PhysicsCasting
One of the most common run-time interactions with a PhysicsSpace is casting, which queries for all objects within a region of space. This allows common operations such as line-of-sight queries, volume queries, and so on.
Typically a cast will take 3 arguments:
The shape to cast
How many results to receive at max. This is needed for internal optimizations in physics. For Ray/Segments, the results will be sorted by the t-value.
The CastFilter describes how to filter out results when casting. Common operations include skipping objects of certain configurations (Static, Kinematic, CollisionGroups, etc...).
Currently, the physics systems supports a few common casting types:
Ray Casting
ray casting checks for all shapes in a direction. Ray casts are common for things like line-of-sight tests.
Segment Casting
A segment cast is like a ray cast except it has an end position. Segment casts are used when there is a known max distance for the cast.
Sphere Casting
sphere casting checks to see what objects are within a sphere. Useful for simple volume queries such as finding all objects within an explosion radius.
Aabb Casting
aabb casting checks what objects are within an axis-aligned box. Sometimes a box is a better shape for casting, especially when the query area is long an thin.
Frustum Casting
frustum casting checks what objects are within a frustum. Useful for queries that come from a camera where perspective should be taken into account.
Collider Casting
Sometimes a more complicated shape query is desired. Collider casting allows the user to say: "What if this collider was over there". This is commonly used for a simple preventative collision check.
CastFirst
Ray and Segments have an additional "CastFirst" operation for convenience. These cast functions implicitly have a max object count of 1.
DispatchWithin
In addition to regular casting, the physicsspace.md contains other common cast related functions. Sometimes casts are performed just to send events to all shapes within a region. This is common for a generic interaction system where each object may or may-not handle some event. Instead of casting and iterating over all results, the PhysicsSpace has the "DispatchWithin" functions. Currently only Sphere and Aabb dispatch functions exist.
Sweeping
While a cast can be used as a preventative check, sometimes the accuracy is not enough. This is where the SweepCollider function comes in. Sweeping can be thought of as extending a collider's volume in a direction to find the exact times that a collision would happen with static objects. This allows writing Time-of-Impact logic to avoid missing any collisions.
NOTE: Swept casts are expensive operations and should be used only when important, such as a player.