Mesh from an ISceneNode

[Kapitan]

Hi all!!!

I've created my scene on IrrEdit and
loaded with loadscene(), but now i have
to take the mesh of an ISceneNode
(grabbed with getSceneNodeFromId).

Is that possible?

Here:
http://www.irrlicht3d.org/wiki/index.ph ... gCollision

He serialize the node and then
take the name of the mesh.

Is the only way?

Thanks and sorry but i really an
Irrlicht newbie.

[Acki]

if you have the node, can't you get the mesh with node->getMesh() ?!?!?
(maybe a type cast to IMeshSceneNode needed)

Code: Select all

IMesh* m = ((IMeshSceneNode*)node)->getMesh();

[lovloss]

if you have the node, can't you get the mesh with node->getMesh() ?!?!?
(maybe a type cast to IMeshSceneNode needed)

Code: Select all

IMesh* m = ((IMeshSceneNode*)node)->getMesh();

Sometimes Sometimes you go node->getMesh()->getMesh(0)... i think?

[Halifax]

if you have the node, can't you get the mesh with node->getMesh() ?!?!?
(maybe a type cast to IMeshSceneNode needed)

Code: Select all

IMesh* m = ((IMeshSceneNode*)node)->getMesh();

Sometimes Sometimes you go node->getMesh()->getMesh(0)... i think?

I think you are thinking of an animated scene node:

Code: Select all

IMesh* m = ((IAnimatedMeshSceneNode*)node)->getMesh(0);

[rogerborg]

First, call ISceneNode::getType(), then cast to the appropriate type based on the result.

[Kapitan]

I've tried both (Mesh and AnimatedMesh cast),
but the result is a null pointer...maybe a bug
or my fault....

I'll try again and i'll post some code.

[kornwaretm]

read rogerborg's post above
something like :

Code: Select all

IMesh* mesh = 0;
switch(node->getType()){
case(ESNT_ANIMATED_MESH):{
     mesh = ((IAnimatedMeshSceneNode*)node)->getMesh();
}
case(ESNT_MESH):{
     mesh = ((IMeshSceneNode*)node)->getMesh();
}
//etc.............................. other cast
}

if mesh still 0. check console messages. any model missing?

[Kapitan]

Yes it works, i was using the dynamic_cast
keyword and it told me that there were not
the RTTI.

I've switched using the static_cast keyword
and it works.

Now is:

IMeshNode *msn = static_cast<IMeshNode*>(var)
and perfectly found my mesh.

[wuallen]

Yes it works, i was using the dynamic_cast
keyword and it told me that there were not
the RTTI.

I've switched using the static_cast keyword
and it works.

I encounted the same problem. I don't know why there is no RTTI.

I use VC2009, is it due to the config of VC2009 or something?

[hybrid]

Well, you shouldn't simply use a dynamic_cast when all you want to do is going down the inheritance hierarchy. That's what static cast is meant for, in the worst case you'd use a reinterpret_cast. dynamic_cast is for navigating across different inheritance branches. RTTI needs to be activated in the project settings, but remember that there's a major runtime penalty related to dynamic_casts.

[vitek]

Well, you shouldn't simply use a dynamic_cast when all you want to do is going down the inheritance hierarchy.

Not true. The dynamic_cast<> operator is there to ensure that object is a complete object of the requested type. Given an ISceneNode* you don't know if you can safely cast down the inheritance heirarchy to IMeshSceneNode*.

As mentioned above, you can use getType() to find the actual type before doing a static_cast<>. That would be safe. This is essentially the same as a dynamic_cast<> because of the virtual dispatch that happens.

That's what static cast is meant for, in the worst case you'd use a reinterpret_cast.

A reinterpret_cast<> would be dangerous, as it might give wrong results in the face of multiple inheritance.

dynamic_cast is for navigating across different inheritance branches. RTTI needs to be activated in the project settings, but remember that there's a major runtime penalty related to dynamic_casts.

Have you ever profiled the use of RTTI? The runtime cost of RTTI depends on the implementation and the inheritance heirarchy. For a simple heirarchy like that used by ISceneNode*, the runtime cost should be minimal.

Travis

[hybrid]

I simply rely on the number given in the C++ optimization guides from Agner Fog and the C++ performance report. I've never profiled any apps for these comparisons.

[Kapitan]

As mentioned above, you can use getType() to find the actual type before doing a static_cast<>. That would be safe. This is essentially the same as a dynamic_cast<> because of the virtual dispatch that happens.

A reinterpret_cast<> would be dangerous, as it might give wrong results in the face of multiple inheritance.

I quote this because there's a big difference.
The getType() + static_cast is the same theorically
of the dynamic_cast...i don't know the profiling,
i will test it.

[vitek]

Don't bother. I wrote up some code and the results were in-line with what hybrid had posted...

Code: Select all

static_cast<IMeshSceneNode>: 2.37s
static_cast<IAnimatedMeshSceneNode>: 2.29s
dynamic_cast<IMeshSceneNode>: 21.35s
dynamic_cast<IAnimatedMeshSceneNode>: 34.97s

The static_cast<> tests used a call to getType() followed by a static_cast<>, while the dynamic_cast<> tests just did a dynamic_cast<>. Each test was 500,000,000 iterations. I'm open to posting the code if anyone wants to see it.

Travis

[wuallen]

For choosing static_cast, dynamic_cast or reinterpret_cast, I agree with vitek, and for the performance penalty, I agree hybrid. thanks to every one.