Kayne Ruse
120 lines
3.4 KiB
C++
120 lines
3.4 KiB
C++
/* Copyright: (c) Kayne Ruse 2014
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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*
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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*
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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*
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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*
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* 3. This notice may not be removed or altered from any source
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* distribution.
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*/
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#include "map_generator.hpp"
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#include "vector2.hpp"
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#include <cmath>
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//-------------------------
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//Utility functions
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//-------------------------
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//snap to a grid (floating point version)
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static double snap(double x, double base) {
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return floor(x / base) * base;
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}
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//A.K.A.: the dot product
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static double scalarProduct(Vector2 lhs, Vector2 rhs) {
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return lhs.x * rhs.x + lhs.y * rhs.y;
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}
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//curved interpolation
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static double curve(double x) {
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//param: 0 to 1 inclusive
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return 3.0 * pow(x, 2.0) - 2.0 * pow(x, 3.0);
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}
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//fix the overflow
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static double curl(double x) {
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if (x > 1.0) {
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return -curl(x-1) +1;
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}
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if (x < 0.0) {
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return curl(-x);
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}
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return x;
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}
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static double cut(double x) {
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if (x > 1.0) {
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return 1.0;
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}
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if (x < 0.0) {
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return 0.0;
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}
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return x;
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}
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//-------------------------
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//Public methods
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//-------------------------
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Vector2 MapGenerator::RawNoise(Vector2 const& gridPoint) {
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double angle = rng(gridPoint.x * 0xffff + gridPoint.y);
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Vector2 v = {cos(angle), sin(angle)};
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v.Normalize();
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return v;
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}
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double MapGenerator::Influence(Vector2 const& gridPoint, Vector2 const& queryPoint, double width, double height) {
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//note: inverting the distance here, so the smaller the distance the more influence it has
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Vector2 distance = queryPoint - gridPoint;
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Vector2 inverted = {width - distance.x, height - distance.y};
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double ret = scalarProduct(RawNoise(gridPoint), inverted);
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return ret > 0 ? ret : -ret;
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}
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double MapGenerator::ScaledNoise(double x, double y, double width, double height) {
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Vector2 queryPoint = {x, y};
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//the "grid points"
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Vector2 tl = {snap(x, width), snap(y, height)};
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Vector2 tr = {tl.x + width, tl.y};
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Vector2 bl = {tl.x, tl.y + height};
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Vector2 br = {tl.x + width, tl.y + height};
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//influence equasion
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double s = Influence(tl, queryPoint, width, height);
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double t = Influence(tr, queryPoint, width, height);
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double u = Influence(bl, queryPoint, width, height);
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double v = Influence(br, queryPoint, width, height);
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//Finally, calc the value
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double a = s + curve((t - s) / width);
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double b = u + curve((v - u) / width);
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return curve((b - a) / height);
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}
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double MapGenerator::ScaledOctave(double x, double y, double width, double height, double octave) {
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double ret = 0;
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if (octave > 1) {
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ret += ScaledOctave(x, y, width/2, height/2, octave-1);
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}
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return ret / octave + ScaledNoise(x, y, width, height);
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}
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double MapGenerator::GetPixel(double x, double y, double width, double height, double octave) {
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//use this as a decorator function
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return curl(ScaledOctave(x, y, width, height, octave));
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} |