Functions for plotting polyhedra

class sage.geometry.polyhedron.plot.Projection(polyhedron, proj=<function projection_func_identity at 0x7fd8a53a79b0>)

Bases: sage.structure.sage_object.SageObject

The projection of a Polyhedron.

This class keeps track of the necessary data to plot the input polyhedron.

coord_index_of(v)

Convert a coordinate vector to its internal index.

EXAMPLES:

sage: p = polytopes.hypercube(3)
sage: proj = p.projection()
sage: proj.coord_index_of(vector((1,1,1)))
7

coord_indices_of(v_list)

Convert list of coordinate vectors to the corresponding list of internal indices.

EXAMPLES:

sage: p = polytopes.hypercube(3)
sage: proj = p.projection()
sage: proj.coord_indices_of([vector((1,1,1)),vector((1,-1,1))])
[7, 5]

coordinates_of(coord_index_list)

Given a list of indices, return the projected coordinates.

EXAMPLES:

sage: p = polytopes.simplex(4, project=True).projection()
sage: p.coordinates_of([1])
[[-0.7071067812, 0.4082482905, 0.2886751346, 0.2236067977]]

identity()

Return the identity projection of the polyhedron.

EXAMPLES:

sage: p = polytopes.icosahedron(exact=False)
sage: from sage.geometry.polyhedron.plot import Projection
sage: pproj = Projection(p)
sage: ppid = pproj.identity()
sage: ppid.dimension
3

render_0d(point_opts={}, line_opts={}, polygon_opts={})

Return 0d rendering of the projection of a polyhedron into 2-dimensional ambient space.

INPUT:

See plot().

OUTPUT:

A 2-d graphics object.

EXAMPLES:

sage: print(Polyhedron([]).projection().render_0d().description())

sage: print(Polyhedron(ieqs=[(1,)]).projection().render_0d().description())
Point set defined by 1 point(s):    [(0.0, 0.0)]

render_1d(point_opts={}, line_opts={}, polygon_opts={})

Return 1d rendering of the projection of a polyhedron into 2-dimensional ambient space.

INPUT:

See plot().

OUTPUT:

A 2-d graphics object.

EXAMPLES:

sage: Polyhedron([(0,), (1,)]).projection().render_1d()
Graphics object consisting of 2 graphics primitives

render_2d(point_opts={}, line_opts={}, polygon_opts={})

Return 2d rendering of the projection of a polyhedron into 2-dimensional ambient space.

EXAMPLES:

sage: p1 = Polyhedron(vertices=[[1,1]], rays=[[1,1]])
sage: q1 = p1.projection()
sage: p2 = Polyhedron(vertices=[[1,0], [0,1], [0,0]])
sage: q2 = p2.projection()
sage: p3 = Polyhedron(vertices=[[1,2]])
sage: q3 = p3.projection()
sage: p4 = Polyhedron(vertices=[[2,0]], rays=[[1,-1]], lines=[[1,1]])
sage: q4 = p4.projection()
sage: q1.plot() + q2.plot() + q3.plot() + q4.plot()
Graphics object consisting of 17 graphics primitives

render_3d(point_opts={}, line_opts={}, polygon_opts={})

Return 3d rendering of a polyhedron projected into 3-dimensional ambient space.

EXAMPLES:

sage: p1 = Polyhedron(vertices=[[1,1,1]], rays=[[1,1,1]])
sage: p2 = Polyhedron(vertices=[[2,0,0], [0,2,0], [0,0,2]])
sage: p3 = Polyhedron(vertices=[[1,0,0], [0,1,0], [0,0,1]], rays=[[-1,-1,-1]])
sage: p1.projection().plot() + p2.projection().plot() + p3.projection().plot()
Graphics3d Object

It correctly handles various degenerate cases:

sage: Polyhedron(lines=[[1,0,0],[0,1,0],[0,0,1]]).plot()           # whole space
Graphics3d Object
sage: Polyhedron(vertices=[[1,1,1]], rays=[[1,0,0]],
....:            lines=[[0,1,0],[0,0,1]]).plot()                   # half space
Graphics3d Object
sage: Polyhedron(vertices=[[1,1,1]],
....:            lines=[[0,1,0],[0,0,1]]).plot()                   # R^2 in R^3
Graphics3d Object
sage: Polyhedron(rays=[[0,1,0],[0,0,1]], lines=[[1,0,0]]).plot()   # quadrant wedge in R^2
Graphics3d Object
sage: Polyhedron(rays=[[0,1,0]], lines=[[1,0,0]]).plot()           # upper half plane in R^3
Graphics3d Object
sage: Polyhedron(lines=[[1,0,0]]).plot()                           # R^1 in R^2
Graphics3d Object
sage: Polyhedron(rays=[[0,1,0]]).plot()                            # Half-line in R^3
Graphics3d Object
sage: Polyhedron(vertices=[[1,1,1]]).plot()                        # point in R^3
Graphics3d Object

