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FIX: make sure scalarmappable updates are handled correctly in 3D #18929

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merged 4 commits into from
Nov 11, 2020
Merged

FIX: make sure scalarmappable updates are handled correctly in 3D #18929

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4ceec69
FIX: make sure scalarmappable updates are handled correctly in 3D
tacaswell Nov 10, 2020
3b4b88e
MNT: standardize pluralization of private names in 3D Collections
tacaswell Nov 10, 2020
d58647b
DOC: fix formatting and typos
tacaswell Nov 11, 2020
2bbe60a
STY: fix line length
tacaswell Nov 11, 2020
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105 changes: 90 additions & 15 deletions lib/mpl_toolkits/mplot3d/art3d.py
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Original file line number Diff line number Diff line change
Expand Up @@ -301,6 +301,8 @@ def do_3d_projection(self, renderer=None):
"""
Project the points according to renderer matrix.
"""
# see _update_scalarmappable docstring for why this must be here
_update_scalarmappable(self)
xyslist = [proj3d.proj_trans_points(points, self.axes.M)
for points in self._segments3d]
segments_2d = [np.column_stack([xs, ys]) for xs, ys, zs in xyslist]
Expand Down Expand Up @@ -486,6 +488,8 @@ def set_3d_properties(self, zs, zdir):

@cbook._delete_parameter('3.4', 'renderer')
def do_3d_projection(self, renderer=None):
# see _update_scalarmappable docstring for why this must be here
_update_scalarmappable(self)
xs, ys, zs = self._offsets3d
vxs, vys, vzs, vis = proj3d.proj_transform_clip(xs, ys, zs,
self.axes.M)
Expand Down Expand Up @@ -592,6 +596,8 @@ def set_linewidth(self, lw):

@cbook._delete_parameter('3.4', 'renderer')
def do_3d_projection(self, renderer=None):
# see _update_scalarmappable docstring for why this must be here
_update_scalarmappable(self)
xs, ys, zs = self._offsets3d
vxs, vys, vzs, vis = proj3d.proj_transform_clip(xs, ys, zs,
self.axes.M)
Expand Down Expand Up @@ -635,6 +641,77 @@ def do_3d_projection(self, renderer=None):
return np.min(vzs) if vzs.size else np.nan


def _update_scalarmappable(sm):
"""
Update a 3D ScalarMappable.

With ScalarMappable objects if the data, colormap, or norm are
changed, we need to update the computed colors. This is handled
by the base class method update_scalarmappable. This method works
by, detecting if work needs to be done, and if so stashing it on
the ``self._facecolors`` attribute.

With 3D collections we internally sort the components so that
things that should be "in front" are rendered later to simulate
having a z-buffer (in addition to doing the projections). This is
handled in the ``do_3d_projection`` methods which are called from the
draw method of the 3D Axes. These methods:

- do the projection from 3D -> 2D
- internally sort based on depth
- stash the results of the above in the 2D analogs of state
- return the z-depth of the whole artist

the last step is so that we can, at the Axes level, sort the children by
depth.

The base `draw` method of the 2D artists unconditionally calls
update_scalarmappable and rely on the method's internal caching logic to
lazily evaluate.

These things together mean you can have the sequence of events:

- we create the artist, do the color mapping and stash the results
in a 3D specific state.
- change something about the ScalarMappable that marks it as in
need of an update (`ScalarMappable.changed` and friends).
- We call do_3d_projection and shuffle the stashed colors into the
2D version of face colors
- the draw method calls the update_scalarmappable method which
overwrites our shuffled colors
- we get a render that is wrong
- if we re-render (either with a second save or implicitly via
tight_layout / constrained_layout / bbox_inches='tight' (ex via
inline's defaults)) we again shuffle the 3D colors
- because the CM is not marked as changed update_scalarmappable is
a no-op and we get a correct looking render.

This function is an internal helper to:

- sort out if we need to do the color mapping at all (has data!)
- sort out if update_scalarmappable is going to be a no-op
- copy the data over from the 2D -> 3D version

This must be called first thing in do_3d_projection to make sure that
the correct colors get shuffled.

