to do an other refactor for that)
> >
> > As Sergej pointed out, Mano Wii and I has been in talks on making the
> > collision system better for cloth and also make it have move options so
> > they user can make trade-offs if they want to.
> >
> > If you have any specific fixes or changes in mind. We would love to hear
> > them.
> >
> > Welcome back.
> >
> > On Tue, Oct 20, 2020 at 01:39:01PM +0200, Sergej Reich via Bf-committers
> wrote:
> > > Bullet's cloth system is no replacement for what Blender currently has
> and
> > > I'm not aware of any available library that we could use without
> having to
> > > do a lot of modifications to make it work.
> > >
> > > Am Di., 20. Okt. 2020 um 12:26 Uhr schrieb Brecht Van Lommel via
> > > Bf-committers :
> > >
> > > > The most important thing for cloth is that you can get it to give
> good
> > > > results in real world cases, and the cloth simulation changes were
> based on
> > > > work done for Agent 327.
> > > > https://www.youtube.com/watch?v=jU6-cI-z8HA
> > > >
> > > > In practice you use smaller time steps and the fast-moving cube will
> get
> > > > collided with anyway.
> > > >
> > > > Continuous collision detection is great for handling fast-moving
> objects,
> > > > but arguably handling cloth that is nearly at rest and continuously
> > > > colliding with the character is a much harder problem. Most cloth
> > > > simulation demo videos stop while everything is still in motion, but
> what
> > > > happens after is just as important.
> > > >
> > > > Anyway, there's definitely much room for improvement here, but it
> should be
> > > > tested on real-world cases. For example from what I've seen, Bullet
> cloth
> > > > is more reliable at high frame rates, but does not produce good
> results or
> > > > wrinkling details when turning up the quality. I've not yet seen an
> > > > open-source cloth library that we could just plug in and get much
> better
> > > > results, but it would be great if there was one.
> > > >
> > > > Some work on cloth collision is being done here:
> > > > https://developer.blender.org/D8577
> > > >
> > > > On Tue, Oct 20, 2020 at 11:52 AM Ton Roosendaal via Bf-committers <
> > > > bf-committers@blender.org> wrote:
> > > >
> > > > > Hi Joe,
> > > > >
> > > > > This is a bit harsh, there have been good cloth contributions to
> Blender
> > > > > by Luca Rood. The current module owner for it is Sebastian Parborg
> > > > though.
> > > > >
> > > > > I'd suggest to connect with them to see what steps forward c

Re: [Bf-committers] It's time to get rid of cloth

[darkdefende--- via Bf-committers]

I see that my name isn't with my email address.
So just so clarify, I'm Sebastian Parborg.

