C# Class Axiom.Components.Terrain.TerrainQuadTreeNode

A node in a quad tree used to store a patch of terrain.

Algorithm overview: Our goal is to perform traditional chunked LOD with geomorphing. But, instead of just dividing the terrain into tiles, we will divide them into a hierarchy of tiles, a quadtree, where any level of the quadtree can be a rendered tile (to the exclusion of its children). The idea is to collect together children into a larger batch with their siblings as LOD decreases, to improve performance. The minBatchSize and maxBatchSize parameters on Terrain a key to defining this behaviour. Both values are expressed in vertices down one axis. maxBatchSize determines the number of tiles on one side of the terrain, which is numTiles = (terrainSize-1) / (maxBatchSize-1). This in turn determines the depth of the quad tree, which is sqrt(numTiles). The minBatchSize determines the 'floor' of how low the number of vertices can go in a tile before it has to be grouped together with its siblings to drop any lower. We also do not group a tile with its siblings unless all of them are at this minimum batch size, rather than trying to group them when they all end up on the same 'middle' LOD; this is for several reasons; firstly, tiles hitting the same 'middle' LOD is less likely and more transient if they have different levels of 'roughness', and secondly since we're sharing a vertex / index pool between all tiles, only grouping at the min level means that the number of combinations of buffer sizes for any one tile is greatly simplified, making it easier to pool data. To be more specific, any tile / quadtree node can only have log2(maxBatchSize-1) - log2(minBatchSize-1) + 1 LOD levels (and if you set them to the same value, LOD can only change by going up/down the quadtree). The numbers of vertices / indices in each of these levels is constant for the same (relative) LOD index no matter where you are in the tree, therefore buffers can potentially be reused more easily.

Inheritance: IDisposable

Show file Open project: WolfgangSt/axiom Class Usage Examples

Public Properties

Property	Type	Description
DELTA_BUFFER	short
POSITION_BUFFER	short

Protected Properties

Property	Type	Description
mAABB	Axiom.Math.AxisAlignedBox
mBaseLod	ushort
mBoundaryX	ushort
mBoundaryY	ushort
mBoundingRadius	float
mChildWithMaxHeightDelta	TerrainQuadTreeNode
mChildren	TerrainQuadTreeNode[]
mCurrentLod	int
mDepth	ushort
mLocalCentre	Vector3
mLodLevels	List
mLodTransition	float
mMaterialLodIndex	ushort
mNodeWithVertexData	TerrainQuadTreeNode
mOffsetX	ushort
mOffsetY	ushort
mParent	TerrainQuadTreeNode
mQuadrant	ushort
mRend	TerrainRendable
mSelfOrChildRendered	bool
mSize	ushort
mTerrain	Terrain
mVertexDataRecord	VertexDataRecord

Public Methods

Method	Description
AssignVertexData ( ushort treeDepthStart, ushort treeDepthEnd, ushort resolution, ushort sz ) : void	Assign vertex data to the tree, from a depth and at a given resolution.
CalculateCurrentLod ( Camera cam, float cFactor ) : bool	Calculate appropriate LOD for this node and children
Dispose ( ) : void
FinaliseDeltaValues ( Rectangle rect ) : void	Promote the delta values calculated to the runtime ones (this must be called in the main thread).
GetChild ( ushort child ) : TerrainQuadTreeNode	Get child node
GetLodLevel ( ushort lod ) : LodLevel	Get the LodLevel information for a given lod.
GetSquaredViewDepth ( Camera cam ) : float
GetWorldTransforms ( Matrix4 xform ) : void
Load ( ) : void	Load node and children (perform GPU tasks, will be render thread)
MergeIntoBounds ( long x, long y, Vector3 pos ) : void	Merge a point (relative to terrain node) into the local bounds, and that of children if applicable.
NotifyDelta ( ushort x, ushort y, ushort lod, float delta ) : void	Notify the node (and children) of a height delta value.
PointIntersectsNode ( long x, long y ) : bool	Returns true if the given point is in the terrain area that this node references.
PostDeltaCalculation ( Rectangle rect ) : void	Notify the node (and children) that deltas are going to be calculated for a given range.
PreDeltaCalculation ( Rectangle rect ) : void	Notify the node (and children) that deltas are going to be calculated for a given range.
Prepare ( ) : void	Prepare node and children (perform CPU tasks, may be background thread)
RectContainsNode ( Rectangle rect ) : bool	Returns true if the given rectangle completely contains the terrain area that this node references.
RectIntersectsNode ( Rectangle rect ) : bool	Returns true if the given rectangle overlaps the terrain area that this node references.
ResetBounds ( Rectangle rect ) : void	Reset the bounds of this node and all its children for the region given.
TerrainQuadTreeNode ( Axiom.Components.Terrain.Terrain terrain, TerrainQuadTreeNode parent, ushort xOff, ushort yOff, ushort size, ushort lod, ushort depth, ushort quadrant ) : System	Default constructor.
Unload ( ) : void	Unload node and children (perform GPU tasks, will be render thread)
Unprepare ( ) : void	Unprepare node and children (perform CPU tasks, may be background thread)
UpdateRenderQueue ( RenderQueue queue ) : void
UpdateVertexData ( bool positions, bool deltas, Rectangle rect, bool cpuData ) : void	Tell the node to update its vertex data for a given region.
UseAncestorVertexData ( TerrainQuadTreeNode owner, int treeDepthEnd, int resolution ) : void	Tell a node that it should use an anscestor's vertex data.
VisitRenderables ( bool debugRenderables ) : void

