Further improvements for ExpUtil

exp_util/module/aabb.lua

@@ -0,0 +1,100 @@
+--[[-- ExpUtil - AABB
+Provides a set of common functions for working with axis aligned bounding boxes
+]]
+
+local floor = math.floor
+local ceil = math.ceil
+local min = math.min
+local max = math.max
+
+--- @class ExpUtil_AABB
+local AABB = {}
+
+--- Check if an area is valid
+--- @param aabb BoundingBox
+--- @return boolean # True if the area is valid
+function AABB.valid(aabb)
+    return aabb.left_top.x < aabb.right_bottom.x and aabb.left_top.y < aabb.right_bottom.y
+end
+
+--- Clone an area, allows for safe mutation of an input value
+--- @param aabb BoundingBox
+--- @return BoundingBox
+function AABB.clone(aabb)
+    return {
+        left_top = { x = aabb.left_top.x, y = aabb.left_top.y },
+        right_bottom = { x = aabb.right_bottom.x, y = aabb.right_bottom.y },
+    }
+end
+
+--- Expand an area to be integer aligned, expanding away from 0
+--- @param aabb BoundingBox
+--- @return BoundingBox
+function AABB.expand(aabb)
+    return {
+        left_top = { x = floor(aabb.left_top.x), y = floor(aabb.left_top.y) },
+        right_bottom = { x = ceil(aabb.right_bottom.x), y = ceil(aabb.right_bottom.y) },
+    }
+end
+
+--- Contract an area to be integer aligned, contracting towards 0
+--- @param aabb BoundingBox
+--- @return BoundingBox
+function AABB.contract(aabb)
+    return {
+        left_top = { x = ceil(aabb.left_top.x), y = ceil(aabb.left_top.y) },
+        right_bottom = { x = floor(aabb.right_bottom.x), y = floor(aabb.right_bottom.y) },
+    }
+end
+
+--- Expand an area to include all other areas
+--- @param aabb BoundingBox
+--- @param ... BoundingBox
+--- @return BoundingBox
+function AABB.union(aabb, ...)
+    local rtn = AABB.clone(aabb)
+    for _, next_aabb in ipairs{ ... } do
+        rtn.left_top.x = min(rtn.left_top.x, next_aabb.left_top.x)
+        rtn.left_top.y = min(rtn.left_top.y, next_aabb.left_top.y)
+        rtn.right_bottom.x = max(rtn.right_bottom.x, next_aabb.right_bottom.x)
+        rtn.right_bottom.y = max(rtn.right_bottom.y, next_aabb.right_bottom.y)
+    end
+    return rtn
+end
+
+--- Contract an area to include to the overlap of all areas
+--- @param aabb BoundingBox
+--- @param ... BoundingBox
+--- @return BoundingBox? # Nil if there is no intersection
+function AABB.intersect(aabb, ...)
+    local rtn = AABB.clone(aabb)
+    for _, next_aabb in ipairs{ ... } do
+        rtn.left_top.x = max(rtn.left_top.x, next_aabb.left_top.x)
+        rtn.left_top.y = max(rtn.left_top.y, next_aabb.left_top.y)
+        rtn.right_bottom.x = min(rtn.right_bottom.x, next_aabb.right_bottom.x)
+        rtn.right_bottom.y = min(rtn.right_bottom.y, next_aabb.right_bottom.y)
+        if not AABB.valid(rtn) then
+            return nil
+        end
+    end
+    return rtn
+end
+
+--- Check if a point is contained within an area
+--- @param aabb BoundingBox
+--- @param point MapPosition
+--- @return boolean # True if the point is within or on the edge of the bounding box
+function AABB.contains_point(aabb, point)
+    return point.x >= aabb.left_top.x and point.y >= aabb.left_top.y
+        and point.x <= aabb.right_bottom.x and point.y <= aabb.right_bottom.y
+end
+
+--- Check if an area is fulling contained within another area
+--- @param aabb BoundingBox
+--- @param other BoundingBox
+--- @return boolean # True if the point is within or on the edge of the bounding box
+function AABB.contains_area(aabb, other)
+    return AABB.contains_point(aabb, other.left_top) and AABB.contains_point(aabb, other.right_bottom)
+end
+
+return AABB