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I want to 'plot' a curve (for which I know the parametric expression,
i.e. the three coordinates as a function of a single parameter) and
give it some thickness (like a thick rope). So I'm looking for
something like sphere_sweep, but with the curved described by my
parametric expression, not by a spline.
What is the best/most efficient way to do this?
Kasper
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My first thoughts would be to make lots of spheres, like a "fake" sphere
sweep. And then, my next feeling is that making lots of little cylinders from
point to point would also be worth looking at. It will depend on the interval
you choose for your resolution.
A hybrid of the two might also work- little cylinders from point to point
with a sphere at each point.
Cheers!
Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
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Sir Charles W. Shults III wrote:
> A hybrid of the two might also work- little cylinders from point
> to point with a sphere at each point.
Yes, this works relatively well, and is very easy to implement.
What works better though is a smooth mesh object, generated on the fly,
but this is slightly more difficult to implement. (Not very hard
though.)
I've tried both, and the mesh renders way faster while being more smooth
at the same time (because you can afford many more segments).
Rune
--
3D images and anims, include files, tutorials and more:
rune|vision: http://runevision.com (updated Oct 19)
POV-Ray Ring: http://webring.povray.co.uk
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Kasper Peeters wrote:
> I want to 'plot' a curve (for which I know the parametric expression,
> i.e. the three coordinates as a function of a single parameter) and
> give it some thickness (like a thick rope). So I'm looking for
> something like sphere_sweep, but with the curved described by my
> parametric expression, not by a spline.
>
Why don't you evaluate your function at regular points (regarding to the
single parameter) and feed that to the sphere_sweep?
--
POV-Ray Objects Collection: http://objects.povworld.org
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Great idea- thanks, Rune. I will have to try that sometimes soon.
Cheers!
Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
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Kasper Peeters wrote:
> I want to 'plot' a curve (for which I know the parametric expression,
> i.e. the three coordinates as a function of a single parameter) and
> give it some thickness (like a thick rope). So I'm looking for
> something like sphere_sweep, but with the curved described by my
> parametric expression, not by a spline.
>
> What is the best/most efficient way to do this?
>
> Kasper
I think you can apply the method used to plot knots. Starting from the
curve you construct a surface in the following way. In each point of
the curve you calculate the normal to the curve. In the plane through
the point that is perpendicular to the normal you consider the circle
with a (small) constant radius and with the given point on the curve as
center. As you have parametric equations of the curve you can derive
the parametric equations of the surface and plot the surface.
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Kasper Peeters wrote:
>
> I want to 'plot' a curve (for which I know the parametric expression,
> i.e. the three coordinates as a function of a single parameter) and
> give it some thickness (like a thick rope). So I'm looking for
> something like sphere_sweep, but with the curved described by my
> parametric expression, not by a spline.
>
> What is the best/most efficient way to do this?
>
> Kasper
You can draw the graph and use that as a heightmap ;)
I've done something similar to what you need with lots of spheres at a
regular distance. I believe I made a blob out of it in the end to get a
smoother effect, but I'm not sure anymore... 8)
Remco
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On 17 May 2003 19:16:44 +0200, Kasper Peeters <kas### [at] aei mpgde> wrote:
> I want to 'plot' a curve (for which I know the parametric expression,
> i.e. the three coordinates as a function of a single parameter) and
> give it some thickness (like a thick rope). So I'm looking for
> something like sphere_sweep, but with the curved described by my
> parametric expression, not by a spline.
>
> What is the best/most efficient way to do this?
If the parametric equation gives you only a location than you can use this
location to make other objects like blob, sphere_sweep, union of other objects.
If the parametric equation gives you also direction vector without much
calculations and then it can give you set of circles along path then you could
consider making parametric surface as parametric{} object or as mesh{} from
'Meshmerizing Mesh Maker Macros' http://members.home.nl/seedseven/#MMMM
ABX
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