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] > >> <https://mmacklin.com/sdfcontact.pdf> > >> > >> 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 > _______________________________________________ Bf-committers mailing list Bf-committers@blender.org https://lists.blender.org/mailman/listinfo/bf-committers
