summing bounding boxes

[terrorchrist]

Hi!
I thing almost everyone here already knows that I want to load an md3 model into my game ^^
Now I encountered the following problem:
an md3 model consists of three md3 files.
now I want to calculate a boundingbox over ALL THREE MESHES!
so I want to sum all the three boundingboxes to a single new one!

I already tried to use the method aabbox3d<T>::addInternalBox() but that function does not take into account that these meshes are not at the same point! so it makes just a bounding box for all three meshes as if they were all at point (0,0,0)

can anyone tell me how to achieve my task?

[vitek]

I'm assuming that you're loading each md3 model into a seperate ISceneNode derived class... the scene node stores a bounding box that is in local coordinates. If you want the bounding box in world coordinates, then you have to specifically ask for that.

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   box.addInternalBox(node->getTransformedBoundingBox());

Also, don't forget that the box is initialized so that the world origin [coordinate 0, 0, 0] is already in the box. If you want a box that just includes your nodes, you must initialize the box properly.

Travis

[terrorchrist]

hmmm
I already tried to do it like this:

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aabbox3d<f32> meshBox1 = md31->getBoundingBox();
		aabbox3d<f32> meshBox2 = node2->getTransformedBoundingBox();
		aabbox3d<f32> meshBox3 = node3->getTransformedBoundingBox();

		meshBox1.addInternalBox(meshBox2);
		meshBox1.addInternalBox(meshBox3);

		vector3df size = meshBox1.getExtent();

and like this

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aabbox3d<f32> meshBox1 = node1->getTransformedBoundingBox();
		aabbox3d<f32> meshBox2 = node2->getTransformedBoundingBox();
		aabbox3d<f32> meshBox3 = node3->getTransformedBoundingBox();

		meshBox1.addInternalBox(meshBox2);
		meshBox1.addInternalBox(meshBox3);

		vector3df size = meshBox1.getExtent();

[terrorchrist]

aas

[vitek]

Works just fine for me...

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   // add a few dwarfs at random positions
   core::array<scene::ISceneNode*> dwarfs;

   u32 d;
   for (d = 0; d < 4; ++d)
      {
      const core::vector3df origin(rand() % 60, rand() % 60, rand() % 60);
		const f32 radius   = (30.f * rand() / RAND_MAX);
		const f32 velocity = (.01f * rand() / RAND_MAX);

      scene::ISceneNode* dwarf = smgr->addAnimatedMeshSceneNode(smgr->getMesh("../../media/dwarf.x"));
      dwarf->setMaterialFlag(video::EMF_LIGHTING, false);

      // move this dwarf in a unique circle
      scene::ISceneNodeAnimator* anim = smgr->createFlyCircleAnimator(origin, radius, velocity);
         dwarf->addAnimator(anim);
      anim->drop();

      // show the bounding box of the dwarf
      dwarf->setDebugDataVisible(true);

      dwarfs.push_back(dwarf);
      }

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   if (dwarfs.size())
      {
      core::aabbox3df bbox = dwarfs[0]->getTransformedBoundingBox();

      u32 d;
      for (d = 1; d < dwarfs.size(); ++d)
         bbox.addInternalBox(dwarfs[d]->getTransformedBoundingBox());

      core::matrix4 identity;
      video::SMaterial material;
      material.Lighting = false;

      driver->setTransform(video::ETS_WORLD, identity);
      driver->setMaterial(material);

      driver->draw3DBox(bbox);
      }

[terrorchrist]

hmmm
looks interresting
maby my error is someone else ^^

[terrorchrist]

ok
now i found out that summing the boxes was not the problem:

the problem is, that I need to get a bounding box that covers all three meshes of my model
and then transfer it back to the "root point" (vector3df(0,0,0))
afterwards I need to get the size of the box as a vector
and THEN I can use it properly to make a NewtonCollision geometry....

but I just have no idea how I can translate the calculated bountingbox back to the origin (0,0,0)

any ideas?

[terrorchrist]

ok!
now I found out that it was not the bounding boxes!
the problem was, that I added the torso and the head mesh to the legs, so the middle of the "motherscenenode" was not the middle of all three meshes, but the middle of the legs mesh of course.
so I had to make a new empty scene node and make this the parent for all three other ones. then I had to move all the three meshes so that the middle of the total model was in the origin...
and now it works...

it is just a pity that if you use the method node->getTransferredBoundingBox(), you always get the boudning box for the mesh at it*s actual animation state.
I would appreciate if threr was a node->getTransferredBoundingBox(node->getMesh()->getMesh(0));, so you can chose which animation frame of the mesh is chosen for calculating the transferred bounding box....

[vitek]

Just keep a pointer to the IAnimatedMesh, or add an accessor for the IAnimatedMesh held by the CAnimatedMeshSceneNode. Then you'd be able to do something like this...

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  core::aabbox3df mbox = node->getAnimatedMesh()->getMesh(0)->getBoundingBox();
  node->getAbsoluteTransformation().transformBox(mbox);

  box.addInternalBox( mbox );

[terrorchrist]

ooooh! nice!!
thank you very much vitek!