ISO/IEC 14496-16:2006/Amd 1:2007

INTERNATIONAL ISO/IEC
STANDARD 14496-16
Second edition
2006-12-15
AMENDMENT 1
2007-10-01

Information technology — Coding of
audio-visual objects —
Part 16:
Animation Framework eXtension (AFX)
AMENDMENT 1: Geometry and shadow
Technologies de l'information — Codage des objets audiovisuels —
Partie 16: Extension du cadre d'animation (AFX)
AMENDEMENT 1: Géométrie et ombre




Reference number
ISO/IEC 14496-16:2006/Amd.1:2007(E)
©
ISO/IEC 2007

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ISO/IEC 14496-16:2006/Amd.1:2007(E)
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ISO/IEC 14496-16:2006/Amd.1:2007(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
Amendment 1 to ISO/IEC 14496-16:2006 was prepared by Joint Technical Committee ISO/IEC JTC 1,
Information technology, Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia
information.

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ISO/IEC 14496-16:2006/Amd.1:2007(E)

Information technology — Coding of audio-visual objects —
Part 16:
Animation Framework eXtension (AFX)
AMENDMENT 1: Geometry and shadow
Add subclause 4.3.6 MultiResolution FootPrint-Based Representation:
4.3.6 MultiResolution FootPrint-Based Representation
4.3.6.1 Introduction
MultiResolution FootPrint-Based representation is a solution to represent any set of objects based on
footprints (a set of IndexedLineSet, or for a near future, buildings, cartoons…). The main interests in this
representation are its progressivity, view dependency, and compression.
4.3.6.2 FootPrintSetNode
4.3.6.2.1 Node Interface
FootPrintSetNode { #NDT=%SFGeometryNode

exposedField MFGeometryNode children []
}

4.3.6.2.2 Functionality and semantics
The children field specifies the list of all footprints rendered according to the current viewpoint. This list
contains currently FootPrintNode representing the set of footprints rendered from the current viewpoint. This
list can be updated at each displacement of the viewpoint in order to adapt the scene complexity to the view.
This representation can be extended to be used with any object based on footprints such as buildings,
cartoons, etc. In this case, the children field can contain BuildingPartNode to represent buildings.
4.3.6.3 FootPrintNode
4.3.6.3.1 Node Interface
FootPrintNode { #NDT=%SFGeometryNode

exposedField SFInteger
index -1
exposedField SFIndexLineSet2D footprint NULL
}

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ISO/IEC 14496-16:2006/Amd.1:2007(E)
4.3.6.3.2 Functionality and semantics
Index: this is the index of the node corresponding to a footprint elevation at a specific level of detail. This
index is essential for streaming, due to the synchronization between the representation on the server and on
the client. This index will be sent to the server as a refinement request.
Footprint: this is an IndexLineSet2D describing the footprint.
4.3.6.4 BuildingPartPrintNode
4.3.6.4.1 Node Interface
BuildingPartNode { #NDT=%SFGeometryNode

exposedField SFInteger index -1
exposedField SFIndexLineSet2D footprint NULL
exposedField SFUnsigned integer buildingIndex  -1
exposedField SFFloat height 0
exposedField SFFloat altitude 0
exposedField MFGeometryNode alternativeGeometry []
exposedField MFRoofNode roofs []
exposedField MFFacadeNode facades []
}

4.3.6.4.2 Functionality and semantics
Index: this is the index of the node corresponding to a footprint elevation at a specific level of detail. This
index is essential for streaming, due to the synchronization between the representation on the server and on
the client (this index will be sent to the server as a refinement request).
Footprint: this is a IndexLineSet2D describing the footprint.
buildingIndex: this is the index of the building to which this part is connected. A building corresponds to a
group of building parts having the same buildingIndex.
Height: this is the height of the building.
Altitude: this is the altitude of the building (corresponding to the floor of the prism).
alternativeGeometry: this is a geometry node corresponding to an optional object used to replace the normal
building. This alternative geometry can be used to swap a building with a more detailed model (used for
example to replace a footprint elevation based model of a monument, by a more detailed model). In this case,
the footprint-based elevation model will not be rendered, since the alternative model will be.
roofs: this is a node array allowing to describe complete roofs that will be reconstructed on top of the footprint
elevation.
facades: this is a node array allowing to describe in detail the modelling of the façades corresponding to this
building part. The size of this array corresponds to the number of facades, equivalent to the number of edges
of the polygon defining the footprint.
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ISO/IEC 14496-16:2006/Amd.1:2007(E)
4.3.6.5 RoofNode
4.3.6.5.1 Node Interface
RoofNode { #NDT=%SFGeometryNode

