ActiViz .NET
5.8.0
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vtkOpenGLHAVSVolumeMapper - Hardware-Assisted Visibility Sorting unstructured grid mapper, OpenGL implementation More...
Public Member Functions | |
vtkOpenGLHAVSVolumeMapper (IntPtr rawCppThis, bool callDisposalMethod, bool strong) | |
Automatically generated constructor - called from generated code. DO NOT call directly. | |
vtkOpenGLHAVSVolumeMapper () | |
Undocumented Block. | |
override int | IsA (string type) |
Undocumented Block. | |
new vtkOpenGLHAVSVolumeMapper | NewInstance () |
Undocumented Block. | |
override void | ReleaseGraphicsResources (vtkWindow arg0) |
Description Release any graphics resources that are being consumed by this volume renderer. | |
override void | Render (vtkRenderer ren, vtkVolume vol) |
Render the volume. | |
override void | SetGPUDataStructures (bool arg0) |
Set/get whether or not the data structures should be stored on the GPU for better peformance. | |
override bool | SupportedByHardware (vtkRenderer r) |
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. | |
Static Public Member Functions | |
static new vtkOpenGLHAVSVolumeMapper | New () |
Undocumented Block. | |
static new int | IsTypeOf (string type) |
Undocumented Block. | |
static new vtkOpenGLHAVSVolumeMapper | SafeDownCast (vtkObjectBase o) |
Undocumented Block. | |
Public Attributes | |
new const string | MRFullTypeName = "Kitware.VTK.vtkOpenGLHAVSVolumeMapper" |
Automatically generated type registration mechanics. | |
Static Public Attributes | |
static new readonly string | MRClassNameKey = "25vtkOpenGLHAVSVolumeMapper" |
Automatically generated type registration mechanics. | |
Protected Member Functions | |
override void | Dispose (bool disposing) |
Automatically generated protected Dispose method - called from public Dispose or the C# destructor. DO NOT call directly. | |
Private Member Functions | |
static internal IntPtr | vtkOpenGLHAVSVolumeMapper_New (ref uint mteStatus, ref uint mteIndex, ref uint rawRefCount) |
static internal int | vtkOpenGLHAVSVolumeMapper_IsA_01 (HandleRef pThis, string type) |
static internal int | vtkOpenGLHAVSVolumeMapper_IsTypeOf_02 (string type) |
static internal IntPtr | vtkOpenGLHAVSVolumeMapper_NewInstance_04 (HandleRef pThis, ref uint mteStatus, ref uint mteIndex, ref uint rawRefCount) |
static internal void | vtkOpenGLHAVSVolumeMapper_ReleaseGraphicsResources_05 (HandleRef pThis, HandleRef arg0) |
static internal void | vtkOpenGLHAVSVolumeMapper_Render_06 (HandleRef pThis, HandleRef ren, HandleRef vol) |
static internal IntPtr | vtkOpenGLHAVSVolumeMapper_SafeDownCast_07 (HandleRef o, ref uint mteStatus, ref uint mteIndex, ref uint rawRefCount) |
static internal void | vtkOpenGLHAVSVolumeMapper_SetGPUDataStructures_08 (HandleRef pThis, byte arg0) |
static internal byte | vtkOpenGLHAVSVolumeMapper_SupportedByHardware_09 (HandleRef pThis, HandleRef r) |
Static Private Member Functions | |
static | vtkOpenGLHAVSVolumeMapper () |
Automatically generated type registration mechanics. |
vtkOpenGLHAVSVolumeMapper - Hardware-Assisted Visibility Sorting unstructured grid mapper, OpenGL implementation
Description
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)).
Notes
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.
The work was supported by grants, contracts, and gifts from the National Science Foundation, the Department of Energy, the Army Research Office, and IBM.
The port of HAVS to VTK and ParaView has been primarily supported by Sandia National Labs.
static Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper | ( | ) | [static, private] |
Automatically generated type registration mechanics.
Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper | ( | IntPtr | rawCppThis, |
bool | callDisposalMethod, | ||
bool | strong | ||
) |
Automatically generated constructor - called from generated code. DO NOT call directly.
Undocumented Block.
override void Kitware.VTK.vtkOpenGLHAVSVolumeMapper.Dispose | ( | bool | disposing | ) | [protected] |
Automatically generated protected Dispose method - called from public Dispose or the C# destructor. DO NOT call directly.
