Obi Official Forum - Obi Cloth

Artifacts on simulated cloth but not original mesh (something to do with normals)

Thu, 30 Apr 2026 06:54:38 +0200

Hi,

We have a system that procedurally generates cloth garments, then generates blueprints and simulates them on a virtual mannequin. One issue we’ve noticed with one of our garments is strange, dark artifacting on the bust and one of the thighs, that isn’t present on the regular mesh but appears once simulation starts. The artifacting shifts and changes when the garment is dragged (using ObiParticlePicker), which suggests it has something to do with the cloth particles’ positions and normals. The dark spots must be the shader's lighting rendering those section as in shadow.

Pictures (I can't show too much because of NDAs)
The first two are the problem areas, the second two are the same areas with ObiSkinnedClothRenderer disabled: (so rendering the unsimulated mesh using SkinnedMeshRenderer).

My theory was that the particles might be too constrained and forced to bunch up in unnatural ways, but I tried increasing the skin radius and that didn’t help (it just made the rest of the garment fall away too much). I'm not sure what else could be doing it that's specifically because of the cloth simulation. If it was because of the normals not being calculated properly, I imagine the artifacts would appear even without simulation. Any idea of what could be doing this? I tried searching but wasn't sure how to articulate the question.

Additional details:

Obi Cloth 7.0.3, in Unity 2022.3.62f3
The material’s shader uses custom code to calculate the texture, but the lighting data is default for Unity’s URP so that shouldn't be causing any weird lighting behaviour. The artifacts also occur when using the completely standard URP Lit shader, and don't appear when rendering with a shader that doesn't have any lighting code.
I also made a slight modification to ObiSkinnedClothBlueprint.CommitBlueprintChanges(). It ran the base function followed by an override that’s basically identical except for one different value (CreateDefaultSkinmap's 'mapBonesToParticles' bool being true instead of false), resulting in severe lag spikes when generating complex garment shapes. I modified the ObiClothBlueprint’s base function to replace the one boolean with a reference to a property that’s overridden in ObiSkinnedClothBlueprint, and deleted the override. This seems to perform the same functions with considerably better performance, but could this change be affecting the normals in some way?

Thanks!

How did they do with with Obi Cloth?

Thu, 05 Mar 2026 15:26:03 +0100

I'd like to put together something similar, can you give me a high level explanation on how they achieved this please:
https://www.youtube.com/watch?v=mpKB8z-lT8k

Thanks.

Procedurally applying different skin constraints to different particles

Wed, 18 Feb 2026 10:29:22 +0100

I have a function that alters skin constraints on a procedurally generated cloth mesh at runtime. The code currently applies the same constraints to the entire cloth, but I’ve realised I need to be able to separate them. Some parts need to be quite tight to prevent creases and crinkles, but tightening everything up prevents other parts of the cloth from moving freely, so it barely looks simulated at all.

I’m looking at the code in ObiSkinnedClothBlueprint for creating constraints, and it’s my understanding that the number of active constraints lines up with the number of clusters in the cloth mesh topology. So I would use each cluster’s vertices to calculate data about the surrounding mesh, and use that to calculate the mesh values.

Is this correct? My code isn’t giving the results I want, but before I redo my own functions to try and fix it, I want to make sure I’m actually applying the values in a way that’s intended. The Obi Cloth code is complicated stuff, and my solution feels suspiciously easy.

Thanks!

Code:
public delegate float CalculateClusterData(ObiMesh.Cluster cluster);

public void ApplySkinConstraints(ObiSkinnedClothBlueprint blueprint, CalculateClusterData getSkinRadiusMultiplier = null, CalculateClusterData getBackStopSphereRadiusMultiplier = null, CalculateClusterData getBackstopSphereDistanceMultiplier = null)

{

    ObiSkinConstraintsBatch clothSkinConstraintsBatch = blueprint.skinConstraintsData.batches[0];

    for (int i = 0; i < clothSkinConstraintsBatch.activeConstraintCount; i++)

    {

        float skinRadius = this.skinRadius;

        float backstopSphereRadius = this.backstopSphereRadius;

        float backstopSphereDistance = this.backstopSphereDistance;

