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Commitde8739f

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Merge pull request#23914 from oscargus/shaderefactor
Add shading of Poly3DCollection
2 parents185a421 +d9d75f2 commitde8739f

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-124
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3 files changed

+166
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Lines changed: 33 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,33 @@
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``Poly3DCollection`` supports shading
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-------------------------------------
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It is now possible to shade a `.Poly3DCollection`. This is useful if the
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polygons are obtained from e.g. a 3D model.
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..plot::
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:include-source: true
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import numpy as np
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import matplotlib.pyplot as plt
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from mpl_toolkits.mplot3d.art3d import Poly3DCollection
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# Define 3D shape
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block = np.array([
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[[1, 1, 0],
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[1, 0, 0],
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[0, 1, 0]],
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[[1, 1, 0],
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[1, 1, 1],
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[1, 0, 0]],
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[[1, 1, 0],
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[1, 1, 1],
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[0, 1, 0]],
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[[1, 0, 0],
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[1, 1, 1],
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[0, 1, 0]]
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])
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ax = plt.subplot(projection='3d')
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pc = Poly3DCollection(block, facecolors='b', shade=True)
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ax.add_collection(pc)
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plt.show()

‎lib/mpl_toolkits/mplot3d/art3d.py

Lines changed: 113 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -12,7 +12,8 @@
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importnumpyasnp
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frommatplotlibimport (
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artist,cbook,colorsasmcolors,lines,textasmtext,pathasmpath)
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artist,cbook,colorsasmcolors,lines,textasmtext,
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pathasmpath)
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frommatplotlib.collectionsimport (
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LineCollection,PolyCollection,PatchCollection,PathCollection)
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frommatplotlib.colorsimportNormalize
@@ -808,7 +809,8 @@ class Poly3DCollection(PolyCollection):
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triangulation and thus generates consistent surfaces.
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"""
810811

811-
def__init__(self,verts,*args,zsort='average',**kwargs):
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def__init__(self,verts,*args,zsort='average',shade=False,
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lightsource=None,**kwargs):
812814
"""
813815
Parameters
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----------
@@ -819,6 +821,17 @@ def __init__(self, verts, *args, zsort='average', **kwargs):
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zsort : {'average', 'min', 'max'}, default: 'average'
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The calculation method for the z-order.
821823
See `~.Poly3DCollection.set_zsort` for details.
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shade : bool, default: False
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Whether to shade *facecolors* and *edgecolors*. When activating
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*shade*, *facecolors* and/or *edgecolors* must be provided.
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.. versionadded:: 3.7
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lightsource : `~matplotlib.colors.LightSource`
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The lightsource to use when *shade* is True.
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.. versionadded:: 3.7
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822835
*args, **kwargs
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All other parameters are forwarded to `.PolyCollection`.
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@@ -827,6 +840,23 @@ def __init__(self, verts, *args, zsort='average', **kwargs):
827840
Note that this class does a bit of magic with the _facecolors
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and _edgecolors properties.
829842
"""
843+
ifshade:
844+
normals=_generate_normals(verts)
845+
facecolors=kwargs.get('facecolors',None)
846+
iffacecolorsisnotNone:
847+
kwargs['facecolors']=_shade_colors(
848+
facecolors,normals,lightsource
849+
)
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851+
edgecolors=kwargs.get('edgecolors',None)
852+
ifedgecolorsisnotNone:
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kwargs['edgecolors']=_shade_colors(
854+
edgecolors,normals,lightsource
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)
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iffacecolorsisNoneandedgecolorsinNone:
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raiseValueError(
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"You must provide facecolors, edgecolors, or both for "
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"shade to work.")
830860
super().__init__(verts,*args,**kwargs)
831861
ifisinstance(verts,np.ndarray):
832862
ifverts.ndim!=3:
@@ -1086,3 +1116,84 @@ def _zalpha(colors, zs):
10861116
sats=1-norm(zs)*0.7
10871117
rgba=np.broadcast_to(mcolors.to_rgba_array(colors), (len(zs),4))
10881118
returnnp.column_stack([rgba[:, :3],rgba[:,3]*sats])
1119+
1120+
1121+
def_generate_normals(polygons):
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"""
1123+
Compute the normals of a list of polygons, one normal per polygon.
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1125+
Normals point towards the viewer for a face with its vertices in
1126+
counterclockwise order, following the right hand rule.
1127+
1128+
Uses three points equally spaced around the polygon. This method assumes
1129+
that the points are in a plane. Otherwise, more than one shade is required,
1130+
which is not supported.
1131+
1132+
Parameters
1133+
----------
1134+
polygons : list of (M_i, 3) array-like, or (..., M, 3) array-like
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A sequence of polygons to compute normals for, which can have
1136+
varying numbers of vertices. If the polygons all have the same
1137+
number of vertices and array is passed, then the operation will
1138+
be vectorized.
1139+
1140+
Returns
1141+
-------
1142+
normals : (..., 3) array
1143+
A normal vector estimated for the polygon.
1144+
"""
1145+
ifisinstance(polygons,np.ndarray):
1146+
# optimization: polygons all have the same number of points, so can
1147+
# vectorize
1148+
n=polygons.shape[-2]
1149+
i1,i2,i3=0,n//3,2*n//3
1150+
v1=polygons[...,i1, :]-polygons[...,i2, :]
1151+
v2=polygons[...,i2, :]-polygons[...,i3, :]
1152+
else:
1153+
# The subtraction doesn't vectorize because polygons is jagged.
1154+
v1=np.empty((len(polygons),3))
1155+
v2=np.empty((len(polygons),3))
1156+
forpoly_i,psinenumerate(polygons):
1157+
n=len(ps)
1158+
i1,i2,i3=0,n//3,2*n//3
1159+
v1[poly_i, :]=ps[i1, :]-ps[i2, :]
1160+
v2[poly_i, :]=ps[i2, :]-ps[i3, :]
1161+
returnnp.cross(v1,v2)
1162+
1163+
1164+
def_shade_colors(color,normals,lightsource=None):
1165+
"""
1166+
Shade *color* using normal vectors given by *normals*,
1167+
assuming a *lightsource* (using default position if not given).
1168+
*color* can also be an array of the same length as *normals*.
1169+
"""
1170+
iflightsourceisNone:
1171+
# chosen for backwards-compatibility
1172+
lightsource=mcolors.LightSource(azdeg=225,altdeg=19.4712)
1173+
1174+
withnp.errstate(invalid="ignore"):
1175+
shade= ((normals/np.linalg.norm(normals,axis=1,keepdims=True))
1176+
@lightsource.direction)
1177+
mask=~np.isnan(shade)
1178+
1179+
ifmask.any():
1180+
# convert dot product to allowed shading fractions
1181+
in_norm=mcolors.Normalize(-1,1)
1182+
out_norm=mcolors.Normalize(0.3,1).inverse
1183+
1184+
defnorm(x):
1185+
returnout_norm(in_norm(x))
1186+
1187+
shade[~mask]=0
1188+
1189+
color=mcolors.to_rgba_array(color)
1190+
# shape of color should be (M, 4) (where M is number of faces)
1191+
# shape of shade should be (M,)
1192+
# colors should have final shape of (M, 4)
1193+
alpha=color[:,3]
1194+
colors=norm(shade)[:,np.newaxis]*color
1195+
colors[:,3]=alpha
1196+
else:
1197+
colors=np.asanyarray(color).copy()
1198+
1199+
returncolors

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