Pyvista

It's been three months since the last release and there are quite a few bug fixes and features!

Major API Changes
-----------------
- Moved `BackgroundPlotter` and `QtInteractor` to `pyvistaqt`. See 719 for the reasoning, but as a summary, this boils down to licensing, unit testing, and improved development. See [pyvistaqt](https://github.com/pyvista/pyvistaqt) to test out the new module. Wheels will be released for that as soon as we've released wheels for `pyvista==0.25.0` as it's a dependency.
- Added better support for VTKv9. There were several changes under the hood to VTK's `UnstructuredGrids` that need to be implemented here, as well as many changes to our unit testing and CI to support Python 3.8 and VTKv9. See 732, 772, and 693.
- When using PyVista with Sphinx-Gallery, we require you to set `pyvista.BUILDING_GALLERY = True` in your `conf.py`

Features
--------
- Removing cells or faces (653)
- Progress bar using `tqdm` (608)
- Plotting floors (424)
- Additional geometry features (449)
- Subplot groups (696)
- Custom orientation widget (702)

Bug Fixes
---------
- Checking vectors when setting vectors 763
- Check overwriting dataset to avoid segfault 738
- Fix faulthandler (694 and 645)
- Implicit point setters (769)
- Ellipsoid wrapping (705)

CI Improvements
---------------
- Unit testing is between 25-40% faster. MacOS testing no supports multiple testing processes using `pytest-xdist`. See 739 and 744
- Improved code coverage 745 and 709
- Removed all example downloading from unit testing. Greatly improves test stability (731)
- Various speedups (661)

Refactoring
-----------
- Removed untested `pyansys` quality method.
- Using underscore numpy types (762)
- Optimized imports (743)
- Line break consistent (737)
- Use new style super() calls (741)
- Generic load/save (736)
- Refactored active scalars/vectors (746)
- Better error types (759)
- And many many more...


Contributors
------------
Thanks to all those who contributed to this release! In no particular order:
- JevinJ
- mli0603
- banesullivan
- GuillaumeFavelier
- dcbr
- tomsal
- tkoyama010
- ralovich
- florian-wagner
- imsodin
- larsoner
- adeak
- akaszynski

New Features

- Huge Refactor of `QtInteractor` to improve stability of `BackgroundPlotter` (603, 619).
- Rename extract edges filters (610)
- Exposing tip resolution in `pyvista.Arrow` (624)

Squashed Bugs

- Minor doc fixes (616)
- Disabled depth peeling by default (618)
- Fix increment point size (609)
- Disabled rendering on close (638)

Behind the scenes & MISC

- Using Azure Devops for testing. We made this decision to keep all the testing in one place for Linux, Mac OS, and Windows.
- Added Mac OS CI testing. Azure made this easy.
- Added a development docs website at https://dev.pyvista.org/. Anything merged with Master will show up here. Docs are only updated to https://docs.pyvista.org when a release is created
- Printed directions for movie example.
- Using `meshio>=4.0.0`

Contributors

Thanks to all those who contributed PRs for this release. Ping me if I missed you, because there was a lot this time around.

- adeak
- keurfonluu
- GuillaumeFavelier
- banesullivan
- RubendeBruin
- imsodin
- tkoyama010

New Contributors

Be sure to welcome and thank these folks for their contributions!

- tkoyama010
- MatthewFlamm
- math-artist

New Features

- New experimental plotter class with [`itkwidgets`](https://github.com/InsightSoftwareConsortium/itkwidgets) for interactive Jupyter Notebook plotting (see #389)
- Add file drag ’n’ drop to `BackgroundPlotter` (see 567)
- New `extract_subset` filter for `UniformGrid` (see 569)
- New GPU details in `Report` (see 512)
- New text slider widget (see 518)
- Enable depth peeling by default (see 529)
- New sample over line filter (see 525)
- New checkbox button widget (see 528)
- Refactor axes widget to be on any renderer in subplots (see 536 and 565)
- Refactor `BasePlotter`’s wrapping of `Renderer` to improve interface and docs (see 552)
- Improve `meshio` support and enable `meshio` objects to be passed to PyVista (see 559 and 568)
- Improve repr for camera position (see 537)
- Updates to visible cell selecting (see 571)
- Add original point IDs to `geodesic` filter (see 544)

