Cloth Sculpting improvements in Blender 2.91

Collisions

The Sculpt Cloth Solver in 2.91 features initial support for collisions, both in the brush and in the Cloth Filter. The simulated cloth collides with objects which have a collision modifier, just like the regular cloth modifier.

The cloth solver collisions in 2.91 are raycast based. This means that they can collide with any type of geometry (even non-manifold) and vertices will be stopped by the surface of the collider. Which translates to a new level of precision. 

As a disadvantage, if a vertex from the cloth is inside the collider, the solver won’t be able to move it outside. The plan is to implement SDF (Signed Distance Fields) collisions as a way of solving this issue. This should make it possible to choose between more precision or more stability.

Self collisions are also planned. At the moment, they can’t be implemented efficiently for technical reasons. For those who are interested, the issue is the leaf node size of the PBVH. Reducing the leaf node size is also planned as part of Blender’s sculpt optimization project. After this is complete, self collisions should not be hard to implement. 

Soft Body Plasticity

The Cloth Brush now supports plasticity, which controls how much the object tries to preserve its previous shape. This means that when the solver deforms the mesh, it tries to preserve the deformed shape during the simulation. This help to make some brushes more controllable and predictable, as well as allowing the simulation of different materials. 

Support for plasticity collisions is also planned after SDF (Signed Distance Field) collisions are implemented.

Cloth Deformation Target

In 2.91, the Boundary and Pose brush can also be used for cloth simulation by setting the Deformation Target to Cloth Simulation.

The deformation these brushes produce allows the creation of common cloth effects, like curtains or sleeves folds…without relying on collisions.

In the future, all brushes in Sculpt Mode will support the cloth deformation target, so it will be possible to run the cloth solver on top of any brush deformation. 

Dynamic Simulation Area

In the first versions of the Cloth Brush, the cloth simulation was constrained by the initial area of the stroke. The alternative would have been to run a full cloth simulation on high poly meshes, which puts huge pressure on a machine’s performance.

In 2.91, the dynamic simulation area initializes and activates the constraints and the simulation as the brush moves. As the stroke is drawn, more constraints are created and added to the solver, but the simulation only runs using the constraints that are closer to the brush tip. So you can use the brush continuously without interruption, which means you can focus on the creative process.  

Thanks to the fade areas defined by the simulation falloff, the brush can blend the simulated and not simulated mesh seamlessly. 

Other improvements

The cloth brush and filter also include other improvements:

• The cloth brush can now define a persistent base. This means that the same initial cloth shape can be simulated multiple times with different strokes. So you can start and stop whenever you need.
• The cloth brush can apply global gravity and simulate the entire mesh during the stroke. In other words, the cloth effect is applied consistently throughout the scene.

• There is a new “pin simulation boundary” which allows creating better anchored stroke cloth brushes.
• The cloth filter now supports custom orientation and has a new Scale mode.
• There is a new Snake Hook deformation mode, which moves the cloth without creating artefacts in the simulation.

You can help the project by testing the new tools and hunting for bugs. If you find any please report it from within Blender, simply go to the menu Help → Report a Bug, or watch this video about the process.

Daily builds are available as always on blender.org/experimental.

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