Machine-Readable: Ballistica Mechanic

Technical reference page for the Ballistica line-of-sight and pathfinding system.

File: `RemixedDungeon/src/main/java/com/watabou/pixeldungeon/mechanics/Ballistica.java`

Class: `com.watabou.pixeldungeon.mechanics.Ballistica`

• `public static int[] trace` - Array storing the path cells (size: 32, dynamically resized)
• `public static int distance` - Length of the calculated path

cast(int from, int to, boolean magic, boolean hitChars)

• Delegates to full cast method with hitObjects = false
• Parameters:
  • `from` - Starting cell index
  • `to` - Target cell index
  • `magic` - If true, continues tracing even after reaching target
  • `hitChars` - If true, stops when hitting characters

cast(int from, int to, boolean magic, boolean hitChars, boolean hitObjects)

• Main pathfinding method using Bresenham's line algorithm
• Returns the final cell index that the trace reaches
• Stops when encountering:
  • Non-passable terrain (unless avoid cell)
  • LOS-blocking terrain
  • Characters (if hitChars is true)
  • Level objects (if hitObjects is true and object has layer >= 0)
  • LOS-blocking level objects

getBacktraceCell(int distFromEnd)

• Returns a cell from the trace, counting from the end
• Parameter: `distFromEnd` - Distance from the end of the trace (clamped to distance - 1)
• Returns: Cell index at position (distance - 1 - distFromEnd)

The Ballistica system uses Bresenham's line algorithm for path calculation:

1. Calculate starting (x0, y0) and target (x1, y1) coordinates 2. Determine step direction for X and Y axes 3. Use major/minor axis stepping with error accumulation 4. Trace cells until target is reached or obstacle is encountered 5. Store each cell in the trace array

Ballistica is used by:

• Zapping mobs (Warlock, etc.) for attack validation
• Wand targeting system
• Projectile weapon targeting
• Trap trigger detection
• Line-of-sight calculations

• Ballistica.java on GitHub
• Warlock.java - uses Ballistica for canAttack
• Tengu.java - uses Ballistica for distance attacks
• Level.java - Field of View integration

The `getBacktraceCell` method is exposed to Lua via @LuaInterface annotation for scripting support.