mtcontrib/mapgen_rivers
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Move geometry helpers back to heightmap.lua

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Gael-de-Sailly 2022-01-26 11:09:51 +01:00
parent 6564d40b85
commit 0983c27cca
2 changed files with 38 additions and 43 deletions
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40
geometry.lua
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@ -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

41
heightmap.lua
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@ -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)