pcolormesh no longer wraps around

[mathause]

Description

pcolormesh no longer draws the "other half" of gridpoints that have their center at the edge of the maps - see the example and figure. This may very well be an 'indended' consequence of #1646 but I thought I report it anyway.

This used to work in older versions of cartopy/ matplotlib (e.g. cartopy=0.19 and matplotlib=3.4)

Code to reproduce

import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import numpy as np

lon = np.arange(-180, 151, 30)
lat = np.arange(75, -76, -30)

LON, LAT = np.meshgrid(lon, lat)

lon_edges = np.arange(-195, 181, 30)
lat_edges = np.arange(90, -91, -30)

data = np.ones(shape=lat.shape + lon.shape)

f, axs = plt.subplots(1, 2, subplot_kw=dict(projection=ccrs.PlateCarree()))
f.subplots_adjust(wspace=0.05)

# 1 - using edges

ax = axs[0]

ax.pcolormesh(
    lon_edges,
    lat_edges,
    data,
    transform=ccrs.PlateCarree(),
    cmap="Reds",
    ec="0.3",
    lw=0.5,
)
ax.set_title("using edges")

# 2 - using centers

ax = axs[1]

ax.pcolormesh(
    lon,
    lat,
    data,
    transform=ccrs.PlateCarree(),
    cmap="Reds",
    ec="0.3",
    lw=0.5,
)
ax.set_title("using centers")

for ax in axs:

    ax.plot(LON.flatten(), LAT.flatten(), "o", ms=1)
    ax.coastlines()
    ax.set_global()

