Hi praveee,
There are actually several ways to detect collisions in Unity with Spine. First of all, I don't know how familiar with Unity you are, so forgive if this is just a recap on what you already know. Basically Unity has both PhysX and Box2D as standard now, and you can use either 3D/2D collisions within Unity by using the default colliders provided (Box, Sphere, Capsule, etc...). Spine provides the ability to create Bounding Boxes within the editor and attach those to bones to be animated. In Unity, you can read in the vertices comprising the Bounding Boxes and create meshes to represent them. These meshes can then be used on a Meshcollider type collider to perform the collision detection. You can either update the vertices representing each Bounding Box on a per frame basis (as the main Spine skeleton is don) which results in more overhead, or you can attach to different child GameObjects of your main skeleton and then rotate/scale the child GameObjects to achieve the same result (note that this assumes Bounding Boxes cannot change number of vertices/shape, which currently is true, but may not be once meshes are introduced into Spine (any day now)).
Anyway, once you have reconstructed colliders from the Bounding Boxes, Unity will provide the collision detection for you, and you can use the Unity standard OnCollisionEnter, OnTriggerEnter, etc... functions for the collision detection code. This is the only way to have Spine animations play with the Unity Physics engine easily. You will run into the problem of Concave Bounding boxes not colliding with other Concave Bounding boxes though, and Mesh colliders also have significant overhead. Therefore you could try approximating your bounding boxes in Unity with the primitive types (box, sphere, capsule) but this is also quite a headache, extra work.
Spine does however provide functions for working out Bounding Box intersections with other spine animations, and you can run these in your own script on a frame by frame basis to determine intersections. So basically, the helper functions provide you the ability to see if your skeleton BBoxes have collided with another ones very easily. The thing it does not allow is interaction with Unity physics engine. If you are doing a 2d fighting game this should be all you need for you kick/punch type collision detection. I believe this is all in the SkeletonBounds class.
Hope this info helps you out, if you have any further questions just ask.
Was just wondering what type of game you are making. Is it more Street Fighter/Skull Girls or more like Smash Bros. Is it an online game?
Regards,
Robert
