The Maya Nucleus solver properties control internal forces that affect all of the nodes that are members of a particular solver system. In Maya, you can use Gravity and Wind forces on Nucleus objects to augment the object’s movement and behavior, allowing you to set the environment and atmosphere in which your Nucleus objects exist. Nucleus forces are different from the forces generated by Maya Fields, in that the are internal to the Nucleus system and only affect nCloth, nParticle, nHair, and passive collision objects.
For example, the Gravity and Air Density attributes on the nucleus node affect how your nCloth falls through the air based on the gravitational pull of the planet implicit atmosphere in your scene and the aridity or humidity of your environment. Wind forces also affect the billowing, rippling, waving, or flowing effect of your nCloth based on the Wind Speed and Wind Direction attribute settings.
Setting the Space Scale of your Nucleus system is important to ensure that gravity is appropriately applied to your Nucleus objects during simulation. The Nucleus solver interprets centimeters as meters and therefore, you may need to adjust the Space Scale of your object's Maya Nucleus solver. Otherwise, the large-sized nCloth, nParticle, or nHair objects in your scene may not behave as desired. For example, when Space Scale is 1.0 (default), Gravity treats a 100 centimeter wide nCloth object like it is 100 meters wide. To improve the behavior of your large-sized nCloth objects, reduce the Space Scale value. If you are modeling such that one unit is equal to one centimeter, the Space Scale value should be set to 0.01. You can also experiment with Space Scale values to produce different types of simulation results such as to exaggerate the affect of gravity and wind on your nCloth and nParticle objects. For example, if you have an nCloth object in the middle ground of your scene, you can adjust Space Scale to maintain the object’s correct scale in the scene.
You can use Interactive Playback to interact with the objects in your scene during playback. For example, using Interactive Playback, you can use the Select Tool to select, and then move a passive object so that it collides with an nCloth object. This lets you observe how the collision affects the nCloth. You can then make any needed adjustments to collisions or dynamic attributes before animating your object or caching the simulation.
