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eric-wiesereric-wieser
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MAINT/BUG: Simplify logic in plot_surface
Previously: * "cell" perimeters were clumsily calculated with duplicates, which were then (badly) removed at runtime. As a result, every quadrilateral was drawn with 5 vertices! * code to calculate normals was spread into multiple places * average z was calculated even if not used * normals were sometimes not calculated even when needed * repeated conversion between stride and count was done This will affect shading of plots very slightly, hence the image tests changing in this commit. Adds a `cbook._array_perimeter` function for use here.
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Lines changed: 12158 additions & 15159 deletions

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‎lib/matplotlib/cbook/__init__.py‎

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Original file line numberDiff line numberDiff line change
@@ -2011,6 +2011,45 @@ def method(self, *args, **kwargs):
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return cls
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def _array_perimeter(arr):
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"""
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Get the elements on the perimeter of ``arr``,
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Parameters
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----------
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arr : ndarray, shape (M, N)
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The input array
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Returns
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-------
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perimeter : ndarray, shape (2*(M - 1) + 2*(N - 1),)
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The elements on the perimeter of the array::
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[arr[0,0] ... arr[0,-1] ... arr[-1, -1] ... arr[-1,0] ...]
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Examples
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--------
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>>> i, j = np.ogrid[:3,:4]
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>>> a = i*10 + j
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>>> a
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array([[ 0, 1, 2, 3],
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[10, 11, 12, 13],
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[20, 21, 22, 23]])
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>>> _array_perimeter(arr)
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array([ 0, 1, 2, 3, 13, 23, 22, 21, 20, 10])
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"""
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# note we use Python's half-open ranges to avoid repeating
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# the corners
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forward = np.s_[0:-1] # [0 ... -1)
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backward = np.s_[-1:0:-1] # [-1 ... 0)
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return np.concatenate((
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arr[0, forward],
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arr[forward, -1],
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arr[-1, backward],
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arr[backward, 0],
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))
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@contextlib.contextmanager
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def _setattr_cm(obj, **kwargs):
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"""Temporarily set some attributes; restore original state at context exit.

‎lib/mpl_toolkits/mplot3d/axes3d.py‎

Lines changed: 36 additions & 48 deletions
Original file line numberDiff line numberDiff line change
@@ -1683,72 +1683,60 @@ def plot_surface(self, X, Y, Z, *args, **kwargs):
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if shade and cmap is not None and fcolors is not None:
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fcolors = self._shade_colors_lightsource(Z, cmap, lightsource)
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# evenly spaced, and including both endpoints
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row_inds = list(range(0, rows-1, rstride)) + [rows-1]
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col_inds = list(range(0, cols-1, cstride)) + [cols-1]
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colset = [] # the sampled facecolor
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polys = []
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# Only need these vectors to shade if there is no cmap
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if cmap is None and shade :
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totpts = int(np.ceil((rows - 1) / rstride) *
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np.ceil((cols - 1) / cstride))
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v1 = np.empty((totpts, 3))
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v2 = np.empty((totpts, 3))
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# This indexes the vertex points
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which_pt = 0
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#colset contains the data for coloring: either average z or the facecolor
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colset = []
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for rs in range(0, rows-1, rstride):
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for cs in range(0, cols-1, cstride):
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ps = []
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for a in (X, Y, Z):
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ztop = a[rs,cs:min(cols, cs+cstride+1)]
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zleft = a[rs+1:min(rows, rs+rstride+1),
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min(cols-1, cs+cstride)]
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zbase = a[min(rows-1, rs+rstride), cs:min(cols, cs+cstride+1):][::-1]
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zright = a[rs:min(rows-1, rs+rstride):, cs][::-1]
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z = np.concatenate((ztop, zleft, zbase, zright))
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ps.append(z)
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# The construction leaves the array with duplicate points, which
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# are removed here.
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ps = list(zip(*ps))
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lastp = np.array([])
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ps2 = [ps[0]] + [ps[i] for i in range(1, len(ps)) if ps[i] != ps[i-1]]
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avgzsum = sum(p[2] for p in ps2)
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polys.append(ps2)
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for rs, rs_next in zip(row_inds[:-1], row_inds[1:]):
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for cs, cs_next in zip(col_inds[:-1], col_inds[1:]):
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ps = [
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# +1 ensures we share edges between polygons
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cbook._array_perimeter(a[rs:rs_next+1, cs:cs_next+1])
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for a in (X, Y, Z)
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]
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# ps = np.stack(ps, axis=-1)
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ps = np.array(ps).T
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polys.append(ps)
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if fcolors is not None:
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colset.append(fcolors[rs][cs])
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else:
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colset.append(avgzsum / len(ps2))
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# Only need vectors to shade if no cmap
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if cmap is None and shade:
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i1, i2, i3 = 0, int(len(ps2)/3), int(2*len(ps2)/3)
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v1[which_pt] = np.array(ps2[i1]) - np.array(ps2[i2])
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v2[which_pt] = np.array(ps2[i2]) - np.array(ps2[i3])
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which_pt += 1
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if cmap is None and shade:
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normals = np.cross(v1, v2)
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else :
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normals = []
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def get_normals(polygons):
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"""
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Takes a list of polygons and return an array of their normals
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"""
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v1 = np.empty((len(polygons), 3))
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v2 = np.empty((len(polygons), 3))
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for poly_i, ps in enumerate(polygons):
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# pick three points around the polygon at which to find the normal
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# doesn't vectorize because polygons is jagged
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i1, i2, i3 = 0, len(ps)//3, 2*len(ps)//3
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v1[poly_i, :] = ps[i1, :] - ps[i2, :]
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v2[poly_i, :] = ps[i2, :] - ps[i3, :]
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return np.cross(v1, v2)
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# note that the striding causes some polygons to have more coordinates
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# than others
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polyc = art3d.Poly3DCollection(polys, *args, **kwargs)
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if fcolors is not None:
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if shade:
1739-
colset = self._shade_colors(colset, normals)
1726+
colset = self._shade_colors(colset, get_normals(polys))
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polyc.set_facecolors(colset)
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polyc.set_edgecolors(colset)
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elif cmap:
1743-
colset = np.array(colset)
1744-
polyc.set_array(colset)
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# doesn't vectorize because polys is jagged
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avg_z = np.array([ps[:,2].mean() for ps in polys])
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polyc.set_array(avg_z)
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if vmin is not None or vmax is not None:
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polyc.set_clim(vmin, vmax)
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if norm is not None:
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polyc.set_norm(norm)
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else:
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if shade:
1751-
colset = self._shade_colors(color, normals)
1739+
colset = self._shade_colors(color, get_normals(polys))
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else:
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colset = color
17541742
polyc.set_facecolors(colset)

‎lib/mpl_toolkits/tests/baseline_images/test_mplot3d/mixedsubplot.pdf‎

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‎lib/mpl_toolkits/tests/baseline_images/test_mplot3d/mixedsubplot.png‎

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