Reimplemented from Kitware.VTK.vtkHAVSVolumeMapper.
override int Kitware.VTK.vtkOpenGLHAVSVolumeMapper.IsA | ( | string | type | ) | [virtual] |
Undocumented Block.
Reimplemented from Kitware.VTK.vtkHAVSVolumeMapper.
static new int Kitware.VTK.vtkOpenGLHAVSVolumeMapper.IsTypeOf | ( | string | type | ) | [static] |
Undocumented Block.
Reimplemented from Kitware.VTK.vtkHAVSVolumeMapper.
static new vtkOpenGLHAVSVolumeMapper Kitware.VTK.vtkOpenGLHAVSVolumeMapper.New | ( | ) | [static] |
Undocumented Block.
Reimplemented from Kitware.VTK.vtkHAVSVolumeMapper.
Undocumented Block.
Reimplemented from Kitware.VTK.vtkHAVSVolumeMapper.
override void Kitware.VTK.vtkOpenGLHAVSVolumeMapper.ReleaseGraphicsResources | ( | vtkWindow | arg0 | ) | [virtual] |
Description Release any graphics resources that are being consumed by this volume renderer.
Reimplemented from Kitware.VTK.vtkUnstructuredGridVolumeMapper.
override void Kitware.VTK.vtkOpenGLHAVSVolumeMapper.Render | ( | vtkRenderer | ren, |
vtkVolume | vol | ||
) | [virtual] |
Render the volume.
Reimplemented from Kitware.VTK.vtkUnstructuredGridVolumeMapper.
static new vtkOpenGLHAVSVolumeMapper Kitware.VTK.vtkOpenGLHAVSVolumeMapper.SafeDownCast | ( | vtkObjectBase | o | ) | [static] |
Undocumented Block.
Reimplemented from Kitware.VTK.vtkHAVSVolumeMapper.
override void Kitware.VTK.vtkOpenGLHAVSVolumeMapper.SetGPUDataStructures | ( | bool | arg0 | ) | [virtual] |
Set/get whether or not the data structures should be stored on the GPU for better peformance.
Reimplemented from Kitware.VTK.vtkHAVSVolumeMapper.
override bool Kitware.VTK.vtkOpenGLHAVSVolumeMapper.SupportedByHardware | ( | vtkRenderer | r | ) | [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 from Kitware.VTK.vtkHAVSVolumeMapper.
static internal int Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper_IsA_01 | ( | HandleRef | pThis, |
string | type | ||
) | [private] |
static internal int Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper_IsTypeOf_02 | ( | string | type | ) | [private] |
static internal IntPtr Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper_New | ( | ref uint | mteStatus, |
ref uint | mteIndex, | ||
ref uint | rawRefCount | ||
) | [private] |
static internal IntPtr Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper_NewInstance_04 | ( | HandleRef | pThis, |
ref uint | mteStatus, | ||
ref uint | mteIndex, | ||
ref uint | rawRefCount | ||
) | [private] |
static internal void Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper_ReleaseGraphicsResources_05 | ( | HandleRef | pThis, |
HandleRef | arg0 | ||
) | [private] |
static internal void Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper_Render_06 | ( | HandleRef | pThis, |
HandleRef | ren, | ||
HandleRef | vol | ||
) | [private] |
static internal IntPtr Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper_SafeDownCast_07 | ( | HandleRef | o, |
ref uint | mteStatus, | ||
ref uint | mteIndex, | ||
ref uint | rawRefCount | ||
) | [private] |
static internal void Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper_SetGPUDataStructures_08 | ( | HandleRef | pThis, |
byte | arg0 | ||
) | [private] |
static internal byte Kitware.VTK.vtkOpenGLHAVSVolumeMapper.vtkOpenGLHAVSVolumeMapper_SupportedByHardware_09 | ( | HandleRef | pThis, |
HandleRef | r | ||
) | [private] |
new readonly string Kitware.VTK.vtkOpenGLHAVSVolumeMapper.MRClassNameKey = "25vtkOpenGLHAVSVolumeMapper" [static] |
Automatically generated type registration mechanics.
Reimplemented from Kitware.VTK.vtkHAVSVolumeMapper.
new const string Kitware.VTK.vtkOpenGLHAVSVolumeMapper.MRFullTypeName = "Kitware.VTK.vtkOpenGLHAVSVolumeMapper" |
Automatically generated type registration mechanics.
Reimplemented from Kitware.VTK.vtkHAVSVolumeMapper.