mirror of
https://gitlab.kitware.com/vtk/vtk-m
synced 2024-10-05 09:59:12 +00:00
66 lines
1.9 KiB
C++
66 lines
1.9 KiB
C++
//============================================================================
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// Copyright (c) Kitware, Inc.
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// All rights reserved.
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// See LICENSE.txt for details.
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//
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// This software is distributed WITHOUT ANY WARRANTY; without even
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// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the above copyright notice for more information.
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//============================================================================
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#include <cmath>
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#include <iostream>
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#include <vector>
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#include <vtkm/cont/DataSetBuilderUniform.h>
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#include <vtkm/io/ImageWriterPNG.h>
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int main()
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{
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size_t height = 1800;
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size_t width = height * 1.618;
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vtkm::cont::DataSetBuilderUniform dsb;
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vtkm::cont::DataSet ds = dsb.Create(vtkm::Id2(width, height));
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std::vector<double> x(width, 0.5);
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double rmin = 2.9;
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for (size_t i = 0; i < width; ++i)
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{
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double r = rmin + (4.0 - rmin) * i / (width - 1);
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int n = 0;
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// 2048 should be enough iterations to be "converged";
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// though of course the iterations actually don't all converge but cycle or are chaotic.
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while (n++ < 2048)
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{
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x[i] = r * x[i] * (1 - x[i]);
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}
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}
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vtkm::Vec4f v(1.0, 0.5, 0.0, 0.0);
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std::vector<vtkm::Vec4f> pixelValues(width * height, vtkm::Vec4f(0, 0, 0, 0));
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size_t iterates = 0;
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// We don't need more iterates than pixels of height,
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// by the pigeonhole principle.
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while (iterates++ < height)
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{
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for (size_t i = 0; i < width; ++i)
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{
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double r = rmin + (4.0 - rmin) * i / (width - 1);
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double y = x[i];
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assert(y >= 0 && y <= 1);
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size_t j = std::round(y * (height - 1));
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pixelValues[j * width + i] = v;
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x[i] = r * x[i] * (1 - x[i]);
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}
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}
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std::string colorFieldName = "pixels";
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ds.AddPointField(colorFieldName, pixelValues);
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std::string filename = "logistic.png";
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vtkm::io::ImageWriterPNG writer(filename);
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writer.WriteDataSet(ds, colorFieldName);
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std::cout << "Now open " << filename << "\n";
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}
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