From 838e5f77478e5648769439e191e3ff0a8e6405ab Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Mon, 22 Feb 2021 20:12:59 +0000
Subject: Add meandering support

Add rail links between existing nodes and arbitrary points
---
 game/network/rail.cpp | 39 +++++++++++++++++++++++++++++++++++++++
 game/network/rail.h   |  2 ++
 2 files changed, 41 insertions(+)

(limited to 'game')

diff --git a/game/network/rail.cpp b/game/network/rail.cpp
index bf1d71d..c1a72fb 100644
--- a/game/network/rail.cpp
+++ b/game/network/rail.cpp
@@ -10,6 +10,7 @@
 #include <glm/gtx/transform.hpp>
 #include <initializer_list>
 #include <maths.h>
+#include <stdexcept>
 #include <type_traits>
 #include <utility>
 
@@ -36,6 +37,44 @@ RailLinks::joinLinks(const LinkPtr & l) const
 	}
 }
 
+std::shared_ptr<RailLink>
+RailLinks::addLinksBetween(glm::vec3 start, glm::vec3 end)
+{
+	auto node1ins = nodes.insert(std::make_shared<Node>(start));
+	auto node2ins = nodes.insert(std::make_shared<Node>(end));
+	if (node1ins.second && node2ins.second) {
+		// Both nodes are new, direct link, easy
+		return addLink<RailLinkStraight>(start, end);
+	}
+	if (node1ins.second && !node2ins.second) {
+		// node1 is new, node2 exists, but we build from existing outwards
+		std::swap(node1ins, node2ins);
+		std::swap(start, end);
+	}
+	// Find start link/end - opposite entry dir to existing link; so pi +...
+	float dir = pi + [this](const auto & n) {
+		for (const auto & l : links.objects) {
+			for (const auto & e : l->ends) {
+				if (e.first == n) {
+					return e.second;
+				}
+			}
+		}
+		throw std::runtime_error("Node exists but couldn't find it");
+	}(*node1ins.first);
+	const glm::vec2 flatStart {start.x, start.z}, flatEnd {end.x, end.z};
+	// if (node2ins.second) { // Unimplemented second arc/stright required
+	const auto diff {end - start};
+	const auto vy {vector_yaw(diff)};
+	const auto n2ed {(vy * 2) - dir - pi};
+	const auto centre {find_arc_centre(flatStart, dir, flatEnd, n2ed)};
+
+	if (centre.second) { // right hand arc
+		std::swap(start, end);
+	}
+	return addLink<RailLinkCurve>(start, end, centre.first);
+}
+
 void
 RailLinks::render(const Shader & shader) const
 {
diff --git a/game/network/rail.h b/game/network/rail.h
index ac944f3..5837ac1 100644
--- a/game/network/rail.h
+++ b/game/network/rail.h
@@ -71,6 +71,8 @@ public:
 		return l;
 	}
 
+	std::shared_ptr<RailLink> addLinksBetween(glm::vec3 start, glm::vec3 end);
+
 private:
 	using Nodes = std::set<NodePtr, PtrSorter<NodePtr>>;
 	Collection<RailLink> links;
-- 
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