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Hello, Eitan. Please do not post HTML. Plain text works just fine in
all of these news groups. Please also do not post binary attachments in
p.general, as Christoph kindly mentioned to you on 23-Jan-2001. For your
benefit, please read "Where can I post my binary or text file?", which
is posted in the p.announce.frequently-asked-questions group.
Please immediately cancel your post with the HTML and image attachment
in this group. Post your question again *without* attachments. Post the
image (and not HTML) in the p.binaries.images group with "Geometry
Question" as the Subject line and a line of text in the body stating
that the image is in reference to a question asked in p.general.
Thank you, Eitan, for your cooperation.
--
Alan - ako### [at] povray org - a k o n g <at> p o v r a y <dot> o r g
http://www.povray.org - Home of the Persistence of Vision Ray Tracer
On Wed, 24 Jan 2001 22:26:37 +0200 Eitan Tal wrote:
><!doctype html public "-//w3c//dtd html 4.0 transitional//en">
><html>
><img SRC="cid:par### [at] netvisionnetil" height=126 width=285>
><p>I have these two points. there's also Distance X, and an angle between
>the arch and
><br>the line. if this angle is 45, the radius will become infinite. if
>this angle is 90, the radius
><br>equals one. (shown above)
><p>a = that angle
><p>from here, it is possible that r = tan(1/2a) + sin(a)
><br>is that correct? anyone got the exact eqution? and what's the link
>between x and a?</html>
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Eitan Tal wrote:
> I have these two points. there's also Distance X, and an angle between
> the arch and
> the line. if this angle is 45, the radius will become infinite. if
> this angle is 90, the radius
> equals one. (shown above)
>
> a = that angle
>
> from here, it is possible that r = tan(1/2a) + sin(a)
> is that correct? anyone got the exact eqution? and what's the link
> between x and a?
You have an imaginary icosciles triangle with the
chord/secantintersecting the two points and two radii (everything that
follows is with the assumption you're using a 45-45-90 triangle (not the
imaginary one I just mentioned, the one in your figure) with two sides
of length 1)...
You know the three angles; two are 90-(a-45) == 135-a and the other is
180-2(135-a) == 2a-90. You also know the length of the chord/secant,
which is always sqrt(2). Now take law of sines:
a b c
----- = ----- = -----
sin A sin B sin C
and solve it for the radius:
r = sqrt(2)*sin(135-a)/sin(2a-90)
If you want the conversion x<->a...
Take the part of x that goes beyond the line connecting the two points,
the of that part is x-sqrt(2)/2. Then take the distance from either
point to x, which is always sqrt(2)/2. (Note sqrt(2)/2 is the same as
sqrt(.5).) These make two legs of a right triangle. So now you can use
arctangent on it; atan((x-sqrt(2)/2)/(sqrt(2)/2)) which can be
simplified as atan(x*sqrt(2)-1). This angle is half of the angle between
the circle and the chord/secant at either point. So simply double this
angle and add 45 (angle between chord/secant and the leg of your
45-45-90 triangle) and you have a:
a = 45+2*atan(x*sqrt(2)-1)
<->
x = (tan((a-45)/2)+1)/sqrt(2)
Answer your question?
--
David Fontaine <dav### [at] faricynet> ICQ 55354965
My raytracing gallery: http://davidf.faricy.net/
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Had nothing to do waiting for the last few lines of a render to finish, so I
drew ya a pic. It's in povray.binaries.images.
--
David Fontaine <dav### [at] faricynet> ICQ 55354965
My raytracing gallery: http://davidf.faricy.net/
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I had to post HTML and an image!
someone told me that if its small enough, I can post it..or at least that was what
I understood from him
Alan Kong wrote:
> Hello, Eitan. Please do not post HTML. Plain text works just fine in
> all of these news groups. Please also do not post binary attachments in
> p.general, as Christoph kindly mentioned to you on 23-Jan-2001. For your
> benefit, please read "Where can I post my binary or text file?", which
> is posted in the p.announce.frequently-asked-questions group.
>
> Please immediately cancel your post with the HTML and image attachment
> in this group. Post your question again *without* attachments. Post the
> image (and not HTML) in the p.binaries.images group with "Geometry
> Question" as the Subject line and a line of text in the body stating
> that the image is in reference to a question asked in p.general.
>
> Thank you, Eitan, for your cooperation.
>
> --
> Alan - ako### [at] povrayorg - a k o n g <at> p o v r a y <dot> o r g
> http://www.povray.org - Home of the Persistence of Vision Ray Tracer
>
> On Wed, 24 Jan 2001 22:26:37 +0200 Eitan Tal wrote:
>
> ><!doctype html public "-//w3c//dtd html 4.0 transitional//en">
> ><html>
> ><img SRC="cid:par### [at] netvisionnetil" height=126 width=285>
> ><p>I have these two points. there's also Distance X, and an angle between
> >the arch and
> ><br>the line. if this angle is 45, the radius will become infinite. if
> >this angle is 90, the radius
> ><br>equals one. (shown above)
> ><p>a = that angle
> ><p>from here, it is possible that r = tan(1/2a) + sin(a)
> ><br>is that correct? anyone got the exact eqution? and what's the link
> >between x and a?</html>
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Eitan Tal <eit### [at] netvisionnetil> wrote:
: someone told me that if its small enough, I can post it..or at least that was what
No, binaries nor html are not allowed in non-binaries groups.
