[Blindmath] A 3d to 2d description resource?

[Richard Baldwin]

Hi Pranav,

I'm guessing here, but I suspect that what you perceive with the voice is
the result of the viewpoint of the camera in your glasses relative to the
position of the glass.

If your glass is opaque with the same diameter at the top and the bottom
(like a can of beans), and you were to position the camera in your glasses
such that the camera lens is half the height of the can above the table and
pointing directly at the glass, you should see a rectangle or something
very close to a rectangle.

When viewed from any other angle, it probably looks like a rectangle with
half an ellipse at each end. The ellipse results from the projection of the
circular end of the glass on the 2D plane.

If you were to take the viewpoint into account when drawing the glass on
paper, the silhouette of the glass that you draw should look just like the
image that you see with the voice.

When the video camera in your glasses takes a picture of the glass, it
produces a set of colored pixels that represent the projection of the 3D
glass onto a 2D plane inside the camera that contains thousands of tiny
light sensors. That is essentially the same as projecting the glass onto a
2D piece of paper and drawing it.

The projection of the 3D object onto the 2D plane should be the same
regardless of whether it is done with a camera lens or a pencil, provided
that it is done correctly in both cases.

Dick Baldwin

On Wed, Feb 8, 2012 at 11:21 AM, Pranav Lal <pranav.lal at gmail.com> wrote:

> Hi Michael,
> <snip Are you sure you have never encountered a picture of a tree in a 2D
> representation? The VOICE uses a 2D representation from what I know (stereo
> headphones, left and right, vertical position pitch in sound). So you tell
> us what a tree is like in 2D compared to the act of feeling it.
> PL] I was thinking more about this question. Let us consider a glass on a
> table.  When using the vOICe, I can see the full glass. However, when that
> same glass is drawn on paper, I will only see a rectangle. How does this
> happen?
>
> I now understand how that glass becomes a rectangle when drawn on paper but
> I am trying to distinguish between this and what I see with the vOICe.
>
> I hope I am making sense.
> Pranav
>
>
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-- 
Richard G. Baldwin (Dick Baldwin)
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Professor of Computer Information Technology
Austin Community College
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