Minetest-WorldEditAdditions/worldeditadditions/lib/conv/convolve.lua

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local wea = worldeditadditions
local Vector3 = wea.Vector3
--[[
Convolves over a given 2D heightmap with a given matrix.
Note that this *mutates* the given heightmap.
Note also that the dimensions of the matrix must *only* be odd.
@param {number[]} heightmap The 2D heightmap to convolve over.
@param Vector3 heightmap_size The size of the heightmap as an X/Z Vector3 instance.
@param {number[]} matrix The matrix to convolve with.
@param Vector3 matrix_size The size of the convolution matrix as an X/Z Vector3 instance.
]]--
function worldeditadditions.conv.convolve(heightmap, heightmap_size, matrix, matrix_size)
if matrix_size.x % 2 ~= 1 or matrix_size.z % 2 ~= 1 then
return false, "Error: The matrix size must contain only odd numbers (even number detected)"
end
-- We need to reference a *copy* of the heightmap when convolving
-- This is because we need the original values when we perform a
-- convolution on a given pixel
local heightmap_copy = wea.table.shallowcopy(heightmap)
local border_size = Vector3.new(
(matrix_size.x-1) / 2, -- x = height
0,
(matrix_size.z-1) / 2 -- z = width
)
-- print("[convolve] matrix_size", matrix_size.x, matrix_size.z)
-- print("[convolve] border_size", border_size.x, border_size.z)
-- print("[convolve] heightmap_size: ", heightmap_size.z, heightmap_size.x)
--
-- print("[convolve] z: from", (heightmap_size.z-border_size.x) - 1, "to", border_size.x, "step", -1)
-- print("[convolve] x: from", (heightmap_size.x-border_size.z) - 1, "to", border_size.z, "step", -1)
-- Convolve over only the bit that allows us to use the full convolution matrix
for z = (heightmap_size.z-border_size.x) - 1, border_size.x, -1 do
for x = (heightmap_size.x-border_size.z) - 1, border_size.z, -1 do
local total = 0
local hi = (z * heightmap_size.x) + x
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-- print("[convolve/internal] z", z, "x", x, "hi", hi)
-- No continue statement in Lua :-/
if heightmap_copy[hi] ~= -1 then
for mz = matrix_size.x-1, 0, -1 do
for mx = matrix_size.z-1, 0, -1 do
local mi = (mz * matrix_size.z) + mx
local cz = z + (mz - border_size.x)
local cx = x + (mx - border_size.z)
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local i = (cz * heightmap_size.x) + cx
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-- A value of -1 = nothing in this column (so we should ignore it)
if heightmap_copy[i] ~= -1 then
total = total + (matrix[mi] * heightmap_copy[i])
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end
end
end
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-- Rounding hack - ref https://stackoverflow.com/a/18313481/1460422
-- heightmap[hi] = math.floor(total + 0.5)
heightmap[hi] = math.ceil(total)
end
end
end
return true, heightmap
end