noise: implement 2d perlin noise (#42) (#87)

Author: boonsboos

.github/workflows/ci.yml

@@ -45,8 +45,8 @@ jobs:
 
       - name: Validate Docs
         run: |
-          cd ./vsl
-          v check-md .
+          cd ~
+          v check-md ~/.vmodules/vsl
 
   ci:
     runs-on: ${{ matrix.os }}

noise/perlin.v

@@ -0,0 +1,69 @@
+module noise
+
+import math
+import rand
+
+// implemented according to the example implementation on wikipedia
+// https://en.wikipedia.org/wiki/Perlin_noise#Implementation
+
+struct Vec2 {
+	x f32
+	y f32
+}
+
+[inline]
+fn random_gradient() ?Vec2 {
+	nr := rand.f32_in_range(0.0, math.pi * 2)?
+	return Vec2{
+		x: math.cosf(nr)
+		y: math.sinf(nr)
+	}
+}
+
+[inline]
+fn interpolate(a f32, b f32, w f32) f32 {
+	return ((a - b) * w) + a
+}
+
+[inline]
+fn dot(ix int, iy int, x f32, y f32) ?f32 {
+	vec := random_gradient()?
+	dx := x - f32(ix)
+	dy := y - f32(iy)
+	return dx * vec.x + dy * vec.y
+}
+
+// gets the noise value at coordinate (x, y)
+[inline]
+pub fn perlin(x f32, y f32) ?f32 {
+	x1 := int(math.floor(x))
+	y1 := int(math.floor(y))
+	x2 := x1 + 1
+	y2 := y1 + 1
+
+	sx := x - f32(x1)
+	sy := y - f32(y2)
+
+	n0 := dot(x1, y1, x, y)?
+	n1 := dot(x2, y1, x, y)?
+	first := interpolate(n0, n1, sx)
+
+	n2 := dot(x1, y2, x, y)?
+	n3 := dot(x2, y2, x, y)?
+	second := interpolate(n2, n3, sx)
+
+	return interpolate(first, second, sy)
+}
+
+// creates a 2d array of perlin noise of size `w` times `h`
+pub fn perlin_many(w int, h int) ?[][]f32 {
+	mut res := [][]f32{len: h, init: []f32{len: w}}
+	for i, a in res {
+		for j, _ in a {
+			val := perlin(j, i)?
+			println(f64(val))
+			res[i][j] = val
+		}
+	}
+	return res
+}

noise/perlin_test.v

@@ -0,0 +1,16 @@
+module noise
+
+import rand
+
+fn test_perlin() {
+	rand.seed([u32(1), 0])
+	assert perlin(0.0, 0.0) or { assert false } == -0.6457864046096802
+}
+
+fn test_perlin_many() {
+	rand.seed([u32(1), 0])
+	assert perlin_many(2, 2) or { assert false } == [
+		[f32(-0.6457864046096802), 0.0279612485319376],
+		[f32(0.2286834865808487), -0.5146363377571106],
+	]
+}

noise/readme.md

@@ -0,0 +1,18 @@
+# noise
+
+This module aims to to implement noise algorithms.
+
+It uses the `rand` module in vlib to generate random numbers,
+so you may seed the generator as you see fit.
+
+Example:
+```v
+import vsl.noise
+import rand
+
+fn main() {
+	rand.seed([u32(1), 0])
+	println(noise.perlin(0.0, 0.0)?)
+}
+```
+Output: `-0.6457864`