exposedField SFInteger type 0
exposedField SFFloat height 0.0
exposedField MFFloat slopeAngle [0.0]
exposedField SFFloat eaveProjection 0.0
exposedField SFInt edgeSupportIndex -1
exposedField SFURL roofTextureURL ""
exposedField SFBool isGenericTexture TRUE
exposedField SFFloat textureXScale 1.0
exposedField SFFloat textureYScale 1.0
exposedField SFFloat textureXPosition 0.0
exposedField SFFloat textureYPosition 0.0
exposedField SFFloat textureRotation 0.0
}

4.3.6.5.2 Functionality and semantics
type: this is the type of the roof. 0 – Flat Roof, 1 – Symmetric Hip Roof, 2 – Gable Roof, 3 – Salt
Box roof, 4 – Non Symmetric Hip Roof.
height: this is the height of the roof that allows cropping it. (This is not used for flat roofs).
slopeAngle: this is the angle of the roof slopes in degrees (useless for flat roofs). In the case of a
Symmetric Hip Roof, all slopes have the same angle. In the case of a Non Symmetric Hip Roof,
each slope has a specific angle.
eaveProjection: this is the projection of the eave (useless for flat roofs).
edgeSupportIndex: this is the index of the edge in the footprint that supports the roof (use only for
Salt Box roofs)
roofTextureURL: this is the URL of the texture that is orthogonally mapped onto the roof
isGenericTexture: this specifies whether the texture mapped onto the roof is generic or not. In the
case of a generic texture, the reference system is centred on the top left vertex of the roof pan, and
axed perpendicularly to the gutter. In the case of an aerial photograph, the reference system is
centred on the first vertex of the footprint, and axed on the world coordinate system.
textureXScale: this is the scaling of the roof texture along X-axis
textureYScale: this is the scaling of the roof texture along Y-axis
textureXPosition: this is the displacement of the texture along X-axis
textureYPosition: this is the displacement of the texture along Y-axis
textureRotation: this is an angle in radian specifying the rotation to apply to the texture.
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ISO/IEC 14496-16:2006/Amd.1:2007(E)
4.3.6.6 FacadefNode
4.3.6.6.1 Node Interface
FacadeNode { #NDT=%SFGeometryNode
}
exposedField SFFloat
WidthRatio 1.0
exposedField SFFloat XScale 1.0
exposedField SFFloat
YScale 1.0
exposedField SFFloat XPosition 0.0
exposedField SFFloat YPosition 0.0
exposedField SFFloat XRepeatInterval 0.0
exposedField SFFloat
YRepeatInterval 0.0
exposedField SFBool Repeat FALSE
exposedField SFURL
FacadePrimitive ""
exposedField SFInteger NbStories 0
exposedField MFInteger NbFacadeCellsByStorey 0
exposedField MFFloat StoreyHeight 1.0
exposedField MFFacadeNode
FacadeCellsArray []

