Parameter Setting

Introduction

In order to achieve ideal movement, parameter adjustment is indispensable.
Here, we will explain the concept of baseline, which is deeply related to parameters, and the role of each parameter.

Understand the baseline

The concept of baselines is essential to understand when setting parameters.
The baseline is the path starting at the fixed vertex of the proxy mesh and following the surface connection to the moving vertex at the end.

For example, let’s say you have a hierarchy of Transforms like this.

If you create a BoneCloth starting from the [Fixed] bone of this structure, the baseline will be assigned as follows.

This line can be confirmed by checking [Base Line] in the gizmo.

MagicaCloth restores the shape along this baseline.
As a result, we have achieved a 2.5D-like behavior that combines 2D-like movements while retaining physically realistic movements.

start/end and depth

A baseline contains start and end points, as well as depth information.
You can check this by turning on [Base Line] and [Depth] in the gizmo settings.
Let’s take the Transform structure from earlier as an example.
The white numbers represent the depth, and the starting point is (0.0) and the ending point is (1.0), so you can check which depth each vertex corresponds to.
This depth value is an essential index for parameter setting.

Depth is automatically assigned so that (1.0) is the end of the longest baseline in the proxy mesh.

Baseline with Bone Cloth

In BoneCloth, baselines are simply constructed from a tree structure of Transforms.
So it’s the same as the Transform hierarchy.

Baseline with Mesh Cloth

MeshCloth is a little more complicated, and the baseline is automatically calculated according to the connection of the surface around fixed vertices.
For example, with KAGURA’s skirt, the baseline is automatically formed as follows.

Keep in mind that the MeshCloth’s baseline will change in various ways depending on the connection state of the surface and the distribution of fixed vertices.

Relationship between depth and parameters

As mentioned above, when the baseline is created a depth is set for each vertex.
The depth of this vertex is an important index when adjusting parameters.
MagicaCloth has many parameters that determine values based on this depth.

As an example, let’s look at the Angle Limit movement that limits the angle.
Angle Limit limits the angle at which the edges of the baseline can bend.
The settings panel for this Angle Limit looks like this:

Currently, the curve setting is turned off, so a uniform 60 degrees is set regardless of the depth.
Let’s press [C] on the right here.

Then the inspector will expand and you will be able to set the curve.
This operation allows you to set different limit angles for each vertex depth.
Let’s take a look at the contents of the set curve.

The horizontal axis is the depth (0.0 to 1.0) and the vertical axis is the strength of the parameter (0.0 to 1.0).

When the depth is 0.0, the strength is 0.2, so the limit angle is 60 x 0.2 = 12 degrees.
At depth (0.5) the strength is 0.6, so the limit angle is 60 x 0.6 = 36 degrees.
At depth (1.0) the strength is 1.0, so the limit angle is 60 x 1.0 = 60 degrees.

Combine this with the BoneCloth depth diagram from earlier.
The vertex depth (0.0~1.0) corresponds directly to the horizontal axis of the curve.
I hope you can understand how the limiting angle each vertex receives is determined.

In this way, the curve parameter has a mechanism in which the final value is calculated in conjunction with the depth.
This is the relationship between depth and parameters.
Remember that this applies to all parameters with a [C] button.

Parameter type

Here, we will introduce what kind of parameters actually exist by type.
If you explain each function of each parameter in detail, the amount of pages will be enormous, so here we will focus on the overview of the parameters and the guideline for setting.
Please refer to the separate reference for the details of the parameters.

Force

Controls forces such as gravity and air resistance (Damping).
Adding some gravity will make the movement more realistic.
If you lower the air resistance, the vertices will not come to rest easily.
Conversely, if you increase the air resistance, the top will move slowly.

Gravity Falloff reduces the effect of gravity depending on the orientation of the cloth.
For example, if Falloff is 1.0, if the cloth is at the same angle as the initial posture, no gravity will be applied.

Angle Restoration

Rotate each edge of the baseline back to its original position.
This Angle Restoration is the most important parameter for controlling movement.
It is no exaggeration to say that the majority of movement is determined here.

Stiffness is the amount of rotation angle corrected in one pass.
Increasing Stiffness speeds up restoration.

Velocity Attenuation is the amount of velocity attenuation applied to vertices during restoration.
If you lower it, the acceleration will be stronger and it will bounce like a spring.

Adjusting these two properties requires a certain amount of familiarity and experience.
A good place to start is to load a preset and try to imitate it.

Angle Limit

Limits the angle each edge of the baseline can bend from its original pose.
It is effective when you do not want to bend too much like bangs.
It is also a good idea to limit the angle of skirts to a certain extent in order to maintain their shape.

Shape Restoration

It does three movements to maintain the shape of the proxy mesh.

 Distance Stretchability of the mesh.Moves to keep the distance between each vertex and the connected vertex constant.Normally 1.0 is fine. However, if it looks better if the outside is stretched a little like a skirt that rotates, it is also effective to use a curve to weaken the restoring force near the end point. Tether Limits how close a vertex can be to the start of its baseline.Only the shrink range can be set.If Compression is lowered, vertices will not be able to get close to their starting point.Conversely, if you raise it, the vertex will be able to move freely. Lowering the value makes it harder to deform the shape of the mesh.This can avoid the phenomenon that the cloth shrinks excessively.However, in some cases, the movement may be awkward because the degree of freedom of movement is reduced.Generally, it is recommended to set it to 0.8 or higher and reduce it in a limited manner. Triangle Bending The resistance of the mesh to bending.It works to return adjacent triangles to their original angles.This plays an important role in keeping the shape of the mesh.1.0 is usually fine.Do nothing if no triangles exist in the proxy mesh.
Inertia

Determines how cloth movement affects vertices.
This is the second most important parameter after Angle Restoration in determining movement.

