Comments on: Simple Scene Graph in C++

By: Hariprasad

Hariprasad — Sat, 30 Jul 2011 18:06:55 +0000

Very nice article. Simple and easy to understand. Thanks Eddy.

By: G P

G P — Tue, 04 May 2010 16:57:48 +0000

Well, that’s the thing, I wasn’t really talking about the actual math. I was talking about how the math would be applied within this structure. I would suggest that people look to create a system that is bi-directional and consists of area/space aware classes for culling and collisions, a node wrapper and a geometry class. Rendering is called from a node which extends the area aware class (this contains your transform class which consists of translation, rotation and scale data). Once these transforms are recursivly applied to all children of that node, the bounding box data is traversed back up the tree so that collisions and culling can be perfomed on the geometry leaves. GP

By: Eddy Luten

Eddy Luten — Mon, 03 May 2010 13:38:22 +0000

GP you're right, the code provided is only an abstract skeleton created to make it easier to visualize a scene graph's data structure. Maybe in the future we could go into the matrix and vector math, but for now I don't see how that has to do anything with scene graphs. Until I get a little bit of time to throw together new posts, and if you really wish to learn the mathematics required to rotate an object (and more), the only thing I can recommend to you is: Mathematics for 3D Game Programming and Computer Graphics by Eric Lengyel.

By: G P

G P — Mon, 03 May 2010 02:17:50 +0000

Hi, thanks for the overview code, but you don’t show alot here other than a abstract skeleton of an expanded composite, that you then say not to use. I think I might speak for a few when I say that I would like to know how this relates to an actual scenegraph. For example, what sort of classes extend this to become the actual implementation of a scene graph. Do we override the update functionality? If so, with what kind of logic? ‘How do I rotate my object in my world?’ Please please please could you expand or I think maybe this could end up being another one of those articles that will gather dust bunnies

By: Stephen

Stephen — Mon, 20 Jul 2009 18:45:43 +0000

The getChildNodeByName function doesn’t work.

I create a small tree of nodes in a Constructor for my Scene Graph. This scene graph ‘sg’ is a member of my main.cpp file

Now, the code that doesn’t work is:

Node *test = sg.getNodeByName("five");
// already created this Node with this name in sg's constructor

if(test!=NULL)
    std::cout << "Found Node: " 
The If statement always returns false.  The function in my SceneGraph class is:
SceneGraph::getNodeByName(const char* nName)
{
     return root->getChildNodeByName(nName);
}
I’m not experienced with C++.  Did a second year Uni Course, so did have proper instruction however.
Could you help?  Can you see what I’m doing wrong, or does it really not return the pointer properly?

By: Eddy Luten

Eddy Luten — Tue, 14 Jul 2009 20:08:36 +0000

The post is only meant to give you a foot in the door in creating your own scene graph, I never meant it to be a complete implementation. If you want a fully working production-ready scene graph, there are plenty of Open Source libraries out there.

By: Joshua

Joshua — Fri, 10 Jul 2009 01:54:56 +0000

This is extremely promising, but there is no actual code in Node::Update() for performing the transformations

This is good code for creating a tree structure, but unfortunately it’s really not useful as a scene graph.

-j

By: c++ Lover

c++ Lover — Wed, 08 Apr 2009 14:45:15 +0000

Great! It is so amazingly simple and useful !