Blender Cloth Simulation: Pressure, Sewing and Pin Group Settings

What will you learn in this guide?

Blender’s cloth physics is not limited to creating a piece of fabric that falls to the ground. You can pin specific areas with vertex groups, pull sections together with sewing springs, create volumetric forms with internal springs, and shape soft-shell objects with pressure. This guide walks through what each setting does and how you might use it in architectural visualization examples such as curtains, drapes and soft decorative forms.

The settings described in the source documentation are covered under Blender’s cloth physics features. Since the documentation headings do not specify a particular Blender version, this guide does not promise compatibility with a specific version. The sources also provide no information about account, plugin or hardware requirements.

Requirements and initial settings

You need a mesh to work with cloth physics in Blender. The physics settings documentation gives the panel path as “Physics > Cloth,” while shape settings are described under “Physics > Cloth > Shape.” Because the sources do not describe setup steps, the full interface layout or recommended simulation resolution, this guide focuses only on the documented features.

When deciding how a piece of cloth should behave, first consider its material resistance, then how the object will be held or how its volume will be maintained. You can adjust its response to tension, compression, shear and bending separately. Changing one variable at a time and observing the result makes it easier to understand the effect of each setting.

1. Set the cloth’s basic behavior

In the Cloth settings, Vertex Mass and Air Viscosity define the mass of the cloth material and the effect of air slowing down falling objects, respectively. The Bending Model section has two options: Linear is the older model, which uses linear bending springs, while Angular uses angular bending springs.

Consider the values in the Stiffness section according to the type of resistance you want to control:

• Tension: Resistance to stretching.

• Compression: Resistance to compression.

• Shear: Resistance to shearing.

• Bending: The wrinkle coefficient; higher values create larger folds.

• Structural: General stiffness used only with the Linear bending model.

The corresponding settings in the Damping section control the damping of tension, compression, shear and bending. Structural damping is also available only with the Linear model. For a curtain, for example, examine its tension and bending properties separately first; avoid changing too many values at once, which can make it difficult to tell which setting affects the folds.

2. Choose where the cloth is held

Pin Group in the Shape section uses a vertex group to pin the cloth. The group’s weights determine how strongly each point is held in place. The source also gives Weight Painting as an example of how to assign these weights.

If you want to attach a curtain along its top edge or keep a particular part of a drape fixed, add the points that should stay in place to the group and evaluate the effect of their weights. Pinning holds cloth points in place or attaches them to another object. For that reason, avoid pinning areas that are expected to move freely during the simulation to the same degree.

3. Use sewing springs where edges should come together

Sewing is a different constraint method from pinning. Sewing springs pull points in one section of a cloth mesh toward points in another section; they do not have to hold the points at a fixed position. The official documentation gives the example of bringing the corners of a cloak together with a clasp that holds it around the neck. This approach can allow the cloth to slide around the neck and shoulders.

Sewing springs are created using extra edges that are not part of the surface. Connect the corners that should be pulled together with these edges. The Max Sewing Force value limits the maximum force the springs can apply. If the value is zero, there is no upper force limit. When the endpoints are far apart at the start of the simulation, sudden pulls can occur, so setting an appropriate force limit is a safer starting point for stability. Shrinking Factor controls how much the cloth shrinks; a negative value controls how much it grows.

4. Consider internal springs and pressure for volumetric objects

Surface springs interact only with points on the mesh surface and apply to 2D surfaces. Internal Springs can be used to create more volumetric, soft-body-like behavior. After enabling this feature, values such as Max Spring Creation Length and Max Creation Diversion limit which points internal springs can be created between. Setting the length limit to zero removes the length restriction. Check Surface Normals requires the connected points to have opposing normal directions.

For internal springs, Tension and Compression define resistance to stretching and compression. Vertex Group can control the areas where internal springs are applied or the spring force. Max Tension and Max Compression are the upper limits for the corresponding stiffness values.

Pressure can be used for soft-shell objects such as balloons or balls. Once the pressure panel is enabled, Pressure sets the continuous pressure applied to the mesh; negative values can represent inward pressure, or implosion-like behavior. When Custom Volume is enabled, the starting volume is defined by Target Volume instead of being calculated from the mesh. If Target Volume is zero, changes to the object’s volume do not affect the pressure.

Pressure Scale is the ambient pressure scale that determines the balance between internal and external pressure at the target volume. Increasing this value raises resistance to changes in volume. Fluid Density creates a hydrostatic pressure gradient based on the density of the fluid inside, but the fluid itself is not simulated. This setting therefore does not provide realistic fluid dynamics. If the mesh has holes, pressure can escape, potentially producing drag or lift forces. The source documentation suggests using a Vertex Group to exclude these areas from the relevant effects as a possible solution.

What does this offer in an architectural visualization workflow?

Pin groups can be useful to visualization artists who want to control the top of a curtain, a corner of a drape or another area of fabric that should stay fixed. Sewing springs provide an option for designs where two sections need to come together rather than be pinned in place. Internal springs and pressure can be considered for soft-shell decorative forms or volumetric cloth-like objects.

The sources do not provide information about specific hardware, licensing costs or compatibility with other software. If you plan to use these features in a real project, check that the settings are available in your target Blender version, that the simulation works with the other elements in your scene, and that the licensing terms fit your production workflow. Pay particular attention to openings in meshes when using pressure.

Common mistakes and next steps

• Pinning every point: Pin Group weights determine the strength of the pinning. Strongly pinning areas that need to move freely can restrict the expected motion.

• Using unlimited force with sewing springs: A Max Sewing Force of zero means there is no limit. If points start far apart, sudden pulls can cause instability.

• Overlooking holes in a pressurized mesh: Pressure can escape through holes in non-manifold meshes. Consider using a Vertex Group to restrict the areas where pressure is applied.

• Mistaking Fluid Density for a fluid simulation: This feature helps create a hydrostatic pressure gradient; it does not simulate fluid motion.

• Changing several settings at once: To understand cloth behavior, change one group of settings and compare the result first; then evaluate the others in sequence.

As a next step, try pinning and sewing springs separately on the same cloth mesh. If you need a volumetric form, explore internal springs; if you want soft-shell behavior, look at the pressure settings. If maintaining volume is important, check the relationship between Pressure Scale and Target Volume. If you see pressure leaks, inspect openings in the mesh and the scope of the Vertex Group.

Sources and license

This guide is adapted into Turkish from the “Physical Properties” and “Shape” pages in Blender’s official manual. Both sources are licensed under CC BY-SA 4.0.