        ObiMesh.Cluster cluster = blueprint.topology.clusters[i];

        if (getSkinRadiusMultiplier != null) skinRadius *= getSkinRadiusMultiplier.Invoke(cluster);

        if (getBackStopSphereRadiusMultiplier != null) backstopSphereRadius *= getBackStopSphereRadiusMultiplier.Invoke(cluster);

        if (getBackstopSphereDistanceMultiplier != null) backstopSphereDistance *= getBackstopSphereDistanceMultiplier.Invoke(cluster);

        clothSkinConstraintsBatch.skinRadiiBackstop[i * 3] = skinRadius;

        clothSkinConstraintsBatch.skinRadiiBackstop[i * 3 + 1] = backstopSphereRadius;

        clothSkinConstraintsBatch.skinRadiiBackstop[i * 3 + 2] = backstopSphereDistance;

    }

}

Partially connect to Skinned Cloth Renderer

Fri, 30 Jan 2026 16:35:43 +0100

I have a particular problem that baffles me that I can't get around it. I'll try to explain it succinctly.

Working in Unity 6000.3.4f1 and Obi Cloth 7.1 in a game studio on a 3rd person AA game and the main character is wearing a long leather coat
The coat (green) is complicated, double sided, extra loops, buckles, belts, etc... so I need to use a proxy mesh (purple) that's bound to the high poly mesh
Tried simulating using a proxy for the entire coat and making the top static using skin constraints, but I wasn't able to make that part perfectly still, it was still bouncing and wobbling. Also I don't want to simulate stuff that doesn't need to move.
I'm currently simulating a proxy of just the bottom part (purple).
However when I bind the proxy of the lower coat to the entire high poly coat, the top of the coat gets pulled down to the origin because it doesn't have an influence while I want it to stay skinned to the skeleton. I tried tweaking the falloff and radius values without any luck.

Is there a way to connect only a part of a mesh to a proxy? If not, what would be the best way to deal with this?

Many thanks for any help you can offer!

(7.0.3) Updating skin constraints for noobs

Mon, 19 Jan 2026 02:26:01 +0100

I’m trying to get cloth garments on a character model to behave looser without entirely slipping off, and from my research I think modifying the skin constraints will be the best solution. I’m following the documentation (https://obi.virtualmethodstudio.com/manu...aints.html) and these look like exactly the right settings I need to alter, but I’m having trouble understanding how to change them, since there are no clearly exposed properties or functions.

I had a look at the documentation for scripting constraints (https://obi.virtualmethodstudio.com/manu...aints.html), but I haven’t really figured out how to access specific settings. From what I can tell, constraint batches are created only when a particle is created with different settings, and they’re grouped into batches at runtime to limit the number of different settings in memory. But I don’t really know how to add new ones. For now I only need one set of constraints for the entire cloth actor, and they don’t really need to change after being generated (although if they can that might help with debugging). The cloth shapes are being generated procedurally from procedural meshes, so it needs to all work through code.

I looked at the example in that documentation (which is conveniently already for setting the skin constraints), and tried copying it and turning it into a standalone function with parameters instead of hardcoded values. But I got null errors when trying to retrieve the batches, so there didn’t seem to be values there to edit. I realised that the example code uses an ObiSkinnedCloth, whereas our current system just uses regular ObiCloth components, so I switched the cloth, renderer and mesh renderer components to the right ones. But now I'm getting an out of range error when trying to get the index offset and access the correct batches.

I’m sure I’m going about this completely the wrong way. Maybe I’m running this code at the wrong point during the generation, or I’m meant to modify values in the blueprint rather than the cloth itself. Any help would be greatly appreciated.

Thanks!

Cloth backside collision with box

Wed, 17 Dec 2025 11:03:28 +0100

Hi, I have quite simple question - I have simple piece of cloth with surface collsions (actually does not matter, both modes give me the same result) and there is simple rigidbody box collider.
This collider slowly comes from the back of the cloth, and it should collide with it, but it does not. Is that expected result?

