vtkHAVSVolumeMapper Class Reference

#include <vtkHAVSVolumeMapper.h>

Inheritance diagram for vtkHAVSVolumeMapper:

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Collaboration diagram for vtkHAVSVolumeMapper:

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List of all members.


Detailed Description

Hardware-Assisted Visibility Sorting unstructured grid mapper.

vtkHAVSVolumeMapper is a class that renders polygonal data (represented as an unstructured grid) using the Hardware-Assisted Visibility Sorting (HAVS) algorithm. First the unique triangles are sorted in object space, then they are sorted in image space using a fixed size A-buffer implemented on the GPU called the k-buffer. The HAVS algorithm excels at rendering large datasets quickly. The trade-off is that the algorithm may produce some rendering artifacts due to an insufficient k size (currently 2 or 6 is supported) or read/write race conditions.

A built in level-of-detail (LOD) approach samples the geometry using one of two heuristics (field or area). If LOD is enabled, the amount of geometry that is sampled and rendered changes dynamically to stay within the target frame rate. The field sampling method generally works best for datasets with cell sizes that don't vary much in size. On the contrary, the area sampling approach gives better approximations when the volume has a lot of variation in cell size.

The HAVS algorithm uses several advanced features on graphics hardware. The k-buffer sorting network is implemented using framebuffer objects (FBOs) with multiple render targets (MRTs). Therefore, only cards that support these features can run the algorithm (at least an ATI 9500 or an NVidia NV40 (6600)).

Attention:
Several issues had to be addressed to get the HAVS algorithm working within the vtk framework. These additions forced the code to forsake speed for the sake of compliance and robustness.

The HAVS algorithm operates on the triangles that compose the mesh. Therefore, before rendering, the cells are decomposed into unique triangles and stored on the GPU for efficient rendering. The use of GPU data structures is only recommended if the entire geometry can fit in graphics memory. Otherwise this feature should be disabled.

Another new feature is the handling of mixed data types (eg., polygonal data with volume data). This is handled by reading the z-buffer from the current window and copying it into the framebuffer object for off-screen rendering. The depth test is then enabled so that the volume only appears over the opaque geometry. Finally, the results of the off-screen rendering are blended into the framebuffer as a transparent, view-aligned texture.

Instead of using a preintegrated 3D lookup table for storing the ray integral, this implementation uses partial pre-integration. This improves the performance of dynamic transfer function updates by avoiding a costly preprocess of the table.

A final change to the original algorithm is the handling of non-convexities in the mesh. Due to read/write hazards that may create undesired artifacts with non-convexities when using a inside/outside toggle in the fragment program, another approach was employed. To handle non-convexities, the fragment shader determines if a ray-gap is larger than the max cell size and kill the fragment if so. This approximation performs rather well in practice but may miss small non-convexities.

For more information on the HAVS algorithm see:

"Hardware-Assisted Visibility Sorting for Unstructured Volume Rendering" by S. P. Callahan, M. Ikits, J. L. D. Comba, and C. T. Silva, IEEE Transactions of Visualization and Computer Graphics; May/June 2005.

For more information on the Level-of-Detail algorithm, see:

"Interactive Rendering of Large Unstructured Grids Using Dynamic Level-of-Detail" by S. P. Callahan, J. L. D. Comba, P. Shirley, and C. T. Silva, Proceedings of IEEE Visualization '05, Oct. 2005.

Acknowledgments:
This code was developed by Steven P. Callahan under the supervision of Prof. Claudio T. Silva. The code also contains contributions from Milan Ikits, Linh Ha, Huy T. Vo, Carlos E. Scheidegger, and Joao L. D. Comba.
Acknowledgments:
The work was supported by grants, contracts, and gifts from the National Science Foundation, the Department of Energy, the Army Research Office, and IBM.
Acknowledgments:
The port of HAVS to VTK and ParaView has been primarily supported by Sandia National Labs.
Tests:
vtkHAVSVolumeMapper (Tests)

Definition at line 134 of file vtkHAVSVolumeMapper.h.


