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27 Dec 2024 06:12:52 EST (-0500)
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From: stm31415
Subject: Two point perspective?
Date: 8 Nov 2004 19:25:00
Message: <web.41900d2ea5c8de82ef4cb4b10@news.povray.org>
I've been fooling around with hand drawn perspective lately, and I learned
how to find the optimum viewing point for a perspective drawing. (Find a
tiled section of the ground, as in an old-style painting there always is
one, and then connect a *diagonal* line running through the corners of the
tiles to the horizon. the distance from the intersection of the line and
the horizon and the vanishing point is the distance away, perpendicularly,
your eye should be form the vanishing point.) So I immediately tried it out
on POV-Ray. And, indeed, at the right distance, all warping goes away, and
the image looks truly 3 dimentional.

So my question is, how can I predict/change this distance?  Say I want an
image to be viewed from three feet away, instead of 5 inches? (It seems to
be proportional to the size of the image) My guess is the angle of the
camera is the key, but I don't know exactly how the angle definition works
(I can *use* it, I just don't know the math. I'm looking into it now.).

Anyhoo, any ideas? Thanks for the help.

-S
5TF!


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From: stm31415
Subject: Re: Two point perspective?
Date: 14 Nov 2004 14:20:01
Message: <web.4197af5e494d4da98369f8b0@news.povray.org>
I figured out how to do this, if anyone is interested. The angle is
indirectly related: the direction vector's *length* is equal to the
distance to the second point, and therefor to the ideal location of the
viewers eye. This makes sense: your eye is placed in the same place as the
camera, in relation to the image plane. I am going to attempt to write a
macro that gives similar ideal viewing location for different size images,
if anyone is interested. The trade-off here is distortion vs. depth. In the
ideal location you wont see any distortion, but the further that location
is from the image plane, the less depth is recorded. Any comments or help
would be great.

-S
5TF!


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From: Rick Measham
Subject: Re: Two point perspective?
Date: 1 Mar 2005 07:50:36
Message: <4224651B.7090704@nomail>
stm31415 wrote:
> I figured out how to do this, if anyone is interested. The angle is
> indirectly related: the direction vector's *length* is equal to the
> distance to the second point, and therefor to the ideal location of the
> viewers eye. This makes sense: your eye is placed in the same place as the
> camera, in relation to the image plane. I am going to attempt to write a
> macro that gives similar ideal viewing location for different size images,
> if anyone is interested. The trade-off here is distortion vs. depth. In the
> ideal location you wont see any distortion, but the further that location
> is from the image plane, the less depth is recorded. Any comments or help
> would be great.

This all sounds fascinating .. hows it going?

Cheers!
Rick


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