I want to note that in general those objects can collide with each other and it works, but currently the box need to pass nearly half of it's size to create reaction from back.
Also other actors are capable of collision from two sides, for example rod, so I assumed it's the case for all objects, but it's not.
Is it possible for cloth to collide with both sides?

cloth_rigidbody.png (Size: 50.65 KB / Downloads: 0)

Setting velocity to 0

Sat, 06 Dec 2025 21:37:51 +0100

Hello

I am trying to set the velocity of cloth particles to 0 so that there is no more movement with the following code:

Code:
ObiNativeVector4List velocities = actor.solver.velocities;

ObiNativeVector4List angularVelocities = actor.solver.angularVelocities;

ObiNativeVector4List forces = actor.solver.externalForces;

ObiNativeVector4List torques = actor.solver.externalTorques;

    for (int i = 0; i < actor.solverIndices.count; i++)

    {

        int solverIndex = actor.solverIndices[i];

        velocities[solverIndex] = Vector3.zero;

        angularVelocities[solverIndex] = Vector3.zero;

        forces[solverIndex] = Vector3.zero;

        torques[solverIndex] = Vector3.zero;

    }

actor.UpdateParticleProperties();

I execute this code once a certain action occurs in the game.
It works when damping is set to 0.5 but when I reduce the damping I see particles start to move again.
Can you point me in the right direction and verify if I am using the right code to do the job?

Thanks
Aroosh

Dynamic particle attachment question

Sat, 08 Nov 2025 19:25:19 +0100

Hi -- I've read through the manual and tried a number of things, but I'm encountering an issue with particle attachments that I'm hoping to get some insight on.

You can see in the video that the corner of the sail (this is a dynamic particle attachment to a rigidbody at the end of the rope) tends to jitter considerably.

I'd thought that this was a matter of solver settings, but have been unable to make any meaningful improvements -- even cranking iterations up to goofy amounts (20+).

Regarding settings, collision is off, both on a cloth blueprint/particle level, and for the obi rigidbodies involved. The mass of the attached rigidbody and the attaching particles are close (I've tried varying these as well. The only change is that if I increase the mass of the particles to be considerably higher than the attached rb, the issue reverses and the rigidbody starts flickering.)

Worth noting that the issue remains even if the attachment is set to static, and the attached rb is kinematic.

This issue is unchanged on CPU/GPU solving.
This issue is unchanged on RB Interpolation ON/OFF (For both the solver and hierarchy of rigidbodies).

I'm inclined to think that it's due to being a child of a rigidbody, but from my understanding that should be permissable. (Essentially the ship is a rigidbody, which is a parent to all other dynamic elements.)

Suggestions appreciated.

https://www.youtube.com/watch?v=ya3jV_JDYSU

Collision Rope / Cloth

Fri, 24 Oct 2025 15:10:50 +0200

Hey,

I want to collide ropes with cloths but can't figure out how.

My setup (one example):

I go in the Obi Cloth "Intercollisions" demo scene.
I add a Obi Rope to the Solver, the settings I leave at default.
I place the rope above the cloths.

I hit play, but the rope falls through the cloths.

Obi 7.1

Thanks!

Invalid Skinmap in Cloth Renderer

Fri, 24 Oct 2025 14:26:19 +0200

Hey,

I get this error message:
Invalid skinmap in cloth renderer (Obi Tearable Cloth). Make sure the skinmap is not null and suitable for the mesh and cloth blueprint being used.

I cannot use the tearable cloth, this error also occurs in the TearableCloth demo scene.

Unity 6.2 URP
Obi Cloth 7.1 (latest version)

Thanks!

Cloth has stretchy behaviour with stiff settings

Wed, 23 Jul 2025 15:39:06 +0200

Hello,

I'm trying to make a garment simulator in real time using ObiCloth. The clothes are behaving a bit oddly, i went through all the settings within the Obi Cloth component as a test hoping to make my garments stiff, and yet they stretch a lot during runtime, especially falling off the shoulders. I have also tried increasing iterations on each obi solver component, but the behaviour persisted.

Here is a swimsuit example:

Before hitting play

  default.png (Size: 70.72 KB / Downloads: 0)

During play mode

  slid off..png (Size: 55.89 KB / Downloads: 0)

Note: My colliders aren't yet perfect which is why the cloth comes a bit inside the avatar in some parts, please ignore this. In case this context matters, the avatar is divided into many colliders using distance fields, which are then assigned to each bone in order to "allow" for avatar animation. In addition, the colliders have a material collider assigned to them, with 1 dynamic friction and 0.95 static friction (this should make it so it barely slides).

ObiCloth settings:

  obiclothsettings.png (Size: 54.53 KB / Downloads: 1)

The Obisolver is essentially at default settings, i only changed the distance constraint to be Parallel and have 6 iterations to remove some jittering i was having, and I'm using CPU (Burst) to develop for a Web environment (The compute GPU mode uses too many buffers, there's a buffer limit in browsers).

