diff --git a/geometry.lua b/geometry.lua
deleted file mode 100644
index 26b2214..0000000
--- a/geometry.lua
+++ /dev/null
@@ -1,40 +0,0 @@
-local sqrt, abs = math.sqrt, math.abs
-local unpk = unpack
-
-local function distance_to_segment(x1, y1, x2, y2, x, y)
-	-- get the distance between point (x,y) and segment (x1,y1)-(x2,y2)
-	local a = (x1-x2)^2 + (y1-y2)^2 -- square of distance
-	local b = (x1-x)^2 + (y1-y)^2
-	local c = (x2-x)^2 + (y2-y)^2
-	if a + b < c then
-		-- The closest point of the segment is the extremity 1
-		return sqrt(b)
-	elseif a + c < b then
-		-- The closest point of the segment is the extremity 2
-		return sqrt(c)
-	else
-		-- The closest point is on the segment
-		return abs(x1 * (y2-y) + x2 * (y-y1) + x * (y1-y2)) / sqrt(a)
-	end
-end
-
-local function transform_quadri(X, Y, x, y)
-	-- To index points in an irregular quadrilateral, giving x and y between 0 (one edge) and 1 (opposite edge)
-	-- X, Y 4-vectors giving the coordinates of the 4 vertices
-	-- x, y position to index.
-	local x1, x2, x3, x4 = unpk(X)
-	local y1, y2, y3, y4 = unpk(Y)
-
-	-- Compare distance to 2 opposite edges, they give the X coordinate
-	local d23 = distance_to_segment(x2,y2,x3,y3,x,y)
-	local d41 = distance_to_segment(x4,y4,x1,y1,x,y)
-	local xc = d41 / (d23+d41)
-
-	-- Same for the 2 other edges, they give the Y coordinate
-	local d12 = distance_to_segment(x1,y1,x2,y2,x,y)
-	local d34 = distance_to_segment(x3,y3,x4,y4,x,y)
-	local yc = d12 / (d12+d34)
-	return xc, yc
-end
-
-return transform_quadri
diff --git a/heightmap.lua b/heightmap.lua
index 3532818..97fbd0b 100644
--- a/heightmap.lua
+++ b/heightmap.lua
@@ -1,16 +1,51 @@
 local modpath = mapgen_rivers.modpath
 
-local transform_quadri = dofile(modpath .. 'geometry.lua')
-
 local sea_level = mapgen_rivers.settings.sea_level
 local riverbed_slope = mapgen_rivers.settings.riverbed_slope * mapgen_rivers.settings.blocksize
 
 local out_elev = mapgen_rivers.settings.margin_elev
 
 -- Localize for performance
-local floor, min, max = math.floor, math.min, math.max
+local floor, min, max, sqrt, abs = math.floor, math.min, math.max, math.sqrt, math.abs
 local unpk = unpack
 
+-- Geometrical helpers
+local function distance_to_segment(x1, y1, x2, y2, x, y)
+	-- get the distance between point (x,y) and segment (x1,y1)-(x2,y2)
+	local a = (x1-x2)^2 + (y1-y2)^2 -- square of distance
+	local b = (x1-x)^2 + (y1-y)^2
+	local c = (x2-x)^2 + (y2-y)^2
+	if a + b < c then
+		-- The closest point of the segment is the extremity 1
+		return sqrt(b)
+	elseif a + c < b then
+		-- The closest point of the segment is the extremity 2
+		return sqrt(c)
+	else
+		-- The closest point is on the segment
+		return abs(x1 * (y2-y) + x2 * (y-y1) + x * (y1-y2)) / sqrt(a)
+	end
+end
+
+local function transform_quadri(X, Y, x, y)
+	-- To index points in an irregular quadrilateral, giving x and y between 0 (one edge) and 1 (opposite edge)
+	-- X, Y 4-vectors giving the coordinates of the 4 vertices
+	-- x, y position to index.
+	local x1, x2, x3, x4 = unpk(X)
+	local y1, y2, y3, y4 = unpk(Y)
+
+	-- Compare distance to 2 opposite edges, they give the X coordinate
+	local d23 = distance_to_segment(x2,y2,x3,y3,x,y)
+	local d41 = distance_to_segment(x4,y4,x1,y1,x,y)
+	local xc = d41 / (d23+d41)
+
+	-- Same for the 2 other edges, they give the Y coordinate
+	local d12 = distance_to_segment(x1,y1,x2,y2,x,y)
+	local d34 = distance_to_segment(x3,y3,x4,y4,x,y)
+	local yc = d12 / (d12+d34)
+	return xc, yc
+end
+
 -- Linear interpolation
 local function interp(v00, v01, v11, v10, xf, zf)
 	local v0 = v01*xf + v00*(1-xf)