Full environment definition

Operating system

Linux

Cartopy version

0.20.2

matplotlib.version
3.5.1

conda list

# packages in environment at /home/mathause/.conda/envs/regionmask-docs:
#
# Name                    Version                   Build  Channel
_libgcc_mutex             0.1                 conda_forge    conda-forge
_openmp_mutex             4.5                       1_gnu    conda-forge
affine                    2.3.0                      py_0    conda-forge
aiohttp                   3.8.1           py310h6acc77f_0    conda-forge
aiosignal                 1.2.0              pyhd8ed1ab_0    conda-forge
alabaster                 0.7.12                     py_0    conda-forge
alsa-lib                  1.2.3                h516909a_0    conda-forge
appdirs                   1.4.4              pyh9f0ad1d_0    conda-forge
argon2-cffi               21.3.0             pyhd8ed1ab_0    conda-forge
argon2-cffi-bindings      21.2.0          py310h6acc77f_1    conda-forge
asttokens                 2.0.5              pyhd8ed1ab_0    conda-forge
async-timeout             4.0.2              pyhd8ed1ab_0    conda-forge
attrs                     21.4.0             pyhd8ed1ab_0    conda-forge
babel                     2.9.1              pyh44b312d_0    conda-forge
backcall                  0.2.0              pyh9f0ad1d_0    conda-forge
backports                 1.0                        py_2    conda-forge
backports.functools_lru_cache 1.6.4              pyhd8ed1ab_0    conda-forge
black                     21.12b0            pyhd8ed1ab_0    conda-forge
bleach                    4.1.0              pyhd8ed1ab_0    conda-forge
blosc                     1.21.0               h9c3ff4c_0    conda-forge
bokeh                     2.4.2           py310hff52083_0    conda-forge
boost-cpp                 1.74.0               h359cf19_5    conda-forge
branca                    0.4.2              pyhd8ed1ab_0    conda-forge
brotli                    1.0.9                h7f98852_6    conda-forge
brotli-bin                1.0.9                h7f98852_6    conda-forge
brotlipy                  0.7.0           py310h6acc77f_1003    conda-forge
bzip2                     1.0.8                h7f98852_4    conda-forge
c-ares                    1.18.1               h7f98852_0    conda-forge
ca-certificates           2021.10.8            ha878542_0    conda-forge
cairo                     1.16.0            ha00ac49_1009    conda-forge
cartopy                   0.20.2          py310he9c7799_3    conda-forge
certifi                   2021.10.8       py310hff52083_1    conda-forge
cffi                      1.15.0          py310h0fdd8cc_0    conda-forge
cfitsio                   4.0.0                h9a35b8e_0    conda-forge
cftime                    1.5.2           py310h96516ba_0    conda-forge
charset-normalizer        2.0.10             pyhd8ed1ab_0    conda-forge
click                     8.0.3           py310hff52083_1    conda-forge
click-plugins             1.1.1                      py_0    conda-forge
cligj                     0.7.2              pyhd8ed1ab_1    conda-forge
cloudpickle               2.0.0              pyhd8ed1ab_0    conda-forge
colorama                  0.4.4              pyh9f0ad1d_0    conda-forge
cryptography              36.0.1          py310h685ca39_0    conda-forge
curl                      7.81.0               h2574ce0_0    conda-forge
cycler                    0.11.0             pyhd8ed1ab_0    conda-forge
cytoolz                   0.11.2          py310h6acc77f_1    conda-forge
dask                      2022.1.0           pyhd8ed1ab_0    conda-forge
dask-core                 2022.1.0           pyhd8ed1ab_0    conda-forge
dataclasses               0.8                pyhc8e2a94_3    conda-forge
dbus                      1.13.6               h5008d03_3    conda-forge
debugpy                   1.5.1           py310h122e73d_0    conda-forge
decorator                 5.1.1              pyhd8ed1ab_0    conda-forge
defusedxml                0.7.1              pyhd8ed1ab_0    conda-forge
distributed               2022.1.0        py310hff52083_0    conda-forge
docutils                  0.17.1          py310hff52083_1    conda-forge
entrypoints               0.3             pyhd8ed1ab_1003    conda-forge
executing                 0.8.2              pyhd8ed1ab_0    conda-forge
expat                     2.4.3                h9c3ff4c_0    conda-forge
fiona                     1.8.20          py310hfb73927_4    conda-forge
flit-core                 3.6.0              pyhd8ed1ab_0    conda-forge
folium                    0.12.1.post1       pyhd8ed1ab_1    conda-forge
font-ttf-dejavu-sans-mono 2.37                 hab24e00_0    conda-forge
font-ttf-inconsolata      3.000                h77eed37_0    conda-forge
font-ttf-source-code-pro  2.038                h77eed37_0    conda-forge
font-ttf-ubuntu           0.83                 hab24e00_0    conda-forge
fontconfig                2.13.1            hba837de_1005    conda-forge
fonts-conda-ecosystem     1                             0    conda-forge
fonts-conda-forge         1                             0    conda-forge
fonttools                 4.28.5          py310h6acc77f_0    conda-forge
freetype                  2.10.4               h0708190_1    conda-forge
freexl                    1.0.6                h7f98852_0    conda-forge
frozenlist                1.2.0           py310h6acc77f_1    conda-forge
fsspec                    2022.1.0                 pypi_0    pypi
gdal                      3.4.1                    pypi_0    pypi
geopandas                 0.10.2             pyhd8ed1ab_1    conda-forge