The origin is not included, if it is not in the polyhedron (trac ticket #23555):

sage: Q = Polyhedron([[100],[101]])
sage: P = Q*Q*Q; P
A 3-dimensional polyhedron in ZZ^3 defined as the convex hull of 8 vertices
sage: p = P.plot()
sage: p.bounding_box()
((100.0, 100.0, 100.0), (101.0, 101.0, 101.0))

render_fill_2d(**kwds)

Return the filled interior (a polygon) of a polyhedron in 2d.

EXAMPLES:

sage: cps = [i^3 for i in srange(-2,2,1/5)]
sage: p = Polyhedron(vertices = [[(t^2-1)/(t^2+1),2*t/(t^2+1)] for t in cps])
sage: proj = p.projection()
sage: filled_poly = proj.render_fill_2d()
sage: filled_poly.axes_width()
0.8

render_line_1d(**kwds)

Return the line of a polyhedron in 1d.

INPUT:

• **kwds – options passed through to line2d().

OUTPUT:

A 2-d graphics object.

EXAMPLES:

sage: outline = polytopes.hypercube(1).projection().render_line_1d()
sage: outline._objects[0]
Line defined by 2 points

render_outline_2d(**kwds)

Return the outline (edges) of a polyhedron in 2d.

EXAMPLES:

sage: penta = polytopes.regular_polygon(5)
sage: outline = penta.projection().render_outline_2d()
sage: outline._objects[0]
Line defined by 2 points

render_points_1d(**kwds)

Return the points of a polyhedron in 1d.

INPUT:

• **kwds – options passed through to point2d().

OUTPUT:

A 2-d graphics object.

EXAMPLES:

sage: cube1 = polytopes.hypercube(1)
sage: proj = cube1.projection()
sage: points = proj.render_points_1d()
sage: points._objects
[Point set defined by 2 point(s)]

render_points_2d(**kwds)

Return the points of a polyhedron in 2d.

EXAMPLES:

sage: hex = polytopes.regular_polygon(6)
sage: proj = hex.projection()
sage: hex_points = proj.render_points_2d()
sage: hex_points._objects
[Point set defined by 6 point(s)]

render_solid_3d(**kwds)

Return solid 3d rendering of a 3d polytope.

EXAMPLES:

sage: p = polytopes.hypercube(3).projection()
sage: p_solid = p.render_solid_3d(opacity = .7)
sage: type(p_solid)
<type 'sage.plot.plot3d.index_face_set.IndexFaceSet'>

render_vertices_3d(**kwds)

Return the 3d rendering of the vertices.

EXAMPLES:

sage: p = polytopes.cross_polytope(3)
sage: proj = p.projection()
sage: verts = proj.render_vertices_3d()
sage: verts.bounding_box()
((-1.0, -1.0, -1.0), (1.0, 1.0, 1.0))

render_wireframe_3d(**kwds)

Return the 3d wireframe rendering.

EXAMPLES:

sage: cube = polytopes.hypercube(3)
sage: cube_proj = cube.projection()
sage: wire = cube_proj.render_wireframe_3d()
sage: print(wire.tachyon().split('\n')[77])  # for testing
FCylinder base -1.0 1.0 -1.0 apex -1.0 -1.0 -1.0 rad 0.005 texture...

schlegel(projection_direction=None, height=1.1)

Return the Schlegel projection.

• The polyhedron is translated such that its center() is at the origin.
• The vertices are then normalized to the unit sphere
• The normalized points are stereographically projected from a point slightly outside of the sphere.

INPUT:

• projection_direction – coordinate list/tuple/iterable or None (default). The direction of the Schlegel projection. For a full-dimensional polyhedron, the default is the first facet normal; Otherwise, the vector consisting of the first n primes is chosen.
• height – float (default: \(1.1\)). How far outside of the unit sphere the focal point is.

EXAMPLES:

sage: cube4 = polytopes.hypercube(4)
sage: from sage.geometry.polyhedron.plot import Projection
sage: Projection(cube4).schlegel([1,0,0,0])
The projection of a polyhedron into 3 dimensions
sage: _.plot()
Graphics3d Object

stereographic(projection_point=None)

Return the stereographic projection.

