mirror of
https://github.com/sbrl/Minetest-WorldEditAdditions.git
synced 2024-12-23 12:05:01 +00:00
48 lines
2.2 KiB
Lua
48 lines
2.2 KiB
Lua
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local wea = worldeditadditions
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local Vector3 = wea.Vector3
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--- Calculates a normal map for the given heightmap.
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-- Caution: This method (like worldeditadditions.make_heightmap) works on
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-- X AND Z, and NOT x and y. This means that the resulting 3d normal vectors
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-- will have the z and y values swapped.
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-- @param heightmap table A ZERO indexed flat heightmap. See worldeditadditions.terrain.make_heightmap().
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-- @param heightmap_size int[] The size of the heightmap in the form [ z, x ]
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-- @return Vector[] The calculated normal map, in the same form as the input heightmap. Each element of the array is a Vector3 instance representing a normal.
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local function calculate_normals(heightmap, heightmap_size)
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-- print("heightmap_size: "..heightmap_size.x.."x"..heightmap_size.z)
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local result = {}
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for z = heightmap_size.z-1, 0, -1 do
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for x = heightmap_size.x-1, 0, -1 do
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-- Algorithm ref https://stackoverflow.com/a/13983431/1460422
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-- Also ref Vector.mjs, which I implemented myself (available upon request)
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local hi = z*heightmap_size.x + x
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-- Default to this pixel's height
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local up = heightmap[hi]
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local down = heightmap[hi]
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local left = heightmap[hi]
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local right = heightmap[hi]
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if z - 1 > 0 then up = heightmap[(z-1)*heightmap_size.x + x] end
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if z + 1 < heightmap_size.z-1 then down = heightmap[(z+1)*heightmap_size.x + x] end
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if x - 1 > 0 then left = heightmap[z*heightmap_size.x + (x-1)] end
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if x + 1 < heightmap_size.x-1 then right = heightmap[z*heightmap_size.x + (x+1)] end
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-- print("[normals] UP | index", (z-1)*heightmap_size.x + x, "z", z, "z-1", z - 1, "up", up, "limit", 0)
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-- print("[normals] DOWN | index", (z+1)*heightmap_size.x + x, "z", z, "z+1", z + 1, "down", down, "limit", heightmap_size.x-1)
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-- print("[normals] LEFT | index", z*heightmap_size.x + (x-1), "x", x, "x-1", x - 1, "left", left, "limit", 0)
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-- print("[normals] RIGHT | index", z*heightmap_size.x + (x+1), "x", x, "x+1", x + 1, "right", right, "limit", heightmap_size.x-1)
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result[hi] = Vector3.new(
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left - right, -- x
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2, -- y - Z & Y are flipped
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down - up -- z
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):normalise()
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-- print("[normals] at "..hi.." ("..x..", "..z..") normal "..result[hi])
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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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return calculate_normals
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