geopandas-base            0.10.2             pyha770c72_1    conda-forge
geos                      3.10.2               h9c3ff4c_0    conda-forge
geotiff                   1.7.0                h6593c0a_6    conda-forge
gettext                   0.19.8.1          h73d1719_1008    conda-forge
giflib                    5.2.1                h36c2ea0_2    conda-forge
gst-plugins-base          1.18.5               hf529b03_3    conda-forge
gstreamer                 1.18.5               h9f60fe5_3    conda-forge
hdf4                      4.2.15               h10796ff_3    conda-forge
hdf5                      1.12.1          nompi_h2750804_103    conda-forge
heapdict                  1.0.1                      py_0    conda-forge
icu                       69.1                 h9c3ff4c_0    conda-forge
idna                      3.3                pyhd8ed1ab_0    conda-forge
imagesize                 1.3.0              pyhd8ed1ab_0    conda-forge
importlib-metadata        4.10.1          py310hff52083_0    conda-forge
importlib_metadata        4.10.1               hd8ed1ab_0    conda-forge
importlib_resources       5.4.0              pyhd8ed1ab_0    conda-forge
intake                    0.6.5              pyhd8ed1ab_0    conda-forge
intake-geopandas          0.4.0                    pypi_0    pypi
ipykernel                 6.7.0           py310hfdc917e_0    conda-forge
ipython                   8.0.1           py310hff52083_0    conda-forge
ipython_genutils          0.2.0                      py_1    conda-forge
ipywidgets                7.6.5              pyhd8ed1ab_0    conda-forge
jbig                      2.1               h7f98852_2003    conda-forge
jedi                      0.18.1          py310hff52083_0    conda-forge
jinja2                    3.0.3              pyhd8ed1ab_0    conda-forge
joblib                    1.1.0              pyhd8ed1ab_0    conda-forge
jpeg                      9d                   h36c2ea0_0    conda-forge
json-c                    0.15                 h98cffda_0    conda-forge
jsonschema                4.4.0              pyhd8ed1ab_0    conda-forge
jupyter                   1.0.0           py310hff52083_7    conda-forge
jupyter_client            7.1.2              pyhd8ed1ab_0    conda-forge
jupyter_console           6.4.0              pyhd8ed1ab_0    conda-forge
jupyter_core              4.9.1           py310hff52083_1    conda-forge
jupyterlab_pygments       0.1.2              pyh9f0ad1d_0    conda-forge
jupyterlab_widgets        1.0.2              pyhd8ed1ab_0    conda-forge
kealib                    1.4.14               h87e4c3c_3    conda-forge
kiwisolver                1.3.2           py310h91b1402_1    conda-forge
krb5                      1.19.2               hcc1bbae_3    conda-forge
lcms2                     2.12                 hddcbb42_0    conda-forge
ld_impl_linux-64          2.36.1               hea4e1c9_2    conda-forge
lerc                      3.0                  h9c3ff4c_0    conda-forge
libblas                   3.9.0           13_linux64_openblas    conda-forge
libbrotlicommon           1.0.9                h7f98852_6    conda-forge
libbrotlidec              1.0.9                h7f98852_6    conda-forge
libbrotlienc              1.0.9                h7f98852_6    conda-forge
libcblas                  3.9.0           13_linux64_openblas    conda-forge
libclang                  13.0.0          default_hc23dcda_0    conda-forge
libcurl                   7.81.0               h2574ce0_0    conda-forge
libdap4                   3.20.6               hd7c4107_2    conda-forge
libdeflate                1.8                  h7f98852_0    conda-forge
libedit                   3.1.20191231         he28a2e2_2    conda-forge
libev                     4.33                 h516909a_1    conda-forge
libevent                  2.1.10               h9b69904_4    conda-forge
libffi                    3.4.2                h7f98852_5    conda-forge
libgcc-ng                 11.2.0              h1d223b6_11    conda-forge
libgdal                   3.4.1                h7b6f8d3_2    conda-forge
libgfortran-ng            11.2.0              h69a702a_11    conda-forge
libgfortran5              11.2.0              h5c6108e_11    conda-forge
libglib                   2.70.2               h174f98d_1    conda-forge
libgomp                   11.2.0              h1d223b6_11    conda-forge
libiconv                  1.16                 h516909a_0    conda-forge
libkml                    1.3.0             h238a007_1014    conda-forge
liblapack                 3.9.0           13_linux64_openblas    conda-forge
libllvm13                 13.0.0               hf817b99_0    conda-forge
libnetcdf                 4.8.1           nompi_hb3fd0d9_101    conda-forge
libnghttp2                1.43.0               h812cca2_1    conda-forge
libnsl                    2.0.0                h7f98852_0    conda-forge
libogg                    1.3.4                h7f98852_1    conda-forge
libopenblas               0.3.18          pthreads_h8fe5266_0    conda-forge
libopus                   1.3.1                h7f98852_1    conda-forge
libpng                    1.6.37               h21135ba_2    conda-forge
libpq                     14.1                 hd57d9b9_1    conda-forge
librttopo                 1.1.0                hf69c175_9    conda-forge
libsodium                 1.0.18               h36c2ea0_1    conda-forge
libspatialindex           1.9.3                h9c3ff4c_4    conda-forge
libspatialite             5.0.1               h0e567f8_14    conda-forge
libssh2                   1.10.0               ha56f1ee_2    conda-forge
