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 particles, 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 [ Dynamics ] for more information.
To create an obstacle:
1. Select the particle clouds, hair, cloth objects, or soft-body objects (not clusters or tagged points) that you want to have collide with the obstacles.
2. From the Simulate toolbar or Hair panel, choose Modify > Environment > Set Obstacle.
3. Pick one or more objects in the scene that will act as obstacles for the emitted particles, hair, cloth object, or soft body object. Right-click to end the picking session, and this property editor appears.
When you set an obstacle for particles, a Particle Event Property Editor is automatically created for the currently selected particle type.
• For details on setting up collisions for the particle, fluid, or explosion simulators, see Setting Up Particle Collisions.
• 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). 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.
Name
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.
Mute
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.
General
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.
Physical
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 particle type or cloth object. If you set the Collision mode for the particle type’s event to Bounce or Bounce & Emit, the values here also have an impact.
To keep this relationship simple, it’s usually best to set the values here first, then tweak the parameters for the particle types or cloth objects. This way you can maintain the obstacle’s parameters as a constant.
The Friction and Elasticity parameters here are not used in calculating obstacle collisions with hair.
Friction
Controls the drag, or resistance, acted on objects or particles as they strike the obstacle.
Set this to a high value if you want the particles or 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.
Elasticity
Controls the resilience of objects or particles as they bounce off the obstacle. Set this to a high value if you want the particles or 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
For particle-related collisions, however, a value of 0 (zero) for this may be desirable.
Tolerance
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.
