Minetest-WorldEditAdditions/worldeditadditions/utils/terrain/calculate_slopes.lua

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local wea = worldeditadditions
local Vector3 = wea.Vector3
--- Converts a 2d heightmap into slope values in radians.
-- Convert a radians to degrees by doing (radians*math.pi) / 180 for display,
-- but it is STRONGLY recommended to keep all internal calculations in radians.
-- @param heightmap table A ZERO indexed flat heightmap. See worldeditadditions.terrain.make_heightmap().
-- @param heightmap_size int[] The size of the heightmap in the form [ z, x ]
-- @return Vector[] The calculated slope map, in the same form as the input heightmap. Each element of the array is a (floating-point) number representing the slope in that cell in radians.
local function calculate_slopes(heightmap, heightmap_size)
local normals = wea.terrain.calculate_normals(heightmap, heightmap_size)
local slopes = { }
local up = wea.Vector3.new(0, 1, 0) -- Z & Y are flipped
for z = heightmap_size.z-1, 0, -1 do
for x = heightmap_size.x-1, 0, -1 do
local hi = z*heightmap_size.x + x
-- Ref https://stackoverflow.com/a/16669463/1460422
-- slopes[hi] = wea.Vector3.dot_product(normals[hi], up)
slopes[hi] = math.acos(normals[hi].y)
end
end
return slopes
end
return calculate_slopes