Cloth panel

Cloth Simulation

Cloth simulation tries to simulate the look and behaviour of fabric. For example a flag in the wind. Or a shirt.

Cloth simulation requires a mesh object. It can be closed or open. Beware of the backside of faces then. And for closed meshes you better use soft bodies.

Once you add a cloth to a mesh a modifier gets created in the modifier properties tab. Here you can add other modifiers that may interact with the cloth simulation, like an SDS modifier. And order them in the proper way. It makes a difference if the SDS modifier is added before or after the cloth modifier.

And you can apply the cloth modifier, which freezes the simulation at the current frame. But the cloth settings are just accessible from the physics tab.

Workflow

Add a cube.

Add a grid plane. Move it up and scale it a bit bigger. So that it is above the cube.

Add a collision physics to the cube. It is then set as a collider for the cloth simulation.

Add a cloth physics to the grid plane.

Add a subdivision surface modifier to the grid plane, and set it to simple.

Now play the simulation. Playing it creates the simulation frames. Don't jump to frames. This will skip frames for the simulation.

The cloth will fall down now, collide with the cube, and deform like a fabric.

Adjust the cloth settings to your needs.

Pinning

Enter edit mode with the grid mesh. Grab one or more vertices. Add them to a vertex group. Don't forget to press Assign ...

In the Shape subpanel, choose the vertex group int the Pin Group.

Switch to object mode. Play the animation again. You will notice that the two vertices in the vertex group are now pinned. And don't move down anymore.

For a character you could now weight the pinned vertices to a bone. And the pinned vertices would move with the bone then.

Cloth Panel

Presets

Cloth presets.

To add your own preset type in a name and click at the plus button behind the edit box. To remove a preset click at the minus button behind the preset.

Physical Properties subpanel

The physical settings for the cloth.

Bending Model

Some settings are just available in angular bending model. Some just in linear bending model.

Stiffness sub subpanel

Damping sub subpanel

Internal Springs sub subpanel

Cloth physics are simulated through Springs connecting vertices on the surface of a mesh. But these springs only interact on the surface and only apply to 2D surfaces. 3D or Internal Springs can be used to make a mesh behave similarly to a Soft Body. Internal springs can be enabled by toggling the checkbox in the Internal Springs panel header.

You need to use the bending model Angular.

Pressure sub subpanel

Cloth pressure allows the simulation of soft-shelled objects such as balloons or balls that are filled with some sort of fluid. Cloth pressure can be enabled by toggling the checkbox in the Pressure panel header.

Cache subpanel

The cloth simulation can be cached in memory or stored on a drive. This improves real-time response and avoids unnecessary recalculation of particles. But creates also big files.

The cloth system uses a unified system for caching and baking (together with Soft Body and Emitter particle).

Hints

The simulation is only calculated for positive frames in between the Start and End frames of the Cache panel, whether you bake or not. So if you want a simulation that is longer than the default frame range, you have to change the End frame.

When an animation is played, each physics system writes each frame to the cache. Note that for the cache to fill up, one has to start the playback before or on the frame that the simulation starts.

The cache is cleared automatically on changes. But not on all changes, so it may be necessary to free it manually. For example if you change a force field.

The system is protected against changes after baking. If for example the mesh changes the simulation is not calculated anew.

The bake result can be cleared by clicking on the Free Bake button in the simulation cache settings.

A simulation can only be edited in Particle Edit Mode when it has been baked in memory. And cannot be edited if the Disk Cache is used.

If you are not allowed to write to the required sub directory caching will not happen. For example if your blend-file path is very long and your operating system has a limit on the path length that is supported.

Be careful with the sequence of modifiers in the modifier stack. You may have a different number of faces in the 3D Viewport and for rendering (For example when using subdivision surface). Then the rendered result may be very different from what you see in the 3D Viewport.

Caches List

The list of available caches. The caches have no name by default. Double click to add a name.

You can store and manage multiple caches at once for the same physics object. The active cache is the one that gets used.

Disk Cache

Save the cache externally in a folder instead inside of the blend file. The cache of a baked simulation will be stored inside the blend-file when you save it. A folder named blendcache_[filename] will then be created alongside the blend-file. The blend-file must be saved first and then again.

Use Library Path

Share the disk cache when the physics object is linked into another blend-file.

When this option is enabled, linked versions of the object will reference the same disk cache. Otherwise linked versions of the object will use independent caches.

Compression

The compression level for cached files.

