TestOpenVDBStaggeredGrid.cpp

struct SillyFunction
{
  SillyFunction() {}
  Vec3d operator()(const Vec3d& xyz) const
  {
    return Vec3d(3.0 * xyz.y() + 1.0, 5.0 * xyz.z() + 7.0, -1.0 * xyz.x() - 9.0);
  }
};

TEST(Grids, MacGrid)
{
  Vec3dGrid::Ptr grid = Vec3dGrid::create(Vec3d(0));
  grid->setGridClass(GRID_STAGGERED);

  CoordBBox bbox(Coord(0, 0, 0), Coord(2, 2, 2));

  Vec3dGrid::Accessor acc = grid->getAccessor();
  SillyFunction func;

  for (int i = bbox.min()[0]; i < bbox.max()[0]; ++i)
    for (int j = bbox.min()[1]; j < bbox.max()[1]; ++j)
      for (int k = bbox.min()[2]; k < bbox.max()[2]; ++k) {
        Coord ijk(i, j, k);
        Vec3d value = func(Vec3d(i, j, k));
        // When setting the velocity on a staggered grid, despite this being a single call,
        // what you're actually accomplishing is equivalent to the fictitious calls:
        // acc.setValueForX(Coord(i-0.5, j, k), value);
        // acc.setValueForY(Coord(i, j-0.5, k), value);
        // acc.setValueForZ(Coord(i, j, k-0.5), value);
        acc.setValue(ijk, value);
      }


//  tools::Sampler<2, false> sampler; // ==> this works!
  tools::Sampler<2, true> sampler;  // ==> now this works too!

  for (int i = bbox.min()[0]; i < bbox.max()[0]; ++i)
    for (int j = bbox.min()[1]; j < bbox.max()[1]; ++j)
      for (int k = bbox.min()[2]; k < bbox.max()[2]; ++k)
      {
        Vec3d sampledValue_a = sampler.sample(grid->tree(), Vec3R(i-0.5, j, k));
        Vec3d sampledValue_b = sampler.sample(grid->tree(), Vec3R(i, j-0.5, k));
        Vec3d sampledValue_c = sampler.sample(grid->tree(), Vec3R(i, j, k-0.5));
        Vec3d expected = func(Vec3d(i, j, k));

        EXPECT_EQ(sampledValue_a.x(), expected.x());
        EXPECT_EQ(sampledValue_b.y(), expected.y());
        EXPECT_EQ(sampledValue_c.z(), expected.z());
      }
}