Smart Collision is a collision deformation that is part of the main Muscle deformer. This collision lets you set up regions and a cSmartCollide plane node to determine how to handle collision. The collision results can be a simple planar collision effect, or can be switched to a true mesh-mesh collision for more accurate results.
In addition to providing collision, the cSmartCollide node and deformation also allow for several other weight types that augment basic skinning effects. These weights can help bulk or bulge out parts of a mesh, create wrinkle effects, slide points, and otherwise get better deformation at joint locations, all without using extra joints or muscles.
For example, a cSmartCollide node provides weights that bulge out the parts of the mesh where two joints rotate together, and thus can provide very quick volume effects for things like fingers, without the overhead of using actual muscles.
Smart Collision is the fastest of the three collision methods offered by Maya Muscle.
One of the main purposes of the Smart Collision nodes is to fix typical problems encountered with skinning. You can use Smart Collision without activating real collision. The Muscle Smart Collide node has several attributes for movement. The attributes control the strength or amount of motion applied on weighted points, and each has a corresponding weight map. For example, the bulkA/bulkB attributes are related to the Smart Bulk weights that you can paint.
The painted weights or attributes affect the mesh more or less as the two joints become more or less aligned. That is, the effects of the movement weights are “triggered” based the rotation of the joints. As the B joint rotates towards the A joint, the effects increase. Each point is adjusted based on the painted weight and by the attribute. For example, a weight painted at 1.0 for Bulk is multiplied by the Bulk A or Bulk B attribute depending on if the point is also in the A or B “region” weight. If a point is not included in the original “region” weights, then it is not deformed.
It is important to note that most of the weights move points more on the side that the joints are rotating together, than on the opposite side. For example, if a finger bend inwards, the Bulk weights, even if painted around the entire mesh, mostly affect the “inside” parts of the finger. In this way, you can apply weights to things like a spine or belly all around your character, but the actual area that bulges only occurs as the joints rotate in that direction. The falloff angle for this can be set using the angleMin and angleMax attributes on the Muscle Smart Collide node. This falloff angle is implied based on the joint rotation to be the bisect of the two joints.
Besides movement options, the Smart Collision node also offers either planar or mesh-mesh collision. Both weights for the areas of flattening/collision can be painted, as well as areas to be volumized or puffed based on the collision.
For detailed descriptions of the Collision attributes refer to cMuscleSmartCollide node.
Smart Collision region weights
Once created and connected, you must set weights for each Muscle Smart Collide node. This can be done manually, or using the Default Weights window. There are two main features to Smart Collision nodes: weights that affect motion of the skin results of the mesh, and actual collision-related weights and attributes. For example, there are bulk or sliding weights that affect how points move, which can help remove unwanted skinning artifacts such as pinching. In order to use all of these tools, you must weight two sets or “regions” of points so that the deformer knows which area is which.
