POV-Ray : Newsgroups : povray.general : Planar Span-Vector problems... Server Time
4 Aug 2024 14:26:36 EDT (-0400)
  Planar Span-Vector problems... (Message 1 to 3 of 3)  
From: Tim Nikias v2 0
Subject: Planar Span-Vector problems...
Date: 18 Mar 2003 04:53:19
Message: <3e76ec8f@news.povray.org>
So, working on my Water-Script, here's an idea I had:
Give two corner-points for the planar mesh.
Give surface normal for that plane.

The system should then construct a grid and generate
the appropriate vectors in order to calculate differences
in heights (in relation to the normal vector) needed for the
algorithm to work.

Problem is, this method only gets me squared meshes
(no rectangles) and the angles of the original spanvectors
aren't exactly aligned with the axis'.

So, question:
Should I rather have the User define three corners, and any
point "above" the water plane (the above is required to get
the correct direction for the surface normal and thus for the
algorithm to work properly), this would lead to four vectors the
user has to set.

Otherwise, the system would have to be limited to a y-plane.


--
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: Tim### [at] gmxde


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From: The Grand Adept of Evil Sex Magic
Subject: Re: Planar Span-Vector problems...
Date: 18 Mar 2003 13:28:43
Message: <3E77656C.FFCC5C9E@hotmail.com>
Tim Nikias v2.0 wrote:
> 
> So, working on my Water-Script, here's an idea I had:
> Give two corner-points for the planar mesh.
> Give surface normal for that plane.
> 
> The system should then construct a grid and generate
> the appropriate vectors in order to calculate differences
> in heights (in relation to the normal vector) needed for the
> algorithm to work.
> 
> Problem is, this method only gets me squared meshes
> (no rectangles) and the angles of the original spanvectors
> aren't exactly aligned with the axis'.
> 
> So, question:
> Should I rather have the User define three corners, and any
> point "above" the water plane (the above is required to get
> the correct direction for the surface normal and thus for the
> algorithm to work properly), this would lead to four vectors the
> user has to set.
> 
> Otherwise, the system would have to be limited to a y-plane.

Use three points, and make the ordering of the points significant.

Regards,
John


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From: Tim Nikias v2 0
Subject: Re: Planar Span-Vector problems...
Date: 18 Mar 2003 13:34:08
Message: <3e7766a0@news.povray.org>
Thanks for at least one reply! :-)

I already went that way to try the feeling of it, and it seemed
good to me. It's now using three points to span the rectangle,
and a fourth point to mark the outside of the water-plane.
The fourth point need not be aligned with the surface normal
or the axis, it just needs to be above or below the rectangle
for the algorithm to figure out.

It spans one axis from point 1 to 2, and then a second axis
from point 2 to 3. It thus gets its span-vectors, and is also
easy to set up for skewed rectangles, like rombus and such.

--
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: Tim### [at] gmxde

>
> Use three points, and make the ordering of the points significant.
>
> Regards,
> John


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