Public Types

typedef
vtkUnstructuredGridVolumeMapper 
Superclass

Public Member Functions

virtual const char * GetClassName ()
virtual int IsA (const char *type)
virtual void PrintSelf (ostream &os, vtkIndent indent)
virtual bool SupportedByHardware ()
virtual void SetPartiallyRemoveNonConvexities (bool)
virtual bool GetPartiallyRemoveNonConvexities ()
virtual void SetLevelOfDetailTargetTime (float)
virtual float GetLevelOfDetailTargetTime ()
virtual void SetLevelOfDetail (bool)
virtual bool GetLevelOfDetail ()
void SetLevelOfDetailMethod (int)
virtual int GetLevelOfDetailMethod ()
void SetLevelOfDetailMethodField ()
void SetLevelOfDetailMethodArea ()
virtual void SetKBufferSize (int)
virtual int GetKBufferSize ()
void SetKBufferSizeTo2 ()
void SetKBufferSizeTo6 ()
virtual void SetGPUDataStructures (bool)=0
virtual bool GetGPUDataStructures ()

Static Public Member Functions

static vtkHAVSVolumeMapperNew ()
static int IsTypeOf (const char *type)
static vtkHAVSVolumeMapperSafeDownCast (vtkObject *o)

Protected Types

enum  {
  NO_INIT_ERROR = 0, NON_TETRAHEDRA = 1, UNSUPPORTED_EXTENSIONS = 2, NO_SCALARS = 3,
  CELL_DATA = 4, NO_CELLS = 5
}

Protected Member Functions

 vtkHAVSVolumeMapper ()
 ~vtkHAVSVolumeMapper ()
virtual void Initialize (vtkRenderer *ren, vtkVolume *vol)=0
void InitializePrimitives (vtkVolume *vol)
void InitializeScalars ()
void InitializeLevelOfDetail ()
void InitializeLookupTables (vtkVolume *vol)
void FRadixSort (vtkHAVSSortedFace *array, vtkHAVSSortedFace *temp, int lo, int up)
void FRadix (int byte, int len, vtkHAVSSortedFace *source, vtkHAVSSortedFace *dest, int *count)
void UpdateLevelOfDetail (float targetTime)
void PartialVisibilitySort (float *eye)
bool CheckInitializationError ()

Protected Attributes

float * Vertices
float * Scalars
double ScalarRange [2]
unsigned int * Triangles
unsigned int * OrderedTriangles
vtkHAVSSortedFace * SortedFaces
vtkHAVSSortedFace * RadixTemp
float * Centers
unsigned int NumberOfVertices
unsigned int NumberOfCells
unsigned int NumberOfScalars
unsigned int NumberOfTriangles
unsigned int NumberOfBoundaryTriangles
unsigned int NumberOfInternalTriangles
unsigned int * BoundaryTriangles
unsigned int * InternalTriangles
unsigned int LevelOfDetailTriangleCount
float CurrentLevelOfDetail
float LevelOfDetailTargetTime
bool LevelOfDetail
int LevelOfDetailMethod
int KBufferState
float MaxEdgeLength
float LevelOfDetailMaxEdgeLength
float UnitDistance
bool GPUDataStructures
float Diagonal
bool PartiallyRemoveNonConvexities
int KBufferSize
float * TransferFunction
int TransferFunctionSize
bool Initialized
int InitializationError
int FrameNumber
float TotalRenderTime
vtkTimeStamp ColorTransferFunctionMTime
vtkTimeStamp AlphaTransferFunctionMTime
vtkTimeStamp UnstructuredGridMTime
vtkTimeStamp ScalarsMTime
vtkVolumeLastVolume

Member Typedef Documentation

Reimplemented from vtkUnstructuredGridVolumeMapper.

Reimplemented in vtkOpenGLHAVSVolumeMapper.

Definition at line 139 of file vtkHAVSVolumeMapper.h.


Member Enumeration Documentation

anonymous enum [protected]

Enumerator:
NO_INIT_ERROR 
NON_TETRAHEDRA 
UNSUPPORTED_EXTENSIONS 
NO_SCALARS 
CELL_DATA 
NO_CELLS 

Definition at line 212 of file vtkHAVSVolumeMapper.h.


Constructor & Destructor Documentation

vtkHAVSVolumeMapper::vtkHAVSVolumeMapper (  )  [protected]

vtkHAVSVolumeMapper::~vtkHAVSVolumeMapper (  )  [protected]


Member Function Documentation

static vtkHAVSVolumeMapper* vtkHAVSVolumeMapper::New (  )  [static]

Create an object with Debug turned off, modified time initialized to zero, and reference counting on.

Reimplemented from vtkAlgorithm.

Reimplemented in vtkOpenGLHAVSVolumeMapper.

virtual const char* vtkHAVSVolumeMapper::GetClassName (  )  [virtual]

Reimplemented from vtkUnstructuredGridVolumeMapper.

