Range constraints

[anssiko]

Creating a standalone issue for this discussion started in #100:

@jan-ivar:
I naively imagine I'd probably want a different setting for pointing my kinect out my window vs. pointing it at my couch?

@martinthomson:
@jan-ivar, that would be a separate constraint, probably two. minimumRange: 1, maximumRange: 100. If that's a real concern, then a separate issue. For this one, I think that @anssiko has the right approach: find out how do the devices actually measure and work from there.

@huningxin:
@jan-ivar, Kinect SDK allows to configure depth camera range (Default or Near) [1]. libealsense [2] allows to configure several ranges to RealSense front facing depth camera as well (Common, ShortRange, LongRange etc.,). I am not aware Tango SDK allows to configure working range of its depth camera.

[martinthomson]

As long as these different configuration options leave the browser able to determine the resulting range, then I think that's fine. I think that having constraints on near and far would be good. ConstrainDouble seems right. I can imagine that users will probably only set a maximum near and minimum far, though I imagine cases where a shorter or longer overall range might be good.

[anssiko]

(Copying feedback from #100 that is relevant to this issue here:)

@martinthomson said:

1. use metres
2. the form is { depthNear: { min: 0, max: 2 }, depthFar: { ideal: 5 } }
3. we should be able to use the constraints in two ways:
   • to pick the camera mode that best fits, and
   • to adjust the range over which the value is converted to the 8-bit value

@alvestrand said:

Adjusting near and far as constraints seems good to me.
The main purpose of near and far is driving the conversion algorithm.

The camera driver would then use the settings on the particular device that make the most sense with those constraints - ie it would set "shortRange" on the RealSense if a "far" of less than (say) 1m was acceptable to the user.

In a later version, I would think that adding a way to get something deeper than an 8-bit map makes sense - since most video codecs are growing 10, 12 and even 14 bit modes these days, there will be other people clamoring for such an option too. But that's a different topic.