When the mesh body type is set to 'blob', nodal points are treated as a spherical data set with an estimated center point. During interpolation, the length of radius vectors to unknown points are calculated using different algorithms like Inverse Distance Weighting or iterative algorithms. Adaptation of these algorithms to the spherical coordinate system involves first mapping points to Cartesian coordinates before processing them as usual.

1. BLOB BODY TYPE

2. BASIC IDEA
When mesh
body type is set
to 'blob',
extension treats
nodal points as a
spherical data
set.

3. Extension
estimates
position of an
average point
from given nodal
points and
places center of
a spherical data
set at it.
BASIC IDEA

4. During
interpolation
length of radius
vectors to
unknown points
are calculated
according to
selected
interpolation
algorithm.
BASIC IDEA

5. Inverse Distance Weighting
IDW ALGORITHM

6. IDW ALGORITHM
Inverse Angle
Weighting
(IAW) would be
a more accurate
name because
algorithm
actually uses
angle to
measure
'amount of
proximity'

7. 'Average' and 'minimize' algorithms
ITERATIVE ALGORITHMS

8. First stage is a
preliminary
calculation,
which sets the
same length to a
radius vector to
a point being
calculated as a
length of a
vector to a
closest* known
nodal point.
ITERATIVE ALGORITHMS
* - «closest» in terms of spherical coordinate
system here

9. The second
stage is an
iterative
smoothing itself:
points within a
cell size angle
from known
points stay
where they are,
others gradually
move along their
radius vectors.
ITERATIVE ALGORITHMS

10. So the process is
similar to the
one that takes
place during
conventional
'terrain-like'
mesh
processing. It is
just adapted a
bit for spherical
coordinate
system.
ITERATIVE ALGORITHMS

11. TREND AND PREDICT
Mapped surface

12. Adaptation of
these
algorithms for
spherical
coordinate
system is a bit
more tricky.
Extension maps
given points to
Cartesian
coordinate
system at first...
TREND AND PREDICT

13. TREND AND PREDICT
...then processes
mapped set as
usual.

14. IDW VS PREDICT
Radius vector
to each given
nodal point is
normal to a
surface tangent
plane at this
point, when
algorithm is set
to IDW. So
known points
are local
extrema.
IDW

15. IDW VS PREDICT
The idea of
'predict'
algorithm is to
estimate surface
tangent planes
at given nodal
points.
'Predict'

16. IDW VS PREDICT
Known
points are
not necessarily
local extrema in
case when
'predict'
algorithm is
chosen so result
of interpolation
can be more
convincing.