On Tue, Oct 20, 2020 at 02:20:46PM +0200, darkdefe...@gmail.com wrote:
> To fix the cloth tunneling though the cube, activate "Single sided" in
> the cube's collision settings and it should work much better.
> 
> Anyways, during my recent work with Bullet, I tested some things that
> are currently not integrated into blender.
> 
> Mainly Bullet softbodies and cloth.
> 
> Both have their use cases, but as Brecht pointed out, the Bullet cloth
> physics is way more unstable and doesn't have no where near as many
> features as our current cloth sim. So outright replacing our current
> system with that would just be a downgrade on so many levels (except
> speed).
> 
> I would say that all of our physics simulations currently needs a lot of
> work to be faster, more stable, and nicer to use. The majority of them
> feels half baked at the moment I my opinion. (And it shows as it seems a
> lot of people does not use them in production because they are simply not
> good enough yet)
> 
> My current plan was to first make Bullet integration in Blender better.
> As I deem this to be the easier task. However I have a lot of other work
> I need to do, so progress is slow.
> This is also because I want the Bullet refactor to align nicely with our
> new node system. (So we don't have to do an other refactor for that)
> 
> As Sergej pointed out, Mano Wii and I has been in talks on making the
> collision system better for cloth and also make it have move options so
> they user can make trade-offs if they want to.
> 
> If you have any specific fixes or changes in mind. We would love to hear
> them.
> 
> Welcome back.
> 
> On Tue, Oct 20, 2020 at 01:39:01PM +0200, Sergej Reich via Bf-committers 
> wrote:
> > Bullet's cloth system is no replacement for what Blender currently has and
> > I'm not aware of any available library that we could use without having to
> > do a lot of modifications to make it work.
> > 
> > Am Di., 20. Okt. 2020 um 12:26 Uhr schrieb Brecht Van Lommel via
> > Bf-committers :
> > 
> > > The most important thing for cloth is that you can get it to give good
> > > results in real world cases, and the cloth simulation changes were based 
> > > on
> > > work done for Agent 327.
> > > https://www.youtube.com/watch?v=jU6-cI-z8HA
> > >
> > > In practice you use smaller time steps and the fast-moving cube will get
> > > collided with anyway.
> > >
> > > Continuous collision detection is great for handling fast-moving objects,
> > > but arguably handling cloth that is nearly at rest and continuously
> > > colliding with the character is a much harder problem. Most cloth
> > > simulation demo videos stop while everything is still in motion, but what
> > > happens after is just as important.
> > >
> > > Anyway, there's definitely much room for improvement here, but it should 
> > > be
> > > tested on real-world cases. For example from what I've seen, Bullet cloth
> > > is more reliable at high frame rates, but does not produce good results or
> > > wrinkling details when turning up the quality. I've not yet seen an
> > > open-source cloth library that we could just plug in and get much better
> > > results, but it would be great if there was one.
> > >
> > > Some work on cloth collision is being done here:
> > > https://developer.blender.org/D8577
> > >
> > > On Tue, Oct 20, 2020 at 11:52 AM Ton Roosendaal via Bf-committers <
> > > bf-committers@blender.org> wrote:
> > >
> > > > Hi Joe,
> > > >
> > > > This is a bit harsh, there have been good cloth contributions to Blender
> > > > by Luca Rood. The current module owner for it is Sebastian Parborg
> > > though.
> > > >
> > > > I'd suggest to connect with them to see what steps forward could be.
> > > >
> > > > We are also in the process of making a good node physics system to allow
> > > > solvers like this in a more generic setting. Design for this is ongoing.
> > > >
> > > > It's super cool to see you want to come back, just give it a bit of time
> > > > to figure out who's doing what now.
> > > >
> > > > Als note that we (including Blender Foundation / Institute) are in the
> > > > process of organizing ourselves much better, including onboarding, best
> > > > practices, engineering standards amd strict requirements for a good
> > > > design process - including the docs.
> > > >
> > > > We lack in a lot of areas, and the consensus is to especially put
> > > > efforts in bringing the current state of the code in control (functional
> > > > and technical specs), before recoding modules entirely.
> > > >
> > > > -Ton-
> > > > --
> > > > Ton Roosendaal - t...@blender.org - www.blender.org
> > > > Chairman Blender Foundation, Director Blender Institute
> > > > Buikslotermeerplein 161, 1025 ET Amsterdam, the Netherlands
> > > >
> > > >
> > > > On 20/10/2020 00:30, Joe Eagar via Bf-committers wrote:
> > > > > So

Re: [Bf-committers] It's time to get rid of cloth

[darkdefende--- via Bf-committers]

To fix the cloth tunneling though the cube, activate "Single sided" in
the cube's collision settings and it should work much better.

Anyways, during my recent work with Bullet, I tested some things that
are currently not integrated into blender.

Mainly Bullet softbodies and cloth.

Both have their use cases, but as Brecht pointed out, the Bullet cloth
physics is way more unstable and doesn't have no where near as many
features as our current cloth sim. So outright replacing our current
system with that would just be a downgrade on so many levels (except
speed).

I would say that all of our physics simulations currently needs a lot of
work to be faster, more stable, and nicer to use. The majority of them
feels half baked at the moment I my opinion. (And it shows as it seems a
lot of people does not use them in production because they are simply not
good enough yet)

My current plan was to first make Bullet integration in Blender better.
As I deem this to be the easier task. However I have a lot of other work
I need to do, so progress is slow.
This is also because I want the Bullet refactor to align nicely with our
new node system. (So we don't have to do an other refactor for that)

As Sergej pointed out, Mano Wii and I has been in talks on making the
collision system better for cloth and also make it have move options so
they user can make trade-offs if they want to.

If you have any specific fixes or changes in mind. We would love to hear
them.

Welcome back.