Someone also told you that if the question really needs images, better just
post the question in povray.binaries.images.
--
char*i="b[7FK@`3NB6>B:b3O6>:B:b3O6><`3:;8:6f733:>::b?7B>:>^B>C73;S1";
main(_,c,m){for(m=32;c=*i++-49;c&m?puts(""):m)for(_=(
c/4)&7;putchar(m),_--?m:(_=(1<<(c&3))-1,(m^=3)&3););} /*- Warp -*/
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Image illustrating Eitan's question has been posted in p.b.i.
continuing thread begun by David Fontaine in that group.
--
Alan - ako### [at] povrayorg - a k o n g <at> p o v r a y <dot> o r g
http://www.povray.org - Home of the Persistence of Vision Ray Tracer
>From: "Eitan Tal" <eit### [at] netvisionnetil>
>Subject: Geometry Question
>Date: Wednesday, January 24, 2001 12:26 PM
>
>[Image]
>
>I have these two points. there's also Distance X, and an angle between
>the arch and
>the line. if this angle is 45, the radius will become infinite. if this
>angle is 90, the radius
>equals one. (shown above)
>
>a = that angle
>
>from here, it is possible that r = tan(1/2a) + sin(a)
>is that correct? anyone got the exact eqution? and what's the link
>between x and a?
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On Thu, 25 Jan 2001 15:18:04 +0200 Eitan Tal wrote:
>I had to post HTML and an image!
Hi, Eitan. You certainly may post an image in the *proper* group. HTML
is unnecessary. Plain text is preferred. This can be set in Netscape's
Options or Preferences.
Once again, please read "Where can I post my binary or text file" in
the p.announce.frequently-asked-questions group. You might want to read
all of the other articles in that group while you're there.
For an example of one acceptable way to post your image and your
question, see the example I posted in the p.BINARIES.images group. It
can be found as a reply in the thread, "Pic for Eitan Tal's geometry
question", and I posted it on 25-Jan-2001 07:52am -08:00 UTC.
Familiarizing yourself with posting guidelines will make your visit to
this news server more productive and more fun <s>.
--
Alan - ako### [at] povrayorg - a k o n g <at> p o v r a y <dot> o r g
http://www.povray.org - Home of the Persistence of Vision Ray Tracer
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Alan Kong wrote:
> Once again, please read "Where can I post my binary or text file" in
> the p.announce.frequently-asked-questions group. You might want to read
> all of the other articles in that group while you're there.
Let's make it easy for him. Below is the exact text from our binaries
guideline -
Put simply, a binary is any file that is not a plain text file. For our
newsgroup purposes, the following are examples of binary files:
- JPEGs, or other graphic file formats,
- HTML-encoded text (many people who follow our newsgroups use
newsreaders that cannot automatically read HTML posts without
launching an external Web browser. Please post plain text messages or,
at least a combination of plain text and HTML),
- any executable file,
- any other file that is sent as an attachment to a posted message, even
if it is readable text. This includes POV-Ray scene (.pov) files
sent as message attachments.
For the sake of newsgroup organization we ask that you post binary
attachments to the appropriate groups, such as:
- images to "povray.binaries.images",
- animations to "povray.binaries.animations",
- program utilities to "povray.binaries.utilities", and
- any attached scene files, whether text or binaries, to
"povray.binaries.scene.files".
Simple POV-Ray (.pov) scene files, text include files, and text macros
may be 'cut and pasted' into the body of your message and posted in the
group "povray.text.scene.files". Please be reasonable and don't paste a
10mb mesh include file into the body of a message :) If your scene
source needs to be this large then you might consider providing a .url
so that people may download it from a remote location.
If you post an image to a binary group and then decide to provide the
scene source (due to overwhelming demand), post the source in the
appropriate binary (for attachments) or text (when your source is typed
or pasted into the body of your message) group and make a reference to
your posted image in the subject line.
Please consider converting 24-bit bitmap images, such as targas and
Windows .bmp, to JPEG (.jpg) file format which uses a compression
algorithm to reduce the file size considerably. This conserves space on
the news.povray.org server for everyone.
Animations can be of various popular file formats such as Windows .avi,
.fli, MPEG, or Apple QuickTime, but one should consider that some
animation formats may not be viewable on all platforms and therefore may
not reach as wide of an audience. Again, using an available compression
scheme with your animation program will benefit all who use this server
by conserving disk space.
Thank you all for your consideration and happy raytracing!
--
Alan
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