lua scene support with one example, general improvements

scenes/randomspheres.lua

@@ -0,0 +1,52 @@
+local unpack = table.unpack or _G.unpack
+math.randomseed(os.time())
+
+local function randab(a, b)
+    return math.random() * (b-a) + a
+end
+
+local function randtable(n, a, b)
+    local t = {}
+    for i=1, n do
+        t[i] = randab(a, b)
+    end
+    return t
+end
+
+local function choice(list)
+    return list[math.random(1, #list)]
+end
+
+local function randomsphere()
+    local pos = vec3.new(unpack(randtable(3, -2, 2)))
+    local radius = randab(0, 0.5)
+	local emission = colorvec.new(unpack(randtable(4, 0, 1)))
+    local reflection = colormat.new(unpack(randtable(16, 0, 1)))
+    local surfacetype = choice({surfacetype.DIFFUSE, surfacetype.REFLECTIVE, surfacetype.STOP})
+
+    return obj.withmaterial(
+        obj.sphere(pos, radius),
+        material.new(emission, reflection, surfacetype)
+    )
+end
+
+local function union(objs)
+    local n = #objs
+    if n == 1 then return objs[1] end
+
+    local mid = n//2
+    local left, right = {}, {}
+    for i=1, mid do
+        left[i] = objs[i]
+    end
+    for i=mid+1, n do
+        right[i-mid] = objs[i]
+    end
+	return obj.union(union(left), union(right))
+end
+
+local spheres = {}
+for i=1, 100 do
+    spheres[i] = randomsphere()
+end
+return union(spheres)