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New Feature
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Resolution: Unresolved
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Medium
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None
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Starting out with a simply merge function signature such as:
template <typename GridT> void merge(std::vector<GridT>& grids);
To extend this to support stealing, there are three states of each VDB Grid that are acceptable to the merge method:
- Const
- Non-Const, Non-Unique
- Non-Const, Unique (and hence Stealable)
One such implementation could thus be:
template <typename GridT>
void merge(std::vector<typename GridT::Ptr>& nonConstGrids,
std::vector<typename GridT::ConstPtr>& constGrids)
{
for (auto& grid : nonConstGrids)
{
if (grid->tree().isUnique()) // steal
else // deep-copy
}
for (const auto& grid : constGrids)
{
// deep-copy
}
}
Another possible approach is to introduce a VDB Primitive along the same kind of lines as the Houdini GEO_PrimVDB:
template <typename GridT>
struct VDBPrimitive
{
using PtrT = typename GridT::Ptr;
using ConstPtrT = typename GridT::ConstPtr;
explicit VDBPrimitive(ConstPtrT& grid) : mGrid(grid) { }
explicit VDBPrimitive(PtrT& grid) : mGrid(grid), mConst(false) { }
ConstPtrT getConst() const { return mGrid; }
PtrT get() { return mConst ? PtrT() : openvdb::ConstPtrCast<gridT>(mGrid); }
private:
ConstPtrT mGrid;
bool mConst = true;
};
The VDBPrimitive approach would have two main benefits - being able to intersperse const and non-const grids in a single container as desired and to be able to provide a simpler function signature such as:
template <typename GridT> void merge(std::vector<VDBPrimitive<GridT>>& grids);
I'm not confident that this approach is the right way to go, so I'm not so much proposing using a VDBPrimitive as I am simply floating the idea and looking for feedback.