Performs advections of an arbitrary type of volume in a static velocity field. The advections are performed by means of various derivatives of Semi-Lagrangian integration, i.e. backwards tracking along the hyperbolic characteristics followed by interpolation.
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#include <VolumeAdvect.h>
template<typename VelocityGridT = Vec3fGrid, bool StaggeredVelocity = false, typename InterrupterType = util::NullInterrupter>
class openvdb::v8_2::tools::VolumeAdvection< VelocityGridT, StaggeredVelocity, InterrupterType >
Performs advections of an arbitrary type of volume in a static velocity field. The advections are performed by means of various derivatives of Semi-Lagrangian integration, i.e. backwards tracking along the hyperbolic characteristics followed by interpolation.
- Note
- Optionally a limiter can be combined with the higher-order integration schemes MacCormack and BFECC. There are two types of limiters (CLAMP and REVERT) that supress non-physical oscillations by means of either claminging or reverting to a first-order schemes when the function is not bounded by the cell values used for tri-linear interpolation.
The supported integrations schemes:
///
/// ================================================================
/// | Lable | Accuracy | Integration Scheme | Interpolations |
/// | |Time/Space| | velocity/volume |
/// ================================================================
/// | SEMI | 1/1 | Semi-Lagrangian | 1/1 |
/// | MID | 2/1 | Mid-Point | 2/1 |
/// | RK3 | 3/1 | 3rd Order Runge-Kutta | 3/1 |
/// | RK4 | 4/1 | 4th Order Runge-Kutta | 4/1 |
/// | MAC | 2/2 | MacCormack | 2/2 |
/// | BFECC | 2/2 | BFECC | 3/2 |
/// ================================================================
///
| VolumeAdvection |
( |
const VelocityGridT & |
velGrid, |
|
|
InterrupterType * |
interrupter = nullptr |
|
) |
| |
|
inline |
Constructor.
- Parameters
-
| velGrid | Velocity grid responsible for the (passive) advection. |
| interrupter | Optional interrupter used to prematurely end computations. |
- Note
- The velocity field is assumed to be constant for the duration of the advection.
| VolumeGridT::Ptr advect |
( |
const VolumeGridT & |
inGrid, |
|
|
double |
timeStep |
|
) |
| |
|
inline |
- Returns
- Returns a new grid that is the result of passive advection of all the active values the input grid by timeStep.
- Parameters
-
| inGrid | The input grid to be advected (unmodified) |
| timeStep | Time-step of the Runge-Kutta integrator. |
This method will advect all of the active values in the input inGrid. To achieve this a deep-copy is dilated to account for the material transport. This dilation step can be slow for large time steps dt or a velocity field with large magnitudes.
- Warning
- If the VolumeSamplerT is of higher order than one (i.e. tri-linear interpolation) instabilities are known to occure. To suppress those monotonicity constrains or flux-limiters need to be applies.
- Exceptions
-
| VolumeGridT::Ptr advect |
( |
const VolumeGridT & |
inGrid, |
|
|
const MaskGridT & |
mask, |
|
|
double |
timeStep |
|
) |
| |
|
inline |
- Returns
- Returns a new grid that is the result of passive advection of the active values in inGrid that intersect the active values in
mask. The time of the output grid is incremented by timeStep.
- Parameters
-
| inGrid | The input grid to be advected (unmodified). |
| mask | The mask of active values defining the active voxels in inGrid on which to perform advection. Only if a value is active in both grids will it be modified. |
| timeStep | Time-step for a single Runge-Kutta integration step. |
This method will advect all of the active values in the input inGrid that intersects with the active values in mask. To achieve this a deep-copy is dilated to account for the material transport and finally cropped to the intersection with mask. The dilation step can be slow for large time steps dt or fast moving velocity fields.
- Warning
- If the VolumeSamplerT is of higher order the one (i.e. tri-linear interpolation) instabilities are known to occure. To suppress those monotonicity constrains or flux-limiters need to be applies.
- Exceptions
-
| RuntimeError | if inGrid is not aligned with mask or if its voxels are not uniform. |
| size_t getGrainSize |
( |
| ) |
const |
|
inline |
- Returns
- the grain-size used for multi-threading
- Note
- A grainsize of 0 implies serial execution
Return the integrator (see details in the table above)
Retrun the limiter (see details above)
| int getMaxDistance |
( |
const VolumeGridT & |
inGrid, |
|
|
double |
dt |
|
) |
| const |
|
inline |
- Returns
- Returns the maximum distance in voxel units of inGrid that a particle can travel in the time-step dt when advected in the velocity field defined during construction.
This method is useful when dilating sparse volume grids to pad boundary regions. Excessive dilation can be computationally expensive so use this method to prevent or warn against run-away computation.
- Exceptions
-
| double getMaxVelocity |
( |
| ) |
const |
|
inline |
Return the maximum magnitude of the velocity in the advection velocity field defined during construction.
| int getSubSteps |
( |
| ) |
const |
|
inline |
- Returns
- the number of sub-steps per integration (always larger than or equal to 1).
| bool isLimiterOn |
( |
| ) |
const |
|
inline |
Return true if a limiter will be applied based on the current settings.
| void setGrainSize |
( |
size_t |
grainsize | ) |
|
|
inline |
Set the grain-size used for multi-threading.
- Note
- A grainsize of 0 disables multi-threading
- Warning
- A small grainsize can degrade performance, both in terms of time and memory footprint!
Set the integrator (see details in the table above)
Set the limiter (see details above)
| void setSubSteps |
( |
int |
substeps | ) |
|
|
inline |
Set the number of sub-steps per integration.
- Note
- The only reason to increase the sub-step above its default value of one is to reduce the memory footprint due to significant dilation. Values smaller than 1 will be clamped to 1!
| int spatialOrder |
( |
| ) |
const |
|
inline |
Return the spatial order of accuracy of the advection scheme.
- Note
- This is the optimal order in smooth regions. In non-smooth regions the flux-limiter will drop the order of accuracy to add numerical dissipation.
| int temporalOrder |
( |
| ) |
const |
|
inline |
Return the temporal order of accuracy of the advection scheme.
- Note
- This is the optimal order in smooth regions. In non-smooth regions the flux-limiter will drop the order of accuracy to add numerical dissipation.
The documentation for this class was generated from the following file:
1.8.11