On Tue, Oct 20, 2020 at 01:39:01PM +0200, Sergej Reich via Bf-committers wrote:
> Bullet's cloth system is no replacement for what Blender currently has and
> I'm not aware of any available library that we could use without having to
> do a lot of modifications to make it work.
> 
> Am Di., 20. Okt. 2020 um 12:26 Uhr schrieb Brecht Van Lommel via
> Bf-committers :
> 
> > The most important thing for cloth is that you can get it to give good
> > results in real world cases, and the cloth simulation changes were based on
> > work done for Agent 327.
> > https://www.youtube.com/watch?v=jU6-cI-z8HA
> >
> > In practice you use smaller time steps and the fast-moving cube will get
> > collided with anyway.
> >
> > Continuous collision detection is great for handling fast-moving objects,
> > but arguably handling cloth that is nearly at rest and continuously
> > colliding with the character is a much harder problem. Most cloth
> > simulation demo videos stop while everything is still in motion, but what
> > happens after is just as important.
> >
> > Anyway, there's definitely much room for improvement here, but it should be
> > tested on real-world cases. For example from what I've seen, Bullet cloth
> > is more reliable at high frame rates, but does not produce good results or
> > wrinkling details when turning up the quality. I've not yet seen an
> > open-source cloth library that we could just plug in and get much better
> > results, but it would be great if there was one.
> >
> > Some work on cloth collision is being done here:
> > https://developer.blender.org/D8577
> >
> > On Tue, Oct 20, 2020 at 11:52 AM Ton Roosendaal via Bf-committers <
> > bf-committers@blender.org> wrote:
> >
> > > Hi Joe,
> > >
> > > This is a bit harsh, there have been good cloth contributions to Blender
> > > by Luca Rood. The current module owner for it is Sebastian Parborg
> > though.
> > >
> > > I'd suggest to connect with them to see what steps forward could be.
> > >
> > > We are also in the process of making a good node physics system to allow
> > > solvers like this in a more generic setting. Design for this is ongoing.
> > >
> > > It's super cool to see you want to come back, just give it a bit of time
> > > to figure out who's doing what now.
> > >
> > > Als note that we (including Blender Foundation / Institute) are in the
> > > process of organizing ourselves much better, including onboarding, best
> > > practices, engineering standards amd strict requirements for a good
> > > design process - including the docs.
> > >
> > > We lack in a lot of areas, and the consensus is to especially put
> > > efforts in bringing the current state of the code in control (functional
> > > and technical specs), before recoding modules entirely.
> > >
> > > -Ton-
> > > --
> > > Ton Roosendaal - t...@blender.org - www.blender.org
> > > Chairman Blender Foundation, Director Blender Institute
> > > Buikslotermeerplein 161, 1025 ET Amsterdam, the Netherlands
> > >
> > >
> > > On 20/10/2020 00:30, Joe Eagar via Bf-committers wrote:
> > > > So, ten years ago I wrote several continuous collision detection
> > systems
> > > > for cloth/hair, one of which I tried to push into trunk:
> > > >
> > > > https://www.youtube.com/watch?v=QBM3TBKO9w8
> > > >
> > > > And, here's how the cloth sim performs today:
> > > >
> > > > https://www.youtube.com/watch?v=5462m9yEkU8&feature=youtu.be
> > > >
> > > > If the cloth development proc

Re: [Bf-committers] It's time to get rid of cloth

[Sergej Reich via Bf-committers]

Bullet's cloth system is no replacement for what Blender currently has and
I'm not aware of any available library that we could use without having to
do a lot of modifications to make it work.

Am Di., 20. Okt. 2020 um 12:26 Uhr schrieb Brecht Van Lommel via
Bf-committers :