4.3.6.6.2 Functionality and semantics
WidthRatio: this corresponds to a ratio between the width of the cell compared to the width of the parent cells.
XScale: this is a parameter allowing scaling in X-coordinate the model corresponding to the URL Façade
Primitive (2D texture or 3D model). For texture, this scale corresponds to the real size in X-coordinate in
meters of the texture. For 3D Model, this size corresponds to the scale to apply on the model in X-coordinate.
NOTE This scale is very important as the model can be used for different buildings, and must be adjusted to the
current one.
YScale is a parameter allowing scaling in Y-coordinate the model (2D texture or 3D model). For texture, this
scale corresponds to the real size in Y-coordinate in meters of the texture. For 3D Model, this size
corresponds to the scale to apply on the model in Y-coordinate.
NOTE This scale is very important as the model can be used for different buildings, and must be adjusted to the
current one.
XPosition: this is a parameter allowing moving in X-coordinate the model in the cell defined by the
FacadePrimitiveArray of the father node. This position can be essential to place a primitive in the centre of the
cell.
YPosition: this is a parameter allowing moving in Y-coordinate the model in the cell defined by the
FacadePrimitiveArray of the father node. This position can be essential to place a primitive in the center of the
cell.
Repeat: this is a Boolean that is TRUE if and only if the model has to be repeated all over the cell defined by
the father node.
NOTE This is essential for texture mapping, or to repeat regularly a model of windows all over a façade.
FacadePrimitive: this is a link to the corresponding primitive (Texture or 3D model) that have to be mapped
onto the cell.
NbStories: this is the number of stories of the façade.
NbFacadeCellsByStorey: this is an array that defines the number of cells by storey. This parameter is
essential to know on which storey corresponds a cell in FaçadeCellsArray.
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ISO/IEC 14496-16:2006/Amd.1:2007(E)
StoriesHeight: this is an array specifying the height of each storey.
FacadeCellsArray: this is an array of FacadeNode that links each cell to a facadeNode (another array of cells,
and/or a façade primitive like a texture or a 3D model). The size of this array is the sum of all
NbFacadeCellsByStorey[i] , for all i from 0 to NbStories.

Add subclause 4.7.3 BBA Animation Algorithm:
4.7.3 BBA Animation algorithm
The initial pose of an articulated model must contain a skeleton that is aligned with the mesh. Thus some
bones have a non-identity initial transformation. During the animation, the bone transforms are updated. Since
the skeleton and the mesh are originally aligned, only the offset between the new bone transforms and the
initial ones has to be applied to the vertices.
Animating the skinned model consists then in the following steps:
a) for all bones compute the initial transformation in the local space as the combination of the elementary
transform: rotation, translation, center, scale and scaleOrientation; all these components are expressed in the
parent's coordinate system.
b) for all the bones, compute the initial transformation in the world space as a product between the initial
transformation of the bone in the local space and the initial transformation of the bone's parent expressed in
the world space
c) compute the inverse of the previous transformation
d) at each animation frame, update the local elementary transforms: rotation, translation, center, scale and
scaleOrientation
e) at each animation frame, repeat step b)
f) at each animation frame, for all the bones multiply the transformation obtained at step e) with the one
computed at step c)
g) at each animation frame, for each pair bone/vertex, multiply the vertex with the transform obtained at the
previous step and with the corresponding weight.

Add Subclause 4.8 Scene tools:
4.8 Scene tools
4.8.1 Shadows
The Shadow node works as a special grouping node for the author defined creation of hard and soft
shadows caused by 3D-surfaces, shadow properties and SpotLight nodes.
4.8.1.1 Syntax
Shadow {
eventIn MFNode addChildren
eventIn MFNode removeChildren
 exposedField MFNode children []
exposedField SFBool enabled TRUE
exposedField MFBool cast TRUE
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ISO/IEC 14496-16:2006/Amd.1:2007(E)
 exposedField MFBool receive TRUE
exposedField SFFloat penumbra 0
}
4.8.1.2 Semantics
addChildren: the addChildren event appends nodes to the grouping node's children field. Any nodes passed
to the addChildren event that are already in the group's children list are ignored.
removeChildren: the removeChildren event removes nodes from the grouping node's children field. Any
nodes in the removeChildren event that are not in the grouping node's children list are ignored.
children: contains a list of children nodes. The children node’s surfaces are generally invisibly rendered.
Only instances of 3D-surfaces are able to work as occluders and receivers for shadow creation in association
only with SpotLight nodes. Each children[m] and its descendants correspond to the combination of
shadow properties cast[m] and receive[m]. If it is intended, that a 3D-surface has to work as occluder or
receiver, it must fulfil several prerequisites. The assigned children has to be a single instance 3D-surface or
an instance 3D-surface that is part of a sub-graph. A SpotLight must be associated to this 3D-surface in
the same way as shown in Figure AMD1-2. The light source has to illuminate the 3D-surface, for casting or
receiving shadows.
enabled: the functionality of the Shadow node is enabled with the value TRUE. The functionality of the
Shadow node is disabled with the value FALSE.
cast: assigns the capability to a 3D-surface to cast shadows onto other 3D-surfaces. With the value TRUE a
single instance or a branch with instances of 3D-surfaces included becomes an occluder. The field works as
MFBool, so every children[m] (single node or branch) is able to have its own value of cast. The shadow
properties of a 3D-surface’s node instance are transmitted according the ID of MediaObject to all of those
instances of 3D-surfaces existing outside of Shadow nodes in that scene with the same ID (see Figure
AMD1-2).
receive: assigns the capability to a 3D-surface to receive shadows from itself or from other surfaces. With
TRUE a single instance or a branch with instances of 3D-surfaces included becomes a receiver. The field
works as MFBool, so every children[m] (single node or branch) is able to have its own value of receive.
The shadow properties of a 3D-surface’s node instance are transmitted according the ID of MediaObject to all
of those instances of 3D-surfaces existing outside of Shadow nodes in that scene with the same ID (see
Figure AMD1-2). The field works as MFBool, so every children[m] node is able to have its own value of
receive. The shadow properties of a 3D-surface’s node instance become transmitted to all of those instances
of 3D-surfaces existing outside of Shadow nodes in that scene (see Figure AMD1-3).
penumbra: describes the geometrical extension of the related SpotLight as a sphere radius.
4.8.1.3 Annex

