4 files changed, 80 insertions, 51 deletions
diff --git a/game/network/link.cpp b/game/network/link.cpp
index 65aefd6..ad09341 100644
--- a/game/network/link.cpp
+++ b/game/network/link.cpp
@@ -2,7 +2,7 @@
 #include <compare>
 #include <tuple>
 
-Link::Link(End a, End b) : ends {{std::move(a), std::move(b)}} { }
+Link::Link(End a, End b, float l) : ends {{std::move(a), std::move(b)}}, length {l} { }
 
 bool
 operator<(const glm::vec3 & a, const glm::vec3 & b)
diff --git a/game/network/link.h b/game/network/link.h
index 0da413c..b22d0d0 100644
--- a/game/network/link.h
+++ b/game/network/link.h
@@ -26,15 +26,15 @@ using NodePtr = std::shared_ptr<Node>;
 // it joins 2 nodes
 class Link {
 public:
-	// side determines which edges can be moved to next, must alternate
-	using End = std::pair<NodePtr, bool /*side*/>;
+	using End = std::pair<NodePtr, float /*dir*/>;
 
-	Link(End, End);
+	Link(End, End, float);
 	virtual ~Link() = default;
 	NO_COPY(Link);
 	NO_MOVE(Link);
 
 	std::array<End, 2> ends;
+	float length;
 };
 
 template<typename T> struct PtrSorter {
diff --git a/game/network/rail.cpp b/game/network/rail.cpp
index 93fc9f6..0858b66 100644
--- a/game/network/rail.cpp
+++ b/game/network/rail.cpp
@@ -12,6 +12,7 @@
 #include <glm/gtx/transform.hpp>
 #include <glm/gtx/vector_angle.hpp>
 #include <numbers>
+#include <type_traits>
 #include <utility>
 
 RailLinks::RailLinks() : texture {Texture::cachedTexture.get("rails.jpg")} { }
@@ -27,29 +28,6 @@ RailLinks::render(const Shader & shader) const
 	links.apply(&RailLink::render, shader);
 }
 
-template<RailLinkConcept T>
-std::shared_ptr<T>
-RailLinks::addLink(glm::vec3 a, glm::vec3 b)
-{
-	const auto node1 = *nodes.insert(std::make_shared<Node>(a)).first;
-	const auto node2 = *nodes.insert(std::make_shared<Node>(b)).first;
-	// TODO set end flag properly
-	return links.create<T>(Link::End {node1, true}, Link::End {node2, true});
-}
-
-template<RailLinkConcept T>
-std::shared_ptr<T>
-RailLinks::addLink(glm::vec3 a, glm::vec3 b, glm::vec2 centre)
-{
-	const auto node1 = *nodes.insert(std::make_shared<Node>(a)).first;
-	const auto node2 = *nodes.insert(std::make_shared<Node>(b)).first;
-	// TODO set end flag properly
-	return links.create<T>(Link::End {node1, true}, Link::End {node2, true}, centre);
-}
-
-template std::shared_ptr<RailLinkStraight> RailLinks::addLink(glm::vec3, glm::vec3);
-template std::shared_ptr<RailLinkCurve> RailLinks::addLink(glm::vec3, glm::vec3, glm::vec2);
-
 void
 RailLink::render(const Shader &) const
 {
@@ -69,6 +47,8 @@ constexpr const glm::vec3 up {0, 1, 0};
 constexpr const glm::vec3 north {0, 0, 1};
 const auto oneeighty {glm::rotate(std::numbers::pi_v<float>, up)};
 constexpr auto half_pi {glm::half_pi<float>()};
+constexpr auto pi {glm::pi<float>()};
+constexpr auto two_pi {glm::two_pi<float>()};
 constexpr auto sleepers {5.F}; // There are 5 repetitions of sleepers in the texture
 
 template<typename V>
@@ -103,12 +83,14 @@ round_sleepers(const T & v)
 	return std::round(v / sleepers) * sleepers;
 }
 