> The most important thing for cloth is that you can get it to give good
> results in real world cases, and the cloth simulation changes were based on
> work done for Agent 327.
> https://www.youtube.com/watch?v=jU6-cI-z8HA
>
> In practice you use smaller time steps and the fast-moving cube will get
> collided with anyway.
>
> Continuous collision detection is great for handling fast-moving objects,
> but arguably handling cloth that is nearly at rest and continuously
> colliding with the character is a much harder problem. Most cloth
> simulation demo videos stop while everything is still in motion, but what
> happens after is just as important.
>
> Anyway, there's definitely much room for improvement here, but it should be
> tested on real-world cases. For example from what I've seen, Bullet cloth
> is more reliable at high frame rates, but does not produce good results or
> wrinkling details when turning up the quality. I've not yet seen an
> open-source cloth library that we could just plug in and get much better
> results, but it would be great if there was one.
>
> Some work on cloth collision is being done here:
> https://developer.blender.org/D8577
>
> On Tue, Oct 20, 2020 at 11:52 AM Ton Roosendaal via Bf-committers <
> bf-committers@blender.org> wrote:
>
> > Hi Joe,
> >
> > This is a bit harsh, there have been good cloth contributions to Blender
> > by Luca Rood. The current module owner for it is Sebastian Parborg
> though.
> >
> > I'd suggest to connect with them to see what steps forward could be.
> >
> > We are also in the process of making a good node physics system to allow
> > solvers like this in a more generic setting. Design for this is ongoing.
> >
> > It's super cool to see you want to come back, just give it a bit of time
> > to figure out who's doing what now.
> >
> > Als note that we (including Blender Foundation / Institute) are in the
> > process of organizing ourselves much better, including onboarding, best
> > practices, engineering standards amd strict requirements for a good
> > design process - including the docs.
> >
> > We lack in a lot of areas, and the consensus is to especially put
> > efforts in bringing the current state of the code in control (functional
> > and technical specs), before recoding modules entirely.
> >
> > -Ton-
> > --
> > Ton Roosendaal - t...@blender.org - www.blender.org
> > Chairman Blender Foundation, Director Blender Institute
> > Buikslotermeerplein 161, 1025 ET Amsterdam, the Netherlands
> >
> >
> > On 20/10/2020 00:30, Joe Eagar via Bf-committers wrote:
> > > So, ten years ago I wrote several continuous collision detection
> systems
> > > for cloth/hair, one of which I tried to push into trunk:
> > >
> > > https://www.youtube.com/watch?v=QBM3TBKO9w8
> > >
> > > And, here's how the cloth sim performs today:
> > >
> > > https://www.youtube.com/watch?v=5462m9yEkU8&feature=youtu.be
> > >
> > > If the cloth development process is this dysfunctional (this patch
> > actually
> > > passed review?
> > >
> https://developer.blender.org/rB0666ece2e2f96571200d693d9d7bee1ca72d026f
> > )
> > > then I propose we eliminate the cloth code entirely and go with a third
> > > party lib (Bullet?).
> > >
> > > Joe
> > > ___
> > > Bf-committers mailing list
> > > Bf-committers@blender.org
> > > https://lists.blender.org/mailman/listinfo/bf-committers
> > ___
> > Bf-committers mailing list
> > Bf-committers@blender.org
> > https://lists.blender.org/mailman/listinfo/bf-committers
> >
> ___
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> Bf-committers@blender.org
> https://lists.blender.org/mailman/listinfo/bf-committers
>
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Re: [Bf-committers] It's time to get rid of cloth

[Brecht Van Lommel via Bf-committers]

The most important thing for cloth is that you can get it to give good
results in real world cases, and the cloth simulation changes were based on
work done for Agent 327.
https://www.youtube.com/watch?v=jU6-cI-z8HA

In practice you use smaller time steps and the fast-moving cube will get
collided with anyway.

Continuous collision detection is great for handling fast-moving objects,
but arguably handling cloth that is nearly at rest and continuously
colliding with the character is a much harder problem. Most cloth
simulation demo videos stop while everything is still in motion, but what
happens after is just as important.

Anyway, there's definitely much room for improvement here, but it should be
tested on real-world cases. For example from what I've seen, Bullet cloth
is more reliable at high frame rates, but does not produce good results or
wrinkling details when turning up the quality. I've not yet seen an
open-source cloth library that we could just plug in and get much better
results, but it would be great if there was one.

