Previously the coordinate system functionality was split between
coordinateSystem and coordinateRotation. The coordinateRotation stored
the rotation tensor and handled all tensor transformations.
The functionality has now been revised and consolidated into the
coordinateSystem classes. The sole purpose of coordinateRotation
is now just to provide a selectable mechanism of how to define the
rotation tensor (eg, axis-angle, euler angles, local axes) for user
input, but after providing the appropriate rotation tensor it has
no further influence on the transformations.
--
The coordinateSystem class now contains an origin and a base rotation
tensor directly and various transformation methods.
- The origin represents the "shift" for a local coordinate system.
- The base rotation tensor represents the "tilt" or orientation
of the local coordinate system in general (eg, for mapping
positions), but may require position-dependent tensors when
transforming vectors and tensors.
For some coordinate systems (currently the cylindrical coordinate system),
the rotation tensor required for rotating a vector or tensor is
position-dependent.
The new coordinateSystem and its derivates (cartesian, cylindrical,
indirect) now provide a uniform() method to define if the rotation
tensor is position dependent/independent.
The coordinateSystem transform and invTransform methods are now
available in two-parameter forms for obtaining position-dependent
rotation tensors. Eg,
... = cs.transform(globalPt, someVector);
In some cases it can be useful to use query uniform() to avoid
storage of redundant values.
if (cs.uniform())
{
vector xx = cs.transform(someVector);
}
else
{
List<vector> xx = cs.transform(manyPoints, someVector);
}
Support transform/invTransform for common data types:
(scalar, vector, sphericalTensor, symmTensor, tensor).
====================
Breaking Changes
====================
- These changes to coordinate systems and rotations may represent
a breaking change for existing user coding.
- Relocating the rotation tensor into coordinateSystem itself means
that the coordinate system 'R()' method now returns the rotation
directly instead of the coordinateRotation. The method name 'R()'
was chosen for consistency with other low-level entities (eg,
quaternion).
The following changes will be needed in coding:
Old: tensor rot = cs.R().R();
New: tensor rot = cs.R();
Old: cs.R().transform(...);
New: cs.transform(...);
Accessing the runTime selectable coordinateRotation
has moved to the rotation() method:
Old: Info<< "Rotation input: " << cs.R() << nl;
New: Info<< "Rotation input: " << cs.rotation() << nl;
- Naming consistency changes may also cause code to break.
Old: transformVector()
New: transformPrincipal()
The old method name transformTensor() now simply becomes transform().
====================
New methods
====================
For operations requiring caching of the coordinate rotations, the
'R()' method can be used with multiple input points:
tensorField rots(cs.R(somePoints));
and later
Foam::transformList(rots, someVectors);
The rotation() method can also be used to change the rotation tensor
via a new coordinateRotation definition (issue #879).
The new methods transformPoint/invTransformPoint provide
transformations with an origin offset using Cartesian for both local
and global points. These can be used to determine the local position
based on the origin/rotation without interpreting it as a r-theta-z
value, for example.
================
Input format
================
- Streamline dictionary input requirements
* The default type is cartesian.
* The default rotation type is the commonly used axes rotation
specification (with e1/e2/3), which is assumed if the 'rotation'
sub-dictionary does not exist.
Example,
Compact specification:
coordinateSystem
{
origin (0 0 0);
e2 (0 1 0);
e3 (0.5 0 0.866025);
}
Full specification (also accepts the longer 'coordinateRotation'
sub-dictionary name):
coordinateSystem
{
type cartesian;
origin (0 0 0);
rotation
{
type axes;
e2 (0 1 0);
e3 (0.5 0 0.866025);
}
}
This simplifies the input for many cases.
- Additional rotation specification 'none' (an identity rotation):
coordinateSystem
{
origin (0 0 0);
rotation { type none; }
}
- Additional rotation specification 'axisAngle', which is similar
to the -rotate-angle option for transforming points (issue #660).
For some cases this can be more intuitive.
For example,
rotation
{
type axisAngle;
axis (0 1 0);
angle 30;
}
vs.
rotation
{
type axes;
e2 (0 1 0);
e3 (0.5 0 0.866025);
}
- shorter names (or older longer names) for the coordinate rotation
specification.
euler EulerRotation
starcd STARCDRotation
axes axesRotation
================
Coding Style
================
- use Foam::coordSystem namespace for categories of coordinate systems
(cartesian, cylindrical, indirect). This reduces potential name
clashes and makes a clearer declaration. Eg,
coordSystem::cartesian csys_;
The older names (eg, cartesianCS, etc) remain available via typedefs.
- added coordinateRotations namespace for better organization and
reduce potential name clashes.
- 'signed' input parameter only mandatory for distance > 0.
A distance <= 0 is always signed and the input parameter is ignored.
- Use normal distance when distance == 0. This has no effect when
the surface has no open edges, but improves on rounding issues
around the zero crossing when the surface has open edges.
This may still need future revisiting.
- the original intention was to avoid vtp output when the clouds are
empty anyhow. However, it is useful for post-processing to have
clouds with zero parcels (eg, before the start of injection).
Pruning of empty clouds is now an option in the vtkCloud dictionary
controls, with the default being false (no pruning). This represents
a non-breaking change in behaviour since it generates more output
than previously.
Example,
{
type vtkCloud;
//- Suppress writing of empty clouds (default: false)
prune true;
}
- functionObjectLibs -> libs
- redirectType -> name
- change deprecated writeCompression flags types to Switch.
- cleanup some trailing ';;' from some dictionaries
- for larger problems with a smaller region of interest, can apply a
bounding to limit the size of the ensight geometry and fields created.
Since the implementation uses a fvMeshSubset, there is an additional
per-process memory overhead.
A high output frequency should be avoided with moving meshes, since
this indirectly forces a frequent update of the submesh.
- takes a direct approach of determining which cells are cut and walks
the cell faces directly to build the resulting surface.
- better handling of corner cases.
* Avoids redundant points when the cut passes exactly through a
mesh point.
* Supresses generation of duplicates faces when the plane cut
coincides exactly with a mesh face.
- for severely concave cells where the plane cuts a face multiple times
there is currently no remedial action taken, except to note the
failure and unwind the insertion of the corresponding points and
faces.
- signedDistance() method is like distance() but retains
the positive/negative sign for the side of the plane.
- the sign() method returns the sign as -1,0,+1 integer for
classification purposes where it is important to distinguish between
a zero value and a positive value (eg, for cutting). Optional
tolerance can be supplied to round for zero.
- refactor and inlined simple and frequently used methods.
- add boundBox faceCentre() method, which can be useful for creating
clipping planes from a bounding box.
Relocated treeBoundBox faceNormals to boundBox since they apply
equally there - the meaning of the faces (x-min, x-max, etc)
is the same, even if the point addressing for the faces differs.
- some paraview versions (eg, on windows) don't support float, only double.
This mostly affected the vtkSurfaceWriter.
The foamToVTK is also affected, but since it also supports the XML
output formats (vtp, vtu) these can be used instead.
