Add relief map mesh generation function

src/game/cartography/relief-map.cpp

@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2020  Christopher J. Howard
+ *
+ * This file is part of Antkeeper source code.
+ *
+ * Antkeeper source code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Antkeeper source code is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "relief-map.hpp"
+#include <array>
+#include <cmath>
+#include <map>
+
+namespace cart
+{
+
+mesh* map_elevation(const std::function<float(float, float)>& function, float scale, std::size_t subdivisions)
+{
+	// Allocate terrain mesh
+	mesh* mesh = new ::mesh();
+
+	// Determine vertex count and placement
+	std::size_t columns = static_cast<std::size_t>(std::pow(2, subdivisions));
+	std::size_t rows = columns;
+	float uv_scale = 1.0f / static_cast<float>(columns);
+	//std::size_t vertex_count = (columns + 1) * (rows + 1);
+	
+	// Generate mesh vertices
+	float3 position;
+	float2 uv;
+	for (std::size_t i = 0; i <= rows; ++i)
+	{
+		uv.y = static_cast<float>(i) * uv_scale;
+		position.z = (uv.y - 0.5f) * scale;
+		
+		for (std::size_t j = 0; j <= columns; ++j)
+		{
+			uv.x = static_cast<float>(j) * uv_scale;
+			
+			position.x = (uv.x - 0.5f) * scale;
+			position.y = function(uv.x, uv.y);
+			
+			mesh->add_vertex(position);
+		}
+	}
+	
+	// Function to eliminate duplicate edges
+	std::map<std::array<std::size_t, 2>, mesh::edge*> edge_map;
+	auto add_or_find_edge = [&](mesh::vertex* start, mesh::vertex* end) -> mesh::edge*
+	{
+		mesh::edge* edge;
+		if (auto it = edge_map.find({start->index, end->index}); it != edge_map.end())
+		{
+			edge = it->second;
+		}
+		else
+		{
+			edge = mesh->add_edge(start, end);
+			edge_map[{start->index, end->index}] = edge;
+			edge_map[{end->index, start->index}] = edge->symmetric;
+		}
+
+		return edge;
+	};
+
+	const std::vector<mesh::vertex*>& vertices = mesh->get_vertices();
+	for (std::size_t i = 0; i < rows; ++i)
+	{
+		for (std::size_t j = 0; j < columns; ++j)
+		{
+			mesh::vertex* a = vertices[i * (columns + 1) + j];
+			mesh::vertex* b = vertices[(i + 1) * (columns + 1) + j];
+			mesh::vertex* c = vertices[i * (columns + 1) + j + 1];
+			mesh::vertex* d = vertices[(i + 1) * (columns + 1) + j + 1];
+
+			// +---+---+
+			// | \ | / |
+			// |---+---|
+			// | / | \ |
+			// +---+---+
+			if ((j % 2) == (i % 2))
+			{
+				mesh::edge* ab = add_or_find_edge(a, b);
+				mesh::edge* bd = add_or_find_edge(b, d);
+				mesh::edge* da = add_or_find_edge(d, a);
+
+				mesh::edge* ca = add_or_find_edge(c, a);
+				mesh::edge* ad = da->symmetric;
+				mesh::edge* dc = add_or_find_edge(d, c);
+
+				// a---c
+				// | \ |
+				// b---d
+				mesh->add_face({ab, bd, da});
+				mesh->add_face({ca, ad, dc});
+			}
+			else
+			{
+				mesh::edge* ab = add_or_find_edge(a, b);
+				mesh::edge* bc = add_or_find_edge(b, c);
+				mesh::edge* ca = add_or_find_edge(c, a);
+				mesh::edge* cb = bc->symmetric;
+				mesh::edge* bd = add_or_find_edge(b, d);
+				mesh::edge* dc = add_or_find_edge(d, c);
+
+				// a---c
+				// | / |
+				// b---d
+				mesh->add_face({ab, bc, ca});
+				mesh->add_face({cb, bd, dc});
+			}
+		}
+	}
+
+	return mesh;
+}
+
+} // namespace cart

src/game/cartography/relief-map.hpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2020  Christopher J. Howard
+ *
+ * This file is part of Antkeeper source code.
+ *
+ * Antkeeper source code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Antkeeper source code is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef ANTKEEPER_RELIEF_MAP_HPP
+#define ANTKEEPER_RELIEF_MAP_HPP
+
+#include "geometry/mesh.hpp"
+#include <functional>
+
+namespace cart
+{
+
+/**
+ * Generates a relief map mesh given an elevation function.
+ *
+ * @param function Function which returns an elevation given UV coordinates on a unit plane.
+ * @param subdivisions Number of lines of longitude. Minimum value is 3.
+ */
+mesh* map_elevation(const std::function<float(float, float)>& function, float scale, std::size_t subdivisions);
+
+} // namespace cart
+
+#endif // ANTKEEPER_RELIEF_MAP_HPP