From 16bec12e3e75e95d251745f904ac4e15af9c9724 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 28 Oct 2023 02:34:45 +0100
Subject: Initial OpenMesh based terrain data and tests

---
 game/terrain2.cpp | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 game/terrain2.h   | 24 ++++++++++++++++++++
 2 files changed, 90 insertions(+)
 create mode 100644 game/terrain2.cpp
 create mode 100644 game/terrain2.h

(limited to 'game')

diff --git a/game/terrain2.cpp b/game/terrain2.cpp
new file mode 100644
index 0000000..83df3fa
--- /dev/null
+++ b/game/terrain2.cpp
@@ -0,0 +1,66 @@
+#include "terrain2.h"
+#include <fstream>
+
+TerrainMesh::TerrainMesh(const std::filesystem::path & input)
+{
+	size_t ncols = 0, nrows = 0, xllcorner = 0, yllcorner = 0, cellsize = 0;
+	std::map<std::string_view, size_t *> properties {
+			{"ncols", &ncols},
+			{"nrows", &nrows},
+			{"xllcorner", &xllcorner},
+			{"yllcorner", &yllcorner},
+			{"cellsize", &cellsize},
+	};
+	std::ifstream f {input};
+	while (!properties.empty()) {
+		std::string property;
+		f >> property;
+		f >> *properties.at(property);
+		properties.erase(property);
+	}
+	std::vector<VertexHandle> vertices;
+	vertices.reserve(ncols * nrows);
+	for (size_t row = 0; row < nrows; ++row) {
+		for (size_t col = 0; col < ncols; ++col) {
+			float height = 0;
+			f >> height;
+			vertices.push_back(add_vertex({xllcorner + (col * cellsize), yllcorner + (row * cellsize), height}));
+		}
+	}
+	if (!f.good()) {
+		throw std::runtime_error("Couldn't read terrain file");
+	}
+	for (size_t row = 1; row < nrows; ++row) {
+		for (size_t col = 1; col < ncols; ++col) {
+			add_face({
+					vertices[ncols * (row - 1) + (col - 1)],
+					vertices[ncols * (row - 0) + (col - 0)],
+					vertices[ncols * (row - 0) + (col - 1)],
+			});
+			add_face({
+					vertices[ncols * (row - 1) + (col - 1)],
+					vertices[ncols * (row - 1) + (col - 0)],
+					vertices[ncols * (row - 0) + (col - 0)],
+			});
+		}
+	}
+	update_face_normals();
+	update_vertex_normals();
+};
+
+bool
+TerrainMesh::triangleContainsPoint(const glm::vec2 p, const glm::vec2 a, const glm::vec2 b, const glm::vec2 c)
+{
+	const auto det = (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
+
+	return det * ((b.x - a.x) * (p.y - a.y) - (b.y - a.y) * (p.x - a.x)) >= 0
+			&& det * ((c.x - b.x) * (p.y - b.y) - (c.y - b.y) * (p.x - b.x)) >= 0
+			&& det * ((a.x - c.x) * (p.y - c.y) - (a.y - c.y) * (p.x - c.x)) >= 0;
+}
+
+bool
+TerrainMesh::triangleContainsPoint(const glm::vec2 p, FaceHandle face) const
+{
+	auto vertices = cfv_iter(face);
+	return triangleContainsPoint(p, point(*vertices++), point(*vertices++), point(*vertices++));
+}
diff --git a/game/terrain2.h b/game/terrain2.h
new file mode 100644
index 0000000..d2da8d0
--- /dev/null
+++ b/game/terrain2.h
@@ -0,0 +1,24 @@
+#pragma once
+
+#include <OpenMesh/Core/Mesh/TriMesh_ArrayKernelT.hh>
+#include <filesystem>
+#include <glm/vec2.hpp>
+#include <thirdparty/openmesh/glmcompat.h>
+
+struct TerrainTraits : public OpenMesh::DefaultTraits {
+	FaceAttributes(OpenMesh::Attributes::Normal | OpenMesh::Attributes::Status);
+	EdgeAttributes(OpenMesh::Attributes::Status);
+	VertexAttributes(OpenMesh::Attributes::Normal | OpenMesh::Attributes::Status);
+	HalfedgeAttributes(OpenMesh::Attributes::Normal | OpenMesh::Attributes::Status);
+	using Point = glm::vec3;
+	using Normal = glm::vec3;
+};
+
+class TerrainMesh : public OpenMesh::TriMesh_ArrayKernelT<TerrainTraits> {
+public:
+	explicit TerrainMesh(const std::filesystem::path &);
+
+protected:
+	[[nodiscard]] static bool triangleContainsPoint(const glm::vec2, const glm::vec2, const glm::vec2, const glm::vec2);
+	[[nodiscard]] bool triangleContainsPoint(const glm::vec2, FaceHandle) const;
+};
-- 
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