Houdini 20.0 Nodes Geometry nodes

Vellum Attach Constraints geometry node

Edit or create new vellum “attach to geometry” and “stitch” constraints, interactively.

The Vellum Attach Constraints allows you to edit existing or create entirely new “Attach to Geometry” and “Stitch” constraints for Vellum. It allows you to interactively draw connection lines between a point on the cloth mesh and a point or a surface position on the target mesh you want to be attach to or stitch.

To...Do this

Edit connection line

LMB drag the constraint points.

Create a new connection line

⇧ Shift + LMB drag.

Delete a connection

⌃ Ctrl + LMB click the connection.

Switch between edit and transform handle

Press 1.

Toggle enable highlighted constraint on/off

Press 2.

Toggle highlighted constraint target type

Press 3.

Toggle new constraint target type

Press 4.



Subset of the input geometry to consider when creating new connection lines or editing connection line anchor points or when importing constraints.

Shaded Color

The color for the shaded geometry.

Wire Color

The color the wireframe geometry.

New Constraints

These settings apply to newly created constraints.

Target Group

The geometry group for new constraints.

Target Path

The path to the geometry new “attach to geometry” constraints will point to. When left empty, it will use the collision geometry.

Target Type

The default target type for newly created constraints.

Point to Point

Point to Point attach to geometry constraints.

Point to Surface

Point to Surface attach to geometry constraints.


Stitch constraints.

Constraint Geometry

Edit Group

Subset of the constraint geometry to consider when importing existing constraints to edit.

Import Constraints

Recreates connection lines for existing constraints, allowing you to edit their target type and anchor positions.


The number of connection lines representing constraints to be created or edited.


The connection line’s anchor position on the input mesh.


The connection line’s anchor position on the target mesh (or input mesh for stitch constraints).

Target Type

The connection line’s target type.

Injested Prim

The constraint primitive number the connection line represents for imported constraints. Defaults to -1 for new constraints.

Target Path

The path to the geometry “attach to geometry” constraint points to.

Constraint Attributes

Attribute Group

Subset of the imported constraints to apply attributes to.

Sliding Rate

For Attach to Geometry and Stitch Points constraints, the attachment point of the constraint will slide across the target surface at this rate, where 1 matches the constrained point’s velocity. This option only works to slide across primitives, so the constraint’s Target Type must be set to Point to Surface or Stitch. The method used for finding the next closest sliding target can be set with the Vellum Solver’s Sliding Method parameter.

Sliding Attribute

A point attribute that scales the Sliding Rate when set to Scale by Attribute. This attribute will be applied according to the attribute Promotion Method, and will be stored on the constraint to be applied during the simulation. In this way the attachment point can slide across a painted surface, where the painted attribute value controls the Sliding Rate.


The stiffness of the constraint, which controls how strongly the constraint pulls particles back towards its initial rest state. To dial in initial values, change by factors of 10.

Stiffness Attribute

Point attribute to scale the stiffness by.

As effective changes in stiffness requires painting over orders of magnitude, this has a logarithmic effect.


Single slider control over the stiffness.

As effective changes in stiffness requires painting over orders of magnitude, this has a logarithmic effect.

Damping Ratio

Stiff constraints tend to vibrate or jitter unacceptably. Damping reduces this by bleeding energy when evaluating the constraint. Too much damping can prevent the constraint from being satisfied, however. Values less than 1 must be used.

Damping Attribute

Attribute to adjust damping, multiplied into the damping ratio.


Single slider to control damping, multiplied into the damping ratio.

Preserve Rest Length

Imported constraints' restlength attribute will not be updated to their new length.

Rest Length Scale

The rest length of the distance constraints will be the original distance between the points. This scale can be used to increase or decrease this. Setting to 0 will try to collapse the points together.

Compression Stiffness

The stiffness of the constraint when being compressed below its initial rest distance. A very stiff low resolution cloth can become unbendable due to its topology, rather than due to the bend constraints. A network of triangles has very few ways that it can bend if it is fully stiff. By setting a lower compression stiffness, the cloth is allowed to collapse and regain its fluidity. Usually this has to be raised with higher resolution cloth.

