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I'm using c++ and have some problems with the QuadTree design.

I have some components which are not related to the QuadTree directly. These components are eg. RenderableMesh, PointLight, etc. Some of them should be handled by a QuadTree and some of them should not.

I have a "reflection" system, so I can determine the type of a given component, that's not a problem.

A simple restriction is if I want to use a component in a QuadTree, it has to be inherited from the IBoundComponent which can be used to get the bounding box of the object (using a pure virtual function which is implemented in the exact Component)

This seems okay for me but for fast remove/insert operations of "changed components" (eg. the point light's radius is changed) I should store the current node/cell of the QuadTree. And here comes the real problem. Or actually problems.

1)

Because the IBoundComponent does not know about the QuadTree directly, it has to have a public function pair which can be used to set/get the current node. I could use "friend class QuadTree" but that would restrict the spatial implementation to the QuadTree class.

2)

The Node class of the QuadTree is hidden (private). Of course I could store a void* in the IBoundComponent and cast it. Or a base class (eg. ITreeNode) could be used and the QuadTree's Node should inherit from it.

Maybe a cleaner design would be the following:

Don't store anything in the IBoundComponent (expect the bounds...). When a component is changed, I could store the pre-update bounds as well as the post-update bounds. This way I can find which node contains the component and which will contain it. However this is an extra search. So it's a performance loss for cleaner design.

Do you have any good idea? I've searched here but cannot find a good answer for this situation.

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My approach is that there is a IQuadTreeItem class that has a member QuadTreeNode to the parent node and a virtual method ToBounding() that returns the correct bounding container. I think the member variable is very clean and it provides nice and fast access for relocating and removing among other operations.

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  • \$\begingroup\$ I ended up with using friend class, because I have to store and read the QuadTreeNode through the QuadTree only. I don't want to have a public member pointer because everyone could read and/or write it. Is this an acceptable design? \$\endgroup\$ Commented May 22, 2016 at 22:41
  • \$\begingroup\$ Friend sounds always sketcy to me. \$\endgroup\$ Commented May 23, 2016 at 4:05
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    \$\begingroup\$ Better using a public function/member and let everyone modify it? This can be acceptable as well since everyone who has access to the source code can make it crash or malfunctioning. \$\endgroup\$ Commented May 23, 2016 at 7:22
  • \$\begingroup\$ Probably, but it's mostly just all opinnions at this point. \$\endgroup\$ Commented May 23, 2016 at 8:10
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    \$\begingroup\$ I guess the best would be using a dll and simply don't export it. I will follow this way so I accept your answer. Thanks! :) \$\endgroup\$ Commented May 23, 2016 at 8:43

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