Minetest-WorldEditAdditions/worldeditadditions/utils/terrain.lua

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--- Given a manip object and associates, generates a 2D x/z heightmap.
-- Note that pos1 and pos2 should have already been pushed through
-- worldedit.sort_pos(pos1, pos2) before passing them to this function.
-- @param pos1 Vector Position 1 of the region to operate on
-- @param pos2 Vector Position 2 of the region to operate on
-- @param manip VoxelManip The VoxelManip object.
-- @param area area The associated area object.
-- @param data table The associated data object.
-- @return table The ZERO-indexed heightmap data (as 1 single flat array).
function worldeditadditions.make_heightmap(pos1, pos2, manip, area, data)
-- z y x (in reverse for little-endian machines) is the preferred loop order, but that isn't really possible here
local heightmap = {}
local hi = 0
local changes = { updated = 0, skipped_columns = 0 }
for z = pos1.z, pos2.z, 1 do
for x = pos1.x, pos2.x, 1 do
local found_node = false
-- Scan each column top to bottom
for y = pos2.y+1, pos1.y, -1 do
local i = area:index(x, y, z)
if not worldeditadditions.is_airlike(data[i]) then
-- It's the first non-airlike node in this column
-- Start heightmap values from 1 (i.e. there's at least 1 node in the column)
heightmap[hi] = (y - pos1.y) + 1
found_node = true
break
end
end
if not found_node then heightmap[hi] = -1 end
hi = hi + 1
end
end
return heightmap
end
--- Calculates a normal map for the given heightmap.
-- Caution: This method (like worldeditadditions.make_heightmap) works on
-- X AND Z, and NOT x and y. This means that the resulting 3d normal vectors
-- will have the z and y values swapped.
-- @param heightmap table A ZERO indexed flat heightmap. See worldeditadditions.make_heightmap().
-- @param heightmap_size int[] The size of the heightmap in the form [ z, x ]
-- @return Vector[] The calculated normal map, in the same form as the input heightmap. Each element of the array is a 3D Vector (i.e. { x, y, z }) representing a normal.
function worldeditadditions.calculate_normals(heightmap, heightmap_size)
local result = {}
for z = heightmap_size[0], 0, -1 do
for x = heightmap_size[1], 0, -1 do
-- Algorithm ref https://stackoverflow.com/a/13983431/1460422
-- Also ref Vector.mjs, which I implemented myself (available upon request)
local hi = z*heightmap_size[1] + x
-- Default to this pixel's height
local up = heightmap[hi]
local down = heightmap[hi]
local left = heightmap[hi]
local right = heightmap[hi]
if z - 1 > 0 then up = heightmap[(z-1)*heightmap_size[1] + x] end
if z + 1 < heightmap_size[1] then down = heightmap[(z+1)*heightmap_size[1] + x] end
if x - 1 > 0 then left = heightmap[z*heightmap_size[1] + (x-1)] end
if x + 1 < heightmap_size[0] then right = heightmap[z*heightmap_size[1] + (x+1)] end
result[hi] = worldeditadditions.vector.normalize({
x = left - right,
y = 2, -- Z & Y are flipped
z = down - up
})
end
end
return result
end