libstdcxx-ng              11.2.0              he4da1e4_11    conda-forge
libtiff                   4.3.0                h6f004c6_2    conda-forge
libuuid                   2.32.1            h7f98852_1000    conda-forge
libvorbis                 1.3.7                h9c3ff4c_0    conda-forge
libwebp-base              1.2.2                h7f98852_1    conda-forge
libxcb                    1.13              h7f98852_1004    conda-forge
libxkbcommon              1.0.3                he3ba5ed_0    conda-forge
libxml2                   2.9.12               h885dcf4_1    conda-forge
libzip                    1.8.0                h4de3113_1    conda-forge
libzlib                   1.2.11            h36c2ea0_1013    conda-forge
locket                    0.2.0                      py_2    conda-forge
lz4-c                     1.9.3                h9c3ff4c_1    conda-forge
mapclassify               2.4.3              pyhd8ed1ab_0    conda-forge
markupsafe                2.0.1           py310h6acc77f_1    conda-forge
matplotlib-base           3.5.1           py310h23f4a51_0    conda-forge
matplotlib-inline         0.1.3              pyhd8ed1ab_0    conda-forge
mistune                   0.8.4           py310h6acc77f_1005    conda-forge
msgpack-python            1.0.3           py310h91b1402_0    conda-forge
multidict                 6.0.1           py310h6acc77f_0    conda-forge
munch                     2.5.0                      py_0    conda-forge
munkres                   1.1.4              pyh9f0ad1d_0    conda-forge
mypy_extensions           0.4.3           py310hff52083_4    conda-forge
mysql-common              8.0.28               ha770c72_0    conda-forge
mysql-libs                8.0.28               hfa10184_0    conda-forge
nbclient                  0.5.10             pyhd8ed1ab_1    conda-forge
nbconvert                 6.4.0           py310hff52083_0    conda-forge
nbformat                  5.1.3              pyhd8ed1ab_0    conda-forge
ncurses                   6.2                  h58526e2_4    conda-forge
nest-asyncio              1.5.4              pyhd8ed1ab_0    conda-forge
netcdf4                   1.5.8           nompi_py310hd7ca5b8_101    conda-forge
networkx                  2.6.3              pyhd8ed1ab_1    conda-forge
notebook                  6.4.7              pyha770c72_0    conda-forge
nspr                      4.32                 h9c3ff4c_1    conda-forge
nss                       3.74                 hb5efdd6_0    conda-forge
numpy                     1.22.1          py310h454958d_0    conda-forge
numpydoc                  1.1.0                      py_1    conda-forge
olefile                   0.46               pyh9f0ad1d_1    conda-forge
openjpeg                  2.4.0                hb52868f_1    conda-forge
openssl                   1.1.1l               h7f98852_0    conda-forge
packaging                 21.3               pyhd8ed1ab_0    conda-forge
pandas                    1.4.0           py310hb5077e9_0    conda-forge
pandoc                    2.17.0.1             h7f98852_0    conda-forge
pandocfilters             1.5.0              pyhd8ed1ab_0    conda-forge
parso                     0.8.3              pyhd8ed1ab_0    conda-forge
partd                     1.2.0              pyhd8ed1ab_0    conda-forge
pathspec                  0.9.0              pyhd8ed1ab_0    conda-forge
pcre                      8.45                 h9c3ff4c_0    conda-forge
pexpect                   4.8.0              pyh9f0ad1d_2    conda-forge
pickleshare               0.7.5                   py_1003    conda-forge
pillow                    8.4.0           py310h07f4688_0    conda-forge
pip                       21.3.1             pyhd8ed1ab_0    conda-forge
pixman                    0.40.0               h36c2ea0_0    conda-forge
platformdirs              2.3.0              pyhd8ed1ab_0    conda-forge
pooch                     1.6.0              pyhd8ed1ab_0    conda-forge
poppler                   21.11.0              ha39eefc_0    conda-forge
poppler-data              0.4.11               hd8ed1ab_0    conda-forge
postgresql                14.1                 h2510834_1    conda-forge
proj                      8.2.1                h277dcde_0    conda-forge
prometheus_client         0.12.0             pyhd8ed1ab_0    conda-forge
prompt-toolkit            3.0.24             pyha770c72_0    conda-forge
prompt_toolkit            3.0.24               hd8ed1ab_0    conda-forge
psutil                    5.9.0           py310h6acc77f_0    conda-forge
pthread-stubs             0.4               h36c2ea0_1001    conda-forge
ptyprocess                0.7.0              pyhd3deb0d_0    conda-forge
pure_eval                 0.2.2              pyhd8ed1ab_0    conda-forge
pycparser                 2.21               pyhd8ed1ab_0    conda-forge
pygeos                    0.12.0          py310h1b8dd88_1    conda-forge
pygments                  2.11.2             pyhd8ed1ab_0    conda-forge
pyopenssl                 21.0.0             pyhd8ed1ab_0    conda-forge
pyparsing                 3.0.7              pyhd8ed1ab_0    conda-forge
pyproj                    3.3.0           py310h9e0d750_1    conda-forge
pyqt                      5.12.3          py310hff52083_8    conda-forge
pyqt-impl                 5.12.3          py310h1f8e252_8    conda-forge
pyqt5-sip                 4.19.18         py310h122e73d_8    conda-forge
pyqtchart                 5.12            py310hfcd6d55_8    conda-forge
pyqtwebengine             5.12.1          py310hfcd6d55_8    conda-forge
pyrsistent                0.18.1          py310h6acc77f_0    conda-forge
pyshp                     2.1.3              pyh44b312d_0    conda-forge
