How to set up TODEDynamic's mass center in BCB6?

[Chen Jau-Huei]

Dear all,
I use the sample file: BCBDemos\physics\simple
( I want to creat a tube which can be out of shape by foce and momen.)
I build a pipe, which has more than one node. And affected by gravity.

  TGLPipe *pipe;
  TGLODEDynamic *dyn;
  TODEElementCylinder **elem;
  pipe = (TGLPipe *)(ODEObjects->AddNewChild(__classid(TGLPipe)));
  pipe->Radius = 1;
  pipe->Position->SetPoint(Random(),5*Random()+2*pipe->Radius,Random());
  pipe->Radius = 0.25*(Random()+1);
  //Add some node
  pipe->AddNode(0,0,0);
  pipe->AddNode(0,1,1);
  pipe->AddNode(0,1,5);

Set up elem and dyn

  for(int i = 0 ; i< pipe->Nodes->Count-1 ; i++)
  {
    elem[i] = (TODEElementCylinder *) dyn>AddNewElement(__classid(TODEElementCylinder));
    elem[i]->Length = sqrt( (pipe->Nodes->Items[i]->X-pipe->Nodes->Items[i+1]->X)*(pipe->Nodes->Items[i]->X-pipe->Nodes->Items[i+1]->X)+
                            (pipe->Nodes->Items[i]->Y-pipe->Nodes->Items[i+1]->Y)*(pipe->Nodes->Items[i]->Y-pipe->Nodes->Items[i+1]->Y)+
                            (pipe->Nodes->Items[i]->Z-pipe->Nodes->Items[i+1]->Z)*(pipe->Nodes->Items[i]->Z-pipe->Nodes->Items[i+1]->Z));
    elem[i]->Density = 1;
    elem[i]->Radius = pipe->Radius;
    elem[i]->Direction->SetVector(0,1,0);
    elem[i]->Position->SetPoint(
                                    (pipe->Nodes->Items[i]->X+pipe->Nodes->Items[i+1]->X)/2.0,
                                    (pipe->Nodes->Items[i]->Y+pipe->Nodes->Items[i+1]->Y)/2.0,
                                    (pipe->Nodes->Items[i]->Z+pipe->Nodes->Items[i+1]->Z)/2.0
                                    );
    elem[i]->Up->SetVector(
                                    pipe->Nodes->Items[i+1]->X-pipe->Nodes->Items[i]->X,
                                    pipe->Nodes->Items[i+1]->Y-pipe->Nodes->Items[i]->Y,
                                    pipe->Nodes->Items[i+1]->Z-pipe->Nodes->Items[i]->Z
                                    );
  }

But the "dyn->Mess.c" allways {0,0,0,0}
event I use

dyn->Mass.c[0] = 100;

to change the value, it still {0,0,0,0}

How can I do?

Thanks

[Pavel Vassiliev]

Hi Chen,
The BCB6 branch is now not active, so I think that nobady could help you in your deal. Please, migrate to more fresh compiler like C++Builder in RAD Studio XE8 or RAD Studio 10.
PW

[Chen Jau-Huei]

Our company just has BCB6 and BCB XE4,
but I think that they will be same code.
Because they use the same library, GLSCENE.

[Pavel Vassiliev]

Chen,
May be your unit code is the same, but the GLScene libraray is different for BCB6 and RAD Studio, so it's better to use XE4 or later. And add in attachments the whole project files.
PW

[Chen Jau-Huei]

Thanks.
I'd think XE4 is beter tnan BCB6.
But I can't setup GLScene to XE4.

[Chen Jau-Huei]

I find a solution :
First creat a TGLDummyCube object (dummy).
Let

pipe->Parent = dummy;

And then Move dummy to pipe mass center (cx,cy,cz)

dummy->Position->SetPoint(cx,cy,cz);

Setup each elem as

   elem->Position->SetPoint(
    (pipe->Nodes->Items[i]->X+pipe->Nodes->Items[i+1]->X)/2.0-cx,
    (pipe->Nodes->Items[i]->Y+pipe->Nodes->Items[i+1]->Y)/2.0-cy,
    (pipe->Nodes->Items[i]->Z+pipe->Nodes->Items[i+1]->Z)/2.0-cz
   );

Note : It should subtract (cx,cy,xz) for each elem

Move pipe back, because pipe's parent has moved (cx,cy,cz)

pipe->Position->SetPoint(-cx,-cy,-cz);

But I don't think it's good answer.