This article discusses the way that range is calcuated for various spells and abilities.
[top]Terminology
- Bounding Box/Bounding Cylinder: The invisible 3-dimensional space that a model occupies. This can be thought of as a large cylinder (like an engine piston) that is centered on your character.
- Model Center: The middle-most point around which your character model is centered.
[top]Point-to-Point
An ability that has a direct point-to-point effect (including most all single-target spells and physical damage attacks) determines whether or not the target is in range using a edge-to-edge boundary check between the two bounding boxes. Essentially, the radius size of the bounding sphere that the player or NPC occupies is expanded by the range of the attack, and the game engine checks to see if this sphere collides with the intended target. If a collision occurs, the attack is in range.
[top]Radius-based
An ability that is radius based such as Arcane Explosion, Psychic Scream, Tree of Life's aura or Sweeping Strikes is calculated from the center of the model taking the action to the edge of the target's bounding sphere. The extra distance from the action-taking model's center to the edge of its bounding sphere is
not always added to the range of the attack (most of the glaring exceptions to this are fixed as of 2.4.2).
[top]Why This Matters
This measurement discrepancy is the reason why players are able to often out-range attacks from bosses or why non-AE attacks will hit targets that an AE will miss from the same range.
For example, a boss with a 30 yard AE ability may not hit a player standing exactly 30 yards away -- the distance from the center of the boss to the edge of his own hit box is usually at least one yard, and this creates "dead space" when comparing a point to point attack range from a radius-based attack. The illustration below shows this example -- this behavior can be seen when fighting Rokmar the Cracker in Slave Pens.