Parameters
----------
sm : ScalarMappable
The ScalarMappable to update and stash the 3D data from

"""
if sm._A is None:
return
copy_state = sm._update_dict['array']
ret = sm.update_scalarmappable()
if copy_state:
if sm._is_filled:
sm._facecolor3d = sm._facecolors
elif sm._is_stroked:
sm._edgecolor3d = sm._edgecolors


def patch_collection_2d_to_3d(col, zs=0, zdir='z', depthshade=True):
"""
Convert a :class:`~matplotlib.collections.PatchCollection` into a
Expand Down Expand Up @@ -757,8 +834,8 @@ def set_3d_properties(self):
self.update_scalarmappable()
self._sort_zpos = None
self.set_zsort('average')
self._facecolors3d = PolyCollection.get_facecolor(self)
self._edgecolors3d = PolyCollection.get_edgecolor(self)
self._facecolor3d = PolyCollection.get_facecolor(self)
self._edgecolor3d = PolyCollection.get_edgecolor(self)
self._alpha3d = PolyCollection.get_alpha(self)
self.stale = True

Expand All @@ -772,17 +849,15 @@ def do_3d_projection(self, renderer=None):
"""
Perform the 3D projection for this object.
"""
# FIXME: This may no longer be needed?
if self._A is not None:
self.update_scalarmappable()
self._facecolors3d = self._facecolors
# see _update_scalarmappable docstring for why this must be here
_update_scalarmappable(self)

txs, tys, tzs = proj3d._proj_transform_vec(self._vec, self.axes.M)
xyzlist = [(txs[sl], tys[sl], tzs[sl]) for sl in self._segslices]

# This extra fuss is to re-order face / edge colors
cface = self._facecolors3d
cedge = self._edgecolors3d
cface = self._facecolor3d
cedge = self._edgecolor3d
if len(cface) != len(xyzlist):
cface = cface.repeat(len(xyzlist), axis=0)
if len(cedge) != len(xyzlist):
Expand All @@ -807,8 +882,8 @@ def do_3d_projection(self, renderer=None):
else:
PolyCollection.set_verts(self, segments_2d, self._closed)

if len(self._edgecolors3d) != len(cface):
self._edgecolors2d = self._edgecolors3d
if len(self._edgecolor3d) != len(cface):
self._edgecolors2d = self._edgecolor3d

# Return zorder value
if self._sort_zpos is not None:
Expand All @@ -826,24 +901,24 @@ def do_3d_projection(self, renderer=None):
def set_facecolor(self, colors):
# docstring inherited
super().set_facecolor(colors)
self._facecolors3d = PolyCollection.get_facecolor(self)
self._facecolor3d = PolyCollection.get_facecolor(self)

def set_edgecolor(self, colors):
# docstring inherited
super().set_edgecolor(colors)
self._edgecolors3d = PolyCollection.get_edgecolor(self)
self._edgecolor3d = PolyCollection.get_edgecolor(self)

def set_alpha(self, alpha):
# docstring inherited
artist.Artist.set_alpha(self, alpha)
try:
self._facecolors3d = mcolors.to_rgba_array(
self._facecolors3d, self._alpha)
self._facecolor3d = mcolors.to_rgba_array(
self._facecolor3d, self._alpha)
except (AttributeError, TypeError, IndexError):
pass
try:
self._edgecolors = mcolors.to_rgba_array(
self._edgecolors3d, self._alpha)
self._edgecolor3d, self._alpha)
except (AttributeError, TypeError, IndexError):
pass
self.stale = True
Expand Down
24 changes: 23 additions & 1 deletion lib/mpl_toolkits/tests/test_mplot3d.py
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Original file line number Diff line number Diff line change
Expand Up @@ -108,7 +108,7 @@ def test_bar3d_lightsource():
# the top facecolors compared to the default, and that those colors are
# precisely the colors from the colormap, due to the illumination parallel
# to the z-axis.
np.testing.assert_array_equal(color, collection._facecolors3d[1::6])
np.testing.assert_array_equal(color, collection._facecolor3d[1::6])


@mpl3d_image_comparison(['contour3d.png'])
Expand Down Expand Up @@ -1302,3 +1302,25 @@ def convert_lim(dmin, dmax):
assert x_center != pytest.approx(x_center0)
assert y_center != pytest.approx(y_center0)
assert z_center != pytest.approx(z_center0)


@pytest.mark.style('default')
@check_figures_equal(extensions=["png"])
def test_scalarmap_update(fig_test, fig_ref):

x, y, z = np.array((list(itertools.product(*[np.arange(0, 5, 1),
np.arange(0, 5, 1),
np.arange(0, 5, 1)])))).T
c = x + y

# test
ax_test = fig_test.add_subplot(111, projection='3d')
sc_test = ax_test.scatter(x, y, z, c=c, s=40, cmap='viridis')
# force a draw
fig_test.canvas.draw()
# mark it as "stale"
sc_test.changed()

# ref
ax_ref = fig_ref.add_subplot(111, projection='3d')
sc_ref = ax_ref.scatter(x, y, z, c=c, s=40, cmap='viridis')