Toy Car
 
 
 
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Create panel (Helpers) reactor Toy Car

Animation menu reactor Create Object Toy Car

reactor toolbar (Create Toy Car)

The reactor Toy Car is a quick way to create and simulate a simple car without having to set up each constraint separately.

The Toy Car helper lets you choose a chassis and wheels for your car, tweak various properties such as the strength of its suspension, and specify whether you would like reactor to turn its wheels during the simulation. reactor then sets up all the necessary constraints to simulate the car.

A Toy Car is simulated if it has a rigid body assigned as a chassis and at least one rigid body assigned as a wheel. When not selected, an invalid Toy Car helper is red in the viewport.

Procedures

To set up a toy car, follow these procedures in order, and make sure the car has a surface to travel on, such as a level plane. For getting started, we suggest you use Icon Orientation and ignore the procedure about Common Local Orientation.

To create a Toy Car helper:

To set up the rigid bodies for a Toy Car:

  1. Create and position the rigid bodies you want to connect using the Toy Car helper.

    A toy car must have a chassis and at least one wheel.

  2. Use the Rigid Body Properties dialog to assign a mass value to each car element.

    The Mass values you specify affect how the toy car behaves. Ideally, the mass of the chassis should not be much greater than the total wheel mass, and the density of the bodies should be such that the Analyze World utility generates no warnings.

To assign rigid bodies to a Toy Car:

  1. Create the Toy Car helper and the objects to connect using it, as described above.
  2. On the Properties rollout, click the Chassis pick button, and then, in one of the viewports, select the object to use as the chassis.

    The Toy Car icon moves to the chosen rigid body. By default, the icon is aligned with the chassis's local space. reactor can use this orientation as a guide for the directions of the suspension and wheel axes.

  3. Add your car's wheels to the helper. You can add wheels to the toy car either by picking or using a selection list:
    • Click the Pick button and then select the object to use as a wheel.
    • Click the Add button and then use the dialog to select one or more objects to use as wheels.

    By default, reactor uses the icon orientation (taken from the chassis) to provide the directions of the wheels' spin and suspension axes. Each spin axis is aligned with the icon's X axis and passes through the relevant wheel's pivot point. The suspension axes are aligned with the icon's Z axis, and also pass through each wheel's pivot point.

    NoteFor this to work, make sure that the wheels are oriented correctly relative to the icon before simulating.

To change the wheel axis orientation (Icon Orientation):

  1. Use the Rotate tool to change the toy car icon's orientation so that it matches that of the actual car model.
  2. Ensure that Toy Car Properties rollout Toy Car Orientation is set to Icon Orientation (the default).

    The wheel axes are aligned with the icon's new orientation during the simulation.

To change the wheel axis orientation (Common Local Orientation):

  1. Ensure that the wheel and chassis local spaces are correctly aligned in world space.

    The initial world space orientation of the wheels relative to the chassis/icon is unimportant when using this option, as reactor reorients the bodies so that their local spaces continue to match during the simulation.

  2. On the Toy Car Properties rollout, set Toy Car Orientation to Common Local Orientation.
  3. Use the radio buttons to change the Suspension and Spin directions relative to the bodies' local spaces. By default, the Spin axes are aligned with the wheel and chassis's local X axes, and the suspension axes with their Z axes.

To spin the Toy Car wheels:

  1. On the Toy Car Properties rollout, turn on the Spin Wheels check box.
  2. Change the default Ang (Angular) Speed and Gain values as necessary.

    Angular Speed is the target angular velocity that reactor attempts to achieve for the wheels. The Gain is the maximum angular impulse that can be applied to the wheels in order to achieve the target velocity.

Interface

Toy Car Properties rollout

Chassis

Displays the name of the rigid body that serves as the chassis. You assign the chassis object by clicking this button and then selecting a rigid body from any viewport.

Wheels

Lists the names of the toy car's wheels.

Pick

Lets you add a wheel to the car. Click this button, and then in the viewport position the cursor over the object you would like to use as a wheel. If the object can be used as a rigid body, the cursor changes from an arrow to a cross and you can select the object to add it to the toy car.

Add

Lets you add one or more rigid bodies from the scene to act as wheels for the toy car. Click the button to open the Select Car Wheels dialog. Make a selection in the provided list, then add the wheels to the car by clicking the Select button.

Delete

Lets you remove wheels from the car. Highlight the wheels to remove from the car in the Wheels list and then click this button.

NoteThe following four parameters are available with Havok 1 only. With Havok 3, use the Havok 3 Wheel Params rollout settings instead.
Angular Strength

The strength of the corrective forces applied to keep the wheels upright and pointing forward.

Linear Strength

The strength of the forces applied to keep the wheels in position relative to the chassis.

Suspension

The suspension strength for the car. The lower the value, the more the chassis bounces when forces are applied to it.

Internal Substeps

Allows the car to be simulated using more substeps per keyframe than the rest of the simulation.

Increasing the Internal Substeps value can be useful if you are simulating a car with unusual parameters, which might require more substeps for stability.

Toy Car Orientation group

Choose how reactor orients the bodies in relation to the spin and suspension axes.

Icon Orientation

The Toy Car icon's initial orientation provides the directions of the wheels' spin and suspension axes. Each spin axis is aligned with the icon's X axis and pass through the relevant wheel's pivot point. The suspension axes are aligned with the icon's Z axis, and also pass through each wheel's pivot point. The wheels' own local orientations are unimportant.

NoteAnimating the orientation of the Toy Car icon has no effect on the direction of motion during the simulation; reactor uses only the orientation at the start of the simulation.
Common Local Orientation

With this option, you align the bodies' local spaces in world space, and specify the Spin and Suspension axes relative to this common orientation. The orientation of the rigid bodies in world space before simulating is unimportant.

This means, for instance, that you can set up your car with its wheels turned sideways and they still spin around the correct axes when simulating. This option allows you to change the spin and suspension axes separately. By default, the spin axes are aligned with the wheel and chassis' local X axes, and the suspension axes with their Z axes.

Allow Wheel Penetration

When on, reactor disables collision detection between the chassis and the wheels.

Spin Wheels

When on, the car's wheels to spin during the simulation and an arrow appears on the Toy Car viewport icon showing the direction of motion.

  • Ang SpeedThe target angular velocity that reactor attempts to achieve for the wheels when Spin Wheels is on. It is specified in radians per second, so the default value of 3.14 (pi) results in 180 degrees of rotation per second or half a revolution per second.
  • GainThe maximum angular impulse that reactor can to the wheels in order to achieve the target velocity.
Disabled

When on, reactor removes the Toy Car helper from the simulation.

Display Size

The size of the Toy Car helper icon as displayed in the viewport.

Reset Default Values

Returns the Toy Car parameters to their default values.

Havok 3 Wheel Params rollout

These parameters apply only when the simulation engine is Havok 3, and reflect the implementation of a subset of Car-Wheel constraint parameters in the Toy Car object in Havok 3.

These parameters replicate the Car-Wheel constraint parameters of the same names.