From 1c385fe716fda927843cdbb83805bc467f517f92 Mon Sep 17 00:00:00 2001
From: Daniel Karbach <daniel.karbach@localhorst.tv>
Date: Fri, 15 Dec 2017 18:40:54 +0100
Subject: [PATCH] real days

---
 src/ui/ui.cpp       |  2 +-
 src/world/Body.hpp  |  4 ++++
 src/world/world.cpp | 10 ++++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/ui/ui.cpp b/src/ui/ui.cpp
index c361df5..05fd499 100644
--- a/src/ui/ui.cpp
+++ b/src/ui/ui.cpp
@@ -546,7 +546,7 @@ void TimePanel::Draw(graphics::Viewport &viewport) noexcept {
 	live->Text(NumberString(sim.LiveCreatures().size()));
 	time->Text(TimeString(sim.Time()));
 	if (body) {
-		clock->Text(TimeString(std::fmod(sim.Time(), body->RotationalPeriod())));
+		clock->Text(TimeString(std::fmod(sim.Time(), body->DayLength())) + " / " + TimeString(body->DayLength()));
 	} else {
 		clock->Text("no reference");
 	}
diff --git a/src/world/Body.hpp b/src/world/Body.hpp
index d908065..6f85efd 100644
--- a/src/world/Body.hpp
+++ b/src/world/Body.hpp
@@ -78,6 +78,10 @@ public:
 	double GravitationalParameter() const noexcept;
 	double OrbitalPeriod() const noexcept;
 	double RotationalPeriod() const noexcept;
+	/// day length relative to parent, not neccessarily a sun
+	/// gives absolute value in seconds
+	/// returns sidereal day for parent-less bodies
+	double DayLength() const noexcept;
 	double SphereOfInfluence() const noexcept;
 
 	math::Sphere CollisionBounds() const noexcept { return math::Sphere{ glm::dvec3(0.0), Radius() }; }
diff --git a/src/world/world.cpp b/src/world/world.cpp
index 1758c5e..525222f 100644
--- a/src/world/world.cpp
+++ b/src/world/world.cpp
@@ -115,6 +115,16 @@ double Body::RotationalPeriod() const noexcept {
 	}
 }
 
+double Body::DayLength() const noexcept {
+	if (!HasParent()) {
+		return RotationalPeriod();
+	}
+	double year = OrbitalPeriod();
+	double sidereal = RotationalPeriod();
+	double grade = (angular < 0.0 ? -1.0 : 1.0) * (std::abs(axis_tilt.x) > PI * 0.5 ? -1.0 : 1.0);
+	return std::abs((year * sidereal) / ( year + (grade * sidereal)));
+}
+
 double Body::SphereOfInfluence() const noexcept {
 	if (HasParent()) {
 		return orbit.SemiMajorAxis() * std::pow(Mass() / Parent().Mass(), 2.0 / 5.0);
-- 
2.39.2