Squashed Bugs

- Fix slider widget coordinate parameters (see 511)
- Fix mesh name issues that prevented plotting in `for`-loops (see 521)
- Fix issues when instantiating `RectilinearGrid` (see 530)
- Fix brown plotting color (see 538)
- Fixes to `CylinderStructured` (see 561 and 577)
- Fix issues managing active scalars in widget plotting routines (see 533)
- Fix issues with getitem on `MultiBlock` datasets (see 563)
- Fix issue when volume rendering 3D NumPy arrays (see 575)
- Fix `combine` filter for `MultiBlock` datasets (see 535)
- Fixes to `pyvista.voxelize` (see 546)
- Update `copy_meta_from` to deep copy textures (see 564)

New Contributors

Be sure to welcome and thank these folks for their contributions!
- keurfonluu
- truenicoco
- imsodin

High Impact

- Resolved Windows crashes and disappearing plotters (see 502)
- Fully dropped support for Python 2.7 (see 493)
- Depth peeling to properly render translucent geometries (see 450)
- Full support for reading/writing files with `meshio` (see 472 and 495)
- Log scale color mapping (see 499)
- Keyword arguments are now strongly enforced across the API (see 432)
- the IPython tools module has been entirely removed (see 403)


New Features & Improvements

- More camera viewing options: e.g. `Plotter.view_zx`
- Gradient background colors when plotting (see 411)
- Gaussian smoothing filter for `pyvista.UniformGrid` meshes (see 420 and 485 )
- Save graphic method for SVG images (see 331)
- More culling options (see 292)
- Array name auto-completion in IPython when getting array (see 425)
- More keypress events in the plotters (see 434)
- New click position tracking in world coordinates (see 466)
- Enabled use of custom bounds with `texture_map_to_plane` (see 407)
- Document how to instantiate `pyvista.MultiBlock` objects (see 413)
- Control the border of the `backgroundPlotter` (see 416)
- Enable access to various contouring algorithms in the `contour` filter (see 421)
- Various widgets enhancements (see 415) and bug fixes
- Added support for passing a `PolyData` mesh as the box for the `clip_box` filter (see 433)
- PyQt improvements (see 424 and see 498)
- Q-key will not automatically bind to embedded Qt apps (see 508)
- Renderers will automatically update when embedded in Qt apps now (see 509)
- Colormaps can be defined as a list of string colors (see 445)
- Add helper method to see if `PolyData` mesh is made of all triangles (see 446)
- Clamping range added to `glyph` filter (see 451)
- Major naming consistency improvements for `*_scalars` and `*_array` (see 456)
- Use the camera transform matrix when getting/setting the camera position in scaled environments (see 476)
- More indexing options for `MultiBlock` objects (see 459)
- Enable `pyvista.read` to handle lists of file names and return `MultiBlock` object
- `FileNotFoundError` used over `IOError` (see 506)


Squashed Bugs

- Fixed `clim` issues with `Plotter.add_mesh_slice_orthogonal`
- Fixed issue when using `rng` keyword with widget plotting helpers
- Fixed Python 3.8 issues
- Fixed usage of `render_points_as_spheres` with `Plotter.add_point_labels`
- Fixed point labeling issues appearing in front of opaque meshes (see 366)
- Fixed issues when importing broken builds of `panel` (see 440)
- Fixed random behavior of `pyvista.CylinderStructured` (see 442)
- Fixed issues when copying `pyvista.MultiBlock` datasets
- Fixed an issue when parsing VTK errors as Python warnings
- Fixed major issues with volume rendering (see 464 and 497)
- Fixed memory leak from plotter not being cleared (484)
- Fixed issue when saving PLY meshes (see 489)