From 947319e25e49027d77543ae5c6f6c01d451a8926 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Thu, 26 Mar 2026 20:46:58 +0000
Subject: Improve light approximations in LightDirection

Twilight replaces astronomical twilight to give a longer fade. Astronomical
twilight is only the darkest part of twilight, which we had skipped right to.
Fixes directional light amount to only be affected by the sun's passing
below th horizon, not it's whole height above it.
Adds a rough approximation of the amount of atmosphere scattering of
directional light (I made this calculation up)
---
 test/test-environment.cpp | 53 +++++++++++++++++++++++++++++++++++++----------
 1 file changed, 42 insertions(+), 11 deletions(-)

(limited to 'test/test-environment.cpp')

diff --git a/test/test-environment.cpp b/test/test-environment.cpp
index a249192..4fb5d13 100644
--- a/test/test-environment.cpp
+++ b/test/test-environment.cpp
@@ -12,7 +12,8 @@
 
 namespace {
 	using SunPosTestData = std::tuple<Direction2D, time_t, Direction2D>;
-	using SunDirTestData = std::tuple<Direction2D, Direction3D, float, float>;
+	using SunDirTestData = std::tuple<Direction2D, Direction3D>;
+	using SunAmtTestData = std::tuple<float, float>;
 	constexpr Direction2D DONCASTER = {-1.1, 53.5};
 	constexpr Direction2D NEW_YORK = {74.0, 40.7};
 	constexpr Direction2D SYNDEY = {-151.2, -33.9};
@@ -41,24 +42,54 @@ BOOST_DATA_TEST_CASE(SunPosition,
 
 BOOST_DATA_TEST_CASE(SunDirection,
 		boost::unit_test::data::make<SunDirTestData>({
-				{{0.F, 0.F}, south, 0.314F, 0.0087F},
-				{{90.F, 0.F}, west, 0.314F, 0.0087F},
-				{{-90.F, 0.F}, east, 0.314F, 0.0087F},
+				{{0.F, 0.F}, south},
+				{{90.F, 0.F}, west},
+				{{-90.F, 0.F}, east},
 				// From above
 				// EqGM midnight, sun below horizon, shining upwards
-				{{181.52F, -66.86F}, {-0.01F, 0.39F, 0.919F}, 0, 0.F},
+				{{181.52F, -66.86F}, {-0.01F, 0.39F, 0.919F}},
 				// EqGM just before sunrise, mostly west, north a bit, up a bit
-				{{113.12F, -0.85F}, {-0.92F, 0.39F, 0.015F}, 0.299F, 0.F},
+				{{113.12F, -0.85F}, {-0.92F, 0.39F, 0.015F}},
 				// EqGM just after sunrise, mostly west, north a bit, down a bit
-				{{113.12F, 6.05F}, {-0.92F, 0.39F, -0.015F}, 0.42F, 0.114F},
+				{{113.12F, 6.05F}, {-0.92F, 0.39F, -0.015F}},
 				// Doncaster noon, roughly from south to north, high in the sky, downward
-				{{176.34F, 59.64F}, {-0.03F, 0.5F, -0.86F}, 1, 1},
+				{{176.34F, 59.64F}, {-0.03F, 0.5F, -0.86F}},
 		}),
-		position, direction, amb, dir)
+		position, direction)
 {
 	const LightDirection lightDir {position * degreesToRads};
 	BOOST_CHECK_CLOSE_VEC(lightDir.vector(), direction);
 	BOOST_CHECK_CLOSE(glm::length(lightDir.vector()), 1.F, 1);
-	BOOST_CHECK_CLOSE(lightDir.ambient(), amb, 5);
-	BOOST_CHECK_CLOSE(lightDir.directional(), dir, 5);
+}
+
+BOOST_DATA_TEST_CASE(SunDirectionalAmount,
+		boost::unit_test::data::make<SunAmtTestData>({
+				{5._degrees, 1.F},
+				{1._degrees, 1.F},
+				{0._degrees, 1.F},
+				{-0.25_degrees, 1.F},
+				{-0.5_degrees, 0.5F},
+				{-0.75_degrees, 0.F},
+				{-1._degrees, 0.F},
+				{-5._degrees, 0.F},
+		}),
+		elevation, amount)
+{
+	const LightDirection lightDir {{0, elevation}};
+	BOOST_CHECK_CLOSE(lightDir.directional(), amount, 1.F);
+}
+
+BOOST_DATA_TEST_CASE(SunAmbientAmount,
+		boost::unit_test::data::make<SunAmtTestData>({
+				{20._degrees, 1.F},
+				{1._degrees, 1.F},
+				{-9._degrees, 0.5F},
+				{-18._degrees, 0.F},
+				{-25._degrees, 0.F},
+				{-50._degrees, 0.F},
+		}),
+		elevation, amount)
+{
+	const LightDirection lightDir {{0, elevation}};
+	BOOST_CHECK_CLOSE(lightDir.ambient(), amount, 1.F);
 }
-- 
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