Protected Methods

Method	Description
CalcSkirtVertexIndex ( ushort mainIndex, bool isCol ) : ushort
CreateCpuIndexData ( ) : void
CreateCpuVertexData ( ) : void
CreateGpuIndexData ( ) : void
CreateGpuVertexData ( ) : void
CreateTriangleStripBuffer ( ushort batchSize, IndexData destData ) : void
DestroyCpuIndexData ( ) : void
DestroyCpuVertexData ( ) : void
DestroyGpuIndexData ( ) : void
DestroyGpuVertexData ( ) : void
UpdateGpuVertexData ( ) : void
UpdateVertexBuffer ( HardwareVertexBuffer posBuff, HardwareVertexBuffer deltaBuf, Rectangle rect ) : void

Private Methods

Method	Description
UpdateVertexBufferr ( HardwareVertexBuffer posbuf, HardwareVertexBuffer deltabuf, Rectangle rect ) : void

Method Details

AssignVertexData() public method

Assign vertex data to the tree, from a depth and at a given resolution.

public AssignVertexData ( ushort treeDepthStart, ushort treeDepthEnd, ushort resolution, ushort sz ) : void
treeDepthStart	ushort
treeDepthEnd	ushort	The end of the depth that should use this data (exclusive)
resolution	ushort	The resolution of the data to use (compared to full terrain)
sz	ushort	The size of the data along one edge
return	void

CalcSkirtVertexIndex() protected method

protected CalcSkirtVertexIndex ( ushort mainIndex, bool isCol ) : ushort
mainIndex	ushort
isCol	bool
return	ushort

CalculateCurrentLod() public method

Calculate appropriate LOD for this node and children

public CalculateCurrentLod ( Camera cam, float cFactor ) : bool
cam	Axiom.Core.Camera	The camera to be used (this should already be the LOD camera)
cFactor	float	The cFactor which incorporates the viewport size, max pixel error and lod bias
return	bool

CreateCpuIndexData() protected method

protected CreateCpuIndexData ( ) : void
return	void

CreateCpuVertexData() protected method

protected CreateCpuVertexData ( ) : void
return	void

CreateGpuIndexData() protected method

protected CreateGpuIndexData ( ) : void
return	void

CreateGpuVertexData() protected method

protected CreateGpuVertexData ( ) : void
return	void

CreateTriangleStripBuffer() protected method

protected CreateTriangleStripBuffer ( ushort batchSize, IndexData destData ) : void
batchSize	ushort
destData	Axiom.Graphics.IndexData
return	void

