From 4aae686c45883bfd6fac12d192dc3f8fa01e5582 Mon Sep 17 00:00:00 2001
From: Alex Clink <alexclink@gmail.com>
Date: Thu, 27 Jan 2022 23:04:24 -0500
Subject: [PATCH] Add noise 1d example - experimental

---
 examples/noise_1d.cr | 49 ++++++++++++++++++++++++++++++++++++++++++++
 spec/noise_spec.cr   | 13 ++++++++++++
 src/lehmer32.cr      |  3 ++-
 src/noise.cr         | 37 +++++++++++++++++++++++++++++++++
 4 files changed, 101 insertions(+), 1 deletion(-)
 create mode 100644 examples/noise_1d.cr
 create mode 100644 spec/noise_spec.cr
 create mode 100644 src/noise.cr

diff --git a/examples/noise_1d.cr b/examples/noise_1d.cr
new file mode 100644
index 0000000..b858ed8
--- /dev/null
+++ b/examples/noise_1d.cr
@@ -0,0 +1,49 @@
+require "../src/game"
+require "../src/controller"
+require "../src/noise"
+
+module PF
+  class Noise1d < Game
+    @noise : Noise = Noise.new
+    @noise_scale : Float64
+    @noise_zoom : Float64
+
+    def initialize(*args, **kwargs)
+      super
+
+      @noise_scale = height / 4
+      @noise_zoom = width / 4
+      @xpos = 0.0
+
+      @controller = PF::Controller(LibSDL::Scancode).new({
+        LibSDL::Scancode::UP    => "scale up",
+        LibSDL::Scancode::DOWN  => "scale down",
+        LibSDL::Scancode::RIGHT => "zoom up",
+        LibSDL::Scancode::LEFT  => "zoom down",
+      })
+    end
+
+    def update(dt, event)
+      @controller.map_event(event)
+      @noise_scale += (@noise_scale * 0.8) * dt if @controller.held?("scale up")
+      @noise_scale -= (@noise_scale * 0.8) * dt if @controller.held?("scale down")
+      @noise_zoom += (@noise_zoom * 0.8) * dt if @controller.held?("zoom up")
+      @noise_zoom -= (@noise_zoom * 0.8) * dt if @controller.held?("zoom down")
+      @xpos += 20.0 * dt
+    end
+
+    def draw
+      clear(50, 127, 200)
+      step = width // 15
+      mid = height // 2
+
+      0.upto(width) do |x|
+        y = mid + (@noise.get((x + @xpos) / @noise_zoom) * @noise_scale).to_i
+        draw_point(x, y, Pixel.yellow)
+      end
+    end
+  end
+end
+
+game = PF::Noise1d.new(300, 200, 2)
+game.run!
diff --git a/spec/noise_spec.cr b/spec/noise_spec.cr
new file mode 100644
index 0000000..c77fe87
--- /dev/null
+++ b/spec/noise_spec.cr
@@ -0,0 +1,13 @@
+require "./spec_helper"
+require "../src/noise"
+
+include PF
+
+describe Noise do
+  describe ".cos_interpolate" do
+    it "interpolates" do
+      i = Noise.cosine_interpolate(0.0, 10.0, 0.5)
+      (4.9..5.1).includes?(i).should eq(true)
+    end
+  end
+end
diff --git a/src/lehmer32.cr b/src/lehmer32.cr
index 7690431..83a8af2 100644
--- a/src/lehmer32.cr
+++ b/src/lehmer32.cr
@@ -1,5 +1,5 @@
 module PF
-  class Lehmer32
+  struct Lehmer32
     include Random
 
     @state : UInt32
@@ -9,6 +9,7 @@ module PF
 
     def new_seed(n : Number)
       @state = n.to_u32!
+      self
     end
 
     # Generate the next number in the squence
diff --git a/src/noise.cr b/src/noise.cr
new file mode 100644
index 0000000..fd2f260
--- /dev/null
+++ b/src/noise.cr
@@ -0,0 +1,37 @@
+require "./lehmer32"
+
+module PF
+  @[Experimental("Undergoing development")]
+  struct Noise
+    # Cosine interpolation
+    def self.cosine_interpolate(point1 : Float64, point2 : Float64, position : Float64)
+      ft = position * Math::PI
+      f = (1 - Math.cos(ft)) * 0.5
+      point1 * (1 - f) + point2 * f
+    end
+
+    # Linear interpolation
+    def self.linear_interpolate(point1 : Float64, point2 : Float64, position : Float64)
+      point1 * (1 - position) + point2 * position
+    end
+
+    @prng : Lehmer32
+    @seed : UInt32
+
+    def initialize(@seed = ::rand(UInt32))
+      @prng = Lehmer32.new
+    end
+
+    # Returns 1d noise
+    def get(x : Float64)
+      x += @seed
+      n1 = @prng.new_seed(x.to_u32!).rand(-1.0..1.0)
+      n2 = @prng.new_seed(x.to_u32! + 1).rand(-1.0..1.0)
+      Noise.cosine_interpolate(n1, n2, x - x.to_u32!)
+    end
+
+    # Returns 2d noise
+    # def get(x : Float64, y : Float64)
+    # end
+  end
+end