grouping node
Shadow SpotLight
USE single node USE branch
...

Figure AMD1-1 — Semantical representation
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ISO/IEC 14496-16:2006/Amd.1:2007(E)
If Shadow and SpotLight nodes own the same grouping node as parent, a shadow relationship is created
automatically between them.

Figure AMD1-2 — Transmission of shadow properties to 3D-surfaces and light sources
The combination of multiple Shadow nodes with one or multiple SpotLight nodes possesses several
shadow properties associated with one SpotLight node. This way a SpotLight node gets several
penumbra values (see Figure AMD1-3). Additionally it can create multiple shadow properties with a single
Shape node.

Figure AMD1-3 — Transmission of shadow properties to multiple 3D-surfaces and light sources
The following rules were formulated for those cases. If a unique 3D-surface is related to the same light source
several times, the shadow properties are handled by the Boolean operation OR. All penumbra values add up
and increase the light body extension.
The occurrence of multiple associated SpotLight nodes combined with only one Shadow node simply
results in each SpotLight node creating another independent relation.

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ISO/IEC 14496-16:2006/Amd.1:2007(E)
Add subclause 5.8 MultiResolution FootPrint-Based Representation:
5.8 MultiResolution FootPrint-Based Representation
5.8.1 Downstream syntax
This is the syntax of the downstream MultiResolution FootPrint-based Representation.
5.8.1.1 FootPrintSetDecoderSpecificInfo
5.8.1.1.1 Syntax
class FootPrintsDecoderConfig extends AFXDecoderSpecificInfo {
SDLInt<16> FPObjectType
SDLInt<32> MaxNbFootPrints
SDLInt<6>  FootPrintNbBits
SDLFloat Step
SDLInt<6>  NbBitsMetricError
SDLFloat  MinX
SDLFloat  MaxX
SDLFloat MinY
SDLFloat  MaxY
SDLInt<1> DEFIdUsed
switch (FPObjectType)
{
 case 1 : FPBuildingDecoderConfig FPBuildingDSI
}
}

