[maybe BUG] in IMeshSceneNode->getMesh()->getBoundingBox()

[gerdb]

Hi,

i created a MeshSceneNode from another, to verify working, i just tried to render the boundingBox

in ctr i have

Code: Select all

BBox = other->getMesh()->getBoundingBox();

which does not work gives me a default constructed Box, then i tried

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for (u32 i=0; i<other->getMesh()->getMeshBufferCount(); i++)
{
if (i==0)
       BBox.reset( other->getMesh()->getMeshBuffer(i)->getBoundingBox());
else
       BBox.addInternalBox( other->getMesh()->getMeshBuffer(i)->getBoundingBox());
}
 

and got the right BBox in size.

so my guess is, that giving a Mesh to IMeshSceneNode does not calculate the Mesh's BBox from its MeshBuffer children.

Question: is this a bug or wished behaviour?

thx for answering

[CuteAlien]

Hm, I'm confused right now. I thought IMesh would have a recalculateBoundingBox function, but it seems only SMesh and the Meshbuffers have that.

So the idea is - if you changed a meshbuffer then call recalculateBoundingBox afterward. And if the MeshBuffer is in a SMesh then also call recalculateBoundingBox for the SMesh (additionally). Maybe that helps you already in your case.

I'm just puzzled right now what to do if you have a meshbuffer and only a an IMesh* ...

[gerdb]

hi, the problem is adding the meshbuffer to mesh, which does not call addInternalBox()

file://include/SMesh.h

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                //! adds a MeshBuffer
                void addMeshBuffer(IMeshBuffer* buf)
                {
                        if (buf)
                        {
                                buf->grab();
                                MeshBuffers.push_back(buf);
                        }
                }

change to

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                //! adds a MeshBuffer
                void addMeshBuffer(IMeshBuffer* buf)
                {
                        if (buf)
                        {
                                buf->grab();
                                MeshBuffers.push_back(buf);
                                //! fix
                                BoundingBox.addInternalBox ( buf->getBoundingBox());
                        }
                }

cya

[REDDemon]

yes I think that should be the right behaviour this way. The problem is to check all other places in wich Irrlicht is using "addMeshBuffer" on SMesh and see if this will change something. For example in geomtry creator

I see few things that after that change should be done and some redundant code that can be removed. The most hard thing will be to update that for all the mesh loaders O_O.


would be nice to add few comments to specify the usage of IMesh class. For now can be safer specify in "addMeshBuffer" that the BB is not updated than apply that little change (wich can messup lot of things).

[hybrid]

Yeah, this is a problem with the long standing heritage of Irrlicht. Most interfaces were not properly documented in these regards, and additions developed in one or the other way. I assume that this update was left out for performance reasons. Also, when adding an empty buffer, the new box could be wrong. So I'd also prefer to first add a hint in the API docs and later on think about a better way to ease the use of meshbuffers.