getSceneNodeAndCollisionPointFromRay works awfully

[AlexAzazel]

On the trivial side, have you set up triangle selectors for all of your objects? Without them, getSceneNodeAnd... returns NULL.
Some nodes create automatically a selector, some doesn't, so check this out

If you mean

Code: Select all

scene::ITriangleSelector* selector = smgr->createTriangleSelector(node);
node->setTriangleSelector(selector);
selector->drop();

Sure. It wouldn't have worked at all without this. My problem here was that it only sometimes fails to work and I have to click on other parts of the node or change the camera angle and then it works.

[AlexAzazel]

I changed createTriangleSelector() with createTriangleSelectorFromBoundingBox(node); and it works fine now.

[kormoran]

Hmm... mesh triangles too small to be collided? Good to know however

[CuteAlien]

OK, glad it works now. I didn't get to look on it this weekend. Size of triangles shouldn't really be a problem. Basically in this kind of problems to debug it I'd have to start reducing it until I have a test-case with a single-line and triangle which should hit but don't.

[kormoran]

Hmm... if it's not a problem of tiny triangles, why alexazazel had troubles with selection until he changed function?
Doesn't this means there is a bug lurking somewhere in the get... function?

[AlexAzazel]

Hmm... mesh triangles too small to be collided? Good to know however

I doubt that's the case, upper part of the mesh (ceiling of the tank) is really big and flat square and very often I couldn't click on it either even when camera was really close. I assume this might be a bug. At least it looks like one.

[kormoran]

I just modified the example win32window, stopping the cam, adding a triangle selector to the cube and trying to select & rotate the cube itself by clicking on it: nothing. Can't select the cube...

[thanhle]

For windows in panel or surface, you have to recompute the mouse position.
Recommend searching both of the help forums.

I don't get a problem with selection when I work in QT and .Net forms with Irrlicht previously.

Also there is one example related to mouse hitting triangle on a animated mesh. That might be relevant here for high precision selection.

Regards

[lumlum]

I haven't read the full thread but as far as I'm concerned I encountered a similar issue a few weeks ago and it was caused by the fact that the farValue of my camera was too big which caused getRayFromScreenCoordinates() to be imprecise and resulted in a bad node selection. Just saying since it might help someone who comes by that thread with that issue.

[kormoran]

the farValue of my camera was too big

How big was "too big"? How much did you set it? (default = 2000)

[lumlum]

I'm not sure but if I remember correctly there was a significant difference between the drawn ray and my cursor's position at pretty big values like 1000000+, it can easily be tested with the draw3DLine function if you want.
I just wanted to say it because one might think "i'm going to set a big farValue so I won't have to bother about it" then end up with a RayCast issue and can't understand where it comes from until he thinks about what's actually behind the function, which is what happened to me when I was doing some tests

[kormoran]

This is interesting. The camera's FarValue shouldn't matter at all for ray calculations... hmmm... maybe the FOV comes in the way?

[lumlum]

Yes it does use the view frustum to make a 3d ray from your screen coordinates, and thus the FarValue of the camera, here is the function's code :

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core::line3d<f32> CSceneCollisionManager::getRayFromScreenCoordinates(
    const core::position2d<s32> & pos, ICameraSceneNode* camera)
{
    core::line3d<f32> ln(0,0,0,0,0,0);
 
    if (!SceneManager)
        return ln;
 
    if (!camera)
        camera = SceneManager->getActiveCamera();
 
    if (!camera)
        return ln;
 
    const scene::SViewFrustum* f = camera->getViewFrustum();
 
    core::vector3df farLeftUp = f->getFarLeftUp();
    core::vector3df lefttoright = f->getFarRightUp() - farLeftUp;
    core::vector3df uptodown = f->getFarLeftDown() - farLeftUp;
 
    const core::rect<s32>& viewPort = Driver->getViewPort();
    core::dimension2d<u32> screenSize(viewPort.getWidth(), viewPort.getHeight());
 
    f32 dx = pos.X / (f32)screenSize.Width;
    f32 dy = pos.Y / (f32)screenSize.Height;
 
    if (camera->isOrthogonal())
        ln.start = f->cameraPosition + (lefttoright * (dx-0.5f)) + (uptodown * (dy-0.5f));
    else
        ln.start = f->cameraPosition;
 
    ln.end = farLeftUp + (lefttoright * dx) + (uptodown * dy);
 
    return ln;
}
 

[kormoran]

No, it does not. The ray is calculated from mouse position and far frustum corners. The farValue is not taken into account, at least not directly. It's used to calculate the transform matrix...

[hendu]

The frustum length, and thus far corners, is determined by farValue.