5.8.1.1.2 Semantics
FPObjectType: This is an integer specifying the type of the multiresolution footprint-based representation (0
for classic footprints, but extended types could be considered.)
MaxNbFootPrints: this is the number of footprints in the footprint-based representation.
FootPrintNbBits: this is the number of bits used to decode the footprint indices. Its value is the lowest integer
superior or equal to to log (MaxNbFootprints).
2
Step: this is the smallest spatial subdivision.
NbBitsMetricError: this is the number of bits on which to encode the metric error (32 or 64 bits)
MinX: this is the minimum X-coordinate of the model
MaxX: this is the maximum X-coordinate of the model
MinY: this is the minimum Y-coordinate of the model
MaxY: this is the maximum Y-coordinate of the model
DEFIDUsed: If DEFIDUsed is TRUE, then the ID used during the Bifs encoding is used as reference.
Otherwise, the string defname is used.
NOTE For future extension, depending of the object type (buildings, cartoons…) other parameters could be added to
this decoder configuration. For current simple footprints, these parameters are enough to configure the decoder.
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5.8.1.2 FPBuildingDecoderSpecificInfo
5.8.1.2.1 Syntax
class FPBuildingDecoderConfig {
SDLFloat MinAltitude;
SDLFloat MaxHeight;
SDLInt<6> NbBitsZBuilding;
SDLInt<6> NbBitsNbStories;
SDLInt<6> NbBitsStoreyHeight;
SDLInt<6> NbBitsFacadeWidth;
SDLInt<6> NbBitsNbFacadeCellsByStorey;
}
5.8.1.2.2 Semantics
MinAltitude: this is the minimum altitude of the set of footprint-based elevations.
MaxHeight: this is the maximum height of the set of footprint-based elevations.
NbBitsZBuilding: this is the number of bits used to encode the altitude and height of buildings.
NbBitsNbStories: this is the number of bits used to specify the number of stories by façade element
NbBitsStoreyHeight: this is the number of bits used to specify the height ratio of each storey.
NbBitsFacadeWidth: this is the number of bits used to specify the width ratio of each façade element.
NbBitsNbFacadeCellsByStorey: this is the number of bits used to specify the number of cells per storey.
5.8.1.3 FootPrintSet Message
The FootPrintSet Message is intended to carry all the set base and refinement information for the design of
footprint sets.
5.8.1.3.1 Syntax
FootPrintSetMessage {
int(32) NbFootPrints
For (int i=0; i  FootPrintMessage  FootPrint;
}
5.8.1.3.2 semantics
NbFootprints: this is an integer giving the number of FootPrintMessage that have to be read in the stream.
5.8.1.4 FootPrint Message
A Footprint message is intended to carry a base or refinement information for the design of footprint sets.
5.8.1.4.1 Syntax
class FootprintMessage {
int(FPNbBits) index
bit(1) type
FPNewVertices FPNV
int(6) IndexNbBits
if (type) {
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int(10) offspring
for (i=0; i int(FPNbBits) localIndex
float(NbBitsMetricError) MetricError
IndexFootprintSet IFPS
switch (FPObjectType)
{
 case 1: FPBuildingParameters FPBP
}
}
}
else
{
float(NbBitsMetricError) MetricError
int(8) NbRings
For (int i=0; i   {
int(IndexNbBits) FirstVertexIndex
switch (FPObjectType)
{
case 1: FPBuildingParameters FPBP
}
  }
}
}

5.8.1.4.2 Semantics
MetricError: this is the geometric error between the original model and the simplified model used by the client
to decide if this node has to be refined.
IndexNbBits: this is the number of bits used to decode the vertices indexes. Its value is the lowest integer
superior or equal to log (FootPrintsDecoderConfig.MaxIndex).
2
Index: this is the index identifying the current footprint.
Type: this is a Boolean with value 0 if the current message describes a primary footprint, and 1 if this is a
refinement.
FPNV: this is a class describing the new vertices used to refine the current footprint.
Offspring: this is the number of children of the current footprint.
localIndex: this is the index identifying the i-th child of the current footprint.
IFPS: this is a class listing the indices of vertices of the footprint.
NbRings: this is the number of rings in the new footprint.
FirstVertexIndex: this is the index in the new vertices array of the first vertex for each ring (there is no index
for the first ring, since it is always equal to 0).
FPBP: this is a class describing the parameters corresponding to the new building based on footprint.
5.8.1.5 FPNewVertices
5.8.1.5.1 Syntax
class FPNewVertices
{
int(6) coordtype
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ISO/IEC 14496-16:2006/Amd.1:2007(E)
int(16) nbNewVertices
for (i=0; i {
if (type == 0 || step == -1.0)
{
float(32) DeltaX
float(32) DeltaY
}
else
{
bool      SignDeltaX
unsigned int(coordtype-1) AbsDeltaX
bool      SignDeltaY
unsigned int(coordtype-1) AbsdeltaY
}
}
}

