Initial commit

src/face_position_cache.cpp

@@ -0,0 +1,110 @@
+/*
+Minetest
+Copyright (C) 2015 Nerzhul, Loic Blot <loic.blot@unix-experience.fr>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program 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 Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "face_position_cache.h"
+#include "threading/mutex_auto_lock.h"
+
+
+std::unordered_map<u16, std::vector<v3s16>> FacePositionCache::cache;
+std::mutex FacePositionCache::cache_mutex;
+
+// Calculate the borders of a "d-radius" cube
+const std::vector<v3s16> &FacePositionCache::getFacePositions(u16 d)
+{
+	MutexAutoLock lock(cache_mutex);
+	std::unordered_map<u16, std::vector<v3s16>>::const_iterator it = cache.find(d);
+	if (it != cache.end())
+		return it->second;
+
+	return generateFacePosition(d);
+}
+
+const std::vector<v3s16> &FacePositionCache::generateFacePosition(u16 d)
+{
+	cache[d] = std::vector<v3s16>();
+	std::vector<v3s16> &c = cache[d];
+	if (d == 0) {
+		c.emplace_back(0,0,0);
+		return c;
+	}
+	if (d == 1) {
+		// This is an optimized sequence of coordinates.
+		c.emplace_back(0, 1, 0); // Top
+		c.emplace_back(0, 0, 1); // Back
+		c.emplace_back(-1, 0, 0); // Left
+		c.emplace_back(1, 0, 0); // Right
+		c.emplace_back(0, 0,-1); // Front
+		c.emplace_back(0,-1, 0); // Bottom
+		// 6
+		c.emplace_back(-1, 0, 1); // Back left
+		c.emplace_back(1, 0, 1); // Back right
+		c.emplace_back(-1, 0,-1); // Front left
+		c.emplace_back(1, 0,-1); // Front right
+		c.emplace_back(-1,-1, 0); // Bottom left
+		c.emplace_back(1,-1, 0); // Bottom right
+		c.emplace_back(0,-1, 1); // Bottom back
+		c.emplace_back(0,-1,-1); // Bottom front
+		c.emplace_back(-1, 1, 0); // Top left
+		c.emplace_back(1, 1, 0); // Top right
+		c.emplace_back(0, 1, 1); // Top back
+		c.emplace_back(0, 1,-1); // Top front
+		// 18
+		c.emplace_back(-1, 1, 1); // Top back-left
+		c.emplace_back(1, 1, 1); // Top back-right
+		c.emplace_back(-1, 1,-1); // Top front-left
+		c.emplace_back(1, 1,-1); // Top front-right
+		c.emplace_back(-1,-1, 1); // Bottom back-left
+		c.emplace_back(1,-1, 1); // Bottom back-right
+		c.emplace_back(-1,-1,-1); // Bottom front-left
+		c.emplace_back(1,-1,-1); // Bottom front-right
+		// 26
+		return c;
+	}
+
+	// Take blocks in all sides, starting from y=0 and going +-y
+	for (s16 y = 0; y <= d - 1; y++) {
+		// Left and right side, including borders
+		for (s16 z =- d; z <= d; z++) {
+			c.emplace_back(d, y, z);
+			c.emplace_back(-d, y, z);
+			if (y != 0) {
+				c.emplace_back(d, -y, z);
+				c.emplace_back(-d, -y, z);
+			}
+		}
+		// Back and front side, excluding borders
+		for (s16 x = -d + 1; x <= d - 1; x++) {
+			c.emplace_back(x, y, d);
+			c.emplace_back(x, y, -d);
+			if (y != 0) {
+				c.emplace_back(x, -y, d);
+				c.emplace_back(x, -y, -d);
+			}
+		}
+	}
+
+	// Take the bottom and top face with borders
+	// -d < x < d, y = +-d, -d < z < d
+	for (s16 x = -d; x <= d; x++)
+	for (s16 z = -d; z <= d; z++) {
+		c.emplace_back(x, -d, z);
+		c.emplace_back(x, d, z);
+	}
+	return c;
+}