Houdini 20.5 Nodes Geometry nodes

RBD Car Deform geometry node

Add Post-Sim Deformations to RBD Cars.

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Since 20.5

This SOP deforms the deformable parts of a vehicle, such as tires and suspensions, defined using the RBD Car Rig SOP. The simulated wheels and body (chassis) packed primitives define the base skeleton which drive the suspension deformations, while the tires are deformed on contact with a Ground Plane.

In order to get bulging tires from an RBD simulation, make sure to reduce the wheel size on the RBD Car Rig SOP to allow some interpenetration with the ground during the simulation.

Note

You can use attributes on the reference input to drive the deformations procedurally. The nodes' second output adds per wheel point attributes and detail attributes which can be used to drive the deformer procedurally. Those attributes can be copied to other vehicles.

For more information, see Using RBD car deform.

Inputs

Geometry

The simulated car geometry to deform.

Reference

The car geometry at rest.

Heightfield Collisions

A heightfield to use as a collider when deforming tires.

Parameters

Local Edits

You can edit individual deformers interactively in the viewport using the provided handles or by setting a selection and manipulating the local edit parameters

Selection

Select the deformers to edit. By default these will have the same name as the car wheels since they are driven off them.

Mode

Tires

Edit tire deformation settings. This allows you to edit the tire rim sizes (inner radius) which prevents the tire deformations inside of it.

Suspensions

Edit the suspension deformer settings. When in Suspensions mode, each deformer is treated as a joint. By default there are as many as there are wheels.

Clear Edits

Resets all Tires or Suspensions settings to default.

Reset Tire

Reset the selected tire(s) to default.

Reset Joint

Reset the selected joint(s) to default.

Add Offset

Create a new joint attached to the currently selected wheel. This allows you to have additional deformers “attached” to a wheel with a positional offset. The wheel’s vertical alignment and direction will affect the joint, allowing you to deform tie rods more accurately.

Delete Offset

Delete the selected offset joint.

Enable

Turn this off to disable the current selections' effect on the deformations.

Tire Rim Size

The rim size defined as a ratio of the wheels' radius. Tire deformations are limited to the geometry outside that radius.

Mirror

When editing multiple joints, these options allow you to mirror the transforms along a central axis.

None

No mirorring, all transforms and edits are applied equally to all selected joints.

X Axis

The transforms and edits will be mirrored across the vehicle’s local X axis (Left/Right).

Z Axis

The transforms and edits will be mirrored across the vehicle’s local Z axis (Front/Back).

Handle

Joint Region

Use the joint region handle to edit the selected joints area of influence.

Joint Offset

Use the joint offset handle to edit the selected joints positional offset. This is the joints anchor position on the wheel it is attached to.

Capture Group

Specify a subset of the suspension geometry affected by the selected joints.

Falloff

Adjust the selected joints' soft falloff radius.

Deform Tires

When tire deformations are turned on, the wheel geometry outside of the Tire Rim Size is deformed when it collides with the the Ground Plane.

Group

Specify a subset of the geometry to be deformed.

Ground Plane

Ground Plane

Specify a ground plane to collide with.

Heightfield

Use the heightfield plugged into the third input to collide with.

Position

The center of the ground plane.

Rotation

The orientation of the ground plane.

Tire Deformer

Constraint Iterations

The number of rounds of deformation the node will apply to resolve the constraints. More iterations results in more fully resolved wrinkles.

Neighbor Distance

The number of edges between the two end points of each surface strut constraint. Higher distances produce larger wrinkles, but also create more constraints that take more time and memory to solve.

Bend Stiffness

The stiffness of the constraint, which controls how strongly the constraint pushes points away when they are closer than its initial rest state.

Stretch Stiffness

The stiffness of the constraint, which controls how strongly the constraint pulls points back towards its initial rest state.

Collision SDF Offset

A buffer distance to leave between the wrinkles and the surface of the Collision Geometry and ground plane.

Set Uniform

Use a buffer with the specified distance.

Use Thickness

Use each point’s pscale attribute that represents its thickness as the buffer distance.

Deform Suspensions

Group

Specify a subset of the geometry to be deformed.

Constrain Brake Calipers

You can specify a subset of the wheel geometry which shouldn’t spin but otherwise align with the wheel.

Group

Specify a subset of the geometry to be deformed.

Visualization

Display Tire Guides

Show the Tire Rim Size guides around the wheels.

Display Suspension Guides

Show the guides in the viewport. Turning this off will only show the output geometry and handles.

Display Output Geometry

When in Suspensions mode, turning this off will hide the geometry that is not currently being deformed. This can help declutter the viewport and focus on the areas of interest.

Display Deformed Guides

When turned on, the suspension geometry is shown deformed, turning this off will show the undeformed geometry as guide. When editing the joints, it is best to show the undeformed geometry as the joint weights are calculated on the undeformed geometry.

Display Unselected Wheel Joints

When turned on, the unselected joint capture regions are shown faintly.

Joint Color Seed

The seed that drives the various joint random colors.

Color Mode

All Joints

Colors the suspension guide geometry by all the joints capture weights.

Selected Joint

Show only the selected joint(s) weights.

Color

When Color Mode is set to Selected Joint, choose a color scheme to help better visualize the joint’s weights.

Joint Color

Inherit the color from the selected joint(s). This scheme can display multiple joint colors at once.

Infra-Red

Displays the last selected joint’s weights as infrared colors.

Grayscale

Displays the last selected joint’s weights as grayscale.

Custom

Use a custom color ramp to show the last selected joint’s weights.

Color Ramp

The custom color ramp to show the last selected joint’s weights.

See also

Geometry nodes