5.8.1.5.2 Semantics
coordType: this is the number of bits to encode the vertex coordinates.
nbNewVertices: this is the number of vertices described in the rest of the class.
DeltaX, DeltaY: these are the 2D coordinates of the newly added vertex,
SignDeltaX, SignDeltaY: these specifiy whether deltaX and deltaY are positive or not.
AbsdeltaX, AbsdeltaY: these are the 2D absolute value coordinates of the newly added vertex, expressed in
a reference system based on the barycentre of the parent footprint vertices. The actual position of the new
vertex is obtained by multiplying AbsDeltax*SignDeltaX by Step (defined in the DecoderSpecificInfo), and
adding the coordinates of the barycentre of the parent footprint vertices.
The decoding process is exposed in Annex J.

5.8.1.6 IndexFootprintSet
5.8.1.6.1 Syntax
class IndexFootprintSet
{
int(16) nbVertexIndices
for (int i=0; i {
int(IndexNbBits) index
}
}

5.8.1.6.2 Semantics
nbVertexIndices: this is the number of indices in the rest of the class. nbVertexIndices=nbVertices in the
footprint + Nulber of rings-1.
index: this is the index of the i-th vertex. If index=-1, a new ring starts.
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5.8.1.7 FPBuildingParameters
5.8.1.7.1 Syntax
class FPBuildingParameters
{
int(FPNbBits) buildingIndex
if (step!=-1.0)
{
int(NbBitsZBuilding) altitude
int(NbBitsZBuilding) height
}
else
{
float(32) altitude
float(32) height
}
For (int i=0; i {
FPFacade facades
}
int(6) nbRoofs
for (int i=0; i {
FPRoof roof
}

int(8) nbSwapNodes
for (int i=0; i {
if (DEFIDUse)
int(32) nodeId
else
{
int(8) nbChar
for (int j=0; j char defname[j]
}
}
}

5.8.1.7.2 Semantics
buildingIndex: this is the index of the building to which this part is connected.
altitude: if step is different from -1.0, the altitude of the building is encoded using a integer. The actual altitude
is given by
Decoded=altitude*Step.
height: if step is different from -1.0, the height of the building is encoded using a integer. The actual height is
gicven by:
DecodedHeight=height*Step.
textureURL: this is the URL of the texture to be applied on the side of the footprint-based elevation.
nbSwapNodes: this is the number of nodes in the scene graph used to swap the block corresponding to the
footprint-based elevation.

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NodeId: this is the index of a node in the scene graph used to swap the block corresponding to the current
footprint-based elevation for a more defined model.
NOTE This footprint-based model swap for a more detailed model is essential if one needs to add a good detailed
model that can be represent using a footprint-based representation. For example, one might need to replace the footprint-
based model of specific buildings like monuments (used as reference points for the user during the navigation) by a more
detailed model that can be representing by a footprint-based elevation.
nbRoofs: this is the number of roofs that are superimposed on top of the footprint elevation.
roof: this is the description of each roof that are superimposed on top of the footprint elevation.
nbfacades: this is the number of facades of the building, equivalent to the number of edges of the polygon
defining by the footprint, i.e. equal to nbVertexIndices.
facades: this is the description of each facade model that are mapped on each face of the footprint elevation.

5.8.1.8 RoofBitStream
5.8.1.8.1 Syntax
class FPRoof {
int(3) roofType
switch (roofType)
{
 case 0 : //Flat Roof

 case 1 : // Symmetric Hip Roof
  float roofHeight
  float roofSlopeAngle
  float roofEaveProjection
 case 2 : // Gable Roof
  float roofHeight
  float roofSlopeAngle
  float roofEaveProjection
 case 3 : // Salt Box Roof
  float roofHeight
  float roofSlopeAngle
  float roofEaveProjection
  int(indexNbBits) roofEdgeSupportIndex
 case 4 : // Non Symmetric Hip Roof
  float roofHeight
  float roofSlopeA
...