"jr" <cre### [at] gmailcom> wrote:

> are the solid
> bits (isosurface fragments?) solid as in can do meaningful 'inside()' tests?  I
> ask because I'm thinking (convert to) DF3.

So, the way I think it works is that my isosurfaces are open

but if you want to do CSG, you need to just do

isosurface {
.....

all_intersections

inverse // for some functions, I don't think all
// or maybe alternatively use the polarity keyword (vide infra)
}

http://wiki.povray.org/content/Reference:Isosurface

When the isosurface is not fully contained within the contained_by object, there
will be a cross section. When this happens, you will see the surface of the
container. Using the open keyword, these cross section surfaces are removed, and
the inside of the isosurface becomes visible.

Note: Using open slows down the render speed, and it is not recommended for use
with CSG operations.

Isosurfaces can be used in CSG shapes since they are solid finite objects - if
not finite by themselves, they are through the cross section with the container.
By default POV-Ray searches only for the first surface which the ray intersects.
However, when using an isosurface in CSG operations, the other surfaces must
also be found. Consequently, the keyword max_trace followed by an integer value,
must be added to the isosurface statement. To check for all surfaces, use the
keyword all_intersections instead. With max_trace it only checks until that
number is reached.

Note: The current implementation has a limit of 10 intersections in all cases.

By default, the inside of an isosurface is defined as the set of all points
inside the contained_by shape where the function values are below the threshold.
New in version 3.8 this can be changed via the polarity keyword. Specifying a
positive setting or on will instead cause function values above the threshold to
be considered inside. Specifying a negative setting or off will give the default
behavior.

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