There's no obvious way to do that:

- the camera FoV cannot be increased without either reducing the resolution or increasing the processor load.
- any form of non-linear lens etc would cause both problems.

I think the more likely answer is that 4m is needed for "accurate" full-body detection for an adult male, at closer distances Natal can either guess body shape (at a slight processor cost), or just track the upper body.  (I would expect the majority of natal games will only focus on upper body position).

Bit of an odd statement:

"To be precise, you’ll want to clear an area extending at least 4 meters (a little more than 13 feet) away from the television.

That’s the back edge of the space to be taken into account by the Natal sensors."

Sounds like 4 meters is as far back as Natal can accurately detect X, Y, and Z movement.  But, given the dimensions, one could calculate the FOV for Natal and the accuracy in terms of pixels at a given distance.  I will work on this later if no one else does.

Also, the video of the dude breakdancing looks closer than 4 meters to me.  That space looks reasonable.

if it is 4 meters then theres no way i could use it.

recently i bought eyepet, and at start of game the video of proffesor tells you to clear room for eyepet to work, it was a joke i simply didnt have the space. so i just keep cam pointed up so critter runs about in mid air.

with natal i dunno, gesture games like eye pet would be fine i suppose

Just watch this vid where guy is doing a breakedance - full body tracking and less than 2m from TV.

http://www.youtube.com/watch?v=0l62CD8Va2Y

That's all for "at least 4m".

Wasn't that rumor already debunked as bullshit a loooong time ago ?

http://www.eurogamer.net/articles/ms-natal-will-work-with-all-ethnicities

Furthermore there was a video of a black guy playing Burnout Paradise on Natal.

Isn't it possible MS are just saying this for health and safety reasons and so they don't get sued when some idiot gets injured?

It's not the player that has to be at least 4m from the screen. It's the area you have to clear for Natal to work properly (apparently, as the source of this thread says) . In that video you don't see what's behind that guy, but it seems there's plenty of room. Also, the guy is not doing anything complex WITH THE GAME, meaning he's just fooling around without interacting with the software's elements. If you were to be tracked by Natal in a tight room with people moving behind your back, and you needed a desirable level of precision to perform in a game, how would that work?

It's a little early to jump to conclusions, but judging by all the presentations MS has made with Natal, it seems they're not really aiming for precision or hardcore gaming at all. MS may be expecting PURE NOVELTY and the right marketing buzz will carry Natal to success.

Someone correct any mistakes I make or any assumptions that I may have incorrect.  Perhaps this will start some good discussion.

FOV of Natal:

Horizontal FOV = tan(x) = a/b

a = 1/2 of the width.  This is because we are measuring 4 meters from the center point of the lens to the mid point of the slice of space at that distance.  The width of the image at 4 meters distance is 4 meters.  So a = 2 meters.

b = distance from camera to center of image.


tan(x) = 2/4

arctan(0.5) = 26.56 degrees.  We need to double this

Horizontal FOV = 53.12 degrees



Vertical FOV = tan(x) = a/b

a = 1.35 meters.
b = 4 meters

tan(x) = 1.35/4

arctan(0.3375) = 18.649 degrees.  We need to double this:

Vertical FOV = 37.298 degrees

XY Accuracy at 4 meters:

Based on the article, at a distance of 4 meters, the dimensions of the detected image is 4000mm x 2700mm.

Given that the sensor in Natal is 640x480, we can determine the distance that 1 pixel represents. 

On the X axis, 1mm = 0.16 pixel.  So 1 pixel = 6.25mm.

On the Y axis, 1mm = 0.17mm.  So 1 pixel = 5.88mm.

XY Accuracy at 2 meters:

Since the dimensions will be linear, we can just divide everything by two.

Dimensions of image = 2000mm x 1350mm

X axis = 1 pixel = 3.125mm

Y axis = 1 pixel = 2.94mm

I do not know how the Z accuracy can be determined since that is based on light intensity of reflected IR, but the only thing we can go by at this point is some specs from a similar product called PrimeSense, which I have listed below.

http://www.primesense.com/category/reference_design

Several things we can use from the specs to make assumptions about Natal.  The Z accuracy at 2 meters is 1cm, so at 4 meters perhaps we can assume it will be 2 cm.  That is with the assumption that it follows a linear function.  The XY accuracy is similar to my calculations.  A maximum distance of 3.5 meters is similar to the stated 4 meter max from the article.  The only big surprise here is that the Vertical field of view is largely different than what I calculated.  Is there an issue with my methods?  Been a while since I have used any trig stuff.

That demo was a fake

WTF?! it never was. It was just something you and other internet-nonames tried to bring up. I don't get why people are hating on Natal, especially on VGC.

http://www.youtube.com/watch?v=i-443dE5-gk

http://www.youtube.com/watch?v=mGBOv4wsddo (a black person with black clothes)

http://www.youtube.com/watch?v=73OBjO1HYOc

Microsoft responds:

http://www.nextgn.com/2009/06/10/microsoft-responds-to-rumors-natal-will-work-with-all-ethnicities/