Bake / Delete Bake

Start baking. Once you have baked the cache the button turns into a Delete bake button. And allows you to remove the bake.

The baking progress can be seen in the footer. You need to be in Object Mode to bake.

Shape subpanel

Pin Group

Vertex group to use for pinning.

The shape of the cloth can be controlled by pinning cloth to a Vertex Group. There are several ways of doing this including Weight Painting areas you want to pin. The weight of each vertex in the group controls how strongly it is pinned.

Stiffness

Target position stiffness.

Sewing

Another method of restraining cloth similar to pinning is sewing springs. Sewing springs are virtual springs that pull vertices in one part of a cloth mesh toward vertices in another part of the cloth mesh. This is different from pinning which binds vertices of the cloth mesh in place or to another object. A clasp on a cloak could be created with a sewing spring. The spring could pull two corners of a cloak about a character’s neck. This could result in a more realistic simulation than pinning the cloak to the character’s neck since the cloak would be free to slide about the character’s neck and shoulders.

Sewing springs are created by adding extra edges to a cloth mesh that are not included in any faces. They should connect vertices in the mesh that should be pulled together. For example the corners of a cloak.

Sewing Force Max

Maximum force that can be applied by sewing springs. Zero means unbounded, but it is not recommended to leave the field at zero in most cases, as it can cause instability due to extreme forces in the initial frames where the ends of the sewing springs are far apart.

Shrinking Factor

Factor by which to shrink the cloth, specifying a negative value controls the amount for the cloth to grow.

Dynamic Mesh

Allows animating the rest shape of cloth using shape keys or modifiers (e.g. an Armature modifier or any deformation modifier) placed above the Cloth modifier. When it is enabled, the rest shape is recalculated every frame, allowing unpinned cloth to squash and stretch following the character with the help of shape keys or modifiers, but otherwise move freely under control of the physics simulation.

Normally cloth uses the state of the object in the first frame to compute the natural rest shape of the cloth, and keeps that constant throughout the simulation. This is reasonable for fully realistic scenes, but does not quite work for clothing on cartoon style characters that use a lot of squash and stretch.

Collisions subpanel

In most cases, a piece of cloth collides with other objects in the environment. To ensure proper simulation, there are several items that have to be set up and working together.

• The Cloth object must be told to participate in collisions.
• Optionally (but recommended) tell the cloth to collide with itself.
• Other objects must be visible to the Cloth object via shared layers.
• The other objects must be mesh objects.
• The other objects may move or be themselves deformed by other objects (like an armature or shape key).
• The other mesh objects must be told to deflect the cloth object.
• The blend-file must be saved in a directory so that simulation results can be saved.
• You then Bake the simulation. The simulator computes the shape of the cloth for a frame range.
• You can then edit the simulation results, or make adjustments to the cloth mesh, at specific frames.
• You can make adjustments to the environment or deforming objects, and then re-run the cloth simulation from the current frame forward.

Troubleshooting

If you encounter some problems with collision detection, there are a few ways to fix them:

The fastest solution is to increase the Distance for Object/Self Collisions. This will be the fastest way to fix the clipping; however, it will be less accurate and will not look as good. Using this method tends to make it look like the cloth is resting on air, and gives it a very rounded look.

A second method is to increase the Quality (in the Cloth panel). This results in smaller steps for the simulator and therefore to a higher probability that fast-moving collisions get caught. You can also increase the Collisions Quality to perform more iterations to get collisions solved.

If none of the methods help, you can easily edit the cached/baked result in Edit Mode afterwards.

If the Cloth is torn by the deforming mesh; increase the stiffness settings.

Quality

A general quality setting. Higher numbers take more time but ensure less tears and penetrations through the cloth.

Object Collisions sub subpanel

If the cloth object needs to be deflected by some other object. To deflect a cloth, the object must be enabled as an object that collides with the cloth object. To enable objects to collide with cloth objects enable collision physics for the collider object (not on the cloth object).

Self-Collisions sub subpanel

Real cloth cannot penetrate itself, so you normally want the cloth to self-collide. Enable this to tell the cloth object that it should not penetrate itself. This adds to the simulation’s compute time, but provides more realistic results.

Property Weights subpanel

This panel is used to constrain certain cloth properties to a certain vertex group. The properties that they control can be found in a combination of the Physical Properties and Shape panels.

Field Weights subpanel

Cloth simulation is also influenced by external force effectors. This panel allows you to adjust these forces.