1 files changed, 61 insertions, 0 deletions
diff --git a/samples/08_lerping_easing_functions/02_cubic_bezier/app/main.rb b/samples/08_lerping_easing_functions/02_cubic_bezier/app/main.rb
new file mode 100644
index 0000000..93dba31
--- /dev/null
+++ b/samples/08_lerping_easing_functions/02_cubic_bezier/app/main.rb
@@ -0,0 +1,61 @@
+def tick args
+  args.outputs.background_color = [33, 33, 33]
+  args.outputs.lines << bezier(100, 100,
+                               100, 620,
+                               1180, 620,
+                               1180, 100,
+                               0)
+
+  args.outputs.lines << bezier(100, 100,
+                               100, 620,
+                               1180, 620,
+                               1180, 100,
+                               20)
+end
+
+
+def bezier x1, y1, x2, y2, x3, y3, x4, y4, step
+  step ||= 0
+  color = [200, 200, 200]
+  points = points_for_bezier [x1, y1], [x2, y2], [x3, y3], [x4, y4], step
+
+  points.each_cons(2).map do |p1, p2|
+    [p1, p2, color]
+  end
+end
+
+def points_for_bezier p1, p2, p3, p4, step
+  points = []
+  if step == 0
+    [p1, p2, p3, p4]
+  else
+    t_step = 1.fdiv(step + 1)
+    t = 0
+    t += t_step
+    points = []
+    while t < 1
+      points << [
+        b_for_t(p1.x, p2.x, p3.x, p4.x, t),
+        b_for_t(p1.y, p2.y, p3.y, p4.y, t),
+      ]
+      t += t_step
+    end
+
+    [
+      p1,
+      *points,
+      p4
+    ]
+  end
+end
+
+def b_for_t v0, v1, v2, v3, t
+  pow(1 - t, 3) * v0 +
+  3 * pow(1 - t, 2) * t * v1 +
+  3 * (1 - t) * pow(t, 2) * v2 +
+  pow(t, 3) * v3
+end
+
+def pow n, to
+  n ** to
+end