Houdini 20.5 Nodes Geometry nodes

Elastic Transform geometry node

Procedural tool for physically based volume sculpting.

This node type is hidden. It is no longer supported.
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Since 18.5

This nodes allows you to apply one physically based transformation to the input geometry. The available transformations are grab, twist, scale, or pinch.

How to

To...Do this

Modify geometry with a grab transformation

  1. Select Grab from the Transform Mode options.

  2. Move the pivot of the vector handle to specify the Origin.

  3. Move the tip of the vector handle to get the desired Displacement of the grab transformation.

Modify geometry with a twist transformation

  1. Select Twist from the Transform Mode options.

  2. Move the pivot of the xform handle to specify the Origin.

  3. Use the x and z rings to specify the Plane Normal represented by the y arrow.

  4. Use the y ring to specify the amount of the twist transformation.

Modify geometry with a scale brush

  1. Select Scale from the Transform Mode options.

  2. Move the pivot handle to specify the Origin.

  3. Specify the Amount to scale.

Modify geometry with a pinch brush

  1. Select Pinch from the Transform Mode options.

  2. Move the pivot of the xform handle to specify the Origin.

  3. Use the x and z rings to specify the Plane Normal represented by the y arrow.

  4. Use the y ring to rotate the Direction of the pinch represented by the x arrow.

Constraint a group of components at the original position

  1. Select a Radius of effect for the constraints

  2. Set Points to Constrain to set the maximum number of points that will be used to calculate the physically based constraints.

  3. Set the Group and Group Type under Displacement Constraints to select a group of components which you want constrained.

Parameters

Group

A subset of components in the input geometry whose position will be affected by the sculpting operations.

Leave this blank to affect the positions for all components in the input.

Group Type

What the group is made of.

Material Parameters

Rigidity

Determines the reaction on the perpendicular axis to the transformation. Lower values produce more bulging and has better volume preservation.

This value is converted to the poisson’s ratio as Poisson’s Ratio = 0.5 - Rigidity. Note that a Poisson’s Ratio of 0.5 (that is a Rigidity of 0) is known as the incompressible limit which means a geometry body cannot gain or lose volume; therefore, the scale transformation will not modify the geometry at this value. See Wikipedia’s Poisson’s Ratio page for more information.

Transform Parameters

Transform Mode

The type of transformation to apply to the geometry group.

Options are Grab, Twist, Scale and Pinch.

Origin

The center of the transformation.

Divide Transformation

If this option is off, it applies a single elastic transformation. If this option is on, it splits the transformation into multiple small transformations which produces a smoother look.

Division Size

If Apply Transformation by Steps is active, this parameter determines the maximum size of the small transformations.

Hard Decay

Applies a decay function so that the Radius determines a hard limit on the geometry that will be modified. If Hard Decay is set to off a stroke could potentially transform all the points in the geometry.

Radius

The radial falloff of the transformation.

Grab Transform

Direction

A vector which indicates the direction in which a point at the Origin will be displaced.

Strength

The amount by which the Origin is displaced along the Direction vector.

Twist Transform

Plane Normal

The normal of the plane in which to apply the twist transformation.

Strength

The magnitude of the twist transformation. Note that even though you can assume the value to be in degrees, it is just an approximation of the rotation. You will get a better result when Divide Transformation is On.

Scale Transform

Strength

The amount by which the geometry will be expanded or contracted.

Pinch Transform

Plane Normal

The normal of the plane in which to apply the pinch transformation.

Direction

The direction in which the geometry will be stretched. Note that this vector will be projected to the plane specified by the Plane Normal. The pinch transformation constracts in a direction perpendicular to the Direction and the Plane Normal.

Strength

The strength of the pinch transformation.

Displacement Constraints

Group

Group of components which are not displaced by applying physically based constraints. This restricts the displacement on the geometry surrounding the constrained components giving the transformation a natural look.

Note that these constraints are applied using a grab transformation at the origin of the constraint which counteract the displacement generated by a transformation. The radius of effect of these brushes is determined by the parameter Radius under Displacement Constraints.

Group Type

What the Group under Displacement Constraints is made of.

Radius

Controls the radius of effect produced of the grab transformations produced by the displacement constraints.

Points to Constrain

Controls how many points will be used to calculate the grab transformations that counteract the displacement generated by our transformation. Decreasing this number improves the performance of the tool but reduces the precision of the constraints.

Visualization

Visualize Falloff

Turn on or off the visualization of the geometry that will be affected by the transformation.

See also

Geometry nodes