Missile Encounter Filter

A Missile consists of the 'missile' itself and 'projectile' within the missile. For example, a missile might contain an arrow or a FUL BOMB. When a Missile contacts a solid object, the Missile Encounter Filter is called. The location of the filter is specified in the Menu/Edit/Global dialog in the 'Special Locations'.

A couple of things should be noted:

1. A missile encounter with a monster or a party member occurs when the missile LEAVES the monster or party member's position within a cell. When a group of monsters or the party moves, it takes two half-steps. For example, if the party consists of a single member in the left rear position and moves forward the member at the left rear first vacates the left rear position and then the left front position in the process of moving to the next cell forward. If a missile occupies either of those two positions then an encounter occurs. So the missile's position at the time of the encounter is the same as the position of the monster or party member encountered.
2. A missile encounter with a wall occurs as the missile leaves the cell in front of the wall and is about to move forward into the wall. So the missile's position at the time of the encounter is one-half cell away from the position of the wall encountered.

The filter receives six parameters:

• 0 - Action to Perform - Default is 0.
• 1 - The type of encounter
• 2 - Location of the encounter
• 3 - The object ID of the containing Missile
• 4 - The object ID of the contained projectile
• 5 - Absolute direction missile is traveling
• 6 - Party/monster Index (types 1 or 7) or -1 (types 2 through 6)

The types are:

• 1 - The missile encountered a monster.
• 2 - The missile encountered a door.
• 3 - The missile encountered a solid trick wall
• 4 - The missile encountered a solid wall
• 5 - The missile ran out of gas and fell to the floor.
• 6 - The missile encountered the exterior wall of the dungeon
• 7 - The missile encountered a party member

The Filter should set the 'action' field to non-zero and return the parameters in order to modify the default result of the encounter. The effect of doing this varies depending on the original type and the action.

The Actions are:

1. Ignore encounter. Missile generally proceeds as if it encountered nothing.
2. Stop missile. The encounter is ignored and the missile stops moving. If the conditions for the encounter remain, the filter will be called again every tick of the clock.
3. Ignore encounter. Turn and move the missile to the absolute direction specified in parameter 5.