library-mirrors/heightmap
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Change indentation.

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Marc Lepage 2011-10-22 22:46:16 -04:00
parent 81297e3a73
commit 8690916fe8
1 changed files with 63 additions and 63 deletions
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heightmap.lua
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@ -7,44 +7,44 @@ module(...)
-- Find power of two sufficient for size -- Find power of two sufficient for size
local function pot(size) local function pot(size)
local pot = 2 local pot = 2
while true do while true do
if size <= pot then return pot end if size <= pot then return pot end
pot = 2*pot pot = 2*pot
end end
end end
-- Create a table with 0 to n zero values -- Create a table with 0 to n zero values
local function tcreate(n) local function tcreate(n)
local t = {} local t = {}
for i = 0, n do t[i] = 0 end for i = 0, n do t[i] = 0 end
return t return t
end end
-- Square step -- Square step
-- Sets map[x][y] from square of radius d using height function f -- Sets map[x][y] from square of radius d using height function f
local function square(map, x, y, d, f) local function square(map, x, y, d, f)
local sum, num = 0, 0 local sum, num = 0, 0
if 0 <= x-d then if 0 <= x-d then
if 0 <= y-d then sum, num = sum + map[x-d][y-d], num + 1 end if 0 <= y-d then sum, num = sum + map[x-d][y-d], num + 1 end
if y+d <= map.h then sum, num = sum + map[x-d][y+d], num + 1 end if y+d <= map.h then sum, num = sum + map[x-d][y+d], num + 1 end
end end
if x+d <= map.w then if x+d <= map.w then
if 0 <= y-d then sum, num = sum + map[x+d][y-d], num + 1 end if 0 <= y-d then sum, num = sum + map[x+d][y-d], num + 1 end
if y+d <= map.h then sum, num = sum + map[x+d][y+d], num + 1 end if y+d <= map.h then sum, num = sum + map[x+d][y+d], num + 1 end
end end
map[x][y] = f(map, x, y, d, sum/num) map[x][y] = f(map, x, y, d, sum/num)
end end
-- Diamond step -- Diamond step
-- Sets map[x][y] from diamond of radius d using height function f -- Sets map[x][y] from diamond of radius d using height function f
local function diamond(map, x, y, d, f) local function diamond(map, x, y, d, f)
local sum, num = 0, 0 local sum, num = 0, 0
if 0 <= x-d then sum, num = sum + map[x-d][y], num + 1 end if 0 <= x-d then sum, num = sum + map[x-d][y], num + 1 end
if x+d <= map.w then sum, num = sum + map[x+d][y], num + 1 end if x+d <= map.w then sum, num = sum + map[x+d][y], num + 1 end
if 0 <= y-d then sum, num = sum + map[x][y-d], num + 1 end if 0 <= y-d then sum, num = sum + map[x][y-d], num + 1 end
if y+d <= map.h then sum, num = sum + map[x][y+d], num + 1 end if y+d <= map.h then sum, num = sum + map[x][y+d], num + 1 end
map[x][y] = f(map, x, y, d, sum/num) map[x][y] = f(map, x, y, d, sum/num)
end end
-- Diamond square algorithm generates cloud/plasma fractal heightmap -- Diamond square algorithm generates cloud/plasma fractal heightmap
@ -52,36 +52,36 @@ end
-- Size must be power of two -- Size must be power of two
-- Height function f must look like f(map, x, y, d, h) and return h' -- Height function f must look like f(map, x, y, d, h) and return h'
local function diamondsquare(size, f) local function diamondsquare(size, f)
-- create map -- create map
local map = { w = size, h = size } local map = { w = size, h = size }
for c = 0, size do map[c] = tcreate(size) end for c = 0, size do map[c] = tcreate(size) end
-- seed four corners -- seed four corners
local d = size local d = size
map[0][0] = f(map, 0, 0, d, 0) map[0][0] = f(map, 0, 0, d, 0)
map[0][d] = f(map, 0, d, d, 0) map[0][d] = f(map, 0, d, d, 0)
map[d][0] = f(map, d, 0, d, 0) map[d][0] = f(map, d, 0, d, 0)
map[d][d] = f(map, d, d, d, 0) map[d][d] = f(map, d, d, d, 0)
d = d/2 d = d/2
-- perform square and diamond steps -- perform square and diamond steps
while 1 <= d do while 1 <= d do
for x = d, map.w-1, 2*d do for x = d, map.w-1, 2*d do
for y = d, map.h-1, 2*d do for y = d, map.h-1, 2*d do
square(map, x, y, d, f) square(map, x, y, d, f)
end end
end end
for x = d, map.w-1, 2*d do for x = d, map.w-1, 2*d do
for y = 0, map.h, 2*d do for y = 0, map.h, 2*d do
diamond(map, x, y, d, f) diamond(map, x, y, d, f)
end end
end end
for x = 0, map.w, 2*d do for x = 0, map.w, 2*d do
for y = d, map.h-1, 2*d do for y = d, map.h-1, 2*d do
diamond(map, x, y, d, f) diamond(map, x, y, d, f)
end end
end end
d = d/2 d = d/2
end end
return map return map
end end
-- Default height function -- Default height function
@ -89,18 +89,18 @@ end
-- h is mean height at map[x][y] (from square/diamond of radius d) -- h is mean height at map[x][y] (from square/diamond of radius d)
-- returns h' which is used to set map[x][y] -- returns h' which is used to set map[x][y]
function defaultf(map, x, y, d, h) function defaultf(map, x, y, d, h)
return h + (random()-0.5)*d return h + (random()-0.5)*d
end end
-- Create a heightmap using the specified height function (or default) -- Create a heightmap using the specified height function (or default)
-- map[x][y] where x from 0 to map.w and y from 0 to map.h -- map[x][y] where x from 0 to map.w and y from 0 to map.h
function create(width, height, f) function create(width, height, f)
f = f and f or defaultf f = f and f or defaultf
-- make heightmap -- make heightmap
local map = diamondsquare(pot(max(width, height)), f) local map = diamondsquare(pot(max(width, height)), f)
-- clip heightmap to desired size -- clip heightmap to desired size
for x = 0, map.w do for y = height+1, map.h do map[x][y] = nil end end for x = 0, map.w do for y = height+1, map.h do map[x][y] = nil end end
for x = width+1, map.w do map[x] = nil end for x = width+1, map.w do map[x] = nil end
map.w, map.h = width, height map.w, map.h = width, height
return map return map
end end