Subject:
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algebra help (was "Re: Darth Maul...")
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Newsgroups:
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lugnet.cad.dat.parts
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Date:
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Wed, 27 Dec 2000 15:48:57 GMT
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Viewed:
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932 times
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> I can't remember how to calculate the Z co-ord for a point
> given that it lies in a known plane (I need this maths
> so I can place the triangles and quads making up the parts
> of the pattern on the upper and lower curved surfaces
> of the face in the right Z position).
I don't know if this will help you,
but this is how I calculate the formula for the X-vs-Z
co-ordinates of the top and bottom edges of the quad
in question (for ex., the quad bordered by the co-ords
(0,4,-13), (0,1.172,-11.536), (4.415,1.172,-10.658),
and (4.975,4,-12.010) has a bottom edge defined by
the line whose endpoints are (0,4,-13) and (4.975,4,-12.010),
and a top edge whose endpoints are (0,1.172,-11.536)
and (4.415,1.172,-10.658)). Since both of these lines
are _horizontal_, they each have no variation in their
respective Y-value, so they are each a simple line
to calculate (Z=MX+B). Then, for any specific X-value,
I find the corresponding Z-values for the top and bottom
edges, and then calculate the line segment connecting
these two new points, and *then* I use this new forula
to calculate the correct Z-value for the corresponding Y-value.
In summation:
For a given (x,y) point;
Find the appropriate Quad;
Determine the Endpoints of the Quad;
Calculate the X-Z Formulae for the Top Edge
and the Bottom Edge;
Find the specific Z-values (for the specific X-value)
for the Top Edge and the Bottom Edge;
Using these two points, caluclate the formula
for the line segment connecting them;
Use this new formula to calculate the Z-value
for the (x,y) point.
I hope this helps.
Franklin
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Message has 1 Reply:
 | | Re: algebra help (was "Re: Darth Maul...")
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| (...) Hi Guys, I have a spreadsheet that might be of some use. It was created to help find a point on a 3 point plane. After a few trial runs with it, you will find yourself using it a lot. Here is a link to my web page that has a bit of info on it. (...) (24 years ago, 28-Dec-00, to lugnet.cad.dat.parts)
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Message is in Reply To:
| | Re: Darth Maul minifig head - hints and tips?
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| "Franklin W. Cain" <fwcain@yahoo.com> wrote in message news:G5znGB.Ewn@lugnet.com... (...) It's getting there. I've got the main parts of the pattern done, I'm currently adding the outer edge around the face. The biggest problem I've got at the (...) (24 years ago, 27-Dec-00, to lugnet.cad.dat.parts)
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