mirror of
https://gitlab.kitware.com/vtk/vtk-m
synced 2024-07-30 18:50:59 +00:00
100 lines
2.5 KiB
C++
100 lines
2.5 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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#ifndef vtk_m_rendering_raytracing_Sampler_h
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#define vtk_m_rendering_raytracing_Sampler_h
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#include <vtkm/Math.h>
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#include <vtkm/VectorAnalysis.h>
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namespace vtkm
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{
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namespace rendering
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{
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namespace raytracing
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{
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template <vtkm::Int32 Base>
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VTKM_EXEC void Halton2D(const vtkm::Int32& sampleNum, vtkm::Vec2f_32& coord)
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{
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//generate base2 halton
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vtkm::Float32 x = 0.0f;
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vtkm::Float32 xadd = 1.0f;
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vtkm::UInt32 b2 = 1 + static_cast<vtkm::UInt32>(sampleNum);
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while (b2 != 0)
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{
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xadd *= 0.5f;
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if ((b2 & 1) != 0)
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x += xadd;
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b2 >>= 1;
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}
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vtkm::Float32 y = 0.0f;
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vtkm::Float32 yadd = 1.0f;
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vtkm::Int32 bn = 1 + sampleNum;
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while (bn != 0)
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{
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yadd *= 1.0f / (vtkm::Float32)Base;
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y += (vtkm::Float32)(bn % Base) * yadd;
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bn /= Base;
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}
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coord[0] = x;
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coord[1] = y;
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} // Halton2D
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VTKM_EXEC
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vtkm::Vec3f_32 CosineWeightedHemisphere(const vtkm::Int32& sampleNum, const vtkm::Vec3f_32& normal)
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{
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//generate orthoganal basis about normal
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int kz = 0;
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if (vtkm::Abs(normal[0]) > vtkm::Abs(normal[1]))
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{
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if (vtkm::Abs(normal[0]) > vtkm::Abs(normal[2]))
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kz = 0;
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else
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kz = 2;
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}
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else
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{
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if (vtkm::Abs(normal[1]) > vtkm::Abs(normal[2]))
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kz = 1;
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else
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kz = 2;
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}
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vtkm::Vec3f_32 notNormal;
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notNormal[0] = 0.f;
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notNormal[1] = 0.f;
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notNormal[2] = 0.f;
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notNormal[kz] = 1.f;
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vtkm::Vec3f_32 xAxis = vtkm::Cross(normal, notNormal);
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vtkm::Normalize(xAxis);
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vtkm::Vec3f_32 yAxis = vtkm::Cross(normal, xAxis);
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vtkm::Normalize(yAxis);
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vtkm::Vec2f_32 xy;
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Halton2D<3>(sampleNum, xy);
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const vtkm::Float32 r = Sqrt(xy[0]);
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const vtkm::Float32 theta = 2 * static_cast<vtkm::Float32>(vtkm::Pi()) * xy[1];
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vtkm::Vec3f_32 direction(0.f, 0.f, 0.f);
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direction[0] = r * vtkm::Cos(theta);
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direction[1] = r * vtkm::Sin(theta);
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direction[2] = vtkm::Sqrt(vtkm::Max(0.0f, 1.f - xy[0]));
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vtkm::Vec3f_32 sampleDir;
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sampleDir[0] = vtkm::dot(direction, xAxis);
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sampleDir[1] = vtkm::dot(direction, yAxis);
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sampleDir[2] = vtkm::dot(direction, normal);
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return sampleDir;
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}
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}
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}
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} // namespace vtkm::rendering::raytracing
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#endif
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