From a9a2a4c8b5aad22d055c670c72eb41fc22b0d812 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 5 Oct 2024 12:17:55 +0100
Subject: Add LightDirection class

---
 gfx/lightDirection.cpp    |  8 ++++++++
 gfx/lightDirection.h      | 32 ++++++++++++++++++++++++++++++++
 test/test-environment.cpp | 27 +++++++++++++++++++++++++++
 3 files changed, 67 insertions(+)
 create mode 100644 gfx/lightDirection.cpp
 create mode 100644 gfx/lightDirection.h

diff --git a/gfx/lightDirection.cpp b/gfx/lightDirection.cpp
new file mode 100644
index 0000000..6d7d1ea
--- /dev/null
+++ b/gfx/lightDirection.cpp
@@ -0,0 +1,8 @@
+#include "lightDirection.h"
+#include "maths.h"
+
+LightDirection::LightDirection(const Direction2D sunPos) :
+	pos {sunPos}, vec {glm::mat3 {rotate_yp(pi + sunPos.x, -sunPos.y)} * north},
+	vert {-glm::clamp(-1.F, 0.F, vec.z - 0.1F)}
+{
+}
diff --git a/gfx/lightDirection.h b/gfx/lightDirection.h
new file mode 100644
index 0000000..f1e1cc4
--- /dev/null
+++ b/gfx/lightDirection.h
@@ -0,0 +1,32 @@
+#pragma once
+
+#include "config/types.h"
+
+class LightDirection {
+public:
+	// NOLINTNEXTLINE(hicpp-explicit-conversions) deliberately a helper
+	LightDirection(Direction2D sunPos);
+
+	[[nodiscard]] Direction2D
+	position() const noexcept
+	{
+		return pos;
+	}
+
+	[[nodiscard]] Direction3D
+	vector() const noexcept
+	{
+		return vec;
+	}
+
+	[[nodiscard]] float
+	vertical() const noexcept
+	{
+		return vert;
+	}
+
+private:
+	Direction2D pos;
+	Direction3D vec;
+	float vert;
+};
diff --git a/test/test-environment.cpp b/test/test-environment.cpp
index b6e0e4f..76144a4 100644
--- a/test/test-environment.cpp
+++ b/test/test-environment.cpp
@@ -1,4 +1,5 @@
 #define BOOST_TEST_MODULE environment
+#include "testHelpers.h"
 #include <boost/test/data/test_case.hpp>
 #include <boost/test/unit_test.hpp>
 #include <cmath>
@@ -7,9 +8,11 @@
 #include <chronology.h>
 #include <config/types.h>
 #include <game/environment.h>
+#include <gfx/lightDirection.h>
 #include <maths.h>
 
 using sunPosTestData = std::tuple<Direction2D, time_t, Direction2D>;
+using sunDirTestData = std::tuple<Direction2D, Direction3D, float>;
 constexpr Direction2D Doncaster = {-1.1, 53.5};
 constexpr Direction2D NewYork = {74.0, 40.7};
 constexpr Direction2D Syndey = {-151.2, -33.9};
@@ -19,6 +22,7 @@ BOOST_DATA_TEST_CASE(sun_position,
 		boost::unit_test::data::make<sunPosTestData>({
 				{EqGM, "2024-01-02T00:00:00"_time_t, {181.52F, -66.86F}},
 				{EqGM, "2024-01-02T06:00:00"_time_t, {113.12F, -0.85F}},
+				{EqGM, "2024-01-02T06:30:00"_time_t, {113.12F, 6.05F}},
 				{EqGM, "2024-01-02T12:00:00"_time_t, {177.82F, 66.97F}},
 				{EqGM, "2024-01-02T18:00:00"_time_t, {246.99F, 0.90F}},
 				{EqGM, "2024-01-03T00:00:00"_time_t, {181.52F, -67.04F}},
@@ -33,3 +37,26 @@ BOOST_DATA_TEST_CASE(sun_position,
 	BOOST_CHECK_CLOSE(sunPos.x, expSunPos.x, 1.F);
 	BOOST_CHECK_CLOSE(sunPos.y, expSunPos.y, 1.F);
 }
+
+BOOST_DATA_TEST_CASE(sun_direction,
+		boost::unit_test::data::make<sunDirTestData>({
+				{{0.F, 0.F}, south, 0.1F},
+				{{90.F, 0.F}, west, 0.1F},
+				{{-90.F, 0.F}, east, 0.1F},
+				// From above
+				// EqGM midnight, sun below horizon, shining upwards
+				{{181.52F, -66.86F}, {-0.01F, 0.39F, 0.919F}, 0},
+				// EqGM just before sunrise, mostly west, north a bit, up a bit
+				{{113.12F, -0.85F}, {-0.92F, 0.39F, 0.015F}, 0.085F},
+				// EqGM just after sunrise, mostly west, north a bit, down a bit
+				{{113.12F, 6.05F}, {-0.92F, 0.39F, -0.015F}, 0.205F},
+				// Doncaster noon, roughly from south to north, high in the sky, downward
+				{{176.34F, 59.64F}, {-0.03F, 0.5F, -0.86F}, 0.96F},
+		}),
+		position, direction, vert)
+{
+	const LightDirection ld {position * degreesToRads};
+	BOOST_CHECK_CLOSE_VEC(ld.vector(), direction);
+	BOOST_CHECK_CLOSE(glm::length(ld.vector()), 1.F, 1);
+	BOOST_CHECK_CLOSE(ld.vertical(), vert, 5);
+}
-- 
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