A cloth always has one center point.
This is automatically determined from the distribution of fixed attributes and is displayed as a gizmo in the scene view as a purple sphere.

When this center moves, its translational and rotational forces are transmitted to the vertices.
It is the inertia parameter that limits the movement force.

For example, if the shaking is too large for the movement of the character, you can add restrictions to suppress the overall shaking.
There are four types of restrictions, each with its own characteristics:

 Movement InertiaRotation Inertia Reduces the movement force or rotation force itself.For example, if the property is 0.1, only 1/10th of the cloth movement will be added to the vertex.This makes it possible to suppress shaking even if the cloth moves at high speed. However, even if the cloth moves slowly, the movement force is reduced, so there is also the adverse effect that the shaking becomes extremely small. Depth Inertia Reduce inertia with vertex depth.Simply put, if you increase this property, the closer the depth is to the starting point, the harder it will be to move.The endpoint is not subject to reduction. This is effective when you don’t want the area around the starting point to move too much, such as with skirts or hair.However, please note that if the inertia near the starting point is reduced, the overall movement will be weaker. Movement Speed LimitRotation Speed Limit Cuts the movement force or rotation force at the set speed.For example, if Movement Speed Limit=2.0, if the character is within 2m/s movement speed, the force will be transmitted as is, and if it exceeds 2m/s, no further force will be applied to the vertices, no matter how fast they move.With this limit, you can limit the shaking to a certain extent whether you move slowly or at high speed. Basically, we recommend using this over Movement Inertia / Rotation Inertia. Particle Speed Limit Limits the maximum velocity per vertex.This can alleviate the phenomenon that the tip of a long belt-like object bulges outward excessively due to centrifugal force. However, if you lower the value below 1.0 (1m/s), the accuracy of collision detection will decrease, so be careful when lowering the value.
Movement Limit

Restricts vertex movement relative to the vertex normal direction of the proxy mesh.
This is also called a backstop.

See the diagram above for how it works.
Simply put, vertices can only move within the MaxDistance range and outside the BackstopCollision.

For example, let’s say you have a T-shirt with all vertex normals pointing outwards from the human body.
Here, we use the backstop function to restrict the vertex from entering beyond a certain distance in the opposite direction of the normal.
This prevents the T-shirt from digging into the human body without using a collision collider.
Using the same principle, it is also possible to easily prevent bangs from digging into the inside of the head.

The important thing is that it is calculated at the proxy mesh vertex normals.
Remember that the vertex normals of the render mesh are irrelevant.
Also, the vertex positions and normals that are the basis for the constraints are obtained from the pose of the skinned proxy mesh before the simulation.
And the proxy mesh normals can also be adjusted.

Backstop explanation is a little long, so please refer to the backstop explanation page for more details.

Collider Collision

This is the most frequently used collision control that uses colliders such as spheres and capsules to restrict the cloth from entering the human body.
Collider collision detection is explained in detail in Collision detection settings, so please refer to that.

Self Collision

🚧beta version🚧

Here you can set self-collision to prevent cloth from digging into itself, and mutual collision to prevent cloth from digging into other cloths.

If you use self-collision, the cloth itself will collide like the image.
However, self-collision requires a large amount of collision calculations, so the load is very high.
Therefore, it is recommended to use it on a desktop PC or high-end console machine.

Also note that self-collision is currently an experimental feature, i.e. in beta.
Therefore, behavior and settings may change in the future.

Tuning tips

So far, I have explained the role of each parameter.
All you have to do is repeat trial and error to get closer to the ideal movement.
However, this work is very difficult, so I would like to post some adjustment tips.

Although the number of parameters is large, there are only a few items that actually determine the movement.

 Force gravity and air resistanceThis has a lot to do with vertex movement. Angle Restoration rotation reconstructionIt is the most important parameter that determines the overall movement.It is best to adjust from here first. Inertia Adjust here if the cloth moves too much when the character runs or jumps.

Parameters can also be adjusted from the inspector during runtime.
Making adjustments while actually playing the game makes trial and error easier.

Presets are shortcuts for setting parameters.
First, let’s load a preset and check if it’s close to the ideal movement.
If you have a preset that is close to the ideal movement, you can reduce the time by adjusting the parameters independently from there.

Saving presets

Parameters can be easily saved as original presets.

Saved presets can be easily set up from the Preset button.
By doing this, you can save a lot of work when setting up similar movements.
Saving presets is also available while running.

The trouble with adjustment is that the contents of the inspector adjusted during execution are all restored when execution ends.
Use the component copy feature to avoid this!
This is a function that allows you to copy the contents of the inspector by pressing the “︙” button of the component during execution.

If the parameter adjustment is successful during execution, copy the contents with this function.
And after the execution is finished, select Paste from the “︙” menu of the component as well.

With this operation, it is possible to restore the running parameter to the inspector after stopping.

What next?

So far, I have explained the basic setup of MagicaCloth.
By applying these, most cloths can be set up.
So unless you’re doing something too complicated, you don’t need to read any further guides.

However, there are some features we haven’t explored in detail yet, such as backstop and self-collision settings.
Continue reading other guides if you want to know more about them.