My Cloth blueprint:

  cloth bp.png (Size: 150.93 KB / Downloads: 0)

Unless i understood the wiki incorrectly, the obicloth settings i have for that cloth should make it very stiff, and not allow for much stretching or deformation. Why is it then, that this swimsuit falls so much off the avatar's chest?

Thank you for your time!

Using a rigidbody/collider attached to cloth

Tue, 24 Jun 2025 10:23:16 +0200

In the SoccerGoal sample scene, I added a kinematic rigidbody and collider to the goal poles with a very bouncy physics material. When shooting a ball at the goal poles, the ball bounces very little. The expected bounciness is only seen if the goal poles are sufficiently far enough from the net cloth.

This 30s video demonstrates the behavior: https://youtu.be/CaCBXBeM1XQ

I assume that if the collision is within some radius of the cloth, the cloth physics are being applied instead of the goal_poles collider physics. Is that accurate? If so, is there a standard way of respecting the physics object's material (the bounciness of the soccer goal poles) while being attached to a cloth (the net)?

I'm new to Obi Cloth, so apologies if I missed something in the documentation. Thanks!

Can I blend in and out of simulation?

Fri, 20 Jun 2025 16:32:12 +0200

I have a cloth which is a skinned mesh renderer, and a looped animation, at the start of the animation I want the cloth to behave as a regular skinned mesh renderer without cloth simulation, at some point in the middle of the animation I want to enable the simulation, and at the end I want to slowly disable it and blend back to regular skinned mesh behaviour.
So essentially I want all particles to be pinned at the start and then unpinn them at some time. Ideally I would like to blend between these 2 states, but if blending is not supported then just switch between pinned and unpinned.

Obi 7 Model Scaling

Tue, 10 Jun 2025 16:01:24 +0200

Hello!

We have been doing some work to migrate from Obi 6 to Obi 7, and we really appreciate a lot of the changes you have made. We had to rewrite our character update, animation, and IK loop etc. but that has resulted in what I feel is a better result.

We have however run into a blocking issue.

We scale our characters by scaling the Position joint on our rig (screenshot of the rig attached).

On Obi 6 this works as it should, but on Obi 7 the scale appears to be ignored. I have attached two videos showing the issue. Are we missing something in the setup of the system?

Obi 6 Scaling:
https://drive.google.com/file/d/1mMd8Mx0...sp=sharing

Obi 7 Scaling:
https://drive.google.com/file/d/1FIU3lcM...sp=sharing

Once this issue is resolved we'll be really close to finally shipping with Obi 7, reauthing assets is taking some time.

Rig.png (Size: 45.25 KB / Downloads: 1)

ObiCloth going through collider

Wed, 14 May 2025 18:39:13 +0200

Hello, I've started to explore Obicloth a few months ago, and I'm really impressed with what it does, and the very handy wiki! I've run into a bit of a wall however.

I have a swimsuit model resting on a manequin, with an attached Obicloth component. When hitting play, I'd expect the swimsuit to hang onto the surface of the mesh collider, settling there, however it seems to collapse inside the collider, and falls off through the bottom.

  Screenshot 2025-05-14 165227.png (Size: 495.74 KB / Downloads: 4)

  Screenshot 2025-05-14 170138.png (Size: 225.16 KB / Downloads: 0)

  Screenshot 2025-05-14 170217.png (Size: 185.48 KB / Downloads: 0)

  Screenshot 2025-05-14 170312.png (Size: 170.11 KB / Downloads: 0)

I did some investigation, and first checked if my ObiCollider was working, so i set up a square plane as a cloth (made in blender to have more vertexes). It is working and colliding with the model as expected, however, when released from above the manequin, a few frames after colliding with the head, the head starts to poke through the cloth, and eventually the whole cloth passes through the manequin when it should be resting on top of it.

  Screenshot 2025-05-14 170920.png (Size: 121.82 KB / Downloads: 1)

Looking into the wiki, i have tried the following:

*Increase and reduce the number of particles (as well as try other bigger/smaller particle sizes) in the blueprint.
*Add more collision iterations and substeps to the ObiSolver (up to 16 for both, rip my pc)
*Enable surface collisions

Note: I'm aware of ObiSkinnedCloth, however i want a true simulation of cloth physics instead of following the mesh for my use case.

Any help would be greatly apreciated, thanks!