OBJECT_INPUT Child Updating



  • Hello,

    I am working on a plugin that will take a child object in with a dynamics tag.

    My problem is that the effects of the dynamic tag are not being applied to the object while it's a child.

    Below I have the code stripped down to its base form.

    class TestClass : public ObjectData
    {
    	INSTANCEOF(TestClass, ObjectData)
    public:
    	virtual SplineObject* GetContour(BaseObject* op, BaseDocument* doc, Float lod, BaseThread* bt);
    	static NodeData* Alloc() { return NewObjClear(TestClass); }
    	
    };
    
    SplineObject* TestClass::GetContour(BaseObject* op, BaseDocument* doc, Float lod, BaseThread* bt)
    {
    	SplineObject *spline = SplineObject::Alloc(2, SPLINETYPE::BEZIER);
    	return spline;
    }
    
    Bool RegisterSimulationReader()
    {
    	return RegisterObjectPlugin(ID_TESTCLASS, "Test"_s, OBJECT_GENERATOR | OBJECT_ISSPLINE | OBJECT_INPUT, TestClass::Alloc, "TestClass"_s, AutoBitmap("circle.tif"_s), 0);
    }
    
    

    The code above prevents the dynamics tag from updating properly. If I remove OBJECT_INPUT from the register the dynamics tag updates properly when it is a child of my plugin

    Given the type of plugin I'm making it seems like I should have OBJECT_INPUT included but if I do it prevents it from updating.

    I'm not sure what I should do to work around this. Any suggestions would be appreciated.

    John Thomas



  • Hi @JohnThomas, thanks for reaching out to us.

    With regard to your support request there are a few points I need to be clarified to proper support:

    • by "dynamic tag" you refer to Rigid/Soft Body Dynamic or Spline Dynamic tag?
    • Is the child to be pinned to your generator a polygonal generator or a spline generator?
    • your code doesn't show how children are handled by your plugin (in the case above an empty spline is returned): can you please elaborate more?
    • by using OBJECT_INPUT as registration flag, you should implement a ObjectData::GetVirtualObjects() method which is responsible for handling you children object: note, however, that this approach to children in Spline-based generators is not officially supported and could lead to unexpected corner cases.

    Looking forward to hear frmo you more, give best.



  • Thanks for the response.

    The dynamics tag I'm referring to are the Rigid/Soft Body Dynamic tag.

    I'm a little confused by what you mean by pinned, I have a object as a child to my plugin from which I am retrieving the points. Removing GetContour and replacing OBJECT_ISSPLINE with OBJECT_POLYGONOBJECT still has the same result of the dynamics tag not updating.

    I stripped my code down to its barest form so that none of my code would be a factor in why the dynamics tag is not updating. With other code I have I can get the points from the child object using GetCache(), my issue is coming in that when I run the code I have above there is no change in the child object as I have the timeline playing. If I don't have OBJECT_INPUT as a flag in my registration the dynamics tag is updating properly.

    Forum.png

    With your last point, in my full code I use GetVirtualObjects() and I still have the same issue and I was able to track it down to having OBJECT_INPUT included. If this method is not officially supported does that mean that Spline-based generators taking in Polygon based objects are not supported?

    John Thomas



  • Hi @JohnThomas, thanks for the clarifications.

    looking at your first post (and code), it was unclear to me if you sticked already to the information we discussed, time ago, about spline generation and child objects (GetVirtualObjects or GetContour) but looks like that your full code was already capable to return the desired output.

    Searching more in depth in Cinema 4D code, I've stumbled across a piece of code about the dynamic tags, mostly related to performances reasons, that ignore tags on virtual objects unless they have been created by cloner/fracture/particle emitter/array. This explains the reason of your plugin failing to retrieve the proper geometrical data due to the dynamic tag being ignored .

    However, as you've experienced already, removing the OBJECT_INPUT flag makes Cinema 4D thinking of your plugin not using virtual objects from children and, consequently, having the dynamics tag ignored no more but still letting you use that data from objects being nested under your plugin.

    Below a simple example obtained by implementing BaseObject::GetContour, BaseObject::GetVirtualObjects() and registering the plugin as OBJECT_GENERATOR | OBJECT_ISSPLINE. This represent a workaround to the actual system limitation so corner cases which might be hard to fix might appear on more complex setups.

    Oct-05-2020 16-04-31.gif



  • Thanks for the reply.

    Other than the corner cases you mentioned would not including OBJECT_INPUT, in a plugin that is using it sub-objects as inputs, result in issues with Cinema outside the scope of my plugin?

    John Thomas



  • Registering a plugin without the OBJECT_INPUT should work with regard to retrieving data from children but it will require you to manually create and touch the dependency list in order to clean children caches and hide them from the scene.

    Best, R



  • Thanks for the response

    I know how to create and touch the dependency list but if I put my object, without the OBJECT_INPUT flag, as the child of something like a Cloner will Cinema be able to properly interact with it or could that lead to problems?

    John Thomas



  • Hi @JohnThomas, looks like it does.

    Oct-07-2020 12-24-49.gif

    Cheers, R



  • Thanks for the response.

    After removing OBJECT_INPUT as a flag the children of my plugin are no longer removed if my object is made editable. Is there a workaround to this without losing the benefits of removing OBJECT_INPUT? I have already implemented the dependence list for the child objects.

    John Thomas



  • I've spent more time working on it and have still not found a solution. Any help would be greatly appreciated.

    John Thomas



  • Hi @JohnThomas, I apologise for late answer but it slipped through.

    As workaround for the specific case mentioned above, you can implement an NodeData::Message() and intercepting the MSG_EDITABLE_END message (please note that it's private and its usage is not recommended) you can delete your children after the "make editable" process has completed.

    Best, R



  • Thanks for the response.

    I tried using the code below to get the children and it does not properly return that there are child objects.

    case MSG_EDITABLE_END:
    {
    	BaseObject*     op = (BaseObject*)node;
    	if (op != nullptr)
    	{
    		if (op->GetDown() != nullptr)
    		{
    			ApplicationOutput("Down");
    			BaseObject *down = op->GetDown();
    		}
    	}
    
            break;
    }
    

    Is there a different way that you are meant to use to get the child objects to do the method you suggested?

    John Thomas



  • Hi @JohnThomas , the data passed in the method is actually carrying the destination object.

    The code should look like

    ...
    	if (type == MSG_EDITABLE_END)
    	{
    		BaseObject* dstObject = static_cast<BaseObject*>(data);
    		if (!dstObject)
    			return false;
    		BaseObject* child = dstObject->GetDown();
    		if (child)
    		{
    			child->Remove();
    			BaseObject::Free(child);
    		}
    	}
    ...
    

    Cheers, R


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