Convert a vdb file to a signed distance field

[Meher Niger]

Hello everyone,

I am kind of new to openvdb language.
The initial step is I need to convert my loaded vdb file to a signed distance field. 
I was trying to do that using openvdb::tools:: :LevelSetFilter. then fixing an offset value. 
I don't think it is giving me the correct result because when I am converting the output vdb file to npy file and plotting in python it seems wrong.
I am not quite sure if my approach or the filter I am using is right. Can anyone give me any suggestions? 
Thanks in advance. 
Here is my code. 

int main()
{
    openvdb::initialize();

    // Load VDB grid from file
    openvdb::io::File file("input.vdb");
    file.open();

    openvdb::GridBase::Ptr baseGrid;
    for (openvdb::io::File::NameIterator nameIter = file.beginName();
        nameIter != file.endName(); ++nameIter)
    {
        // Read in only the grid we are interested in.
        if (nameIter.gridName() == "LevelSetSphere") {
            baseGrid = file.readGrid(nameIter.gridName());
        }
        else {
            std::cout << "skipping grid " << nameIter.gridName() << std::endl;
        }
    }
    file.close();

 

    openvdb::FloatGrid::Ptr grid = openvdb::gridPtrCast<openvdb::FloatGrid>(baseGrid);

    openvdb::tools::LevelSetFilter<openvdb::FloatGrid> lsf(*grid);
    lsf.offset(-0.5);
     

    // Save the modified grid as a new VDB file
    openvdb::io::File output("output.vdb");
    output.write({ grid });
    output.close();

 

    return 0;
}

[andre pradhana]

If I understand you correctly, you want to convert a density field/fog field to a signed distance field. I recommend using

openvdb::v10_0::tools::fogToSdf. You need to include #include <openvdb/tools/FastSweeping.h> to use this tool.

Andre

[Meher Niger]

Thank you so much Andre for your response and clarification.

Following your instructions I was trying to apply openvdb::v10_0::tools::fogToSdf(*grid, ISO value= 0) 

But it seems like still it's not creating the signed distance field. I am not sure if I am using a wrong ISO value or I am misunderstanding something else. 
For your clarification, as input I have 3D grids with zeros and ones. I want to fill the rest of the area with SDF.  Please let me know if you have any questions. 

Thank you again for your time and help.

Sincerely

Meher