INPUT:

• projection_point - The projection point. This must be distinct from the polyhedron’s vertices. Default is \((1,0,\dots,0)\)

EXAMPLES:

sage: from sage.geometry.polyhedron.plot import Projection
sage: proj = Projection(polytopes.buckyball())  #long time
sage: proj                                      #long time
The projection of a polyhedron into 3 dimensions
sage: proj.stereographic([5,2,3]).plot()        #long time
Graphics object consisting of 123 graphics primitives
sage: Projection( polytopes.twenty_four_cell() ).stereographic([2,0,0,0])
The projection of a polyhedron into 3 dimensions

tikz(view=[0, 0, 1], angle=0, scale=2, edge_color='blue!95!black', facet_color='blue!95!black', opacity=0.8, vertex_color='green', axis=False)

Return a string tikz_pic consisting of a tikz picture of self according to a projection view and an angle angle obtained via Jmol through the current state property.

INPUT:

• view - list (default: [0,0,1]) representing the rotation axis (see note below).
• angle - integer (default: 0) angle of rotation in degree from 0 to 360 (see note below).
• scale - integer (default: 2) specifying the scaling of the tikz picture.
• edge_color - string (default: ‘blue!95!black’) representing colors which tikz recognize.
• facet_color - string (default: ‘blue!95!black’) representing colors which tikz recognize.
• vertex_color - string (default: ‘green’) representing colors which tikz recognize.
• opacity - real number (default: 0.8) between 0 and 1 giving the opacity of the front facets.
• axis - Boolean (default: False) draw the axes at the origin or not.

OUTPUT:

• LatexExpr – containing the TikZ picture.

Note

The inputs view and angle can be obtained from the viewer Jmol:

1) Right click on the image
2) Select ``Console``
3) Select the tab ``State``
4) Scroll to the line ``moveto``

It reads something like:

moveto 0.0 {x y z angle} Scale

The view is then [x,y,z] and angle is angle. The following number is the scale.

Jmol performs a rotation of angle degrees along the vector [x,y,z] and show the result from the z-axis.

EXAMPLES:

sage: P1 = polytopes.small_rhombicuboctahedron()
sage: Image1 = P1.projection().tikz([1,3,5], 175, scale=4)
sage: type(Image1)
<class 'sage.misc.latex.LatexExpr'>
sage: print('\n'.join(Image1.splitlines()[:4]))
\begin{tikzpicture}%
    [x={(-0.939161cm, 0.244762cm)},
    y={(0.097442cm, -0.482887cm)},
    z={(0.329367cm, 0.840780cm)},
sage: _ = open('polytope-tikz1.tex', 'w').write(Image1)    # not tested

sage: P2 = Polyhedron(vertices=[[1, 1],[1, 2],[2, 1]])
sage: Image2 = P2.projection().tikz(scale=3, edge_color='blue!95!black', facet_color='orange!95!black', opacity=0.4, vertex_color='yellow', axis=True)
sage: type(Image2)
<class 'sage.misc.latex.LatexExpr'>
sage: print('\n'.join(Image2.splitlines()[:4]))
\begin{tikzpicture}%
    [scale=3.000000,
    back/.style={loosely dotted, thin},
    edge/.style={color=blue!95!black, thick},
sage: _ = open('polytope-tikz2.tex', 'w').write(Image2)    # not tested

sage: P3 = Polyhedron(vertices=[[-1, -1, 2],[-1, 2, -1],[2, -1, -1]])
sage: P3
A 2-dimensional polyhedron in ZZ^3 defined as the convex hull of 3 vertices
sage: Image3 = P3.projection().tikz([0.5,-1,-0.1], 55, scale=3, edge_color='blue!95!black',facet_color='orange!95!black', opacity=0.7, vertex_color='yellow', axis=True)
sage: print('\n'.join(Image3.splitlines()[:4]))
\begin{tikzpicture}%
    [x={(0.658184cm, -0.242192cm)},
    y={(-0.096240cm, 0.912008cm)},
    z={(-0.746680cm, -0.331036cm)},
sage: _ = open('polytope-tikz3.tex', 'w').write(Image3)    # not tested

sage: P=Polyhedron(vertices=[[1,1,0,0],[1,2,0,0],[2,1,0,0],[0,0,1,0],[0,0,0,1]])
sage: P
A 4-dimensional polyhedron in ZZ^4 defined as the convex hull of 5 vertices
sage: P.projection().tikz()
Traceback (most recent call last):
...
NotImplementedError: The polytope has to live in 2 or 3 dimensions.

