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A maxon::VolumeInterface is used to store and handle volume data. It is typically obtained from a VolumeObject ，见 VolumeObject Manual .

VolumeInterface

Volume information can be stored in a file:

maxon::VolumeInterface::LoadFromFile() : Loads a volume from the given file.
maxon::VolumeInterface::WriteToFile() : Writes the volume to the given file.
maxon::VolumeInterface::CreateFromFile() : Static function loading volume data from a *.vdb file.

// This example loads a grid from the given vdb file // and inserts it into the BaseDocument using a VolumeObject.

const maxon::Int gridIndex = 0; const maxon::Volume volume = maxon::VolumeInterface::CreateFromFile (volumeUrl, 1.0, gridIndex) iferr_return ;

// create VolumeObject VolumeObject * const volumeObj = VolumeObject::Alloc (); if (volumeObj == nullptr ) return maxon::OutOfMemoryError( MAXON_SOURCE_LOCATION );

doc-> InsertObject (volumeObj, nullptr , nullptr );

// insert volume volumeObj-> SetVolume (volume);

The grid settings are accessed with:

maxon::VolumeInterface::HasGrid() : Returns true if a grid is attached.
maxon::VolumeInterface::GetGridType() : Returns the grid type ( GRIDTYPE ).
maxon::VolumeInterface::GetGridClass() : Returns the grid class ( GRIDCLASS ).
maxon::VolumeInterface::SetGridClass() : Sets the grid class.
maxon::VolumeInterface::GetGridTransform() : Returns the grid transformation matrix.
maxon::VolumeInterface::SetGridTransform() : Sets the grid transformation matrix.
maxon::VolumeInterface::GetGridName() : Returns the grid name.
maxon::VolumeInterface::SetGridName() : Sets the grid name.
maxon::VolumeInterface::GetWorldBoundingBox() : Returns the bounding box of all active voxels.
maxon::VolumeInterface::GetActiveVoxelDim() : Returns the active voxel dimensions.
maxon::VolumeInterface::GetActiveVoxelCount() : Returns the number of active voxels.
maxon::VolumeInterface::GetBackground() : Returns the background value of the grid.
maxon::VolumeInterface::GetMemUsage() : Returns the size of the memory used.
maxon::VolumeInterface::GetMinMaxValues() : Returns the Min and Max values of the volume.

// This example prints some data on the volumes grid.

// get volume const maxon::Volume volume = volumeObject-> GetVolume ();

// check grid if (volume.HasGrid()) { const maxon::String gridName = volume.GetGridName(); const GRIDCLASS gridClass = volume.GetGridClass(); DiagnosticOutput ( "@ (@)" , gridName, gridClass); }

Iterator

The data stored in a volume is accessed with the maxon::GridIteratorInterface iterator:

maxon::GridIteratorInterface::Init() : Initializes the iterator with the given volume.
maxon::GridIteratorInterface::GetVolume() : Returns the referenced volume.
maxon::GridIteratorInterface::GetValue() : Returns the current value.
maxon::GridIteratorInterface::GetCoords() : Returns the current position.
maxon::GridIteratorInterface::IsNotAtEnd() : Returns true if the iterator is not yet at its end.
maxon::GridIteratorInterface::StepNext() : Steps to the next active voxel.
maxon::GridIteratorInterface::GetVoxelLevel() : Returns the tree level of the current voxel.

// This example iterates over the active cells of the given volume.

// get volume const maxon::Volume volume = volumeObject-> GetVolume ();

// get matrix const maxon::Matrix transform = volume.GetGridTransform();

// create iterator maxon::GridIteratorRef<maxon::Float32, maxon::ITERATORTYPE::ON> iterator = maxon::GridIteratorRef<maxon::Float32, maxon::ITERATORTYPE::ON>::Create () iferr_return ; iterator.Init(volume) iferr_return ;

// iterate for (; iterator.IsNotAtEnd(); iterator.StepNext()) { // get value const Float32 value = iterator.GetValue(); // get coordinates const maxon::IntVector32 coord = iterator.GetCoords(); DiagnosticOutput ( "@: @" , coord, value);

// get world space coordinates 向量 pos; pos. x = coord. x ; pos. y = coord. y ; pos. z = coord. z ; pos = transform * pos; DiagnosticOutput ( "World space coordinates: @" , pos); }

Accessor

The grid accessor can be used to both retrieve and set the volume data:

maxon::GridAccessorInterface::Create() : Creates a new instance.
maxon::GridAccessorInterface::Init() : Initializes the accessor to read the given volume.
maxon::GridAccessorInterface::InitWithWriteAccess() : Initializes the accessor to read and write the given volume.

Volume data is accessed with:

maxon::GridAccessorInterface::GetValue() : Returns the value for the given coordinates or position.
maxon::GridAccessorInterface::GetCoords() : Returns the coordinates for the given position.
maxon::GridAccessorInterface::SetSampler() : Sets the sample (see maxon::VOLUMESAMPLER ).
maxon::GridAccessorInterface::SetValue() : Sets the value at the given coordinates.
maxon::GridAccessorInterface::SetValueOnly() : Sets the value at the given coordinates without activating the voxel.
maxon::GridAccessorInterface::SetActiveState() : Sets the active state of the voxel at the given coordinates.
maxon::GridAccessorInterface::GetActiveState() : Returns the active state of the voxel at the given coordinates.

// This example creates a new VolumeObject and a new volume. // It uses the GridAccessor to set values of the volume.

// create VolumeObject VolumeObject * const volumeObj = VolumeObject::Alloc (); if (volumeObj == nullptr ) return maxon::OutOfMemoryError( MAXON_SOURCE_LOCATION ); doc-> InsertObject (volumeObj, nullptr , nullptr );

// create volume maxon::Volume volume = maxon::VolumeToolsInterface::CreateNewFloat32Volume (0.0) iferr_return ; volume.SetGridClass( GRIDCLASS :: FOG ) iferr_return ; volume.SetGridName("Example Grid"_s); const 向量 scaleFactor { 10.0 }; const maxon::Matrix scaleMatrix = MatrixScale (scaleFactor); volume.SetGridTransform(scaleMatrix) iferr_return ;

// create accessor maxon::GridAccessorRef<Float32> access = maxon::GridAccessorRef<Float32>::Create () iferr_return ; access.InitWithWriteAccess(volume, maxon :: VOLUMESAMPLER ::NEAREST) iferr_return ;

// set values in the shape of a helix Float offset = 0.0; const Float scale = 100.0; const Float scaleY = 10.0; while (offset < 50.0) { Float64 sin; Float64 cos; maxon::SinCos (offset, sin, cos); maxon::IntVector32 pos; pos. x = maxon::Int32 (sin * scale); pos. z = maxon::Int32 (cos * scale); pos. y = maxon::Int32 (offset * scaleY);