-RailLinkStraight::RailLinkStraight(End a, End b) : RailLink(std::move(a), std::move(b))
+RailLinkStraight::RailLinkStraight(const NodePtr & a, const NodePtr & b) : RailLinkStraight(a, b, b->pos - a->pos) { }
+
+RailLinkStraight::RailLinkStraight(NodePtr a, NodePtr b, const glm::vec3 & diff) :
+	RailLink({std::move(a), flat_angle(diff)}, {std::move(b), flat_angle(-diff)}, glm::length(diff))
 {
 	vertices.reserve(2 * railCrossSection.size());
 	indices.reserve(2 * railCrossSection.size());
-	const auto diff {ends[1].first->pos - ends[0].first->pos};
-	const auto len = round_sleepers(glm::length(diff) / 2.F);
+	const auto len = round_sleepers(length / 2.F);
 	const auto e {flat_orientation(diff)};
 	for (int ei = 0; ei < 2; ei++) {
 		const auto trans {glm::translate(ends[ei].first->pos) * e};
@@ -124,36 +106,72 @@ RailLinkStraight::RailLinkStraight(End a, End b) : RailLink(std::move(a), std::m
 	meshes.create<Mesh>(vertices, indices, GL_TRIANGLE_STRIP);
 }
 
-RailLinkCurve::RailLinkCurve(End a, End b, glm::vec2 c) : RailLink(std::move(a), std::move(b)), centre(c)
+constexpr inline glm::vec3
+operator!(const glm::vec2 & v)
+{
+	return {v.x, 0, v.y};
+}
+
+constexpr inline float
+arc_length(const Arc & arc)
+{
+	return arc.second - arc.first;
+}
+
+constexpr inline float
+normalize(float ang)
+{
+	while (ang > pi) {
+		ang -= two_pi;
+	}
+	while (ang <= -pi) {
+		ang += two_pi;
+	}
+	return ang;
+}
+
+inline Arc
+create_arc(const glm::vec3 centre3, glm::vec3 e0p, glm::vec3 e1p)
 {
-	const auto & e0p {ends[0].first->pos};
-	const auto & e1p {ends[1].first->pos};
-	const glm::vec3 centre3 {centre.x, e0p.y, centre.y};
 	const auto diffa = centre3 - e0p;
 	const auto diffb = centre3 - e1p;
 	const auto anga = flat_angle(diffa);
 	const auto angb = [&diffb, &anga]() {
 		const auto angb = flat_angle(diffb);
-		return (angb < anga) ? angb + glm::two_pi<float>() : angb;
+		return (angb < anga) ? angb + two_pi : angb;
 	}();
-	const auto radius = glm::length(e0p - centre3);
-	const auto length = round_sleepers(radius * (angb - anga) / 2.F);
-	const auto segs = std::round(5.F * length / std::pow(radius, 0.7F));
-	const auto step {glm::vec3 {angb - anga, e1p.y - e0p.y, length} / segs};
-	const auto trans {glm::translate(centre3)};
+	return {anga, angb};
+}
+
+RailLinkCurve::RailLinkCurve(const NodePtr & a, const NodePtr & b, glm::vec2 c) :
+	RailLinkCurve(a, b, {c.x, a->pos.y, c.y}, create_arc(!c, a->pos, b->pos))
+{
+}
+
+RailLinkCurve::RailLinkCurve(const NodePtr & a, const NodePtr & b, glm::vec3 c, const Arc arc) :
+	RailLink({a, normalize(arc.first - half_pi)}, {b, normalize(arc.second + half_pi)},
+			(glm::length(a->pos - c)) * arc_length(arc)),
+	centreBase(c)
+{
+	const auto & e0p {ends[0].first->pos};
+	const auto & e1p {ends[1].first->pos};
+	const auto radius = glm::length(e0p - centreBase);
+	const auto slength = round_sleepers(length / 2.F);
+	const auto segs = std::round(5.F * slength / std::pow(radius, 0.7F));
+	const auto step {glm::vec3 {arc_length(arc), e1p.y - e0p.y, slength} / segs};
+	const auto trans {glm::translate(centreBase)};
 