pysocks                   1.7.1           py310hff52083_4    conda-forge
python                    3.10.2          h62f1059_0_cpython    conda-forge
python-dateutil           2.8.2              pyhd8ed1ab_0    conda-forge
python_abi                3.10                    2_cp310    conda-forge
pytz                      2021.3             pyhd8ed1ab_0    conda-forge
pyyaml                    6.0             py310h6acc77f_3    conda-forge
pyzmq                     22.3.0          py310h675a958_1    conda-forge
qt                        5.12.9               ha98a1a1_5    conda-forge
qtconsole                 5.2.2              pyhd8ed1ab_1    conda-forge
qtconsole-base            5.2.2              pyhd8ed1ab_1    conda-forge
qtpy                      2.0.0              pyhd8ed1ab_0    conda-forge
rasterio                  1.2.10          py310h5e0f756_4    conda-forge
readline                  8.1                  h46c0cb4_0    conda-forge
regionmask                0.8.0.post1.dev24+g17855bf.d20220125           dev_0    <develop>
requests                  2.27.1             pyhd8ed1ab_0    conda-forge
rtree                     0.9.7           py310hbdcdc62_3    conda-forge
scikit-learn              1.0.2           py310h1246948_0    conda-forge
scipy                     1.7.3           py310hea5193d_0    conda-forge
send2trash                1.8.0              pyhd8ed1ab_0    conda-forge
setuptools                59.8.0          py310hff52083_0    conda-forge
shapely                   1.8.0           py310h1b8dd88_5    conda-forge
six                       1.16.0             pyh6c4a22f_0    conda-forge
snowballstemmer           2.2.0              pyhd8ed1ab_0    conda-forge
snuggs                    1.4.7                      py_0    conda-forge
sortedcontainers          2.4.0              pyhd8ed1ab_0    conda-forge
sphinx                    4.4.0              pyh6c4a22f_1    conda-forge
sphinx_rtd_theme          1.0.0              pyhd8ed1ab_0    conda-forge
sphinxcontrib-applehelp   1.0.2                      py_0    conda-forge
sphinxcontrib-devhelp     1.0.2                      py_0    conda-forge
sphinxcontrib-htmlhelp    2.0.0              pyhd8ed1ab_0    conda-forge
sphinxcontrib-jsmath      1.0.1                      py_0    conda-forge
sphinxcontrib-qthelp      1.0.3                      py_0    conda-forge
sphinxcontrib-serializinghtml 1.1.5              pyhd8ed1ab_1    conda-forge
sqlite                    3.37.0               h9cd32fc_0    conda-forge
stack_data                0.1.4              pyhd8ed1ab_0    conda-forge
tblib                     1.7.0              pyhd8ed1ab_0    conda-forge
terminado                 0.12.1          py310hff52083_1    conda-forge
testpath                  0.5.0              pyhd8ed1ab_0    conda-forge
threadpoolctl             3.0.0              pyh8a188c0_0    conda-forge
tiledb                    2.6.1                h2038895_0    conda-forge
tk                        8.6.11               h27826a3_1    conda-forge
tomli                     1.2.2              pyhd8ed1ab_0    conda-forge
toolz                     0.11.2             pyhd8ed1ab_0    conda-forge
tornado                   6.1             py310h6acc77f_2    conda-forge
traitlets                 5.1.1              pyhd8ed1ab_0    conda-forge
typed-ast                 1.5.1           py310h6acc77f_0    conda-forge
typing-extensions         4.0.1                hd8ed1ab_0    conda-forge
typing_extensions         4.0.1              pyha770c72_0    conda-forge
tzcode                    2021e                h7f98852_0    conda-forge
tzdata                    2021e                he74cb21_0    conda-forge
urllib3                   1.26.8             pyhd8ed1ab_1    conda-forge
wcwidth                   0.2.5              pyh9f0ad1d_2    conda-forge
webencodings              0.5.1                      py_1    conda-forge
wheel                     0.37.1             pyhd8ed1ab_0    conda-forge
widgetsnbextension        3.5.2           py310hff52083_1    conda-forge
xarray                    0.20.2             pyhd8ed1ab_0    conda-forge
xerces-c                  3.2.3                h8ce2273_4    conda-forge
xorg-kbproto              1.0.7             h7f98852_1002    conda-forge
xorg-libice               1.0.10               h7f98852_0    conda-forge
xorg-libsm                1.2.3             hd9c2040_1000    conda-forge
xorg-libx11               1.7.2                h7f98852_0    conda-forge
xorg-libxau               1.0.9                h7f98852_0    conda-forge
xorg-libxdmcp             1.1.3                h7f98852_0    conda-forge
xorg-libxext              1.3.4                h7f98852_1    conda-forge
xorg-libxrender           0.9.10            h7f98852_1003    conda-forge
xorg-renderproto          0.11.1            h7f98852_1002    conda-forge
xorg-xextproto            7.3.0             h7f98852_1002    conda-forge
xorg-xproto               7.0.31            h7f98852_1007    conda-forge
xyzservices               2022.1.1           pyhd8ed1ab_0    conda-forge
xz                        5.2.5                h516909a_1    conda-forge
yaml                      0.2.5                h7f98852_2    conda-forge
yarl                      1.7.2           py310h6acc77f_1    conda-forge
zeromq                    4.3.4                h9c3ff4c_1    conda-forge
zict                      2.0.0                      py_0    conda-forge
zipp                      3.7.0              pyhd8ed1ab_0    conda-forge
zlib                      1.2.11            h36c2ea0_1013    conda-forge
zstd                      1.5.2                ha95c52a_0    conda-forge

