Updated API documentation

* Clarified that there is only 1 broad phase layer per object layer
* Added information on overriding the DebugRenderer

Docs/Architecture.md

@@ -352,7 +352,7 @@ The narrow phase queries are all handled through the [GJK](@ref GJKClosestPoint)
 Each Body is in an [ObjectLayer](@ref ObjectLayer). If two object layers don't collide, the bodies inside those layers cannot collide. You can define object layers in any way you like, it could be a simple number from 0 to N or it could be a bitmask. Jolt supports 16 or 32 bit ObjectLayers through the JPH_OBJECT_LAYER_BITS define and you're free to define as many as you like as they don't incur any overhead in the system.
 
 When constructing the PhysicsSystem you need to provide a number of filtering interfaces:
-* BroadPhaseLayerInterface: This class defines a mapping from ObjectLayer to BroadPhaseLayer through the BroadPhaseLayerInterface::GetBroadPhaseLayer function. Each Body can only be in 1 BroadPhaseLayer and in general there will be multiple ObjectLayers mapping to the same BroadPhaseLayer (because each broad phase layer comes at a cost). If there are multiple object layers in a single broad phase layer, they are stored in the same tree. When a query visits the tree it will visit all objects whose AABB overlaps with the query and only when the overlap is detected, the actual object layer will be checked. This means that you should carefully design which object layers end up in which broad phase layer, balancing the requirement of having few broad phase layers with the number of needless objects that are visited because multiple object layers share the same broad phase layer. You can define JPH_TRACK_BROADPHASE_STATS to let Jolt print out some statistics about the query patterns your application is using. In general it is wise to start with only 2 broad phase layers as listed in the \ref broad-phase section.
+* BroadPhaseLayerInterface: This class defines a mapping from ObjectLayer to BroadPhaseLayer through the BroadPhaseLayerInterface::GetBroadPhaseLayer function. Each Body can only be in 1 BroadPhaseLayer so an ObjectLayer maps to 1 BroadphaseLayer. In general there will be multiple ObjectLayers mapping to the same BroadPhaseLayer (because each broad phase layer comes at a cost). If there are multiple object layers in a single broad phase layer, they are stored in the same tree. When a query visits the tree it will visit all objects whose AABB overlaps with the query and only when the overlap is detected, the actual object layer will be checked. This means that you should carefully design which object layers end up in which broad phase layer, balancing the requirement of having few broad phase layers with the number of needless objects that are visited because multiple object layers share the same broad phase layer. You can define JPH_TRACK_BROADPHASE_STATS to let Jolt print out some statistics about the query patterns your application is using. In general it is wise to start with only 2 broad phase layers as listed in the \ref broad-phase section.
 * ObjectVsBroadPhaseLayerFilter: This class defines a ObjectVsBroadPhaseLayerFilter::ShouldCollide function that checks if an ObjectLayer collides with objects that reside in a particular BroadPhaseLayer. ObjectLayers can collide with as many BroadPhaseLayers as needed, so it is possible for a collision query to visit multiple broad phase trees.
 * ObjectLayerPairFilter: This class defines a ObjectLayerPairFilter::ShouldCollide function that checks if an ObjectLayer collides with another ObjectLayer.
 
@@ -546,6 +546,10 @@ PhysicsSystems are not completely independent:
 
 These functions / systems need to be registered in advance.
 
+# Debug Rendering {#debug-rendering}
+
+When the define JPH_DEBUG_RENDERER is defined (which by default is defined in Debug and Release but not Distribution), Jolt is able to render its internal state. To integrate this into your own application you must inherit from the DebugRenderer class and implement the pure virtual functions DebugRenderer::DrawLine, DebugRenderer::DrawTriangle, DebugRenderer::CreateTriangleBatch, DebugRenderer::DrawGeometry and DebugRenderer::DrawText3D. The CreateTriangleBatch is used to prepare a batch of triangles to be drawn by a single DrawGeometry call, which means that Jolt can render a complex scene much more efficiently than when each triangle in that scene would have been drawn through DrawTriangle. At run-time create an instance of your DebugRenderer and assign it to DebugRenderer::sInstance. Finally call for example PhysicsSystem::DrawBodies or PhysicsSystem::DrawConstraints to draw the state of the simulation. For an example implementation see [the DebugRenderer from the Samples application](https://github.com/jrouwe/JoltPhysics/blob/master/TestFramework/Renderer/DebugRendererImp.h).
+
 # The Simulation Step in Detail {#the-simulation-step-in-detail}
 
 The job graph looks like this: