mirror of
https://github.com/sbrl/Minetest-WorldEditAdditions.git
synced 2024-11-24 08:03:46 +01:00
95 lines
2.8 KiB
Lua
95 lines
2.8 KiB
Lua
--- Creates a (normalised) box convolutional kernel.
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-- Larger box kernels will obviously be slower, but will produce a more blurred
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-- effect (i.e. smoother terrain).
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-- @param width number The width of the kernel.
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-- @param height number The height of the kernel.
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-- @return The resulting kernel as a ZERO-indexed list of numbers.
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function worldeditadditions.conv.kernel_box(width, height)
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local result = {}
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local total = 0
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for y = 0, height do
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for x = 0, width do
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result[(y*width) + x] = 1
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total = total + 1
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end
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end
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-- Ensure that everything sums up to 1
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for i = 0, #result do
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result[i] = result[i] / total
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end
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return result
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end
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--- Computes the Lth line of Pascal's triangle.
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-- More information: https://en.wikipedia.org/wiki/Pascal%27s_triangle
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-- There are probably more efficient ways to it that don't repeat themselves as
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-- much, but this is my solution.
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-- @param l number The 1-indexed row of Pascal's Triangle to return.
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-- @return number[] A ZERO-indexed list of numbers in the specified row of Pascal's Triangle.
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local function pascal(l)
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local prev = {}
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prev[0] = 1
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if l == 1 then return prev end
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prev[1] = 1
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if l == 2 then return prev end
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local length_last = 2
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for n=3, l do
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local next = {}
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for i=0, length_last do
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if i == 0 or i == length_last then
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next[i] = 1
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else
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next[i] = prev[i - 1] + prev[i]
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end
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end
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prev = next
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length_last = length_last + 1
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end
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return prev
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end
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--- Creates a pascal convolutional kernel.
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-- Larger pascal kernels will obviously be slower, but will produce a more blurred
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-- effect (i.e. smoother terrain).
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-- @param width number The width of the kernel.
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-- @param height number The height of the kernel.
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-- @param normalise=true bool Whether to normalise the resulting kernel (default: true)
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-- @return The resulting kernel as a ZERO-indexed list of numbers.
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function worldeditadditions.conv.kernel_pascal(width, height, normalise)
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if normalise == nil then normalise = true end
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local result = {}
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local pascal_width = width
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local height_middle = ((height - 2) / 2)
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local total = 0
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for y = 0, height-1 do
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local pascal_numbers = pascal(pascal_width)
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local pascal_start = (pascal_width - width) / 2
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for x = 0, width - 1 do
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result[(y*width) + x] = pascal_numbers[pascal_start + x]
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total = total + pascal_numbers[pascal_start + x]
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end
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if y > height_middle then pascal_width = pascal_width - 2
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else pascal_width = pascal_width + 2 end
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end
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if normalise then
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for k,v in pairs(result) do
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result[k] = result[k] / total
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end
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end
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return result
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end
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-- print("box, 5x5")
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-- print_2d(kernel_box(5, 5), 5)
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-- print("pascal, 5x5")
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-- print_2d(kernel_pascal(5, 5), 5)
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-- print("pascal, 7x7")
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-- print_2d(kernel_pascal(7, 7), 7)
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-- print("pascal, 9x9")
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-- print_2d(kernel_pascal(9, 9), 9)
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