pip list

[mathause]

Interestingly if you do lon + 30 or lon_edge + 30 it seems to work.

[greglucas]

Thanks for the analysis @mathause! This appears to be due to the pyproj upgrade actually and wrapping the coordinates over 180, but not less than -180. I put a fix in for that in #1998

[mathause]

Thank you for the quick fix! Feels like I keep throwing "edge" cases at you.

This appears to be due to the pyproj upgrade actually and wrapping the coordinates over 180, but not less than -180.

This also gives me an idea how to create a work around for now (use 0..360 instead of -180..180).

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(Definitely not the same problem but if you try different crs with the above code (e.g.EckertIII or Robinson) you will also see some issues with the border cell)

import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import numpy as np

lon = np.arange(-180, 151, 30)
lat = np.arange(75, -76, -30)

data = np.ones(shape=lat.shape + lon.shape)

f, ax = plt.subplots(1, 1, subplot_kw=dict(projection=ccrs.EckertIII()))

ax.pcolormesh(
    lon_edges,
    lat_edges,
    data,
    transform=ccrs.PlateCarree(),
    cmap="Reds",
    ec="0.3",
    lw=0.5,
)

ax.coastlines()
ax.set_global()

[greglucas]

I think that is to be expected here and I'm not sure how easy it would be to fix. I think what is happening is that the pcolormesh is QuadMesh, so everything is drawn in straight lines. So, your cells from 60-90 are all vertical. Except for the "wrapped" cells, which get drawn as a PolyCollection, and thus there is interpolation along the path that happens. This interpolation causes an extra point in the middle of the path, which is no longer a straight line. Thus, when the QuadMesh straight edges meet up with the PolyCollection interpolated edges, there can be a disconnect between the two.

[mathause]

Thanks, makes sense. Just something I saw trying out different projections.