This is part of a series attempting to remove unhelpful typedefs.

The commit adds a flag to conditionally enable/disable the feature.

This commit fixes the ability to code with neighbourAvailBoundaryLog2=0,
which correctly disabled the contextualisation based on externally
adjacent child neighbours, but failed to disable the atlas update.

This commit fixes an issue with the bytewise occupancy coder caused by
a mismatch (swapping) of the method arguments resulting in a corrupt
bitstream.

Each occupancy bit is contextualised based on the number of occupied
(directly) adjacent child nodes in the (x-1), (y-1), and (z-1)
neighbour nodes used to generate the neighbour pattern.

Three contextualisation states are added:
 - no adjacent neighbours
 - one adjacent neigbour (=adjacencyGt0)
 - two adjacent neighoburs (=adjacencyGt1)

The neighbour pattern for a node indicates occupied neighbouring nodes.

This commit updates the definition of occupancy for the (x-1), (y-1),
and (z-1) neighbours to be occupied if the neighbour's adjoining
children (ie sharing a face with the current node) are occupied.

In the 1-D figure below, at a depth d, the node 'X' has two occupied
neighbours 'R' and 'L'.  When determining the neighbour pattern of X,
the (x-1) state of the neighbour's adjoining child ('r') is used
instead.  For completeness, nodes marked with '?' are not causally
available.

  d+0:   R|X|L
  d+1:  Rr|??|??

This commit provides trisoup_node_size_log2 as a replacement for
the following HLS syntax variables:
 - geom_codec_type (redundant wrt. triangle node size derivation)
 - trisoup_depth (redundant wrt. bounding box)
 - trisoup_triangle_level (semantics simplified)

The following config options have been removed:
 - geometryCodec (redundant wrt. trisoup_node_size_log2)
 - triSoupLevel  (replaced by trisoup_node_size_log2)
 - triSoupDepth  (unnecessary)
 - triSoupIntToOrigScale (redundant wrt. positionQuantizationScale)

A leaf node by definition contains at least one point.  Therefore the
single point flag indicates if there are one or two points in the leaf.
The remainder should be signalled as numpoints - 2 as per the working
draft text.

This commit adds an arithmetic codec interface class that allows a
compile time choice of arithmetic codec implementation.  Context types
are renamed to support compile time selection, and existing support
functions that were added to the third-party arithmetic codec are
moved to the wrapper.

This commit provides a method to predict the child occupancy bits of a
node based on the node's 26 neighbours.  The prediction is used to
contextualise coding of each occupancy bit.

This tool requires the use of the occupancyAtlas for neighbour lookup.
NB: a restriction in the current implementation requires that the
atlas size is at most 8³.

intra_pred_max_node_size_log2: 6

This commit provides the ability to contextualise occupancy bits using
a prediction.  Three context sets cover the not predicted, predicted
unoccupied and predicted occupied cases.

chi wang authored Oct 09, 2018 and David Flynn committed Nov 01, 2018

When restricted neighbour contextualisation is used, this modification
introduces an alternative neighbour reduction table.

NB: the integrated table has been updated to remove the need to add
additional remapping tables.  This is a non-normative change.

Bitwise geometry occupancy coding uses a mapping table to select entropy
contexts.  This commit employs a dynamic mapping which is updated after
each coding operation, replacing the previous static mapping tables.

NB: the proposed version used a context with a halving period
(max_count) of 64 symbols.  However, this conflicts with another
adoption (512 symbols), and a wholesale replacement of the arithmetic
codec and context model.  To resolve the conflict, the existing halving
period (128) is used.

Khaled Mammou authored Sep 19, 2018 and David Flynn committed Nov 01, 2018

This commit allows bytewise encoding of occupancy symbols using the
dual-lut coder.

This commit prepares for the introduction of selectable bitwise
and bytewise occupancy coding methods.

Philip A. Chou authored Jul 19, 2018 and David Flynn committed Nov 01, 2018

This commit integrates a c++ trisoup codec, replacing the previous matlab
implementation.

The provided code has been reworked to avoid duplicating code, dead code,
and operate with the current HLS.

This commit splits the handling of the geometry brick header and octree
geometry coding.  The encoder/decoder classes now take care of coding
the header, while the geometry coder handles the geometry coding itself.

This commit replaces some repetitive code with a loop.

This commit refactors the storage and passing of entropy contexts in the
geometry octree coder.  An encapsulating class with all entropy coding
methods is used to store the context state.

The geometry coder is quite large, especially with trisoup and has no
benefit to being a header only implementation.  This commit moves the
geometry octree coder out of the header files and into
geometry_octree_{en,de}coder.cpp.