Reimplemented in vtkOpenGLHAVSVolumeMapper.

static int vtkHAVSVolumeMapper::IsTypeOf ( const char *  name  )  [static]

Return 1 if this class type is the same type of (or a subclass of) the named class. Returns 0 otherwise. This method works in combination with vtkTypeRevisionMacro found in vtkSetGet.h.

Reimplemented from vtkUnstructuredGridVolumeMapper.

Reimplemented in vtkOpenGLHAVSVolumeMapper.

virtual int vtkHAVSVolumeMapper::IsA ( const char *  name  )  [virtual]

Return 1 if this class is the same type of (or a subclass of) the named class. Returns 0 otherwise. This method works in combination with vtkTypeRevisionMacro found in vtkSetGet.h.

Reimplemented from vtkUnstructuredGridVolumeMapper.

Reimplemented in vtkOpenGLHAVSVolumeMapper.

static vtkHAVSVolumeMapper* vtkHAVSVolumeMapper::SafeDownCast ( vtkObject o  )  [static]

Reimplemented from vtkUnstructuredGridVolumeMapper.

Reimplemented in vtkOpenGLHAVSVolumeMapper.

virtual void vtkHAVSVolumeMapper::PrintSelf ( ostream &  os,
vtkIndent  indent 
) [virtual]

Methods invoked by print to print information about the object including superclasses. Typically not called by the user (use Print() instead) but used in the hierarchical print process to combine the output of several classes.

Reimplemented from vtkUnstructuredGridVolumeMapper.

Reimplemented in vtkOpenGLHAVSVolumeMapper.

virtual void vtkHAVSVolumeMapper::SetPartiallyRemoveNonConvexities ( bool   )  [virtual]

regions by removing ray segments larger than the max cell size.

virtual bool vtkHAVSVolumeMapper::GetPartiallyRemoveNonConvexities (  )  [virtual]

regions by removing ray segments larger than the max cell size.

virtual void vtkHAVSVolumeMapper::SetLevelOfDetailTargetTime ( float   )  [virtual]

Set/get the desired level of detail target time measured in frames/sec.

virtual float vtkHAVSVolumeMapper::GetLevelOfDetailTargetTime (  )  [virtual]

Set/get the desired level of detail target time measured in frames/sec.

virtual void vtkHAVSVolumeMapper::SetLevelOfDetail ( bool   )  [virtual]

Turn on/off level-of-detail volume rendering

virtual bool vtkHAVSVolumeMapper::GetLevelOfDetail (  )  [virtual]

Turn on/off level-of-detail volume rendering

void vtkHAVSVolumeMapper::SetLevelOfDetailMethod ( int   ) 

Set/get the current level-of-detail method

virtual int vtkHAVSVolumeMapper::GetLevelOfDetailMethod (  )  [virtual]

Set/get the current level-of-detail method

void vtkHAVSVolumeMapper::SetLevelOfDetailMethodField (  )  [inline]

Set/get the current level-of-detail method

Definition at line 165 of file vtkHAVSVolumeMapper.h.

void vtkHAVSVolumeMapper::SetLevelOfDetailMethodArea (  )  [inline]

Set/get the current level-of-detail method

Definition at line 167 of file vtkHAVSVolumeMapper.h.

virtual void vtkHAVSVolumeMapper::SetKBufferSize ( int   )  [virtual]

Set the kbuffer size

virtual int vtkHAVSVolumeMapper::GetKBufferSize (  )  [virtual]

Set the kbuffer size

void vtkHAVSVolumeMapper::SetKBufferSizeTo2 (  )  [inline]

Set the kbuffer size

Definition at line 175 of file vtkHAVSVolumeMapper.h.

void vtkHAVSVolumeMapper::SetKBufferSizeTo6 (  )  [inline]

Set the kbuffer size

Definition at line 177 of file vtkHAVSVolumeMapper.h.

virtual bool vtkHAVSVolumeMapper::SupportedByHardware (  )  [inline, virtual]

Check hardware support for the HAVS algorithm. Necessary features include off-screen rendering, 32-bit fp textures, multiple render targets, and framebuffer objects. Subclasses must override this method to indicate if supported by Hardware.

Reimplemented in vtkOpenGLHAVSVolumeMapper.

