# blob body type explanations

Post on 20-Feb-2017

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• BLOB BODY TYPE

• BASIC IDEA

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

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

BASIC IDEA

• During interpolation length of radius vectors to unknown points are calculated according to selected interpolation algorithm.

BASIC IDEA

• Inverse Distance Weighting

IDW ALGORITHM

• IDW ALGORITHM

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

• 'Average' and 'minimize' algorithms

ITERATIVE ALGORITHMS

• 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

• 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

• 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

• TREND AND PREDICT

Mapped surface

• Adaptation of thesealgorithms for spherical coordinate system is a bit more tricky. Extension maps given points to Cartesian coordinate system at first...

TREND AND PREDICT

• TREND AND PREDICT

...then processes mapped set as usual.

• IDW VS PREDICT

Radius vectorto each givennodal point is normal to a surface tangent plane at this point, when algorithm is set to IDW. So known points are local extrema.

IDW

• IDW VS PREDICT

The idea of'predict'algorithm is to estimate surface tangent planes at given nodal points.

'Predict'