LambdaHack- A game engine library for roguelike dungeon crawlers

Safe HaskellNone




DFOV (Digital Field of View) implemented according to specification at This fast version of the algorithm, based on PFOV, has AFAIK never been described nor implemented before.



scan Source #


:: EnumSet Point 
-> Distance

visiblity distance

-> Array Bool 
-> (Bump -> Point)

coordinate transformation

-> EnumSet Point 

Calculates the list of tiles, in Bump coordinates, visible from (0, 0), within the given sight range.

Scanning coordinate system

data Bump Source #

Rotated and translated coordinates of 2D points, so that the points fit in a single quadrant area (e, g., quadrant I for Permissive FOV, hence both coordinates positive; adjacent diagonal halves of quadrant I and II for Digital FOV, hence y positive). The special coordinates are written using the standard mathematical coordinate setup, where quadrant I, with x and y positive, is on the upper right.





Assorted minor operations

Current scan parameters

type Distance = Int Source #

Distance from the (0, 0) point where FOV originates.

type Progress = Int Source #

Progress along an arc with a constant distance from (0, 0).

Geometry in system Bump

data Line Source #

Straight line between points.


Line Bump Bump 


type ConvexHull = [Bump] Source #

Convex hull represented as a list of points.

type Edge = (Line, ConvexHull) Source #

An edge (comprising of a line and a convex hull) of the area to be scanned.

type EdgeInterval = (Edge, Edge) Source #

The area left to be scanned, delimited by edges.

Internal operations

steeper :: Bump -> Bump -> Bump -> Ordering Source #

Check if the line from the second point to the first is more steep than the line from the third point to the first. This is related to the formal notion of gradient (or angle), but hacked wrt signs to work fast in this particular setup. Returns True for ill-defined lines.

addHull Source #


:: (Bump -> Bump -> Ordering)

a comparison function

-> Bump

a new bump to consider

-> ConvexHull

a convex hull of bumps represented as a list

-> ConvexHull 

Extends a convex hull of bumps with a new bump. Nothing needs to be done if the new bump already lies within the hull. The first argument is typically steeper, optionally negated, applied to the second argument.

dline :: Bump -> Bump -> Line Source #

Create a line from two points. Debug: check if well-defined.

dsteeper :: Bump -> Bump -> Bump -> Ordering Source #

Compare steepness of (p1, f) and (p2, f). Debug: Verify that the results of 2 independent checks are equal.

intersect :: Line -> Distance -> (Int, Int) Source #

The X coordinate, represented as a fraction, of the intersection of a given line and the line of diagonals of diamonds at distance d from (0, 0).

_debugSteeper :: Bump -> Bump -> Bump -> Ordering Source #

Debug functions for DFOV:

Debug: calculate steeper for DFOV in another way and compare results.

_debugLine :: Line -> (Bool, String) Source #

Debug: check if a view border line for DFOV is legal.