[Nfb-science] Hello
aerospace1028 at hotmail.com
aerospace1028 at hotmail.com
Tue Jul 13 13:38:38 UTC 2010
>Message: 10
>Date: Mon, 12 Jul 2010 10:51:10 -0500
>From: "qubit" <lauraeaves at yahoo.com>
>To: "NFB Science and Engineering Division List"
><nfb-science at nfbnet.org>
>Subject: Re: [Nfb-science] Hello
>Message-ID: <DA8454D1F6264DE1AC7135F8D9375D24 at bassclef>
>Content-Type: text/plain; charset="iso-8859-1"
>
>no, it is easy to create a 3d tactile picture by simply raising the line
>that is in front and deleting part of the image underneath.
>In fact, it is an optical illusion when it is done in ink, but with a
>tactile picture, you are working in 3 dimensions, so you have a truer
>picture.
>--le
I would like to disagree,
Take, for example, a wire-drawing of a cube in partial profile: the front face would be visible on the page as asquare, and the top and left side faces would be vissible in fore-shorten fassion. I agree that playing around with the thicknesses of the lines would make it vissually more 3-d. However if you close your eyes and use your hands, you don't get the sensation of a cube.
If I were to encounter this tactile diagram, I would find the following.
Starting at the right-hand edge, there is a virticle line: call it line A. At the bottom of line A is a horizontal line attatched to Line A at a ninety-degree angle: call it Line B. Running left along Line B, I would encounter an intersetction of three lines. Line C, intercects Libe B at some angle and slants up and to the left. Line D, conects t Lines B and C at the same juncture and namakes a ninety-degree angle to Line B. At the End fLine C, another line angles the rest of the way to verticle and runs paralel to Line D: call this Line E. Line E sticks up higher than Line D, And at its end isanother 3-way interection. One line--call it Line F-- runs horizontally to the right, while the other line--call it Line G-- slants down to connect to Line D. Another line--Line H--also runns horizontally to the right out of the intersection between Lines D and G. Line H runs over an connects back to line A. A final line--Line I--finishes off the figure running at a slant up and to the left from the top of Line A to the end of Line F.
This figure results in three enclosed spaces. The space bounded by sides A, B, D, and H forms a square. However, the spaces bounded by Lines C, D E and g and by F, G H and I both produce a more trapizoodal shape.
The slanted lines to show perspective (Lines C, G an I) produce the opticle illusion of depth. In an actual cube, all lines would have the same length, all angles between planes will be normal (ninety-degrees). However, this is *NOT* what is conveyed tactically. While i t appears vissually that Lines C, G, and I run into and out of the page, when you put your hand on them, they look like slanted lines. The same sensation of depth is not present.
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