From e40b6bfe346bb93a2d3b38745b8fddba40e759c6 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Fri, 5 Feb 2021 18:53:45 +0000
Subject: Initial commit adding curved rail pieces

---
 application/main.cpp       |  7 ++---
 game/network/rail.cpp      | 68 +++++++++++++++++++++++++++++++++++++++++++++-
 game/network/rail.h        |  9 ++++++
 iwyu.json                  | 16 +++++++++++
 utility/stream_support.hpp | 12 +++++++-
 5 files changed, 106 insertions(+), 6 deletions(-)

diff --git a/application/main.cpp b/application/main.cpp
index 2b62953..a723b20 100644
--- a/application/main.cpp
+++ b/application/main.cpp
@@ -14,7 +14,6 @@
 #include <gfx/manualCameraController.h>
 #include <gfx/renderable.h>
 #include <gfx/window.h>
-#include <glm/glm.hpp>
 #include <memory>
 #include <special_members.hpp>
 #include <utility>
@@ -69,9 +68,9 @@ public:
 		world.create<Terrain>();
 		auto rl = world.create<RailLinks>();
 		auto a = rl->addLink<RailLinkStraight>({-1190, 5, -1190}, {-1190, 6, -1180});
-		auto b = rl->addLink<RailLinkStraight>(a->ends.back().first->pos, glm::vec3 {-1180, 5, -1180});
-		auto c = rl->addLink<RailLinkStraight>(b->ends.back().first->pos, glm::vec3 {-1180, 4, -1190});
-		rl->addLink<RailLinkStraight>(c->ends.back().first->pos, a->ends.front().first->pos);
+		auto b = rl->addLink<RailLinkCurve>(a->ends.back().first->pos, {-1180, 5, -1180}, {-1185, -1180});
+		auto c = rl->addLink<RailLinkStraight>(b->ends.back().first->pos, {-1180, 4, -1190});
+		rl->addLink<RailLinkCurve>(c->ends.back().first->pos, a->ends.front().first->pos, {-1185, -1190});
 
 		Shader shader;
 		Camera camera({-1250.0F, 35.0F, -1250.0F}, 70.0F, (float)DISPLAY_WIDTH / (float)DISPLAY_HEIGHT, 0.1F, 10000.0F);
diff --git a/game/network/rail.cpp b/game/network/rail.cpp
index ecec0c0..2ae65f7 100644
--- a/game/network/rail.cpp
+++ b/game/network/rail.cpp
@@ -7,8 +7,10 @@
 #include <gfx/gl/shader.h>
 #include <gfx/models/texture.h>
 #include <gfx/models/vertex.hpp>
+#include <glm/gtc/constants.hpp>
 #include <glm/gtx/rotate_vector.hpp>
 #include <glm/gtx/transform.hpp>
+#include <glm/gtx/vector_angle.hpp>
 #include <numbers>
 #include <utility>
 
@@ -35,7 +37,19 @@ RailLinks::addLink(glm::vec3 a, glm::vec3 b)
 	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
 {
@@ -54,6 +68,8 @@ constexpr const std::array<std::pair<glm::vec3, float>, 4> railCrossSection {{
 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 sleepers {5.F}; // There are 5 repetitions of sleepers in the texture
 
 template<typename V>
 auto
@@ -65,12 +81,26 @@ flat_orientation(const V & diff)
 	return (std::isnan(e[0][0])) ? oneeighty : e;
 }
 
+template<typename T>
+constexpr auto
+round_frac(const T & v, const T & frac)
+{
+	return std::round(v / frac) * frac;
+}
+
+template<typename T>
+constexpr auto
+round_sleepers(const T & v)
+{
+	return std::round(v / sleepers) * sleepers;
+}
+
 RailLinkStraight::RailLinkStraight(End a, End b) : RailLink(std::move(a), std::move(b))
 {
 	vertices.reserve(2 * railCrossSection.size());
 	indices.reserve(2 * railCrossSection.size());
 	const auto diff {ends[1].first->pos - ends[0].first->pos};
-	const auto len = glm::length(diff) / 2.F;
+	const auto len = round_sleepers(glm::length(diff) / 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};
@@ -85,3 +115,39 @@ 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)
+{
+	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 = glm::orientedAngle(glm::normalize(diffa), north, up) - half_pi;
+	const auto angb = [&diffb, &anga]() {
+		const auto angb = glm::orientedAngle(glm::normalize(diffb), north, up) - half_pi;
+		return (angb < anga) ? angb + glm::radians(360.f) : angb;
+	}();
+	const auto radius = glm::length(e0p - centre3);
+	const auto length = round_sleepers(radius * (angb - anga) / 2.F);
+	const auto step {glm::vec3 {std::abs(angb - anga), e1p.y - e0p.y, length} / std::round(angb - anga) / 5.F};
+	const auto trans {glm::translate(centre3)};
+
+	auto addRcs = [this, trans, radius](auto arc) {
+		const auto t {trans * glm::rotate(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);
+	}
+	addRcs(glm::vec3 {angb, e1p.y - e0p.y, length});
+
+	for (auto n = 4U; n < vertices.size(); n += 1) {
+		indices.push_back(n);
+		indices.push_back(n - 4);
+	}
+	meshes.create<Mesh>(vertices, indices, GL_TRIANGLE_STRIP);
+}
diff --git a/game/network/rail.h b/game/network/rail.h
index ef119bc..7e1f5ac 100644
--- a/game/network/rail.h
+++ b/game/network/rail.h
@@ -33,12 +33,21 @@ public:
 	RailLinkStraight(End, End);
 };
 
+class RailLinkCurve : public RailLink {
+public:
+	RailLinkCurve(End, End, glm::vec2);
+
+private:
+	glm::vec2 centre;
+};
+
 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);
 
 private:
 	using Nodes = std::set<NodePtr, PtrSorter<NodePtr>>;
diff --git a/iwyu.json b/iwyu.json
index 0df2666..763fb95 100644
--- a/iwyu.json
+++ b/iwyu.json
@@ -31,6 +31,22 @@
             "public"
         ]
     },
+    {
+        "include": [
+            "@<glm/gtc/constants.inl>",
+            "private",
+            "<glm/gtc/constants.hpp>",
+            "public"
+        ]
+    },
+    {
+        "include": [
+            "@<glm/gtx/vector_angle.inl>",
+            "private",
+            "<glm/gtx/vector_angle.hpp>",
+            "public"
+        ]
+    },
     {
         "include": [
             "@<glm/gtx/rotate_vector.inl>",
diff --git a/utility/stream_support.hpp b/utility/stream_support.hpp
index 6ab1bd1..9561e58 100644
--- a/utility/stream_support.hpp
+++ b/utility/stream_support.hpp
@@ -5,7 +5,7 @@
 
 template<glm::length_t L, glm::length_t R, typename T, glm::qualifier Q>
 std::ostream &
-operator<<(std::ostream & s, glm::mat<L, R, T, Q> & m)
+operator<<(std::ostream & s, const glm::mat<L, R, T, Q> & m)
 {
 	for (int y = 0; y < m.length(); y++) {
 		const auto & col = m[y];
@@ -17,4 +17,14 @@ operator<<(std::ostream & s, glm::mat<L, R, T, Q> & m)
 	return s;
 }
 
+template<glm::length_t L, typename T, glm::qualifier Q>
+std::ostream &
+operator<<(std::ostream & s, const glm::vec<L, T, Q> & v)
+{
+	for (int x = 0; x < L; x++) {
+		s << v[x] << ", ";
+	}
+	return s;
+}
+
 #endif
-- 
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