Log in or register to post comments

[Unity] What is the unit of the object length value? And how does it scale?

May 19, 2017 - 6:06am #1


I am the latest Vuforia Unity SDK together with the latest Unity Editor on HoloLens. Since I am targeting a rather large object I've printed the object scanning target in DIN A0 size, which is 841mm x 1189mm. Now the default value in the object target prefab in the "Target length" field is 142.5. I assume these are also mm units. On a DIN A0 scale the value I enter here should be 570 I guess (see picture).

But entering 570 there, makes the object scale up to (570, 570, 570), which in default Unity units is huge. Like 570m x 570m x 570m.

The object is then tracked by obsviously since Unity (or Vuforia?) thinks its 570m large, it gets positioned totally wrong. E.g. I stand exactly in front of the object but my augmentations get positioned really far away.

Well, I hope you get the idea of what confuses me. 

Put simple:

How to use the object length field to specify the object size?




Image icon targets.jpg512.13 KB

[Unity] What is the unit of the object length value? And how does it scale?

May 24, 2017 - 12:55am #3


thank you. You actually did help me understand the target scanner a bit more.

[Unity] What is the unit of the object length value? And how does it scale?

May 19, 2017 - 8:33am #2


The units referenced on the object scanner target (mm) are merely for reference. They are not guaranteed to be accurate as that depends upon how it was printed. Thus, if you require accurate values (which is recommended for see-through eyewear - see below), I would suggest that you use a tool to get measurements of your 3D target.

On the topic of units, keep in mind that Vuforia uses 3D scene units, which are arbitrary units of measurements that can be mm, cm, meters, inches, etc. Normally, devs will use a standard measure (like mm), but intrinsic units (like pixels) or arbitrary values can be used. My recommended best practice is to use a standard unit in the same application. Vuforia samples use meters as the default scene units, so if you're basing your experiments upon them you will need to adjust the 3D target's measurements to meet that convention.

Lastly, with see-through eyewear (such as HoloLens), for proper augmentation registration during tracking it is critical that the 3D target's W:L:H measurements of the object (think of a bounding box) match exactly what is entered into the Object Target prefab.

Hope all this helps.



Log in or register to post comments