initial

1 files changed, 74 insertions, 0 deletions

diff --git a/noise.lua b/noise.lua
new file mode 100644
index 0000000..f802ea2
--- /dev/null
+++ b/noise.lua
@@ -0,0 +1,74 @@
+local Pos = require'r.pos'
+local class = require'r.class'
+local rmath = require'r.math'
+local bit = require'bit'
+local tau = 2*math.pi
+
+math.randomseed(os.time())
+
+local function hash_list(t)
+	local h = #t
+	for _,x in ipairs(t) do
+		x = bit.bxor(bit.rshift(x,16),x) * 0x7feb352d
+		x = bit.bxor(bit.rshift(x,15),x) * 0x846ca68b
+		x = bit.bxor(bit.rshift(x,16),x)
+		h = bit.bxor(h,x + 0x9e3779b9 + bit.lshift(h,6) + bit.rshift(h,2))
+	end
+	return h
+end
+
+local function hash_to_unit_vec(t)
+	local h = hash_list(t)
+	math.randomseed(h)
+	local theta = math.random()*tau
+	return Pos:make(math.cos(theta),math.sin(theta))
+end
+
+local PerlinNoise = class()
+function PerlinNoise.make(cls,seed)
+	return setmetatable({seed=seed},cls)
+end
+function PerlinNoise.vertex(self,ix,iy)
+	return hash_to_unit_vec{ix,iy,self.seed}
+end
+
+function PerlinNoise.at(self,x,y)
+	local x0 = math.floor(x)
+	local y0 = math.floor(y)
+	local x1 = x0 + 1
+	local y1 = y0 + 1
+
+	local v00 = self:vertex(x0,y0)
+	local v01 = self:vertex(x0,y1)
+	local v10 = self:vertex(x1,y0)
+	local v11 = self:vertex(x1,y1)
+
+	local p = function(...) return Pos:make(...) end
+	local d00 = v00:dot(p(x-x0,y-y0))
+	local d01 = v01:dot(p(x-x0,y-y1))
+	local d10 = v10:dot(p(x-x1,y-y0))
+	local d11 = v11:dot(p(x-x1,y-y1))
+
+	local q0 = rmath.slerp(d00,d01,y-y0)
+	local q1 = rmath.slerp(d10,d11,y-y0)
+	local z  = rmath.slerp(q0,q1,x-x0)
+	return z
+end
+
+local NoiseAgg = class()
+function NoiseAgg.make(cls,things)
+	return setmetatable({things=things or {}},cls)
+end
+function NoiseAgg.at(self,x,y)
+	local n = 0
+	local t = 0
+	assert(#self.things>0,"can't generate noise with no noise things")
+	for _,thing in ipairs(self.things) do
+		local gen,scale,amp = thing.gen,thing.scale,thing.amp
+		n = n + amp
+		t = t + gen:at(x/scale,y/scale)*amp
+	end
+	return t/n
+end
+
+return {PerlinNoise=PerlinNoise,NoiseAgg=NoiseAgg}