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

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--[[
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 {[number,number]} heightmap_size The size of the heightmap as [ height, width ]
@param {number[]} matrix The matrix to convolve with.
@param {[number, number]} matrix_size The size of the convolution matrix as [ height, width ]
]]--
function worldeditadditions.conv.convole(heightmap, heightmap_size, matrix, matrix_size)
if matrix_size[0] % 2 ~= 1 or matrix_size[1] % 2 ~= 1 then
return false, "Error: The matrix size must contain only odd numbers (even number detected)"
end
local border_size = {
(matrix_size[0]-1) / 2, -- height
(matrix_size[1]-1) / 2 -- width
}
-- Convolve over only the bit that allows us to use the full convolution matrix
for y = heightmap_size[0] - border_size[0], border_size[0], -1 do
for x = heightmap_size[1] - border_size[1], border_size[1], -1 do
local total = 0
for my = matrix_size[0], 0, -1 do
for mx = matrix_size[1], 0, -1 do
local mi = (my * matrix_size[1]) + mx
local cy = y + (my - border_size[0])
local cx = x + (mx - border_size[1])
local i = (cy * heightmap_size[1]) + cx
total = total + matrix[mi] * heightmap[i]
end
end
heightmap[(y * heightmap_size[1]) + x] = total
end
end
return true, heightmap
end