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//
// libavg - Media Playback Engine.
// Copyright (C) 2003-2014 Ulrich von Zadow
//
// This library 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 of the License, or (at your option) any later version.
//
// This library 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 library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
// Current versions can be found at www.libavg.de
//
#include "CubicSpline.h"
#include "Exception.h"
#include "MathHelper.h"
#include <iostream>
using namespace std;
namespace avg {
CubicSpline::CubicSpline(const vector<float>& x, const vector<float>& y, bool bLoop)
{
AVG_ASSERT(x.size() == y.size());
for (unsigned i=0; i<x.size(); ++i) {
m_Pts.push_back(glm::vec2(x[i], y[i]));
}
init();
}
CubicSpline::CubicSpline(const vector<glm::vec2>& pts, bool bLoop)
: m_Pts(pts)
{
init();
}
CubicSpline::~CubicSpline()
{
}
float CubicSpline::interpolate(float orig)
{
int len = m_Pts.size();
int low = 0;
int high = len-1;
// Binary search.
while (high - low > 1) {
int avg = (high+low) / 2;
if (m_Pts[avg].x > orig) {
high = avg;
} else {
low = avg;
}
}
float h = m_Pts[high].x - m_Pts[low].x;
float a = (m_Pts[high].x-orig)/h;
float b = (orig-m_Pts[low].x)/h;
float y = a*m_Pts[low].y + b*m_Pts[high].y
+ ((a*a*a-a)*m_Y2[low] + (b*b*b-b)*m_Y2[high])*(h*h)/6.f;
return y;
}
void CubicSpline::init()
{
int len = m_Pts.size();
for (int i=1; i<len; ++i) {
if (m_Pts[i].x <= m_Pts[i-1].x) {
throw Exception(AVG_ERR_INVALID_ARGS,
"CubicSplines must have increasing x coordinates.");
}
}
vector<float> u(len-1,0);
m_Y2.push_back(0.f);
u[0] = 0.f;
for (int i=1; i<len-1; ++i) {
float sig = (m_Pts[i].x-m_Pts[i-1].x) / (m_Pts[i+1].x-m_Pts[i-1].x);
float p = sig * m_Y2[i-1]+2.0f;
m_Y2.push_back((sig-1.0f)/p);
u[i] = (m_Pts[i+1].y-m_Pts[i].y) / (m_Pts[i+1].x-m_Pts[i].x) -
(m_Pts[i].y - m_Pts[i-1].y) / (m_Pts[i].x-m_Pts[i-1].x);
u[i] = (6.f*u[i]/(m_Pts[i+1].x-m_Pts[i-1].x) - sig*u[i-1]) / p;
}
float qn = 0.f;
float un = 0.f;
m_Y2.push_back((un-qn*u[len-2]) / (qn*m_Y2[len-2]-1.0f));
for (int i=len-2; i>=0; i--) {
m_Y2[i] = m_Y2[i]*m_Y2[i+1]+u[i];
}
}
}
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