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// Copyright 2009-2021 Intel Corporation
// SPDX-License-Identifier: Apache-2.0
#include "distribution2d.h"
namespace embree
{
Distribution2D::Distribution2D()
: width(0), height(0) {}
Distribution2D::Distribution2D(const float* f, const size_t width, const size_t height)
: width(width), height(height)
{
init(f, width, height);
}
void Distribution2D::init(const float* f, const size_t w, const size_t h)
{
/*! create arrays */
width = w; height = h;
xDists.resize(height);
std::vector<float> fy(height);
/*! compute y distribution and initialize row distributions */
for (size_t y=0; y<height; y++)
{
/*! accumulate row to compute y distribution */
fy[y] = 0.0f;
for (size_t x=0; x<width; x++)
fy[y] += f[y*w+x];
/*! initialize distribution for current row */
xDists[y].init(f+y*width, width);
}
/*! initializes the y distribution */
yDist.init(fy.data(), height);
}
Vec2f Distribution2D::sample(const Vec2f& u) const
{
/*! use u.y to sample a row */
float sy = yDist.sample(u.y);
int idx = clamp(int(sy),0,int(height)-1);
/*! use u.x to sample inside the row */
float sx = xDists[idx].sample(u.x);
return Vec2f(sx,sy);
}
float Distribution2D::pdf(const Vec2f& p) const {
int idx = clamp(int(p.y*height),0,int(height)-1);
return xDists[idx].pdf(p.x) * yDist.pdf(p.y);
}
}
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