Solved VolumeObject ReadObject and WriteObject no supported?

I am manually saving objects within my own Generator. It seems that if I write out, then read a VolumeObject that it does not save any volume data at all. Calling GetVolume() returns nullptr; My volumes do have data in them so I would expect it to save and load.

pObj = VolumeObject::Alloc();
pObj->ReadObject(hf, true);
maxon::VolumeInterface* data = pObj->GetVolume();

data is null;

Can someone confirm if this is actually true and the correct behaviour?

Hi Kent, thanks for reaching out us.

With regard to your issue, at the moment writing/reading a VolumeObject using the C4DAtom::WriteObject / C4DAtom::ReadObject using an Hyperfile is not supported if the HyperFile object operates on disk.

At the moment a workaround is represented by using a temporary memory file, write into that, write that to disk. To read/write using MemoryFileStruct please visit here.

The following code shows how to read/write VolumeObject from/to memory-located HF.

	iferr_scope;
	
	// alloc the VolumeObject to write
	AutoAlloc<VolumeObject> volObjWrite;
	if (!volObjWrite)
		return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
	
	// put some data in the VolumeObject
	const maxon::Int    gridIndex = 0;
	const maxon::Url volumeUrl ("<your path to a vdb>"_s);
	const maxon::Volume volume = maxon::VolumeInterface::CreateFromFile(volumeUrl, 1.0, gridIndex) iferr_return;

	// insert volume
	volObjWrite->SetVolume(volume);
	
	// alloc HF
	AutoAlloc<HyperFile> hf;
	if (!hf)
		return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
	
	// alloc MemoryFileStruct
	AutoAlloc<MemoryFileStruct> mfs;
	if (!mfs)
		return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
	
	// alloc Filename and set to memory
	Filename fn;
	fn.SetMemoryWriteMode(mfs);
	
	// open HyperFile to write
	if (!hf->Open(0, fn, FILEOPEN::WRITE, FILEDIALOG::NONE))
		return maxon::UnknownError(MAXON_SOURCE_LOCATION);
	
	// write volume to memory HF
  Bool writeRes = volObjWrite->WriteObject(hf);
	if (writeRes)
		DiagnosticOutput("volume written on HF");
	
	// close written HF
	hf->Close();

        //... write memory-located HF to disk
        //... do your stuff
        //...read from disk the memory-located HF
	
	// open HF to read
	if (!hf->Open(0, fn, FILEOPEN::READ, FILEDIALOG::NONE))
		return maxon::UnknownError(MAXON_SOURCE_LOCATION);
	
	// alloc the VolumeObject to read
	AutoAlloc<VolumeObject> volObjRead;
	if (!volObjRead)
		return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
	
	// read volume from memory HF
	Bool readRes = volObjRead->ReadObject(hf, true);
	const maxon::VolumeInterface* volRead = volObjRead->GetVolume();
	if (readRes && volRead)
		DiagnosticOutput("volume read from HF");
	
	hf->Close();
	
	return maxon::OK;

Best, Riccardo

Hi Kent, thanks for reaching out us.

With regard to your issue, at the moment writing/reading a VolumeObject using the C4DAtom::WriteObject / C4DAtom::ReadObject using an Hyperfile is not supported if the HyperFile object operates on disk.

At the moment a workaround is represented by using a temporary memory file, write into that, write that to disk. To read/write using MemoryFileStruct please visit here.

The following code shows how to read/write VolumeObject from/to memory-located HF.

	iferr_scope;
	
	// alloc the VolumeObject to write
	AutoAlloc<VolumeObject> volObjWrite;
	if (!volObjWrite)
		return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
	
	// put some data in the VolumeObject
	const maxon::Int    gridIndex = 0;
	const maxon::Url volumeUrl ("<your path to a vdb>"_s);
	const maxon::Volume volume = maxon::VolumeInterface::CreateFromFile(volumeUrl, 1.0, gridIndex) iferr_return;

	// insert volume
	volObjWrite->SetVolume(volume);
	
	// alloc HF
	AutoAlloc<HyperFile> hf;
	if (!hf)
		return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
	
	// alloc MemoryFileStruct
	AutoAlloc<MemoryFileStruct> mfs;
	if (!mfs)
		return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
	
	// alloc Filename and set to memory
	Filename fn;
	fn.SetMemoryWriteMode(mfs);
	
	// open HyperFile to write
	if (!hf->Open(0, fn, FILEOPEN::WRITE, FILEDIALOG::NONE))
		return maxon::UnknownError(MAXON_SOURCE_LOCATION);
	
	// write volume to memory HF
  Bool writeRes = volObjWrite->WriteObject(hf);
	if (writeRes)
		DiagnosticOutput("volume written on HF");
	
	// close written HF
	hf->Close();

        //... write memory-located HF to disk
        //... do your stuff
        //...read from disk the memory-located HF
	
	// open HF to read
	if (!hf->Open(0, fn, FILEOPEN::READ, FILEDIALOG::NONE))
		return maxon::UnknownError(MAXON_SOURCE_LOCATION);
	
	// alloc the VolumeObject to read
	AutoAlloc<VolumeObject> volObjRead;
	if (!volObjRead)
		return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
	
	// read volume from memory HF
	Bool readRes = volObjRead->ReadObject(hf, true);
	const maxon::VolumeInterface* volRead = volObjRead->GetVolume();
	if (readRes && volRead)
		DiagnosticOutput("volume read from HF");
	
	hf->Close();
	
	return maxon::OK;

Best, Riccardo

Thanks Riccardo.