# blob body type explanations

Post on 20-Feb-2017

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BLOB BODY TYPE

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BASIC IDEA

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

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

BASIC IDEA

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

BASIC IDEA

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Inverse Distance Weighting

IDW ALGORITHM

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IDW ALGORITHM

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

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'Average' and 'minimize' algorithms

ITERATIVE ALGORITHMS

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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

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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

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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

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TREND AND PREDICT

Mapped surface

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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

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TREND AND PREDICT

...then processes mapped set as usual.

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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

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IDW VS PREDICT

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

'Predict'

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IDW VS PREDICT

Knownpoints arenot necessarilylocal extrema in case when 'predict' algorithm is chosen so result of interpolation can be more convincing.

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