From 2812584e271a62d8edd4d8ec683ea4c644730df2 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Mon, 15 Feb 2021 01:36:51 +0000
Subject: Basic support for rail wagons

---
 application/main.cpp       |  5 ++++-
 game/vehicles/railloco.cpp | 34 ++++++++++++++++++++++++++++++++++
 game/vehicles/railloco.h   | 21 +++++++++++++++++++++
 3 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/application/main.cpp b/application/main.cpp
index ee6bade..04ff9c0 100644
--- a/application/main.cpp
+++ b/application/main.cpp
@@ -73,7 +73,10 @@ public:
 			rl->addLink<RailLinkCurve>(l, k, glm::vec2 {l.x, k.z});
 			auto l3 = rl->addLink<RailLinkStraight>(l, m);
 			rl->addLink<RailLinkCurve>(m, j, glm::vec2 {m.x, j.z});
-			world.create<Brush47>(l3);
+			auto loco = world.create<Brush47>(l3);
+			for (int n = 0; n < 6; n++) {
+				loco->wagons.push_back(world.create<Brush47Wagon>(l3));
+			}
 		}
 
 		Shader shader;
diff --git a/game/vehicles/railloco.cpp b/game/vehicles/railloco.cpp
index a1add29..d61b882 100644
--- a/game/vehicles/railloco.cpp
+++ b/game/vehicles/railloco.cpp
@@ -39,10 +39,44 @@ RailLoco::tick(TickDuration dur)
 	const auto diff = glm::normalize(b2pos.GetPos() - b1pos.GetPos());
 	location.GetRot().x = -vector_pitch(diff);
 	location.GetRot().y = vector_yaw(diff);
+	updateWagons();
 }
 
+void
+RailLoco::updateWagons() const
+{
+	// Drag wagons
+	float trailBy {wheelBase + ((length - wheelBase)) / 2};
+	for (const auto & wagon : wagons) {
+		const auto w {wagon.lock()};
+		auto wTrailBy {trailBy + ((w->length - w->wheelBase) / 2)};
+		float b1linkDist {};
+		const auto b1Link = linkHist.getAt(wTrailBy - linkDist, &b1linkDist);
+		const auto b1Pos = b1Link.first->positionAt(b1linkDist, b1Link.second);
+		wTrailBy += w->wheelBase;
+		float b2linkDist {};
+		const auto b2Link = linkHist.getAt(wTrailBy - linkDist, &b2linkDist);
+		const auto b2Pos = b2Link.first->positionAt(b2linkDist, b2Link.second);
+		w->location.GetPos() = (b1Pos.GetPos() + b2Pos.GetPos()) / 2.F;
+		const auto diff = glm::normalize(b2Pos.GetPos() - b1Pos.GetPos());
+		w->location.GetRot().x = -vector_pitch(diff);
+		w->location.GetRot().y = vector_yaw(diff);
+		trailBy += w->length;
+	}
+}
+
+void RailWagon::tick(TickDuration) { }
+
 Brush47::Brush47(const LinkPtr & l) : RailLoco(l, "brush47.obj", "brush47.png")
 {
 	wheelBase = 15.7F;
+	length = 19.38F;
+	linkDist = wheelBase;
+}
+
+Brush47Wagon::Brush47Wagon(const LinkPtr & l) : RailWagon(l, "brush47.obj", "brush47.png")
+{
+	wheelBase = 15.7F;
+	length = 19.38F;
 	linkDist = wheelBase;
 }
diff --git a/game/vehicles/railloco.h b/game/vehicles/railloco.h
index ff8871b..537d448 100644
--- a/game/vehicles/railloco.h
+++ b/game/vehicles/railloco.h
@@ -1,21 +1,42 @@
 #include "game/network/link.h"
 #include "game/vehicles/vehicle.h"
 #include "game/worldobject.h"
+#include <memory>
 #include <string>
+#include <vector>
 
 class RailVehicle : public Vehicle {
 public:
 	using Vehicle::Vehicle;
 	float wheelBase;
+	float length;
 };
 
+class RailWagon : public RailVehicle {
+public:
+	using RailVehicle::RailVehicle;
+	void tick(TickDuration elapsed) override;
+	friend class RailLoco;
+};
+using RailWagonPtr = std::weak_ptr<RailWagon>;
+
 class RailLoco : public RailVehicle {
 public:
 	using RailVehicle::RailVehicle;
 	void tick(TickDuration elapsed) override;
+
+	std::vector<RailWagonPtr> wagons;
+
+private:
+	void updateWagons() const;
 };
 
 class Brush47 : public RailLoco {
 public:
 	explicit Brush47(const LinkPtr & p);
 };
+
+class Brush47Wagon : public RailWagon {
+public:
+	explicit Brush47Wagon(const LinkPtr & p);
+};
-- 
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