From c1ea14d1c96de18448c0c3779d30b7e1e4451f61 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Fri, 5 Feb 2021 00:30:13 +0000
Subject: Initial commit generating some basic rail network

---
 game/network/rail.cpp | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 game/network/rail.cpp

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

diff --git a/game/network/rail.cpp b/game/network/rail.cpp
new file mode 100644
index 0000000..ecec0c0
--- /dev/null
+++ b/game/network/rail.cpp
@@ -0,0 +1,87 @@
+#include "rail.h"
+#include "game/network/link.h"
+#include <GL/glew.h>
+#include <array>
+#include <cache.h>
+#include <cmath>
+#include <gfx/gl/shader.h>
+#include <gfx/models/texture.h>
+#include <gfx/models/vertex.hpp>
+#include <glm/gtx/rotate_vector.hpp>
+#include <glm/gtx/transform.hpp>
+#include <numbers>
+#include <utility>
+
+RailLinks::RailLinks() : texture {Texture::cachedTexture.get("rails.jpg")} { }
+void RailLinks::tick(TickDuration) { }
+
+static const auto identityModel {glm::identity<glm::mat4>()};
+
+void
+RailLinks::render(const Shader & shader) const
+{
+	shader.setModel(identityModel);
+	texture->Bind();
+	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 std::shared_ptr<RailLinkStraight> RailLinks::addLink(glm::vec3, glm::vec3);
+void
+RailLink::render(const Shader &) const
+{
+	meshes.apply(&Mesh::Draw);
+}
+
+constexpr const std::array<std::pair<glm::vec3, float>, 4> railCrossSection {{
+		//   ___________
+		// _/           \_
+		//  left to right
+		{{-1.F, 0.F, 0.F}, 0.F},
+		{{-.75F, .25F, 0.F}, 0.125F},
+		{{.75F, .25F, 0.F}, 0.875F},
+		{{1.F, 0.F, 0.F}, 1.F},
+}};
+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)};
+
+template<typename V>
+auto
+flat_orientation(const V & diff)
+{
+	const auto flatdiff {glm::normalize(glm::vec3 {diff.x, 0, diff.z})};
+	auto e {glm::orientation(flatdiff, north)};
+	// Handle if diff is exactly opposite to north
+	return (std::isnan(e[0][0])) ? oneeighty : e;
+}
+
+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 e {flat_orientation(diff)};
+	for (int ei = 0; ei < 2; ei++) {
+		const auto trans {glm::translate(ends[ei].first->pos) * e};
+		for (const auto & rcs : railCrossSection) {
+			const glm::vec3 m {(trans * glm::vec4 {rcs.first, 1})};
+			vertices.emplace_back(m, glm::vec2 {rcs.second, ei ? len : 0.F}, up);
+			if (vertices.size() > railCrossSection.size()) {
+				indices.push_back(vertices.size() - railCrossSection.size() - 1);
+				indices.push_back(vertices.size() - 1);
+			}
+		}
+	}
+	meshes.create<Mesh>(vertices, indices, GL_TRIANGLE_STRIP);
+}
-- 
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