Definition at line 185 of file vtkHAVSVolumeMapper.h.

virtual void vtkHAVSVolumeMapper::SetGPUDataStructures ( bool   )  [pure virtual]

Set/get whether or not the data structures should be stored on the GPU for better peformance.

Implemented in vtkOpenGLHAVSVolumeMapper.

virtual bool vtkHAVSVolumeMapper::GetGPUDataStructures (  )  [virtual]

Set/get whether or not the data structures should be stored on the GPU for better peformance.

virtual void vtkHAVSVolumeMapper::Initialize ( vtkRenderer ren,
vtkVolume vol 
) [protected, pure virtual]

Implemented in vtkOpenGLHAVSVolumeMapper.

void vtkHAVSVolumeMapper::InitializePrimitives ( vtkVolume vol  )  [protected]

void vtkHAVSVolumeMapper::InitializeScalars (  )  [protected]

void vtkHAVSVolumeMapper::InitializeLevelOfDetail (  )  [protected]

void vtkHAVSVolumeMapper::InitializeLookupTables ( vtkVolume vol  )  [protected]

Reimplemented in vtkOpenGLHAVSVolumeMapper.

void vtkHAVSVolumeMapper::FRadixSort ( vtkHAVSSortedFace *  array,
vtkHAVSSortedFace *  temp,
int  lo,
int  up 
) [protected]

void vtkHAVSVolumeMapper::FRadix ( int  byte,
int  len,
vtkHAVSSortedFace *  source,
vtkHAVSSortedFace *  dest,
int *  count 
) [protected]

void vtkHAVSVolumeMapper::UpdateLevelOfDetail ( float  targetTime  )  [protected]

void vtkHAVSVolumeMapper::PartialVisibilitySort ( float *  eye  )  [protected]

bool vtkHAVSVolumeMapper::CheckInitializationError (  )  [protected]


Member Data Documentation

float* vtkHAVSVolumeMapper::Vertices [protected]

Definition at line 223 of file vtkHAVSVolumeMapper.h.

float* vtkHAVSVolumeMapper::Scalars [protected]

Definition at line 224 of file vtkHAVSVolumeMapper.h.

double vtkHAVSVolumeMapper::ScalarRange[2] [protected]

Definition at line 225 of file vtkHAVSVolumeMapper.h.

unsigned int* vtkHAVSVolumeMapper::Triangles [protected]

Definition at line 226 of file vtkHAVSVolumeMapper.h.

unsigned int* vtkHAVSVolumeMapper::OrderedTriangles [protected]

Definition at line 227 of file vtkHAVSVolumeMapper.h.

vtkHAVSSortedFace* vtkHAVSVolumeMapper::SortedFaces [protected]

Definition at line 228 of file vtkHAVSVolumeMapper.h.

vtkHAVSSortedFace* vtkHAVSVolumeMapper::RadixTemp [protected]

Definition at line 229 of file vtkHAVSVolumeMapper.h.

float* vtkHAVSVolumeMapper::Centers [protected]

Definition at line 230 of file vtkHAVSVolumeMapper.h.

unsigned int vtkHAVSVolumeMapper::NumberOfVertices [protected]

Definition at line 231 of file vtkHAVSVolumeMapper.h.

unsigned int vtkHAVSVolumeMapper::NumberOfCells [protected]

Definition at line 232 of file vtkHAVSVolumeMapper.h.

unsigned int vtkHAVSVolumeMapper::NumberOfScalars [protected]

Definition at line 233 of file vtkHAVSVolumeMapper.h.

unsigned int vtkHAVSVolumeMapper::NumberOfTriangles [protected]

Definition at line 234 of file vtkHAVSVolumeMapper.h.

Definition at line 237 of file vtkHAVSVolumeMapper.h.

Definition at line 238 of file vtkHAVSVolumeMapper.h.

unsigned int* vtkHAVSVolumeMapper::BoundaryTriangles [protected]

Definition at line 239 of file vtkHAVSVolumeMapper.h.

unsigned int* vtkHAVSVolumeMapper::InternalTriangles [protected]

Definition at line 240 of file vtkHAVSVolumeMapper.h.

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float vtkHAVSVolumeMapper::Diagonal [protected]

Definition at line 253 of file vtkHAVSVolumeMapper.h.

Definition at line 254 of file vtkHAVSVolumeMapper.h.

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The documentation for this class was generated from the following file:

Generated on Wed Jun 3 19:07:02 2009 for VTK by  doxygen 1.5.6