Some work on cloth collision is being done here:
https://developer.blender.org/D8577

On Tue, Oct 20, 2020 at 11:52 AM Ton Roosendaal via Bf-committers <
bf-committers@blender.org> wrote:

> Hi Joe,
>
> This is a bit harsh, there have been good cloth contributions to Blender
> by Luca Rood. The current module owner for it is Sebastian Parborg though.
>
> I'd suggest to connect with them to see what steps forward could be.
>
> We are also in the process of making a good node physics system to allow
> solvers like this in a more generic setting. Design for this is ongoing.
>
> It's super cool to see you want to come back, just give it a bit of time
> to figure out who's doing what now.
>
> Als note that we (including Blender Foundation / Institute) are in the
> process of organizing ourselves much better, including onboarding, best
> practices, engineering standards amd strict requirements for a good
> design process - including the docs.
>
> We lack in a lot of areas, and the consensus is to especially put
> efforts in bringing the current state of the code in control (functional
> and technical specs), before recoding modules entirely.
>
> -Ton-
> --
> Ton Roosendaal - t...@blender.org - www.blender.org
> Chairman Blender Foundation, Director Blender Institute
> Buikslotermeerplein 161, 1025 ET Amsterdam, the Netherlands
>
>
> On 20/10/2020 00:30, Joe Eagar via Bf-committers wrote:
> > So, ten years ago I wrote several continuous collision detection systems
> > for cloth/hair, one of which I tried to push into trunk:
> >
> > https://www.youtube.com/watch?v=QBM3TBKO9w8
> >
> > And, here's how the cloth sim performs today:
> >
> > https://www.youtube.com/watch?v=5462m9yEkU8&feature=youtu.be
> >
> > If the cloth development process is this dysfunctional (this patch
> actually
> > passed review?
> > https://developer.blender.org/rB0666ece2e2f96571200d693d9d7bee1ca72d026f
> )
> > then I propose we eliminate the cloth code entirely and go with a third
> > party lib (Bullet?).
> >
> > Joe
> > ___
> > Bf-committers mailing list
> > Bf-committers@blender.org
> > https://lists.blender.org/mailman/listinfo/bf-committers
> ___
> Bf-committers mailing list
> Bf-committers@blender.org
> https://lists.blender.org/mailman/listinfo/bf-committers
>
___
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Re: [Bf-committers] It's time to get rid of cloth

[Ton Roosendaal via Bf-committers]

Hi Joe,

This is a bit harsh, there have been good cloth contributions to Blender 
by Luca Rood. The current module owner for it is Sebastian Parborg though.


I'd suggest to connect with them to see what steps forward could be.

We are also in the process of making a good node physics system to allow 
solvers like this in a more generic setting. Design for this is ongoing.


It's super cool to see you want to come back, just give it a bit of time 
to figure out who's doing what now.


Als note that we (including Blender Foundation / Institute) are in the 
process of organizing ourselves much better, including onboarding, best 
practices, engineering standards amd strict requirements for a good 
design process - including the docs.


We lack in a lot of areas, and the consensus is to especially put 
efforts in bringing the current state of the code in control (functional 
and technical specs), before recoding modules entirely.


-Ton-
--
Ton Roosendaal - t...@blender.org - www.blender.org
Chairman Blender Foundation, Director Blender Institute
Buikslotermeerplein 161, 1025 ET Amsterdam, the Netherlands


On 20/10/2020 00:30, Joe Eagar via Bf-committers wrote:

So, ten years ago I wrote several continuous collision detection systems
for cloth/hair, one of which I tried to push into trunk:

https://www.youtube.com/watch?v=QBM3TBKO9w8

And, here's how the cloth sim performs today:

https://www.youtube.com/watch?v=5462m9yEkU8&feature=youtu.be

If the cloth development process is this dysfunctional (this patch actually
passed review?
https://developer.blender.org/rB0666ece2e2f96571200d693d9d7bee1ca72d026f )
then I propose we eliminate the cloth code entirely and go with a third
party lib (Bullet?).

Joe
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[Bf-committers] It's time to get rid of cloth

[Joe Eagar via Bf-committers]

So, ten years ago I wrote several continuous collision detection systems
for cloth/hair, one of which I tried to push into trunk:

https://www.youtube.com/watch?v=QBM3TBKO9w8

And, here's how the cloth sim performs today:

https://www.youtube.com/watch?v=5462m9yEkU8&feature=youtu.be

If the cloth development process is this dysfunctional (this patch actually
passed review?
https://developer.blender.org/rB0666ece2e2f96571200d693d9d7bee1ca72d026f )
then I propose we eliminate the cloth code entirely and go with a third
party lib (Bullet?).

Joe
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