 	auto addRcs = [this, trans, radius](auto arc) {
-		const auto t {trans * glm::rotate(glm::half_pi<float>() - arc.x, up)
-				* glm::translate(glm::vec3 {radius, arc.y, 0.F})};
+		const auto t {trans * glm::rotate(half_pi - arc.x, up) * glm::translate(glm::vec3 {radius, arc.y, 0.F})};
 		for (const auto & rcs : railCrossSection) {
 			const glm::vec3 m {(t * glm::vec4 {rcs.first, 1})};
 			vertices.emplace_back(m, glm::vec2 {rcs.second, arc.z}, up);
 		}
 	};
-	for (glm::vec3 arc = {anga, 0.F, 0.F}; arc.x < angb; arc += step) {
-		addRcs(arc);
+	for (glm::vec3 swing = {arc.first, 0.F, 0.F}; swing.x < arc.second; swing += step) {
+		addRcs(swing);
 	}
-	addRcs(glm::vec3 {angb, e1p.y - e0p.y, length});
+	addRcs(glm::vec3 {arc.second, e1p.y - e0p.y, slength});
 
 	for (auto n = 4U; n < vertices.size(); n += 1) {
 		indices.push_back(n - 4);
diff --git a/game/network/rail.h b/game/network/rail.h
index 7e1f5ac..3ab0c83 100644
--- a/game/network/rail.h
+++ b/game/network/rail.h
@@ -10,6 +10,7 @@
 #include <glm/glm.hpp>
 #include <memory>
 #include <set>
+#include <utility>
 #include <vector>
 class Shader;
 class Texture;
@@ -22,7 +23,6 @@ public:
 	void render(const Shader &) const override;
 
 protected:
-	RailLink();
 	Collection<Mesh, false> meshes;
 	std::vector<Vertex> vertices;
 	std::vector<unsigned int> indices;
@@ -30,15 +30,20 @@ protected:
 
 class RailLinkStraight : public RailLink {
 public:
-	RailLinkStraight(End, End);
+	RailLinkStraight(const NodePtr &, const NodePtr &);
+
+private:
+	RailLinkStraight(NodePtr, NodePtr, const glm::vec3 & diff);
 };
 
+using Arc = std::pair<float, float>;
 class RailLinkCurve : public RailLink {
 public:
-	RailLinkCurve(End, End, glm::vec2);
+	RailLinkCurve(const NodePtr &, const NodePtr &, glm::vec2);
 
 private:
-	glm::vec2 centre;
+	RailLinkCurve(const NodePtr &, const NodePtr &, glm::vec3, const Arc);
+	glm::vec3 centreBase;
 };
 
 template<typename T> concept RailLinkConcept = std::is_base_of_v<RailLink, T>;
@@ -46,8 +51,14 @@ template<typename T> concept RailLinkConcept = std::is_base_of_v<RailLink, T>;
 class RailLinks : public Renderable, public WorldObject {
 public:
 	RailLinks();
-	template<RailLinkConcept T> std::shared_ptr<T> addLink(glm::vec3, glm::vec3);
-	template<RailLinkConcept T> std::shared_ptr<T> addLink(glm::vec3, glm::vec3, glm::vec2);
+	template<RailLinkConcept T, typename... Params>
+	std::shared_ptr<T>
+	addLink(glm::vec3 a, glm::vec3 b, Params &&... params)
+	{
+		const auto node1 = *nodes.insert(std::make_shared<Node>(a)).first;
+		const auto node2 = *nodes.insert(std::make_shared<Node>(b)).first;
+		return links.create<T>(node1, node2, std::forward<Params>(params)...);
+	}
 
 private:
 	using Nodes = std::set<NodePtr, PtrSorter<NodePtr>>;