DestroyCpuIndexData() protected method

protected DestroyCpuIndexData ( ) : void
return	void

DestroyCpuVertexData() protected method

protected DestroyCpuVertexData ( ) : void
return	void

DestroyGpuIndexData() protected method

protected DestroyGpuIndexData ( ) : void
return	void

DestroyGpuVertexData() protected method

protected DestroyGpuVertexData ( ) : void
return	void

Dispose() public method

public Dispose ( ) : void
return	void

FinaliseDeltaValues() public method

Promote the delta values calculated to the runtime ones (this must be called in the main thread).

public FinaliseDeltaValues ( Rectangle rect ) : void
rect	Axiom.Core.Rectangle
return	void

GetChild() public method

Get child node

public GetChild ( ushort child ) : TerrainQuadTreeNode
child	ushort
return	TerrainQuadTreeNode

GetLodLevel() public method

Get the LodLevel information for a given lod.

public GetLodLevel ( ushort lod ) : LodLevel
lod	ushort	/// The lod level index relative to this classes own list; if you /// want to use a global lod level, subtract getBaseLod() first. Higher /// LOD levels are lower detail. ///
return	LodLevel

GetSquaredViewDepth() public method

public GetSquaredViewDepth ( Camera cam ) : float
cam	Axiom.Core.Camera
return	float

GetWorldTransforms() public method

public GetWorldTransforms ( Matrix4 xform ) : void
xform	Axiom.Math.Matrix4
return	void

Load() public method

Load node and children (perform GPU tasks, will be render thread)

public Load ( ) : void
return	void

MergeIntoBounds() public method

Merge a point (relative to terrain node) into the local bounds, and that of children if applicable.

public MergeIntoBounds ( long x, long y, Vector3 pos ) : void
x	long	The point on the terrain to which this position corresponds /// (affects which nodes update their bounds)
y	long	The point on the terrain to which this position corresponds /// (affects which nodes update their bounds)
pos	Vector3	The position relative to the terrain centre
return	void

NotifyDelta() public method

Notify the node (and children) of a height delta value.

public NotifyDelta ( ushort x, ushort y, ushort lod, float delta ) : void
x	ushort
y	ushort
lod	ushort
delta	float
return	void

PointIntersectsNode() public method

Returns true if the given point is in the terrain area that this node references.

public PointIntersectsNode ( long x, long y ) : bool
x	long	The point in top-level terrain coords
y	long	The point in top-level terrain coords
return	bool

PostDeltaCalculation() public method

Notify the node (and children) that deltas are going to be calculated for a given range.

public PostDeltaCalculation ( Rectangle rect ) : void
rect	Axiom.Core.Rectangle
return	void

PreDeltaCalculation() public method

Notify the node (and children) that deltas are going to be calculated for a given range.

public PreDeltaCalculation ( Rectangle rect ) : void
rect	Axiom.Core.Rectangle
return	void

Prepare() public method

Prepare node and children (perform CPU tasks, may be background thread)

public Prepare ( ) : void
return	void

RectContainsNode() public method

Returns true if the given rectangle completely contains the terrain area that this node references.

public RectContainsNode ( Rectangle rect ) : bool
rect	Axiom.Core.Rectangle	The region in top-level terrain coords
return	bool

RectIntersectsNode() public method

Returns true if the given rectangle overlaps the terrain area that this node references.

public RectIntersectsNode ( Rectangle rect ) : bool
rect	Axiom.Core.Rectangle	The region in top-level terrain coords
return	bool

ResetBounds() public method

Reset the bounds of this node and all its children for the region given.

public ResetBounds ( Rectangle rect ) : void
rect	Axiom.Core.Rectangle	The region for which bounds should be reset, in top-level terrain coords
return	void

TerrainQuadTreeNode() public method

Default constructor.

public TerrainQuadTreeNode ( Axiom.Components.Terrain.Terrain terrain, TerrainQuadTreeNode parent, ushort xOff, ushort yOff, ushort size, ushort lod, ushort depth, ushort quadrant ) : System
terrain	Axiom.Components.Terrain.Terrain	The ultimate parent terrain
parent	TerrainQuadTreeNode	ptional parent node (in which case xoff, yoff are 0 and size must be entire terrain)
xOff	ushort	Offsets from the start of the terrain data in 2D
yOff	ushort	Offsets from the start of the terrain data in 2D
size	ushort	The size of the node in vertices at the highest LOD
lod	ushort	The base LOD level
depth	ushort	The depth that this node is at in the tree (or convenience)
quadrant	ushort	The index of the quadrant (0, 1, 2, 3)
return	System

