mirror of
https://github.com/sbrl/Minetest-WorldEditAdditions.git
synced 2024-06-02 20:53:04 +00:00
51 lines
1.9 KiB
Lua
51 lines
1.9 KiB
Lua
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--[[
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Convolves over a given 2D heightmap with a given matrix.
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Note that this *mutates* the given heightmap.
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Note also that the dimensions of the matrix must *only* be odd.
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@param {number[]} heightmap The 2D heightmap to convolve over.
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@param {[number,number]} heightmap_size The size of the heightmap as [ height, width ]
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@param {number[]} matrix The matrix to convolve with.
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@param {[number, number]} matrix_size The size of the convolution matrix as [ height, width ]
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]]--
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function worldeditadditions.conv.convolve(heightmap, heightmap_size, matrix, matrix_size)
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if matrix_size[0] % 2 ~= 1 or matrix_size[1] % 2 ~= 1 then
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return false, "Error: The matrix size must contain only odd numbers (even number detected)"
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end
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local border_size = {}
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border_size[0] = (matrix_size[0]-1) / 2 -- height
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border_size[1] = (matrix_size[1]-1) / 2 -- width
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print("[convolve] matrix_size", matrix_size[0], matrix_size[1])
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print("[convolve] border_size", border_size[0], border_size[1])
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-- Convolve over only the bit that allows us to use the full convolution matrix
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for y = (heightmap_size[0]-border_size[0]) - 1, border_size[0], -1 do
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for x = (heightmap_size[1]-border_size[1]) - 1, border_size[1], -1 do
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local total = 0
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for my = matrix_size[0]-1, 0, -1 do
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for mx = matrix_size[1]-1, 0, -1 do
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local mi = (my * matrix_size[1]) + mx
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local cy = y + (my - border_size[0])
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local cx = x + (mx - border_size[1])
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local i = (cy * heightmap_size[1]) + cx
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-- print("[convolve] i", i, "mi", mi, "matrix[mi]", matrix[mi], "heightmap[i]", heightmap[i])
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-- A value of -1 = nothing in this column (so we should ignore it)
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if heightmap[i] ~= -1 then
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total = total + (matrix[mi] * heightmap[i])
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end
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end
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end
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-- Rounding hack - ref https://stackoverflow.com/a/18313481/1460422
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heightmap[(y * heightmap_size[1]) + x] = math.floor(total + 0.5)
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end
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end
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return true, heightmap
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end
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