Todo

Make it possible to draw Schlegel diagram for 4-polytopes.

sage: P=Polyhedron(vertices=[[1,1,0,0],[1,2,0,0],[2,1,0,0],[0,0,1,0],[0,0,0,1]])
sage: P
A 4-dimensional polyhedron in ZZ^4 defined as the convex hull of 5 vertices
sage: P.projection().tikz()
Traceback (most recent call last):
...
NotImplementedError: The polytope has to live in 2 or 3 dimensions.

Make it possible to draw 3-polytopes living in higher dimension.

class sage.geometry.polyhedron.plot.ProjectionFuncSchlegel(projection_direction, height=1.1, center=0)

The Schlegel projection from the given input point.

EXAMPLES:

sage: from sage.geometry.polyhedron.plot import ProjectionFuncSchlegel
sage: proj = ProjectionFuncSchlegel([2,2,2])
sage: proj(vector([1.1,1.1,1.11]))[0]
0.0302...

class sage.geometry.polyhedron.plot.ProjectionFuncStereographic(projection_point)

The stereographic (or perspective) projection.

EXAMPLES:

sage: from sage.geometry.polyhedron.plot import ProjectionFuncStereographic
sage: cube = polytopes.hypercube(3).vertices()
sage: proj = ProjectionFuncStereographic([1.2, 3.4, 5.6])
sage: ppoints = [proj(vector(x)) for x in cube]
sage: ppoints[0]
(-0.0486511..., 0.0859565...)

sage.geometry.polyhedron.plot.cyclic_sort_vertices_2d(Vlist)

Return the vertices/rays in cyclic order if possible.

Note

This works if and only if each vertex/ray is adjacent to exactly two others. For example, any 2-dimensional polyhedron satisfies this.

See vertex_adjacency_matrix() for a discussion of “adjacent”.

EXAMPLES:

sage: from sage.geometry.polyhedron.plot import cyclic_sort_vertices_2d
sage: square = Polyhedron([[1,0],[-1,0],[0,1],[0,-1]])
sage: vertices = [v for v in square.vertex_generator()]
sage: vertices
[A vertex at (-1, 0),
 A vertex at (0, -1),
 A vertex at (0, 1),
 A vertex at (1, 0)]
sage: cyclic_sort_vertices_2d(vertices)
[A vertex at (1, 0),
 A vertex at (0, -1),
 A vertex at (-1, 0),
 A vertex at (0, 1)]

Rays are allowed, too:

sage: P = Polyhedron(vertices=[(0, 1), (1, 0), (2, 0), (3, 0), (4, 1)], rays=[(0,1)])
sage: P.adjacency_matrix()
[0 1 0 1 0]
[1 0 1 0 0]
[0 1 0 0 1]
[1 0 0 0 1]
[0 0 1 1 0]
sage: cyclic_sort_vertices_2d(P.Vrepresentation())
[A vertex at (3, 0),
 A vertex at (1, 0),
 A vertex at (0, 1),
 A ray in the direction (0, 1),
 A vertex at (4, 1)]

sage: P = Polyhedron(vertices=[(0, 1), (1, 0), (2, 0), (3, 0), (4, 1)], rays=[(0,1), (1,1)])
sage: P.adjacency_matrix()
[0 1 0 0 0]
[1 0 1 0 0]
[0 1 0 0 1]
[0 0 0 0 1]
[0 0 1 1 0]
sage: cyclic_sort_vertices_2d(P.Vrepresentation())
[A ray in the direction (1, 1),
 A vertex at (3, 0),
 A vertex at (1, 0),
 A vertex at (0, 1),
 A ray in the direction (0, 1)]

sage: P = Polyhedron(vertices=[(1,2)], rays=[(0,1)], lines=[(1,0)])
sage: P.adjacency_matrix()
[0 0 1]
[0 0 0]
[1 0 0]
sage: cyclic_sort_vertices_2d(P.Vrepresentation())
[A vertex at (0, 2),
 A line in the direction (1, 0),
 A ray in the direction (0, 1)]

sage.geometry.polyhedron.plot.projection_func_identity(x)

The identity projection.

EXAMPLES:

sage: from sage.geometry.polyhedron.plot import projection_func_identity
sage: projection_func_identity((1,2,3))
[1, 2, 3]