Unload() public method

Unload node and children (perform GPU tasks, will be render thread)

public Unload ( ) : void
return	void

Unprepare() public method

Unprepare node and children (perform CPU tasks, may be background thread)

public Unprepare ( ) : void
return	void

UpdateGpuVertexData() protected method

protected UpdateGpuVertexData ( ) : void
return	void

UpdateRenderQueue() public method

public UpdateRenderQueue ( RenderQueue queue ) : void
queue	Axiom.Graphics.RenderQueue
return	void

UpdateVertexBuffer() protected method

protected UpdateVertexBuffer ( HardwareVertexBuffer posBuff, HardwareVertexBuffer deltaBuf, Rectangle rect ) : void
posBuff	Axiom.Graphics.HardwareVertexBuffer
deltaBuf	Axiom.Graphics.HardwareVertexBuffer
rect	Axiom.Core.Rectangle
return	void

UpdateVertexData() public method

Tell the node to update its vertex data for a given region.

public UpdateVertexData ( bool positions, bool deltas, Rectangle rect, bool cpuData ) : void
positions	bool
deltas	bool
rect	Axiom.Core.Rectangle
cpuData	bool
return	void

UseAncestorVertexData() public method

Tell a node that it should use an anscestor's vertex data.

public UseAncestorVertexData ( TerrainQuadTreeNode owner, int treeDepthEnd, int resolution ) : void
owner	TerrainQuadTreeNode
treeDepthEnd	int	The end of the depth that should use this data (exclusive)
resolution	int	The resolution of the data to use
return	void

VisitRenderables() public method

public VisitRenderables ( bool debugRenderables ) : void
debugRenderables	bool
return	void

Property Details

DELTA_BUFFER public static property

Buffer binding used for holding delta values

public static short DELTA_BUFFER
return	short

POSITION_BUFFER public static property

Buffer binding used for holding positions.

public static short POSITION_BUFFER
return	short

mAABB protected property

relative to mLocalCentre

protected AxisAlignedBox,Axiom.Math mAABB
return	Axiom.Math.AxisAlignedBox

mBaseLod protected property

protected ushort mBaseLod
return	ushort

mBoundaryX protected property

protected ushort mBoundaryX
return	ushort

mBoundaryY protected property

protected ushort mBoundaryY
return	ushort

mBoundingRadius protected property

relative to mLocalCentre

protected float mBoundingRadius
return	float

mChildWithMaxHeightDelta protected property

The child with the largest height delta

protected TerrainQuadTreeNode mChildWithMaxHeightDelta
return	TerrainQuadTreeNode

mChildren protected property

protected TerrainQuadTreeNode[] mChildren
return	TerrainQuadTreeNode[]

mCurrentLod protected property

-1 = none (do not render)

protected int mCurrentLod
return	int

mDepth protected property

protected ushort mDepth
return	ushort

mLocalCentre protected property

relative to terrain centre

protected Vector3 mLocalCentre
return	Vector3

mLodLevels protected property

protected List mLodLevels
return	List

mLodTransition protected property

// 0-1 transition to lower LOD

protected float mLodTransition
return	float

mMaterialLodIndex protected property

protected ushort mMaterialLodIndex
return	ushort

mNodeWithVertexData protected property

protected TerrainQuadTreeNode mNodeWithVertexData
return	TerrainQuadTreeNode

mOffsetX protected property

protected ushort mOffsetX
return	ushort

mOffsetY protected property

protected ushort mOffsetY
return	ushort

mParent protected property

protected TerrainQuadTreeNode mParent
return	TerrainQuadTreeNode

mQuadrant protected property

protected ushort mQuadrant
return	ushort

mRend protected property

protected TerrainRendable mRend
return	TerrainRendable

mSelfOrChildRendered protected property

protected bool mSelfOrChildRendered
return	bool

mSize protected property

protected ushort mSize
return	ushort

mTerrain protected property

protected Terrain mTerrain
return	Terrain

mVertexDataRecord protected property

protected VertexDataRecord mVertexDataRecord
return	VertexDataRecord