Initial commit, basic infrastructure

perlin/perlin_noise.cpp

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+/* Copyright: (c) Kayne Ruse 2014
+ * 
+ * This software is provided 'as-is', without any express or implied
+ * warranty. In no event will the authors be held liable for any damages
+ * arising from the use of this software.
+ * 
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ * 
+ * 1. The origin of this software must not be misrepresented; you must not
+ * claim that you wrote the original software. If you use this software
+ * in a product, an acknowledgment in the product documentation would be
+ * appreciated but is not required.
+ * 
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ * misrepresented as being the original software.
+ * 
+ * 3. This notice may not be removed or altered from any source
+ * distribution.
+*/
+#include "perlin_noise.hpp"
+
+#include "vector2.hpp"
+
+#include <cmath>
+
+//-------------------------
+//Public access members
+//-------------------------
+
+double SimpleRNG::operator()(double x) {
+	x = x * seed * 345589144.0 + 1123581321.0;
+	return fmod(x, 21795.0);
+};
+
+Vector2 PerlinNoise::Gradient(Vector2 pos) {
+	//could cache this result
+	double j = rng(pos.y*pos.y + pos.x * 144);
+	double i = rng(pos.x*pos.x + pos.y * 144);
+	Vector2 v(i, j);
+	v.Normalize();
+	return v;
+}
+
+double PerlinNoise::Influcence(Vector2 gridPoint, Vector2 queryPoint) {
+	return ScalarProduct(Gradient(gridPoint), queryPoint - gridPoint);
+}
+
+double PerlinNoise::Noise(double x, double y, double width, double height) {
+	Vector2 point = {x, y};
+
+	x = Snap(x, width);
+	y = Snap(y, height);
+
+	//determine the grid points
+	Vector2 tl = {x, y};
+	Vector2 tr = {x + width, y};
+	Vector2 bl = {x, y + height};
+	Vector2 br = {x + width, y + height};
+
+	//influence equasion
+	double s = Influcence(tl, point);
+	double t = Influcence(tr, point);
+	double u = Influcence(bl, point);
+	double v = Influcence(br, point);
+
+	//get the noise
+	double a = s + Curve((t - s) / width);
+	double b = u + Curve((v - u) / width);
+	return a + Curve((b - a) / height);
+}
+
+//-------------------------
+//Static utility functions
+//-------------------------
+
+double PerlinNoise::Curve(double x) {
+	//param: 0 to 1 inclusive
+	return 3.0 * pow(x, 2.0) - 2.0 * pow(x, 3.0);
+}
+
+double PerlinNoise::Snap(double x, double base) {
+	//snap to a grid (floating point version)
+	return floor(x / base) * base;
+}
+
+double PerlinNoise::ScalarProduct(Vector2 lhs, Vector2 rhs) {
+	//the dot product
+	return lhs.x * rhs.x + lhs.y * rhs.y;
+}