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ARCamera relation to imagetarget

October 22, 2015 - 6:24am #1

I am going through the sample project (using Google Cardboard) and have it all working fine and am trying to decipher the scene with regard to the relationship of all the GameObjects.

I'm a bit confused with the relationship of the ARCamera to the ImageTarget in that in the scene editor the ARCamera is not focused the ImageTarget in the normal way as I am used to in other AR developments using Vuforia.

I can see in the scene that the ARCamera is looking at the Reticle and the ImageTarget and attached model are tiny and appear way above and to the left of the ARCamera

Is there a reason for this?  

I presumed under normal development (as I have always done) the ARCamara is setup so the ImageTarget and attached children are in its FOV

ARCamera relation to imagetarget

October 27, 2015 - 12:25am #5

great explanations, thanks for the clarification...I obvioulsy miss the plot on that one lol....but have it all working regardless!

 

But at least now I understand it better :-)

ARCamera relation to imagetarget

October 25, 2015 - 7:18am #4

does this mean that where I have always ensured in the Unity editor that the ARCamera preview had the imagetarget in sight this is in fact....not necessary

Correct. If you think of it, the relative position of your actual target with respect to the ARCamera will entirely depend on how and where you actually place / move the physical (e.g. printed on paper) target with respect the the device camera of your phone/tablet/webcam... and in the real world, this won't have much relation with the artifically 'frozen' relative positions that you have set in the Scene in the Unity Editor.

 

However, keep also in mind that there are situations where the position of a Target and/or the position of the ARCamera in the scene may matter, e.g.:

- if you are using "World Center Mode" = CAMERA,  the ARCamera position in 3D space will not be updated by Vuforia, while the Trackables positions will be updated so to match their relative position w.r.t. the Camera;  in such a case, you may want to set the ARCamera position at a location that makes sense for your App; for example, in a mixed reality App like the AR-VR sample, in which you start in AR and then move to VR, the position of the ARCamera is basically matching the position of the User Head in the VR virtual world, so you'll want to set it at a position that allows the user to be correctly placed in the VR world when in VR mode

 

- if you are using "World Center Mode" = FIRST_TARGET or SPECIFIC_TARGET, the position of one or more of your Trackables in the Scene may be important, for example you may want to set them to a location that makes sense with respect to other 3D assets present in your scene

 

Hope this helps.

 

 

ARCamera relation to imagetarget

October 24, 2015 - 11:38am #3

Ah, I see.  I am away from my computer presently so cant check this, but does this mean that where I have always ensured in the Unity editor that the ARCamera preview had the imagetarget in sight this is in fact....not necessary and the link for the camera seeing it is the attached dataset that reference the imagetarget?

 

Thanks

ARCamera relation to imagetarget

October 23, 2015 - 7:20am #2

The relative position of the Image Target and the ARCamera in the Scene does not matter, cause Vuforia will automatically adjust the position of the detected Target w.r.t the ARCamera reference frame at runtime, as soon as the target is actually detected and tracked.

 

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