From d421fc8c65a9438d334cf5b669d0c8c640b59f30 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Thu, 1 Oct 2020 09:37:35 +0300
Subject: [PATCH] Add easing function, move gradient to a separate header

---
 examples/cloud.cpp                         |  6 +-
 libs/geom/include/psemek/geom/easing.hpp   | 73 ++++------------------
 libs/geom/include/psemek/geom/gradient.hpp | 63 +++++++++++++++++++
 3 files changed, 79 insertions(+), 63 deletions(-)
 create mode 100644 libs/geom/include/psemek/geom/gradient.hpp

diff --git a/examples/cloud.cpp b/examples/cloud.cpp
index 5e9890ed..3d70dac0 100644
--- a/examples/cloud.cpp
+++ b/examples/cloud.cpp
@@ -7,7 +7,7 @@
 #include <psemek/geom/homogeneous.hpp>
 #include <psemek/geom/constants.hpp>
 #include <psemek/geom/math.hpp>
-#include <psemek/geom/easing.hpp>
+#include <psemek/geom/gradient.hpp>
 #include <psemek/gfx/gl.hpp>
 #include <psemek/gfx/mesh.hpp>
 #include <psemek/gfx/renderer/simple.hpp>
@@ -164,7 +164,7 @@ struct cloud_app
 
 	float step;
 
-	float max_density = 8.f;
+	float max_density = 6.f;
 	geom::interval<float> harmonic_range;
 
 	util::clock<std::chrono::duration<float>> clock;
@@ -241,7 +241,7 @@ struct cloud_app
 
 			pcg::fractal<pcg::perlin<float, 3>> perlin(std::move(grad), std::move(weights));
 
-			geom::gradient<float> g(geom::vector<float, 2>{0.2f, 0.f}, geom::easing::cubic, geom::vector{0.4f, max_density});
+			geom::gradient<float> g(std::make_pair(0.2f, 0.f), geom::easing_type::cubic, std::pair{0.4f, max_density});
 
 			util::array<std::uint8_t, 3> cloud_data({cloud_size[0], cloud_size[1], cloud_size[2]});
 
diff --git a/libs/geom/include/psemek/geom/easing.hpp b/libs/geom/include/psemek/geom/easing.hpp
index efc68db1..40adce6b 100644
--- a/libs/geom/include/psemek/geom/easing.hpp
+++ b/libs/geom/include/psemek/geom/easing.hpp
@@ -1,14 +1,11 @@
 #pragma once
 
-#include <psemek/geom/vector.hpp>
 #include <psemek/util/assert.hpp>
 
-#include <vector>
-
 namespace psemek::geom
 {
 
-	enum class easing
+	enum class easing_type
 	{
 		nearest,
 		constant_left,
@@ -20,64 +17,20 @@ namespace psemek::geom
 	};
 
 	template <typename T>
-	struct gradient
+	T easing(easing_type type, T t)
 	{
-		template <typename ... Args>
-		gradient(Args const & ...  args)
-		{
-			init(args...);
+		switch (type) {
+			case easing_type::nearest: return (2 * t < 1) ? 0 : 1;
+			case easing_type::constant_left: return 0;
+			case easing_type::constant_right: return 1;
+			case easing_type::linear: return t;
+			case easing_type::quadratic_in: return t * t;
+			case easing_type::quadratic_out: return t * (2 - t);
+			case easing_type::cubic: return t * t * (3 - 2 * t);
+			default: assert(false);
 		}
 
-		gradient(std::vector<geom::vector<T, 2>> points, std::vector<easing> segments)
-		{
-			assert(points.size() == segments.size() + 1);
-			points_ = std::move(points);
-			segments_ = std::move(segments);
-		}
-
-		T operator()(T const & t) const
-		{
-			auto it = std::upper_bound(points_.begin(), points_.end(), t, [](T const & t, auto const & p){ return t < p[0]; });
-			if (it == points_.begin())
-				return points_.front()[1];
-			if (it == points_.end())
-				return points_.back()[1];
-
-			std::size_t i = (it - points_.begin()) - 1;
-
-			T s = (t - points_[i][0]) * (points_[i + 1][1] - points_[i][1]);
-
-			switch (segments_[i]) {
-				case easing::nearest: s = (2 * s < 1) ? 0 : 1; break;
-				case easing::constant_left: s = 0; break;
-				case easing::constant_right: s = 1; break;
-				case easing::linear: break;
-				case easing::quadratic_in: s = s * s; break;
-				case easing::quadratic_out: s = s * (2 - s); break;
-				case easing::cubic: s = s * s * (3 - 2 * s); break;
-				default:
-					assert(false);
-			}
-
-			return points_[i][1] + s * (points_[i + 1][1] - points_[i][1]);
-		}
-
-	private:
-		std::vector<geom::vector<T, 2>> points_;
-		std::vector<easing> segments_;
-
-		void init(geom::vector<T, 2> const & p)
-		{
-			points_.push_back(p);
-		}
-
-		template <typename ... Args>
-		void init(geom::vector<T, 2> const & p, easing t, Args const & ... args)
-		{
-			points_.push_back(p);
-			segments_.push_back(t);
-			init(args...);
-		}
-	};
+		return {};
+	}
 
 }
diff --git a/libs/geom/include/psemek/geom/gradient.hpp b/libs/geom/include/psemek/geom/gradient.hpp
new file mode 100644
index 00000000..e7b33b8a
--- /dev/null
+++ b/libs/geom/include/psemek/geom/gradient.hpp
@@ -0,0 +1,63 @@
+#pragma once
+
+#include <psemek/geom/easing.hpp>
+#include <psemek/geom/math.hpp>
+
+#include <vector>
+#include <algorithm>
+
+namespace psemek::geom
+{
+
+	template <typename T, typename R = T>
+	struct gradient
+	{
+		using result_type = R;
+
+		template <typename ... Args>
+		gradient(Args const & ...  args)
+		{
+			init(args...);
+		}
+
+		gradient(std::vector<std::pair<T, R>> points, std::vector<easing_type> segments)
+		{
+			assert(points.size() == segments.size() + 1);
+			points_ = std::move(points);
+			segments_ = std::move(segments);
+		}
+
+		R operator()(T const & t) const
+		{
+			auto it = std::upper_bound(points_.begin(), points_.end(), t, [](T const & t, auto const & p){ return t < p.first; });
+			if (it == points_.begin())
+				return points_.front().second;
+			if (it == points_.end())
+				return points_.back().second;
+
+			std::size_t i = (it - points_.begin()) - 1;
+
+			T s = easing(segments_[i], (t - points_[i].first) / (points_[i + 1].first - points_[i].first));
+
+			return lerp(points_[i].second, points_[i + 1].second, s);
+		}
+
+	private:
+		std::vector<std::pair<T, R>> points_;
+		std::vector<easing_type> segments_;
+
+		void init(std::pair<T, R> const & p)
+		{
+			points_.push_back(p);
+		}
+
+		template <typename ... Args>
+		void init(std::pair<T, R> const & p, easing_type t, Args const & ... args)
+		{
+			points_.push_back(p);
+			segments_.push_back(t);
+			init(args...);
+		}
+	};
+
+}