[SOLVED] How to modify a VDB prim?

[kgmcnamara]

Hi,

 

I want to be able to write data into individual voxels inside of a VDB that is input to my HDK node. 

 

So far I have done the following:

	// Get the first VDB primitive in the geometry
	GEO_PrimVDB* vdbPrim = NULL;
	for (GA_Iterator it(gdp->getPrimitiveRange()); !it.atEnd(); it.advance())
	{
		GEO_Primitive* prim = gdp->getGEOPrimitive(it.getOffset());
		if(dynamic_cast<const GEO_PrimVDB *>(prim))
		{
			vdbPrim = dynamic_cast<GEO_PrimVDB *>(prim);
			break;
		}
	}

	// Make sure we got a valid prim
	if(!vdbPrim)
	{
		addError(SOP_MESSAGE, "Input geometry must contain a VDB");
		return error();
	}

	// Docs say to do this in case the grid is shared
	vdbPrim->makeGridUnique();

Next I try to get the Grid from vdbPrim, but I can't get it to work. I've tried a handful of functions like getGrid(), getGridPtr(), etc. Can anyone recommend what I need to do next?

 

EDIT - SOLVED. Posting for any others who might find themselves in a similar struggle:

 

Some more digging through the VDB docs lead me to this. Works!

	// Docs say to do this in case the grid is shared
	vdbPrim->makeGridUnique();

	// Try to get the vdb's grid
	openvdb::GridBase::Ptr baseGrid;
	if(vdbPrim->hasGrid())
		baseGrid = vdbPrim->getGridPtr();

	openvdb::FloatGrid::Ptr grid = openvdb::gridPtrCast<openvdb::FloatGrid>(baseGrid);
	openvdb::FloatGrid::Accessor accessor = grid->getAccessor();

	openvdb::Coord xyz(0,0,0);
	accessor.setValue(xyz, 1.0);

Edited April 20, 2014 by kgmcnamara