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

---
 game/network/rail.cpp | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 67 insertions(+), 1 deletion(-)

(limited to 'game/network/rail.cpp')

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);
+}
-- 
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