From 1e7a924874050674a103f6927f4a3c5ef6459222 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Fri, 13 Jun 2025 21:53:32 +0100
Subject: Create a list of snap points for the existing network

These form key positions in the world to ease neat creation.
---
 game/network/network.h | 14 ++++++++++++++
 game/network/rail.cpp  | 16 ++++++++++++++++
 game/network/rail.h    |  1 +
 3 files changed, 31 insertions(+)

(limited to 'game')

diff --git a/game/network/network.h b/game/network/network.h
index d3370b3..7bfd2ce 100644
--- a/game/network/network.h
+++ b/game/network/network.h
@@ -35,6 +35,19 @@ struct CreationDefinition {
 	CreationDefinitionEnd toEnd;
 };
 
+struct SnapPoint : CreationDefinitionEnd {
+	template<typename... CDE>
+		requires std::is_constructible_v<CreationDefinitionEnd, CDE...>
+	explicit SnapPoint(GlobalPosition3D snapPosition, CDE &&... cde) :
+		CreationDefinitionEnd {std::forward<CDE>(cde)...}, snapPosition(snapPosition)
+	{
+	}
+
+	GlobalPosition3D snapPosition;
+};
+
+using SnapPoints = std::vector<SnapPoint>;
+
 class Network {
 public:
 	using LinkEnd = std::pair<Link::Ptr, unsigned char>;
@@ -55,6 +68,7 @@ public:
 	[[nodiscard]] static Link::Nexts routeFromTo(const Link::End &, const Node::Ptr &);
 
 	[[nodiscard]] virtual float findNodeDirection(Node::AnyCPtr) const = 0;
+	[[nodiscard]] virtual SnapPoints getSnapPoints() const = 0;
 
 	[[nodiscard]] Link::Collection create(const GeoData *, const CreationDefinition &);
 	[[nodiscard]] Link::Collection createChain(const GeoData *, std::span<const GlobalPosition3D>);
diff --git a/game/network/rail.cpp b/game/network/rail.cpp
index 342a2ad..45d55d6 100644
--- a/game/network/rail.cpp
+++ b/game/network/rail.cpp
@@ -137,3 +137,19 @@ RailLinks::getBaseWidth() const
 	static constexpr auto BASE_WIDTH = 5'700;
 	return BASE_WIDTH;
 }
+
+SnapPoints
+RailLinks::getSnapPoints() const
+{
+	static constexpr auto EXTENSION_SNAP_DIST = 1'200.F;
+	SnapPoints out;
+	for (const auto & link : links) {
+		for (const auto & end : link->ends) {
+			// Link end node; directionless, suitable crossings
+			out.emplace_back(end.node->pos, end.node->pos, std::nullopt);
+			// Link end; with direction, suitable for continuing/joining
+			out.emplace_back(end.node->pos - ((sincos(end.dir) * EXTENSION_SNAP_DIST) || 0.F), end.node->pos, end.dir);
+		}
+	}
+	return out;
+}
diff --git a/game/network/rail.h b/game/network/rail.h
index 15b9ae4..48b1410 100644
--- a/game/network/rail.h
+++ b/game/network/rail.h
@@ -78,6 +78,7 @@ public:
 
 	[[nodiscard]] const Surface * getBaseSurface() const override;
 	[[nodiscard]] RelativeDistance getBaseWidth() const override;
+	[[nodiscard]] SnapPoints getSnapPoints() const override;
 
 private:
 	void tick(TickDuration elapsed) override;
-- 
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