Houdini 18.0 Nodes Dynamics nodes

Vellum Object dynamics node

Creates a DOP Object for use with the Vellum Solver.

The Vellum Object DOP creates a Vellum Object inside a DOP simulation. It creates a new object and attaches the data which is needed for it to be used as a Vellum Object.

The result is ready for use by the Vellum Solver.

Parameters

Creation

Creation Frame Specifies Simulation Frame

Determines if the creation frame refers to global Houdini frames ($F) or to simulation specific frames ($SF). The latter is affected by the offset time and scale time at the DOP network level.

Creation Frame

The frame number on which the object will be created. The object is created only when the current frame number is equal to this parameter value. This means the DOP Network must evaluate a timestep at the specified frame, or the object will not be created.

For example, if this value is set to 3.5, the Timestep parameter of the DOP Network must be changed to 1/(2*$FPS) to ensure the DOP Network has a timestep at frame 3.5.

Number of Objects

Instead of making a single object, you can create a number of identical objects. You can set each object’s parameters individually by using the $OBJID expression.

Object Name

The name for the created object. This is the name that shows up in the details view and is used to reference this particular object externally.

Note

While it is possible to have many objects with the same name, this complicates writing references, so it is recommended to use something like $OBJID in the name.

Solve On Creation Frame

For the newly created objects, this parameter controls whether or not the solver for that object should solve for the object on the timestep in which it was created.

Usually this parameter will be turned on if this node is creating objects in the middle of a simulation rather than creating objects for the initial state of the simulation.

Allow Caching

By preventing a large object from being cached, you can ensure there is enough room in the cache for the previous frames of its collision geometry.

This option should only be set when you are working with a very large sim. It is much better just to use a larger memory cache if possible.

Initial Data

Initial Geometry

Starting geometry for the Vellum simulation. This represents the display or collision geometry.

Usually new objects are created using the Vellum Source DOP, this is most useful when restarting an existing simulation.

Display Geometry

Whether to display the geometry in the viewport.

Initial Constraints

Starting constraint geometry for the Vellum simulation. This represents the constraints between points of the display geometry. It should have a one-to-one point correspondence with the display geometry.

Usually new objects are created using the Vellum Source DOP, this is most useful when restarting an existing simulation.

Display Constraints

Whether to display the constraint geometry in the viewport. Usually constraints are displayed using the guides instead of showing the raw geometry.

Guides

Show Guide Geometry

Whether to display guide geometry in the viewport.

Draw as Wireframe

Forces the guide geometry to draw as wireframe.

Geometry

Thickness

Draw spheres for the pscale of the geometry. If the geometry has already solved it may have set the overlap_self attribute, if so, the actual effective thickness is drawn in cyan. This is useful to detect if the original thickness was too high - if so the extra thickness will be ignored by the simulation and just slow down the collisions.

Extrude

Draw the thickness by offsetting the geometry in opposite directions rather than by using spheres.

Failed Self Collision

Draw failed self collisions as red spheres. These points will no longer collide with their own geometry, nor will any edge or triangle attached to them.

Failed External Collision

Draw failed external collisions as orange spheres. These points will no longer collide with external geometry, nor will any edge or triangle attached to them.

Welds

Draw which points have been semantically fused together with the weld attribute. These can be broken during the solve using the auto break options, or by setting weld to -1.

Radius Scale

Because the thickness may be small, the visualization spheres can sometimes be lost. This scales the visualization spheres allowing them to be readily seen.

Constraints

Group

Constraints are often added to different groups. This allows you to isolate one particular group to visualize.

Pin to Target

Draw spheres over points pinned to the target animation.

Stitch Points

Draw stitch constraints of points stitched together.

Attach to Geometry

Draw attachment constraints for points attached to external geometry.

Radius

The constraint guides are not scaled by the thickness of the object, so this provides an absolute scale for their size.

Visualization

False Color Mode

Visualize properties of the constraints using a blue-to-red infrared coloring.

None

Leave the original colors.

Stretch Stress

Color according to the maximum stretching force applied by the constraints.

Bend Stress

Color according to the maximum bending force applied by the constraints.

Stretch Distance

Color according to how far constraints are stretched.

Stretch Ratio

Color according the ratio between original and current stretch.

Bend Angle

Color according to how many degrees the bend angle has deviated.

Stretch Plastic Flow

Color according to how much the stretch plastic flow has been triggered.

Bend Plastic Flow

Color according to how much the bend plastic flow has been triggered.

Volume Stress

Color according to the maximum volumetric force applied by the constraints.

Volume Distance

Color according to how far volumetric constraints have expanded from their rest state.

Volume Ratio

Color according the ratio between volumetric expansion and the rest state.

Display Visualization Geometry

Toggles if the simulation geometry is false-colored in addition to the constraints.

Max Stretch Stress

Scales the maximum stretch stress to be the maximum coloration.

Max Bend Stress

Scales the maximum bend stress to be the maximum coloration.

Max Stretch Distance

Sets the maximum stretch distance to be the maximum coloration.

Max Stretch Ratio

Sets the maximum stretch ratio to be the maximum coloration.

Max Bend Angle

Sets the maximum bend angle to be the maximum coloration.

Max Stretch Plastic Flow

Sets the maximum stretch plastic flow to be the maximum coloration.

Max Bend Plastic Flow

Sets the maximum bend plastic flow to be the maximum coloration.

Max Volume Stress

Scales the maximum volume stress to be the maximum coloration.

Max Volume Distance

Scales the maximum volume distance to be the maximum coloration.

Max Volume Ratio

Scales the maximum volume ratio to be the maximum coloration.

See also

Dynamics nodes