4. Getting a tag from a Link field

Getting a tag from a Link field

  • H

    On 03/06/2014 at 16:01, xxxxxxxx wrote:

    User Information:
    Cinema 4D Version:   14 
    Platform:      Mac OSX  ; 
    Language(s) :     C++  ;

    ---------
    I my shader parameters I have a link field that can be empty or contain a tag (a custom tag that I created).
    How, in C++ can I get the content of the link field?
    I'm using this code:

    BaseContainer * data = sh->GetDataInstance();
    BaseTag * the_tag = (BaseTag* ) data->GetBaseLink(TAG_OBJECT);

    But this seems to crash Cinema4D.
    Damn! So many castings!!! What am I doing wrong?

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  • H

    On 03/06/2014 at 20:16, xxxxxxxx wrote:

    Try it like this.

    //This is an example of getting the tag the user has dropped into the link gizmo with the ID of MYLINK  
//In this case the tag is a custom tag...So we get it by it's plugin ID#  
  
INITRENDERRESULT MyShader::InitRender(BaseShader *sh, const InitRenderStruct &irs)  
{  
  BaseContainer *data = sh->GetDataInstance();  
  
  BaseTag *myTag = (BaseTag* )data->GetLink(MYLINK, GetActiveDocument(), TAG_PLUGIN_ID);   
  if(myTag) GePrint(myTag->GetName());  
  
  return INITRENDERRESULT_OK;  
}

    -ScottA

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  • H

    On 04/06/2014 at 02:41, xxxxxxxx wrote:

    Thank you so much, Scott. Got it working (still lots to do, though).
    Can't help thinking that this is way more complex than:

    def InitRender(self,sh,irs) :
         the_tag=sh[TAG_OBJECT]
         if the_tag is None: return c4d.INITRENDERRESULT_ASSETMISSING
         print the_tag.GetName()

    Also, GePrint requires a string and not all types of objects can be converted to strings. In python, if I print the_tag, I get something like:

    <c4d.BaseTag object called 'myshader/myshader' with ID 1234567 at 0x1128956b0>

    Can't I do the same in C++?

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  • H

    On 04/06/2014 at 02:55, xxxxxxxx wrote:

    BaseContainer * data = sh->GetDataInstance();
    BaseTag * the_tag = (BaseTag* ) data->GetBaseLink(TAG_OBJECT);

    If you would've used a static_cast instead of a C-style cast, you would've seen an error
    at compilation time.

    Also, GePrint requires a string and not all types of objects can be converted to strings. In python, if I print the_tag, I get something like:

    <c4d.BaseTag object called 'myshader/myshader' with ID 1234567 at 0x1128956b0>

    Can't I do the same in C++?

    You can write yourself a little print function. You can use IsInstanceOf() to check if you
    got a tag, object or shader, etc.

    -Niklas

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  • H

    On 04/06/2014 at 07:25, xxxxxxxx wrote:

    You might want to take a quick look at the second part of my C++ video tutorial Rui.
    I explain a few of the fundamentals like the GePrint().
    C++ requires more typing. But it's not necessarily "harder" than Python.
    More typing != harder.

    One of the most common things that is used in the C4D SDK is descriptions.
    Almost every time you see this in Python: obj[FOO] = fooValue
    It requires this in C++: obj->SetParameter(DescID(FOO), GeData(fooValue), DESCFLAGS_SET_0);

    Python wraps things up into tiny little packages that are short to type. But it's not "easier" than C++.
    Once you type this stuff few hundred times. You won't notice it so much.
    Also once you have built up enough C++ notes. You'll cut an paste a lot of code instead of typing it.

    The way I often work is that I play around in Python and try out a few ideas.
    Then once I have the idea formed into a solid idea. I then switch over to C++ and make the actual plugin there.
    If you can seamlessly jump back and forth from Python & C++. You'll have C4D by the nuts. 😉

    -ScottA

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