Cloth setup

Setting up a cloth actor involves 2 steps:

Creating the the cloth actor itself.
Generating and assigning a cloth blueprint to the actor.

Remember that cloth actors don't do anything by themselves, they need a cloth definition asset (aka blueprint) to simulate. If you're looking for a real-world analogy, you can think of actors as CD players and blueprints as CDs.

Creating a cloth actor

There are 3 different cloth flavors in Obi, each one designed for a specific purpose:

Obi Cloth:: Regular cloth. Cannot be torn, cannot be used with animated meshes. This is the most efficient of the 3.
Obi Tearable cloth:: Can be torn, cannot be used with animated meshes. This tearing capability has an associated memory and runtime cost.
Obi Skinned cloth:: Designed to be used with skeletally animated meshes for character cloth, cannot be torn.

To create a new cloth actor, go to GameObject→3D Object→Obi→Obi Cloth/Obi Tearable Cloth/Obi Skinned Cloth. This will create a new GameObject in your scene and endow it with a cloth actor component and a matching cloth renderer component of the flavor you selected.

If you have an ObiSolver component selected when you create the cloth actor from the menu, the actor will automatically be added as a child of it. If there's no ObiSolver component selected but there's one present in the scene , the actor will automatically be added as a child of it. If case there is no properly setup ObiSolver component in your scene, one will automatically be created and the actor will be added as its child object.

Inspector of a newly created ObiCloth object.

If you've got an existing object that you want to turn into a cloth, you can add the required components from the Component→Physics→Obi menu, or the AddComponent button in the inspector. This is specially useful when setting up cloth for an existing SkinnedMeshRenderer.

Creating a cloth blueprint

To create a cloth blueprint, go to Assets→Create→Obi→Cloth blueprint/Tearable cloth blueprint/Skinned cloth blueprint, or right-click on a project folder and select Create→Obi→Cloth blueprint/Tearable cloth blueprint/Skinned cloth blueprint.

A cloth blueprint takes a mesh as input, and generates a physical representation of it made out of particles and constraints. First the mesh is decimated by collapsing small edges, then one particle is created at each vertex's position, and one distance constraint created at each edge to link particles together. This is how the blueprint inspector looks like:

Input Mesh

Mesh used for particle / cluster generation. Any mesh will work, including non-manifold meshes and polygon soups.

Meshes must be readable, so make sure the Read/Write enabled checkbox is marked in the mesh import settings. See Unity's manual for more info.

Scale

Scale applied to your mesh before using it to generate blueprint data.

Rotation

Rotation applied to your mesh before using it to generate blueprint data.

Vertex weld distance

Vertices that are closer than this distance will be merged together, regardless of connectivity (edges). This is useful to generate single-layered cloth out of double-sided meshes.

Even if you don't want to simplify your input mesh or generate one-sided cloth from a two-sided mesh, using a non-zero, small vertex weld distance (like 0.0001) is useful. This fuses duplicated vertices together and fixes small gaps/fissures in the mesh.

Bear rug of varying thickness, used as input mesh.

Minimum particle size

The mesh will be decimated by collapsing edges until all particles are at a distance larger than this value. This process preserves vertex connectivity, which is useful when you want to simplify a mesh without bridging gaps in between vertices.

Once you've selected an input mesh and adjusted parameters to your liking, you can press the Generate button in the blueprint inspector. This will trigger the generation proccess - can take quite a while for large meshes - during which the following steps take place automatically:

All vertices in the mesh closer than the specified vertex weld distance are fused together.
The resulting mesh is decimated up to the specified minimum particle distance.
Once the mesh has been decimated, one particle per vertex and one distance constraint per edge are generated.
The resulting particle/distance constraint network is analyzed to generate bending, volume, and aerodynamic constraints.
All constraints are sorted and grouped into batches for efficient runtime evaluation.

Once generation is completed, the Edit button will become active. By pressing it you will enter the cloth blueprint editor, which allows you to further edit the particle and constraint data stored in the blueprint.

Feeding the blueprint to the actor

Once you've got a blueprint ready, all you need to do is assign it to the actor's blueprint property. If everything is setup properly, upon pressing "Play" you'll see your cloth being simulated.

Note that if your object's MeshFilter/SkinnedMeshRenderer components don't have any mesh assigned, they will be assigned the blueprint's input mesh at runtime.

Advanced: binding arbitrary meshes to a cloth actor

By default, the blueprint's input mesh is bound to the resulting cloth particles and used to render the cloth. However, you can use completely different meshes to generate the cloth blueprint and render the cloth, and it's even possible to have multiple different meshes bound to / deformed by the same cloth actor. This effectively decouples the physical representation of the cloth from its graphical representation. For information on how to set this up, see cloth rendering.