Obstacle Property Editor


Defines obstacle characteristics for objects as well as the behavior of other objects as they strike the obstacle.

You can define any number of standard geometric objects (polygon or NURBS surface) in your scene to act as obstacles that block the path or collide with hair, cloth, or a soft body object.

Collisions with rigid body objects are done within the rigid body simulation environment where all rigid bodies have their own collision properties. As a result, you do not need to use the Set Obstacle command or its property editor. See Collisions with Rigid Bodies [ Simulation and Effects] for more information.

To create an obstacle:

  1. Select the hair, cloth, or soft-body objects (not clusters or tagged points) that you want to have collide with the obstacles.

  2. From the Simulate toolbar, choose Modify Cloth Set Obstacle or Modify Soft Body Set Obstacle; or from the Hair panel, choose Modify Environment Set Obstacle, depending on the type of object you have selected.

  3. Pick one or more objects in the scene that will act as obstacles for the hair, cloth, or soft-body object. Right-click to end the picking session, and this property editor appears.

    • You can't use implicit objects as obstacles.

    • You can't apply an obstacle to a hierarchy of objects.

    • The parameters in the Obstacle property editor (except Friction and Elasticity) are used in calculating obstacle collisions with hair only if the hair's Collision Type is set to XSI (see Setting Up Hair Collisions [Hair]). If the Collision Type is set to Actual (default) or Exact, the parameters in this property editor are not considered in the collision.

    • When you designate an object to be an obstacle, an obstacle operator is added to its properties. To keep your scene as light as possible, make sure to remove the obstacle operator from all objects that are no longer being used as obstacles.


When you set the obstacle object, its name is automatically used and "_obstacle" is appended to it. For example, if the obstacle object is named Wall, the obstacle property is named Wall_obstacle.

To make it easier to tell apart different obstacles, you can rename an obstacle. For example, if you have two different obstacles for an object, one can be called "floor" while another is called "wall".

To name a force

  • Enter a descriptive name in the Name text box in the obstacle object's Obstacle property editor.

    If you modify the name of the obstacle object after this point, the obstacle property is not renamed.


You can temporarily disable the obstacle property, meaning that you can easily test a simulation with or without the obstacle being calculated as part of it. As well, you can animate the muting.

To mute an obstacle

  • Select the Mute option in the obstacle's property editor.


These parameters set the obstacle's geometry used for the collision, its animated deformation state, and whether it's double-sided.

Obstacle Type

Sets the type of obstacle surface.

B-Plane: Objects strike the object on the surface of its bounding plane.

B-Box: Objects strike the object on the surface of its bounding box.

B-Sphere: Objects strike the object on the surface of its bounding sphere.

Actual Shape: Objects strike the object on the surface of its geometric shape.

If you are using primitive shapes like spheres, grids, and boxes (or geometries with close enough approximations to these shapes), use the bounding shapes (B-shapes) for obstacles rather than Actual Shape. This can save a lot of calculation time.

If you need more precise collision detection (such as with cloth or soft-body objects molding to the actual shape of the obstacle), consider using (hidden) low-resolution objects you've built to "stand in" for the high-resolution visible geometry.

Animatable Deformation

Correctly detects collisions when the obstacle is affected by other deformations, such as shape animation. It is not required for transformations (scale, rotate, translate).

Keep this option off unless you really need it because it can use a lot of memory. It is only needed if the geometry is actually deforming over time.

Double Face Collision

Detects collisions for both faces of a two-sided object, such as a flag or the inside and outside of a container. Keep this option off unless you really need it because it consumes a lot of memory.


These parameters set the colliding object's resistance and resilience to the obstacle, the offset between obstacle's surface and its collision point, and degree of accuracy for all the physical parameters.

The values for the Friction and Elasticity parameters set here for the obstacle are multiplied by the values for the corresponding parameters set for the cloth object.

To keep this relationship simple, it's usually best to set the values here first, then tweak the parameters for the cloth objects. This way you can maintain the obstacle's parameters as a constant.

NoteThe Friction and Elasticity parameters here are not used in calculating obstacle collisions with hair.


Controls the drag, or resistance, acted on objects as they strike the obstacle.

Set this to a high value if you want the soft-body/cloth object to stick to the obstacle. A low value causes the object to slide off the obstacle with little resistance. For example, set this value to 1 if you want to make a ball roll on a floor.


Controls the resilience of objects as they bounce off the obstacle. Set this to a high value if you want the soft-body or cloth object to bounce off the obstacle with great vigor. You can enter values higher than is shown by the slider.

Push Length

The offset between the obstacle's surface and its collision point.

For example, to improve the appearance of the cloth draping over an obstacle or to prevent a cloth or soft-body object from penetrating the obstacle, increase this value. As well, you can create the illusion of thicker cloth by increasing this value


The degree of accuracy in all the Physical parameter settings. The lower the value, the more accurate the collision (like lowering the threshold for inaccuracy), but the more time it takes to calculate.

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