Hello, Some news about this topic,
it seems that the length of the folder where I save the c4d file have an incidence on whether the volumeloader work correctly or not ( C4d R23).
if I save the file to E:\data\tests\export\USD, the volume loader does not work, If I save the same thing to E:\USD, it works.
here are the files ( I renamed the files afterwards, tell me if you find a difference )
Untitled2_longfolder.c4d
Untitled2_shortfolder.c4d Untitled2_Dense Stratus.vdb Untitled2_Cumulus.vdb
the files' reference are relative so they should load fine. ( at least in a short folder)

ok, I did the same with puting "cloud_00.vdb" in the Filename and having in my folder "cloud_00.vdb" to "cloud_64.vdb". It works fine. but somehow it does not work with filename "animmetacloud_Small Cumulonimbus [RefObj]_00.vdb". I tried other filenames, it works fine. I don't know why the particular filename does not work.

we are using the cineware SDK from developers maxon net , I can't say for sure what version it is ( it was updated in june 2020, is there a header file where the exact version is stated?). I downloaded the latest version and builded it to use the command line sample that parses a save file ( to check the difference between what I save and what is saved after loading in C4d ( R23).
I won't be able to give you the whole code ( at least my legal department is likely to fire me ), but I can give you a sample of what we do for the clouds.

			
			
//create cloud object

cineware::BaseObject* c4Cloud;
if (gridNames_.size()>0)
{
	c4Cloud = cineware::BaseObject::Alloc(Ovolumeloader);
	if (startFrame_ != endFrame_)
	{
		cineware::GeData udata;
		udata.SetInt32(1);
		c4Cloud->SetParameter(6001, udata);  //animation
		udata.SetInt32(startFrame_);
		c4Cloud->SetParameter(6003, udata);  //frame range start
		udata.SetInt32(endFrame_);
		c4Cloud->SetParameter(6004, udata); //frame range stop
		cineware::ListViewData* lv = cineware::ListViewData::Alloc();
		for (size_t i = 0; i < gridNames_.size(); ++i)
		{
			cineware::GeData vdata;
			vdata.SetInt32(1);
			lv->AddItem((int)i, ToCinewareString(gridNames_[i]), vdata);
		}
		udata.SetCustomDataType(CUSTOMDATA_LISTVIEW, *lv);
		c4Cloud->SetParameter(6008, udata); //list of activated grids
	}
	else
	{
		cineware::GeData udata;
		udata.SetInt32(0);
		c4Cloud->SetParameter(6001, udata);  //animation
		udata.SetInt32(startFrame_);
		c4Cloud->SetParameter(6002, udata); //frame
	}

}
else
{
	c4Cloud = cineware::BaseObject::Alloc(Ovolume);
}

c4dDoc_->InsertObject(c4Cloud, parentObj);
c4Cloud->SetName(ToC4dStr(name).c_str());

// set vdb file path
cineware::GeData udata;
auto newPath = EONPath(file_);
if (startFrame_ != endFrame_)
{

	cineware::CTrack* xTrack(
		cineware::CTrack::Alloc(c4Cloud,
				cineware::DescLevel(cineware::ID_VOLUME_PATH, cineware::DTYPE_FILENAME, 0),
			"path"));
	c4Cloud->AppendCTrack(xTrack);
	xTrack->t_pseudo = cineware::PSEUDO_DATA; //hack to be able to create pseudo data track
	auto curve = xTrack->GetCurve();
	for (auto time = startFrame_; time <= endFrame_; ++time)
	{
		auto path = newPath;
		// build file name of frame XX
		path.insert_suffix_before_ext_inplace(
			StringFormat(EONString(L"_%0") + boost::lexical_cast<std::wstring>(floor(log(endFrame_ - startFrame_) / log(10) + 1)) + L"d", time));	
		auto mapPath = MakeRelPath(path, GetSettings().localTexturePath_, Filename()); // relative or absolute path
		cineware::GeData data;
		data.SetFilename(cineware::Filename(ToCinewareString(mapPath.local_string())));
		curve->AddKey(cineware::BaseTime(time ,GetSettings().animationFramerate_ ))->SetGeData(curve, data);
	}
    // build file name of frame 0
	newPath.insert_suffix_before_ext_inplace(
		StringFormat(EONString(L"_%0") + boost::lexical_cast<std::wstring>(floor(log(endFrame_ - startFrame_) / log(10) + 1)) + L"d", 0));

}
EONPath mapPath = MakeRelPath(newPath, GetSettings().localTexturePath_, Filename());// relative or absolute path
udata.SetFilename(cineware::Filename(ToCinewareString(mapPath.local_string())));
c4Cloud->SetParameter(cineware::ID_VOLUME_PATH, udata);


// set transformation of object in absolute or relative to parent
if (transfo_.hasParent_)
{
	InitNodeTransform(c4Cloud, transfo_.localPosition_, transfo_.localTransfo_, false);
}
else
{
	InitNodeTransform(c4Cloud, transfo_.vPosition_, transfo_.transfo_, true);
}

also a bug on C4d on Ovolume object ( not sure when to post this).
The reload button modify the postion/scale of the object without taking into account if the object is in a group ( in my case, it is in a group with a 100 scale, that means my cloud is magically transported far away).
The stranger thing, is that the reload seems to be called when I load the scene. But if the object is animated, the reload is applied before the move to the position defined in the position Curve. The result is, the animated cloud is correctly placed whereas the non-animated one is not ( in fact, the position stored in the c4d file is completely ignored)

vdb file uploaded animmetacloud_Small Cumulonimbus [RefObj]_00.vdb

It seems I can't upload a vdb file :sob:

hello, I am trying to export animated vdb clouds (from VUE).
I have a few issue with the Volume loader.
Context: when loading a multi-grid vdb file in c4d (R23 for instance), a Volume loader is created with a list of the internal grids.
So, for my export I tried to do the same thing ( if I split the grids on one per file and create volume objects, it works perfectly).
First issue: the cineware Sdk does not contains the define/param for Ovolumeloader ( #define Ovolumeloader 1039866 is findable on the internet and mentionned in the documentation ).
( that is not really an issue but seems to be a forgotten file)

