Controls the type used for the source points for the constraint.

The group for the source points of the constraint. These are the points or primitives that are turned into the constraint or are used as the starting half of the constraint.

Distance and bend constraints are usually built on a triangle mesh. Rather than forcing the input to be triangulated, it can be implicitly triangulated.

mass value for the points. The mass affects how they interact with POP forces and other pieces of Vellum geometry, and how strong the constraints are.

The volume used in calculating mass is scaled by this value when Mass is set to Calculate Uniform or Calculate Varying. This value can be further set to Scale By Attribute to scale by the specified point attribute in the varying case.

The Density parameter will be scaled by this point attribute.

Thickness of the points, stored in pscale. Used also for the triangle thickness and curve thickness.

Each edge length will be scaled by this value before being used in the Thickness calculation.

Pressure constraints split the object into disjoint pieces to compute and enforce the volume. Mass and Thickness calculations, and Glue and Strut constraints also need a way to define separate pieces.

Distinct values of this integer or string attribute will be used to define different pieces. This can either be a point or a primitive attribute.

The points will be given this as their layer attribute, useful in cloth simulations to define a stacking order for Layer Shock.

The type of group for the constraint targets.

The target group. This group specifies the second half of Attach to Geometry and Stitch constraints.

For Attach to Geometry constraints, the SOP attached to the third input will be read at solve time to get the current animation data. Specifying a path here will override that. This is useful if a different animation is desired at solve time than capture time.

Creates the dragnormal attribute and sets it to this value. This scales the drag of the point when wind forces are applied to it in the normal direction of its surface, or perpendicular to the curve.

Differing normal and tangent drag is essential for flapping flags.

Creates the dragtangent attribute and sets it to this value. This scales the drag of the point when wind forces are applied to it in the tangent direction of its surface, or tangent to the curve.

Points to pin to the target animation. Usually the target animation is the first input of the Vellum solver, but it can be overridden on the Vellum Solver SOP or with the Vellum Source DOP.

How to pin the point position to the target animation.

In addition to holding the location of a point, for hair the orientation often may also be constrained.

Controls if the target is updated from the animation during the solver or if only the initial value is used.

When finding a matching point to a source point, do not go through the target points in order, but pick the point that is closest first.

For Attach to Geometry and Stitch Points constraints, do not just choose the closest point, but the closest position on a primitive. The primitive number and barycentric coordinates are then stored. For Stitch Points constraints, only polylines, triangles, and quads are supported as the Target Geometry for constraint generation when this option is enabled.

Maximum distance to consider eligible for stitching points.

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 Use Closest Location on Primitive must be enabled and the Target Group Type must be set to Primitives. The method used for finding the next closest sliding target can be set with the Vellum Solver’s Sliding Method parameter.

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.

While glue constraints are made between points of different pieces, they will only be made between points of the same cluster. If the cluster value is -1, no gluing will be done.

Minimum distance to look for eligible glue points.

Maximum distance to look for eligible glue points.

Maximum number of points to consider for eligible glue points.

The order in which points should be considered for eligible glue points.

Number of glue constraints to create for each point.

Each piece has this chance to be marked ineligible for gluing and receive and generate no glue constraints. This allows for stray hairs.

Each pair of points has this chance to be being marked ineligible for gluing.

Random seed used to generate the detach chances.

Maximum distance to create struts. Must be large enough to cover the diameter of the object, but avoiding extremely long struts can help avoid artifacts.

Struts are created by sending a ray along the direction attribute in search of the piece. The default direction is to use the normal of the surface.

Invert the sense of the objects normals for sending rays, useful if the incoming geometry has reversed normals.

Verify the goal of the strut has a normal suggesting it was properly hit from the inside.

Jitter the direction the strut is sent in to break symmetry in the struts.

Maximum number of struts to add for each point.

Chance of a point being marked ineligible for struts.

Random seed to control the jitter and detach chances.

The initial ray for the strut needs an offset to avoid hitting the surface it was sent from.

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.

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.

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.

Attribute to adjust damping, multiplied into the damping ratio.

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

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.

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.

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.

If this checkbox is turned on, this value will be the minimum stiffness used when calculating the Stiffness Dropoff.

Enables an adjustment to the stiffness based on orientation, allowing a cloth network to stretch more on one axis than another.

Scale factor for cloth lined up with the material u axis. This is a logarithmic multiplier.

Scale factor for cloth lined up with the material v axis. This is a logarithmic multiplier.

Scale factor for cloth lined up with the diagonal material uv axis. This is a logarithmic multiplier.

Point attribute to use to specify the coordinate frame for warp and weft computations.

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.

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.

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.

Attribute to scale the stretch threshold by.

Single scale slider for the threshold.

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.

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.

Attribute to scale the plastic hardening by.

Single scale slider for plastic hardening.

The generated stretch constraints are all added to this primitive group. This is useful to edit them later with a Vellum Constraint Property DOP.

Ensures that a particular point can only be constrained once by the constraints in the Output Group. When dynamically creating constraints it can be common to re-create constraints between the same points every frame. Keeping the points unique within the output group prevents a constant accumulation of constraints.

When welding points together, two outside edges may become an inside edge. If they do not gain any bend constraints the seam will be weak and noticeably fold or kink. This option generates bend constraints where this is detected.

The value of the generated bend constraints can be copied from the bend of surrounding triangles, ensuring a consistent piece of cloth is built without having to channel link parameters.

The stiffness of bend constraints. To dial in initial values, change by factors of 10.

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.

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 should be used.

Attribute to adjust damping, multiplied into the damping ratio.

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

The rest angle of the bend constraints will be the original dihedral angle between the triangles. This scale can be used to increase or decrease this. Setting to 0 will treat the original configuration as a flat sheet.

The number of degrees away from the rest angle 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 degrees from the rest angle. An Increasing dropoff means the stiffness starts at zero and increases to full stiffness at the specified degrees away from rest angle. If Min Stiffness is enabled, its value is used as the minimum stiffness in these calculations, rather than zero.

A small amount of Increasing dropoff can be useful with cloth to make it buckle from a flat state very easily, adding additional wrinkling without changing the overall bend stiffness and look of the cloth too significantly. Decreasing dropoff can be useful for making stretchy glue constraints that weaken right before breaking without snapping back.

If enabled, the minimum stiffness value when calculating Stiffness Dropoff.

When adding torsion-free string bend constraints, they work best when the rest angle is close to straight. Setting the max branch angle allows something like a net of ropes to only have the bend constraints along the straight ropes, not on the perpendicular sections.

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.

This is an absolute angle measurement. Because rest angles are often flat, the idea of a ratio that exists for stretch constraints does not apply to bend constraints.

Attribute to scale the bend threshold by.

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

Attribute to scale the plastic rate by.

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.

Attribute to scale the plastic hardening by.

The generated stretch constraints are all added to this primitive group. This is useful to edit them later with a Vellum Constraint Property DOP.

Ensures that a particular point can only be constrained once by the constraints in the Output Group. When dynamically creating constraints it can be common to re-create constraints between the same points every frame. Keeping the points unique within the output group prevents a constant accumulation of constraints.

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.

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.

This controls how the solver decides to break distance constraints.

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.

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.