[Anark] Collider for Simulations (Physics Behavior)

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发表于 2011-10-20 15:38:00 |只看该作者 |倒序浏览

            Collider for Simulations (Physics Behavior)


         Summary


         Causes the parent object to interact with any Collision Shells in a semi-realistic manner.


            Category


            Latest Behaviors


            Author


            Gavin Kistner


            Difficulty


            (Reference)


            Time to Complete


            5 Minutes


         Downloads


         Click Here

         to download the associated files.


         (This document covers version 3.1.2 of the 'Collider for Simulations' behavior, current as of 2005-Feb-11)


         Description


         Attach this behavior to an object to cause it to collide with any objects which have the Collision Shell behavior attached.


         When an object collides with a collision shell:


            the Collision Shell fires a ‘Collided With’ event


            this behavior and the object to which it is attached both fire a ‘Collided’ event


            the object ‘bounces’ off of the Collision Shell, with the amount of bounce being proportional to the

            Elasticity

            setting of the Collision Shell behavior


         While the polygons of the Collision Shell are used to find the collision, the geometry of the Collider object is

            NOT

         used. Instead, a ray is projected from the center of the object out to its collision radius, along the direction of movement for the object. It is this ray which is used to detect collisions.


         If the

            Extra Detection?

         advanced property is checked, an additional 6 rays are positioned around the object, offset from its center along the global axes.


         It does not matter whether the parent object is moved due to its positionVelocity, or animation/script setting its position directly; the difference between the previous position of the object and its new position is used in all cases to determine whether the object has moved.


         Note that the parent object must be in ‘global space’; that is, it may not be attached under any parent element which is rotated scaled, or offset. (No such restriction exists for the shells.)


         When the object bounces off an object, the object is set into motion by setting its position velocity. By default, the amount of reflection will be determined by the

            Elasticity

         property of the shell which was collided with. The

            Override Elasticity?

         advanced property may be used to set an elasticity which always applies to the collider, regardless of the elasticity of any shell.


         Note that the collision detection is only based on the movement of the collider itself,

            NOT

         the collision shells. If you have a collider sitting still (a baseball) and you move/rotate a collision shell into it (a baseball bat) the ball will not experience a collision. Similarly if the ball is moving very slowly towards a collision shell which is itself moving very quickly, if a collision occurs (which will only occur if the movement of the object overlaps a face of the shell during one frame) the object will bounce off only in proportion to its own speed,

            NOT

         the combined speed of the object and the collision shell which hit it.


         Finally, while this behavior attempts to simulate realistic collisions and reflections, there are known inaccuracies and edge cases which can cause it to react somewhat incorrectly (the reflection is slightly off) or very incorrectly (the collider passes right through a collision shell). This behavior is not a substitute for real physical simulation.


         Instead of this behavior, use the Collider for Walkthroughs behavior attached to a Camera for better results when creating a ‘walkthrough’ presentation.


         Basic Properties


            Collision Distance


            How far from the center of the object should a collision be looked for?


         Advanced Properties


            Flash On Collision?


            Flash to a color the parent collides?


            Flash Color


            Color to flash when a collision occurs.


            Override Elasticity?


            Use the 'Elasticity' value (below) rather than that of the collider?


            Elasticity


            Elasticity value to use instead of those on any collider.


            Extra Detection?


            Use 7 rays for collision instead of 1? (seven times slower)


         Events


            Collided


            Fires when the parent object collides with a collision shell.


         Demonstration


            View Demonstration Project


            Download Project File