Second issue : when I save my files with a relative path: the loading of the lit of internal grid seems to be broken.
As an exemple: I read the file with the commandline tool after the export from VUE and after saving it in C4d:

absolute / generated: 
Parsing "Small Cumulonimbus [RefObj]" of type (1039866):

        found Param id (6000)
                type(131), values : "D:\Users\C4d\animmetacloud_Small Cumulonimbus [RefObj]_00.vdb"
        found Param id (6001)
                type(15), values : 1
        found Param id (6003)
                type(15), values : 0
        found Param id (6004)
                type(15), values : 56
        found Param id (6008)
                type(1018397), values : listview with 2 items and selected : -1
                        item 0 with id 0 and name density
                                type(15), values : 1
                        item 1 with id 1 and name color
                                type(15), values : 1
								
absolute / saved: 						
Parsing "Small Cumulonimbus [RefObj]" of type (1039866):

        found Param id (6000)
                type(131), values : "D:\Users\C4d\animmetacloud_Small Cumulonimbus [RefObj]_00.vdb"
        found Param id (6001)
                type(15), values : 1
        found Param id (6002)
                type(15), values : 0
        found Param id (6003)
                type(15), values : 0
        found Param id (6004)
                type(15), values : 64
        found Param id (6005)
                type(15), values : 0
        found Param id (6006)
                type(19), values : 1.000000
        found Param id (6007)
                type(15), values : 0
        found Param id (6008)
                type(1018397), values : listview with 2 items and selected : -1
                        item 0 with id 0 and name color
                                type(15), values : 1
                        item 1 with id 1 and name density
                                type(15), values : 1
        found Param id (6010)
                type(200000275), values : Unitscale: 1.000000 / 3
        found Param id (6011)
                type(130), values : "Voxel Amount: 1.182.298   Size: ~3 mb "
        found Param id (6012)
                type(26), values : -1

relative / generated: 		
Parsing "Small Cumulonimbus [RefObj]" of type (1039866):

        found Param id (6000)
                type(131), values : "animmetacloud_Small Cumulonimbus [RefObj]_00.vdb"
        found Param id (6001)
                type(15), values : 1
        found Param id (6003)
                type(15), values : 0
        found Param id (6004)
                type(15), values : 56
        found Param id (6008)
                type(1018397), values : listview with 2 items and selected : -1
                        item 0 with id 0 and name density
                                type(15), values : 1
                        item 1 with id 1 and name color
                                type(15), values : 1
								
								
relative / saved: 							
Parsing "Small Cumulonimbus [RefObj]" of type (1039866):

        found Param id (6000)
                type(131), values : "animmetacloud_Small Cumulonimbus [RefObj]_00.vdb"
        found Param id (6001)
                type(15), values : 1
        found Param id (6002)
                type(15), values : 0
        found Param id (6003)
                type(15), values : 0
        found Param id (6004)
                type(15), values : 56
        found Param id (6005)
                type(15), values : 0
        found Param id (6006)
                type(19), values : 1.000000
        found Param id (6007)
                type(15), values : 0
        found Param id (6008)
                type(1018397), values : listview with 1 items and selected : -1
                        item 0 with id 0 and name Small Cumulonimbus [RefObj]
                                type(15), values : 1
        found Param id (6010)
                type(200000275), values : Unitscale: 1.000000 / 3
        found Param id (6011)
                type(130), values : "Voxel Amount: 591.149   Size: ~2 mb "
        found Param id (6012)
                type(26), values : -1					

As we can see, the param 6008 ( the listview) is modified at the load of the relative path file.

here find attached screenshots of what happens when I load the files in C4d and the save file ( with the _00.vdb file ( assume that the _XX.vdb are identical from _00.vdb file )[0_1631807093381_animmetacloud_Small Cumulonimbus [RefObj]_00.vdb](Uploading 100%)

animmetacloud - absolute.c4d animmetacloud - Relative.c4d

right but when I load my document inside C4d ( R20 or R22), the clipping preset is medium and the clipping near and far are wrong ( back to medium)

hello, I am using the melange sdk to export to c4d files.
it looks like DOCUMENT_CLIPPING_PRESET parameter could not be set :

test:

	c4dDoc = cineware::BaseDocument::Alloc();
	{
		cineware::GeData udata;
		cineware::Bool ret = c4dDoc->SetParameter(cineware::DOCUMENT_CLIPPING_PRESET, cineware::DOCUMENT_CLIPPING_PRESET_HUGE);
		ret = c4dDoc->GetParameter(cineware::DescLevel(cineware::DOCUMENT_CLIPPING_PRESET), udata);
	}

udata correspond to a value of 1 ( MEDIUM, the default value)
I tried with other preset, same issue.

thanks in advance