From 39cd8e00495e1b63bf60d13818dc725a6c737dca Mon Sep 17 00:00:00 2001
From: "C. J. Howard" <cjhoward@protonmail.com>
Date: Thu, 24 Sep 2020 22:14:30 -0700
Subject: [PATCH] Make sky gradients interpolate as time passes

---
 src/game/systems/weather-system.cpp | 21 +++++++++++++++++++--
 src/game/systems/weather-system.hpp |  2 +-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/game/systems/weather-system.cpp b/src/game/systems/weather-system.cpp
index 1833d6d..69814d6 100644
--- a/src/game/systems/weather-system.cpp
+++ b/src/game/systems/weather-system.cpp
@@ -133,7 +133,20 @@ void weather_system::set_time_of_day(float t)
 	
 	if (sky_pass)
 	{
-		sky_pass->set_sky_gradient(sky_gradient);
+		float hour = time_of_day / (60.0f * 60.0f);
+		std::size_t gradient_index = static_cast<std::size_t>(hour);
+		
+		const std::array<float4, 4>& gradient0 = sky_gradients[gradient_index];
+		const std::array<float4, 4>& gradient1 = sky_gradients[(gradient_index + 1) % sky_gradients.size()];
+		float t = hour - std::floor(hour);
+		
+		std::array<float4, 4> gradient;
+		for (int i = 0; i < 4; ++i)
+		{
+			gradient[i] = math::lerp(gradient0[i], gradient1[i], t);
+		}
+		
+		sky_pass->set_sky_gradient(gradient);
 	}
 	
 	shadow_light = sun_light;
@@ -160,6 +173,8 @@ void weather_system::set_sky_palette(const ::image* image)
 		
 		for (unsigned int x = 0; x < w; ++x)
 		{
+			std::array<float4, 4> gradient;
+			
 			for (unsigned int y = 0; y < std::min<unsigned int>(4, h); ++y)
 			{
 				unsigned int i = y * w * c + x * c;
@@ -167,8 +182,10 @@ void weather_system::set_sky_palette(const ::image* image)
 				float g = srgb_to_linear(static_cast<float>(pixels[i + 1]) / 255.0f);
 				float b = srgb_to_linear(static_cast<float>(pixels[i + 2]) / 255.0f);
 				
-				sky_gradient[y] = {r, g, b,  static_cast<float>(y) * (1.0f / 3.0f)};
+				gradient[y] = {r, g, b,  static_cast<float>(y) * (1.0f / 3.0f)};
 			}
+			
+			sky_gradients.push_back(gradient);
 		}
 	}
 }
diff --git a/src/game/systems/weather-system.hpp b/src/game/systems/weather-system.hpp
index d49d4fc..718dcb3 100644
--- a/src/game/systems/weather-system.hpp
+++ b/src/game/systems/weather-system.hpp
@@ -65,7 +65,7 @@ private:
 	material_pass* material_pass;
 	const image* sky_palette;
 	const image* shadow_palette;
-	std::array<float4, 4> sky_gradient;
+	std::vector<std::array<float4, 4>> sky_gradients;
 };
 
 #endif // ANTKEEPER_WEATHER_SYSTEM_HPP