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Small documentation fix

Jorrit Rouwe 1 year ago
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b622c593da
2 changed files with 5 additions and 5 deletions
  1. 4 4
      Docs/Architecture.md
  2. 1 1
      Docs/ReleaseNotes.md

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Docs/Architecture.md

@@ -367,6 +367,10 @@ We also need to implement a ObjectVsBroadPhaseLayerFilter::ShouldCollide that de
 
 So you can see now that when we simulate DEBRIS we only need to visit a single broad phase tree to check for collision, we did this because in our example we know that there are going to be 1000s of debris objects so it is important that their queries are as fast as possible. We could have moved the BULLET layer to its own broad phase layer too because now BP_MOVING contains a lot of bodies that WEAPON is not interested in, but in this example we didn't because we know that there are not enough of these objects for this to be a performance problem.
 
+For convenience two filtering implementations are provided:
+* ObjectLayerPairFilterTable, ObjectVsBroadPhaseLayerFilterTable and BroadPhaseLayerInterfaceTable: These three implement collision layers as a simple table. You construct ObjectLayerPairFilterTable with a fixed number of object layers and then call ObjectLayerPairFilterTable::EnableCollision or ObjectLayerPairFilterTable::DisableCollision to selectively enable or disable collisions between layers. BroadPhaseLayerInterfaceTable is constructed with a number of broad phase layers. You can then map each object layer to a broad phase layer through BroadPhaseLayerInterfaceTable::MapObjectToBroadPhaseLayer.
+* ObjectLayerPairFilterMask, ObjectVsBroadPhaseLayerFilterMask and BroadPhaseLayerInterfaceMask: These split an ObjectLayer in an equal amount of bits for group and mask. Two objects collide if (object1.group & object2.mask) != 0 && (object2.group & object1.mask) != 0. This behavior is similar to e.g. Bullet. In order to map groups to broad phase layers, you call BroadPhaseLayerInterfaceMask::ConfigureLayer for each broad phase layer. You determine which groups can be put in that layer and which group must be excluded from that layer. E.g. a broad phase layer could include everything that has the STATIC group but should exclude everything that has the SENSOR group, so that if an object has both STATIC and SENSOR bits set, this broad phase layer will not be used. The broad phase layers are checked one by one and the first one that meets the condition is the one that the body will be put in. If you use this implementation, consider setting the cmake option OBJECT_LAYER_BITS to 32 to get a 32-bit ObjectLayer instead of a 16-bit one.
+
 Now that we know about the basics, we list the order in which the collision detection pipeline goes through the various collision filters:
 
 * Broadphase layer: At this stage, the object layer is tested against the broad phase trees that are relevant by checking the [ObjectVsBroadPhaseLayerFilter](@ref ObjectVsBroadPhaseLayerFilter).
@@ -378,10 +382,6 @@ Now that we know about the basics, we list the order in which the collision dete
 
 To avoid work, try to filter out collisions as early as possible.
 
-For convenience two filtering implementations are provided:
-* ObjectLayerPairFilterTable, ObjectVsBroadPhaseLayerFilterTable and BroadPhaseLayerInterfaceTable: These three implement collision layers as a simple table. You construct ObjectLayerPairFilterTable with a fixed number of object layers and then call ObjectLayerPairFilterTable::EnableCollision or ObjectLayerPairFilterTable::DisableCollision to selectively enable or disable collisions between layers. BroadPhaseLayerInterfaceTable is constructed with a number of broad phase layers. You can then map each object layer to a broad phase layer through BroadPhaseLayerInterfaceTable::MapObjectToBroadPhaseLayer.
-* ObjectLayerPairFilterMask, ObjectVsBroadPhaseLayerFilterMask and BroadPhaseLayerInterfaceMask: These split an ObjectLayer in an equal amount of bits for group and mask. Two objects collide if (object1.group & object2.mask) != 0 && (object2.group & object1.mask) != 0. This behavior is similar to e.g. Bullet. In order to map groups to broad phase layers, you call BroadPhaseLayerInterfaceMask::ConfigureLayer for each broad phase layer. You determine which groups can be put in that layer and which group must be excluded from that layer. E.g. a broad phase layer could include everything that has the STATIC group but should exclude everything that has the SENSOR group, so that if an object has both STATIC and SENSOR bits set, this broad phase layer will not be used. The broad phase layers are checked one by one and the first one that meets the condition is the one that the body will be put in. If you use this implementation, consider setting the cmake option OBJECT_LAYER_BITS to 32 to get a 32-bit ObjectLayer instead of a 16-bit one.
-
 ### Continuous Collision Detection {#continous-collision-detection}
 
 Each body has a motion quality setting ([EMotionQuality](@ref EMotionQuality)). By default the motion quality is [Discrete](@ref Discrete). This means that at the beginning of each simulation step we will perform collision detection and if no collision is found, the body is free to move according to its velocity. This usually works fine for big or slow moving objects. Fast and small objects can easily 'tunnel' through thin objects because they can completely move through them in a single time step. For these objects there is the motion quality [LinearCast](@ref LinearCast). Objects that have this motion quality setting will do the same collision detection at the beginning of the simulation step, but once their new position is known, they will do an additional CastShape to check for any collisions that may have been missed. If this is the case, the object is placed back to where the collision occurred and will remain there until the next time step. This is called 'time stealing' and has the disadvantage that an object may appear to move much slower for a single time step and then speed up again. The alternative, back stepping the entire simulation, is computationally heavy so was not implemented.

+ 1 - 1
Docs/ReleaseNotes.md

@@ -12,7 +12,7 @@ For breaking API changes see [this document](https://github.com/jrouwe/JoltPhysi
 * Changed the meaning of Constraint::mNumVelocity/PositionStepsOverride. Before the number of steps would be the maximum of all constraints and the default value, now an overridden value of 0 means that the constraint uses the default value, otherwise it will use the value as specified. This means that if all constraints in an island have a lower value than the default, we will now use the lower value instead of the default. This allows simulating an island at a lower precision than the default.
 * Bodies can now also override the default number of solver iterations. This value is used when the body collides with another body and a contact constraint is created (for constraints, the constraint override is always used).
 * Added BodyInterface::SetUseManifoldReduction which will clear the contact cache and ensure that you get consistent contact callbacks in case the body that you're changing already has contacts.
-* Created implementations of BroadPhaseLayerInterface, ObjectVsBroadPhaseLayerFilter and ObjectLayerPairFilter that use a bit table internally. These make it easier to define ObjectLayers which object layers collide.
+* Created implementations of BroadPhaseLayerInterface, ObjectVsBroadPhaseLayerFilter and ObjectLayerPairFilter that use a bit table internally. These make it easier to define ObjectLayers and with which object layers they collide.
 * Added support for less than 1 collision test per simulation step for vehicle wheels. This behavior can be configured differently when the vehicle is active / inactive. This can be used for LODding vehicles.
 * Added wheel index and friction direction to VehicleConstraint::CombineFunction friction callback so you can have more differentiation between wheels.
 * Added ability to disable the lean steering limit for the motorcycle, turning this off makes the motorcycle more unstable, but gives you more control over the final steering angle.