STOP!!** It is preferred that CollisionGroupManager.create is used to create collision groups unless you know how to construct the proper bitmasks. See https://github.com/excaliburjs/Excalibur/issues/1091 for more info.
Name of the collision group
32 bit category for the group, should be a unique power of 2. For example 0b001 or 0b010
32 bit mask of category, or ~category generally. For a category of 0b001, the mask would be 0b110
Static AllThe All CollisionGroup is a special group that collides with all other groups including itself,
it is the default collision group on colliders.
Get the category of the collision group, a 32 bit number which should be a unique power of 2
Get the mask for this collision group
Get the name of the collision group
Evaluates whether 2 collision groups can collide
CollisionGroup
Inverts the collision group. For example, if before the group specified "players", inverting would specify all groups except players
CollisionGroup
Static collidesCreates a collision group that collides with the listed groups
Static combineCombine collision groups with each other. The new group includes all of the previous groups.
CollisionGroups indicate like members that do not collide with each other. Use CollisionGroupManager to create CollisionGroups
For example:
Players have collision group "player"
Enemies have collision group "enemy"
Blocks have collision group "ground"
Players don't collide with each other, but enemies and blocks. Likewise, enemies don't collide with each other but collide with players and blocks.
This is done with bitmasking, see the following pseudo-code
PlayerGroup =
0b001PlayerGroupMask =0b110EnemyGroup =
0b010EnemyGroupMask =0b101BlockGroup =
0b100BlockGroupMask =0b011Should Players collide? No because the bitwise mask evaluates to 0
(player1.group & player2.mask) === 0(0b001 & 0b110) === 0Should Players and Enemies collide? Yes because the bitwise mask is non-zero
(player1.group & enemy1.mask) === 1(0b001 & 0b101) === 1Should Players and Blocks collide? Yes because the bitwise mask is non-zero
(player1.group & blocks1.mask) === 1(0b001 & 0b011) === 1