mapgen_rivers/heightmap.lua

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2021-06-03 19:21:45 +02:00
local modpath = mapgen_rivers.modpath
local make_polygons = dofile(modpath .. 'polygons.lua')
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 MAP_BOTTOM = -31000
-- Linear interpolation
local function interp(v00, v01, v11, v10, xf, zf)
local v0 = v01*xf + v00*(1-xf)
local v1 = v11*xf + v10*(1-xf)
return v1*zf + v0*(1-zf)
end
local function heightmaps(minp, maxp)
local polygons = make_polygons(minp, maxp)
local incr = maxp.z-minp.z+1
local terrain_height_map = {}
local lake_height_map = {}
local i = 1
for z=minp.z, maxp.z do
for x=minp.x, maxp.x do
local poly = polygons[i]
if poly then
local xf, zf = transform_quadri(poly.x, poly.z, x, z)
local i00, i01, i11, i10 = unpack(poly.i)
-- Load river width on 4 edges and corners
local r_west, r_north, r_east, r_south = unpack(poly.rivers)
local c_NW, c_NE, c_SE, c_SW = unpack(poly.river_corners)
-- Calculate the depth factor for each edge and corner.
-- Depth factor:
-- < 0: outside river
-- = 0: on riverbank
-- > 0: inside river
local depth_factors = {
r_west - xf,
r_north - zf,
xf - r_east,
zf - r_south,
c_NW-xf-zf,
xf-zf-c_NE,
xf+zf-c_SE,
zf-xf-c_SW,
}
-- Find the maximal depth factor and determine to which river it belongs
local depth_factor_max = 0
local imax = 0
for i=1, 8 do
if depth_factors[i] >= depth_factor_max then
depth_factor_max = depth_factors[i]
imax = i
end
end
-- Transform the coordinates to have xf and zf = 0 or 1 in rivers (to avoid rivers having lateral slope and to accomodate the surrounding smoothly)
if imax == 0 then
local x0 = math.max(r_west, c_NW-zf, zf-c_SW)
local x1 = math.min(r_east, c_NE+zf, c_SE-zf)
local z0 = math.max(r_north, c_NW-xf, xf-c_NE)
local z1 = math.min(r_south, c_SW+xf, c_SE-xf)
xf = (xf-x0) / (x1-x0)
zf = (zf-z0) / (z1-z0)
elseif imax == 1 then
xf = 0
elseif imax == 2 then
zf = 0
elseif imax == 3 then
xf = 1
elseif imax == 4 then
zf = 1
elseif imax == 5 then
xf, zf = 0, 0
elseif imax == 6 then
xf, zf = 1, 0
elseif imax == 7 then
xf, zf = 1, 1
elseif imax == 8 then
xf, zf = 0, 1
end
-- Determine elevation by interpolation
local vdem = poly.dem
local terrain_height = math.floor(0.5+interp(
vdem[1],
vdem[2],
vdem[3],
vdem[4],
xf, zf
))
-- Spatial gradient of the interpolation
local slope_x = zf*(vdem[3]-vdem[4]) + (1-zf)*(vdem[2]-vdem[1]) < 0
local slope_z = xf*(vdem[3]-vdem[2]) + (1-xf)*(vdem[4]-vdem[1]) < 0
local lake_id = 0
if slope_x then
if slope_z then
lake_id = 3
else
lake_id = 2
end
else
if slope_z then
lake_id = 4
else
lake_id = 1
end
end
local lake_height = math.max(math.floor(poly.lake[lake_id]), terrain_height)
if imax > 0 and depth_factor_max > 0 then
terrain_height = math.min(math.max(lake_height, sea_level) - math.floor(1+depth_factor_max*riverbed_slope), terrain_height)
end
terrain_height_map[i] = terrain_height
lake_height_map[i] = lake_height
else
terrain_height_map[i] = MAP_BOTTOM
lake_height_map[i] = MAP_BOTTOM
end
i = i + 1
end
end
return terrain_height_map, lake_height_map
end
return heightmaps