"""
.. _anti_aliasing_example:

Anti-Aliasing
~~~~~~~~~~~~~
Demonstrate anti-aliasing within PyVista.

PyVista supports three types of anti-aliasing:

* SSAA - Super-Sample Anti-Aliasing
* MSAA - Multi-Sample Anti-Aliasing
* FXAA - Fast Approximate Anti-Aliasing

By default, MSAA anti-aliasing is enabled using 8 samples. This is the default
for VTK.

.. code-block:: python

   >>> import pyvista as pv
   >>> pv.global_theme.multi_samples
   8

You can enable additional line smoothing by enabling SSAA or FXAA

**Which anti-aliasing technique should you use?**

Normally, the default MSAA anti-aliasing should be sufficient as it strikes a
balance between efficiency and quality. If you desire additional smoothing, you
can either increase the number of ``multi_samples`` or use SSAA. Low-end PCs
should consider FXAA.


"""

import pyvista as pv

mesh = pv.Icosphere()

# %%
# No Anti-Aliasing
# ~~~~~~~~~~~~~~~~
# First, let's show a plot without any anti-aliasing
# using :func:`~pyvista.Plotter.disable_anti_aliasing`.
pl = pv.Plotter()
pl.add_mesh(mesh, style='wireframe', color='k', line_width=2)
pl.disable_anti_aliasing()
pl.camera.zoom(1.5)
pl.show()


# %%
# Default: Multi-Sample Anti-Aliasing (MSAA)
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Next, let's show the default anti-aliasing configuration. By default, PyVista
# uses 8 samples of MSAA.
#
# MSAA, or Multi-Sample Anti-Aliasing is an optimization of SSAA that reduces
# the amount of pixel shader evaluations that need to be computed by focusing
# on overlapping regions of the scene. The result is anti-aliasing along edges
# that is on par with SSAA and less anti-aliasing along surfaces as these make
# up the bulk of SSAA computations. MSAA is substantially less computationally
# expensive than SSAA and results in comparable image quality.

pl = pv.Plotter()
pl.add_mesh(mesh, style='wireframe', color='k', line_width=2)
pl.camera.zoom(1.5)
pl.show()


# %%
# You can increase the smoothing by increasing multi_samples
# using :func:`~pyvista.Plotter.enable_anti_aliasing`.

pl = pv.Plotter()
pl.add_mesh(mesh, style='wireframe', color='k', line_width=2)
pl.enable_anti_aliasing('msaa', multi_samples=16)
pl.camera.zoom(1.5)
pl.show()


# %%
# Fast Approximate Anti-Aliasing (FXAA)
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# FXAA is the most performant of all three anti-aliasing techniques. This is
# because, in terms of hardware or GPU, FXAA is not that demanding. It directly
# smooths the 2D image and this reduces the strain on the GPU, making it best
# for low-end PCs.
#
# Because FXAA only operates on the rendered image, FXAA may result in
# smoothing out parts of the visual overlay that are usually kept sharp for
# reasons of clarity as well as smoothing out textures. In general, FXAA is
# inferior to MSAA and SSAA.
#
# Note how the line width has been adjusted for consistency.

pl = pv.Plotter()
pl.add_mesh(mesh, style='wireframe', color='k', line_width=1.5)
pl.camera.zoom(1.5)
pl.enable_anti_aliasing('fxaa')
pl.show()


# %%
# Super-Sample Anti-Aliasing (SSAA)
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# SSAA, or Super-Sample Anti-Aliasing is a brute force method of
# anti-aliasing. It results in the best image quality but comes at a tremendous
# resource cost. SSAA works by rendering the scene at a higher resolution. The
# final image is produced by downsampling the massive source image using an
# averaging filter. This acts as a low pass filter which removes the high
# frequency components that would cause jaggedness.
#
# Note how the line width has been adjusted for consistency.

pl = pv.Plotter()
pl.add_mesh(mesh, style='wireframe', color='k', line_width=4)
pl.camera.zoom(1.5)
pl.enable_anti_aliasing('ssaa')
pl.show()


# %%
# Compare render time
# ~~~~~~~~~~~~~~~~~~~
# You can compare the time to render for each one of the anti-aliasing
# approaches with:
#
# .. code-block:: python
#
#     n_render = 100
#     for anti_aliasing in [False, 'fxaa', 'msaa', 'ssaa']:
#
#         pl = pv.Plotter(off_screen=True)
#         pl.add_mesh(mesh, style='wireframe', color='k', line_width=4)
#         pl.camera.zoom(1.5)
#         if anti_aliasing:
#             pl.enable_anti_aliasing(anti_aliasing)
#         else:
#             pl.disable_anti_aliasing()
#         pl.show(auto_close=False)
#         tstart = time.time()
#         # repeately trigger a render via saving a screenshot
#         for __ in range(n_render):
#             pl.screenshot('tmp.png')
#         telap = (time.time() - tstart)/n_render
#
#         print(f'Render time for {str(anti_aliasing):6}: {telap*1000:.3f} ms')
#
# Here are the timings from an NVIDIA Quadro P2000 and a Intel(R) Xeon(R)
# E-2288G CPU @ 3.70GHz:
#
# .. code-block:: text
#
#     Render time for False : 37.045 ms
#     Render time for fxaa  : 40.458 ms
#     Render time for msaa  : 42.566 ms
#     Render time for ssaa  : 51.450 ms
#

# %%
# .. tags:: plot
