grid_sdf.hpp

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#ifndef PECLET_CORE_GEOM_GRID_SDF_HPP
#define PECLET_CORE_GEOM_GRID_SDF_HPP
 
#include <algorithm>
#include <vector>
 
#include "peclet/core/common/types.hpp"
#include "peclet/core/geom/scene.hpp"
 
namespace peclet::core::geom {
 
struct GridSdf {
  std::vector<float> values;  
  IVec<3> dims{};             
  Vec<3> origin{};            
  Vec<3> spacing{1, 1, 1};    
 
  double at(Index i, Index j, Index k) const {
    return static_cast<double>(values[i + dims[0] * (j + dims[1] * k)]);
  }
 
  GridDesc<double> desc() const {
    GridDesc<double> d;
    d.nx = static_cast<int>(dims[0]);
    d.ny = static_cast<int>(dims[1]);
    d.nz = static_cast<int>(dims[2]);
    d.offset = 0;
    d.origin = Vec3<double>{origin[0], origin[1], origin[2]};
    d.invSpacing = Vec3<double>{spacing[0] != 0.0 ? 1.0 / spacing[0] : 0.0,
                                spacing[1] != 0.0 ? 1.0 / spacing[1] : 0.0,
                                spacing[2] != 0.0 ? 1.0 / spacing[2] : 0.0};
    d.extension = GridExtension::kClamp;  // flat at the box face -- this type's documented contract
    return d;
  }
 
  double eval(const Vec<3>& p) const {
    return sampleGrid(Vec3<double>{p[0], p[1], p[2]}, desc(), PoolPtr<float>{values.data()});
  }
};
 
template <typename S>
GridSdf sample(const S& shape, IVec<3> dims, Vec<3> origin, Vec<3> spacing) {
  GridSdf g;
  g.dims = dims;
  g.origin = origin;
  g.spacing = spacing;
  g.values.resize(static_cast<std::size_t>(dims[0]) * dims[1] * dims[2]);
  for (Index k = 0; k < dims[2]; ++k)
    for (Index j = 0; j < dims[1]; ++j)
      for (Index i = 0; i < dims[0]; ++i) {
        Vec<3> p{origin[0] + i * spacing[0], origin[1] + j * spacing[1],
                 origin[2] + k * spacing[2]};
        g.values[i + dims[0] * (j + dims[1] * k)] = static_cast<float>(shape.eval(p));
      }
  return g;
}
 
}  // namespace peclet::core::geom
 
#endif  // PECLET_CORE_GEOM_GRID_SDF_HPP