#15547: Dimension of a projection of a polyhedron/TikZ method for polyhedron
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Reporter: jipilab | Owner:
Type: defect | Status: new
Priority: minor | Milestone: sage-6.0
Component: geometry | Resolution:
Keywords: tikz, projection | Merged in:
Authors: jipilab | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by jipilab:
Old description:
> Using the new tikz feature, (see http://trac.sagemath.org/ticket/12083)
> there is a problem when drawing polygons embedded in 3d. The error can be
> reproduced:
>
> {{{
> sage: P = Polyhedron(vertices=[[1,0,0],[0,1,0],[0,0,1]])
> sage: P.ambient_dim()
> 3
> sage: P.dim()
> 2
> sage: PProj = P.projection()
> sage: PProj.polyhedron_ambient_dim
> 3
> sage: PProj.dimension
> 3
> }}}
>
> I believe PProj.dimension should be 2, not 3. Because of this, the tikz
> method misbehaves.
>
> In this case, the function _init_from_3d(self, polyhedron) used for
> projection contains:
>
> {{{
> assert polyhedron.ambient_dim() == 3, "Requires polyhedron in 3d"
> self.dimension = 3
> self._init_points(polyhedron)
> }}}
>
> I believe one should replace the second line by
>
> {{{
> self.dimension = polyhedron.dim()
> }}}
New description:
Using the new tikz feature, (see http://trac.sagemath.org/ticket/12083)
there is a problem when drawing polygons embedded in 3d. The error can be
reproduced:
{{{
sage: P = Polyhedron(vertices=[[1,0,0],[0,1,0],[0,0,1]])
sage: P.ambient_dim()
3
sage: P.dim()
2
sage: PProj = P.projection()
sage: PProj.polyhedron_ambient_dim
3
sage: PProj.dimension
3
}}}
I believe PProj.dimension should be 2, not 3. Because of this, the tikz
method misbehaves.
In this case, the function _init_from_3d(self, polyhedron) used for
projection contains:
{{{
assert polyhedron.ambient_dim() == 3, "Requires polyhedron in 3d"
self.dimension = 3
self._init_points(polyhedron)
}}}
I believe one should replace the second line by
{{{
self.dimension = polyhedron.dim()
}}}
There is also a problem with drawing 3d-polytopes: the back edges are not
drawn.
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Ticket URL: <http://trac.sagemath.org/ticket/15547#comment:1>
Sage <http://www.sagemath.org>
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