Tangent Stiffness

The stiffness of the constraint in the direction tangent to the target surface for Attach to Geometry constraints. Tangent stiffness can be useful to help hold up pants or a belt that are attached to a body at the waist, for example.


Setting this parameter to a non-zero value creates an additional constraint from the Vellum point to the line that intersects the closest point on the target surface. This constraint uses the same Breaking, Plasticity, and Scaling settings as the primary Stretch constraint.

Stiffness Dropoff

The distance from the rest length at which the stiffness of the constraint decreases to zero, or increases from zero to full stiffness, depending on the direction of the dropoff. A Decreasing dropoff means that the stiffness starts at full strength and decreases to zero at the Dropoff distance from the rest length. An Increasing dropoff means the stiffness starts at zero and increases to full stiffness at the specified distance from rest length. If Min Stiffness is enabled, its value is used as the minimum stiffness in these calculations, rather than zero.

Decreasing dropoff can be useful for creating glue constraints that lose stiffness as they are stretched, decreasing to zero at the specified distance. Using the same distance in the breaking Threshold with a Break Type of Stretch Distance will cause the constraints to be removed at the same time they reduce to zero stiffness.

Velocity Blend

Constraints that attach to geometry or pin to the target can optionally blend in the target’s velocity. This requires the target to have a v point attribute to provide the local velocity. The blending is done per 24th of a second, so a blend factor of 0.5 will mix in 50% of the target velocity in a standard frame.

Blending in velocity will highly damp the simulation, but can be useful to allow the cloth to anticipate motion, avoiding whiplashing from sudden movements. Zero stiffness attachment constraints can be used to apply only velocity blending without any additional forces.


Enable Plasticity

Plasticity allows an object to flow to a new rest position. Under sufficient stress, the rest coordinates are blended to the current dynamic coordinates, so the object will retain its new shape.


Below this threshold the material will return to its original shape. When deformed past the threshold, it will begin to creep into its new configuration.

Threshold Attribute

Attribute to scale the stretch threshold by.


Single scale slider for the threshold.

Ratio of Current Rest Length

The threshold can either be an absolute distance, or be a percentage distance. A value of 0.1 as a ratio would mean stretching of 110% of compression of 90% will trigger plastic flow.


The speed at which the material adopts its new rest lengths when it begins to flow.

Rate Attribute

Attribute to scale the plastic rate by.


Single scale slider for the plastic rate.


Some plastic materials become stiffer after they've undergone deformation. These will have a hardening greater than 1. Some become softer so will have hardening less than 1. This is a logarithmic multiplier on stiffness.

Hardening Attribute

Attribute to scale the plastic hardening by.


Single scale slider for plastic hardening.


Enable Breaking

Constraint primitives can be removed by the solver when sufficient deformation or stress is applied, effectively breaking those constraints. You can also manually break constraints by deleting them during the solve to gain full control of the timing.

Running the simulation first with visualization enabled can be useful to find what are good values for the thresholds.


The amount of stress or displacement on a constraint to trigger a break.

Threshold Attribute

Point attribute to scale the threshold by.


Single slider to scale the threshold.


This controls how the solver decides to break weld and hair constraints.


No automated tests are performed.

Stretch Stress

The stretch stress must exceed the threshold.

Bend Stress

The bend stress must exceed the threshold.

Stretch Distance

The total distance from the goal location and the current location must exceed the threshold.

Stretch Ratio

The ratio between the current distance and the rest distance must exceed the threshold.

Bend Angle

The difference between the current angle and the rest angle must exceed the threshold. This value is specified in degrees.


Promotion Method

The scale-by-attribute functions have to apply the possible different scale attribute values on the points involved in the constraint to a single constraint. This controls how they are blended together.


The maximum scale factor is used.


The minimum scale factor is used.


The average of the points scale factors is used.


The scale factors are all multiplied together.

Use Source

The source points scale factor is used, such as in a stitch constraint.

Use Target

The target points scale factor is used, such as in a stitch constraint.


A string stored in the constraint_tag primitive attribute for all constraints created by this node. This tag can be used in the Constraint Group parameter on the Vellum Constraint Property SOP to easily to alter specific constraints.

See also

Geometry nodes