Hello!

I worked on a subject posted earlier in the 'new users' thread. I put the
result here because I think the topic does not address ont only new users.
I'll post in p.b.s_f a sample scene with macros that make an elliptical
torus:

   -) sw_elliptical_torus(_major, _minor, _radius, _tolerance)
      for the sphere_sweep version (also providing a macro to generate the
spline),
   -) elliptical_torus(_major, _minor, _radius)
      for the blob version, which is much faster. The blob is made of
spheres with constant linear density to ensure the radius is constant all
along the perimeter.

As the image shows, the scene superimposes the two versions in order to
visualize that they overlap correctly, and proving thay are closely
equivalent. Just comment out one or the other and compare the render speed.

    Bruno

NB: I also use blobs in a rope macro I posted recently here (improving it at
the time).

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Hi!

I was proud of my blob-macro for elliptical torus in response to a recent
thread in p.b.newusers. It works fine for solid torii and renders fast, but
I noticed artifacts when I fill with glass or media. See the eye on the
right and the sparkles on the nose. Where could it come from?

   Thanks

       Bruno

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Bruno Cabasson wrote:
> Hello!

Here's an image of the slow isosurface version
I posted in your thread in p.newuser.

Regards,
Sebastian

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Bruno Cabasson wrote:
> I was proud of my blob-macro for elliptical torus in response to a recent
> thread in p.b.newusers. It works fine for solid torii and renders fast, but
> I noticed artifacts when I fill with glass or media. See the eye on the
> right and the sparkles on the nose. Where could it come from?
> 

could it be that you there are to much overlapping blob components at the
start/end section ?

to put it other words: for a closed path you have n components and n section 
(between the components) while for an open path you just have n-1 sections.
So try to remove the last blob component  or adjust the step-width and see if 
there is still this artifact.

... dave

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David El Tom <dav### [at] t-onlinede> wrote:
> Bruno Cabasson wrote:
> > I was proud of my blob-macro for elliptical torus in response to a recent
> > thread in p.b.newusers. It works fine for solid torii and renders fast, but
> > I noticed artifacts when I fill with glass or media. See the eye on the
> > right and the sparkles on the nose. Where could it come from?
> >
>
> could it be that you there are to much overlapping blob components at the
> start/end section ?
>
> to put it other words: for a closed path you have n components and n section
> (between the components) while for an open path you just have n-1 sections.
> So try to remove the last blob component  or adjust the step-width and see if
> there is still this artifact.
>
> ... dave

Thanks for the comment!

The linear density of the blob (expressed in number of spheres per torus
radius) is auto adjusted by the macro by over-sampling and intergrating the
distance travelled so far and droping a blob component at constant distance.
But, as you said, I also noticed the problem comes from the junction of the
two ends of the blob. I played with the loop control and only one more/less
sphere is sufficient to produce the artifact. I could not see whether I made
a mistake in my loop within the macro, and I could not find any satisfactory
workaround. But the artifact is very sensitive, so my conclusion is that my
macro is OK for solid objects with not too much reflection (the artifact is
not visible, and fast render). If needed, I use the sphere_sweep version
with appropriate bounding box.

     Bruno

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