Opened 2 years ago

Closed 22 months ago

#24886 closed enhancement (fixed)

Implement one-point suspension and face split of polyhedron

Reported by: jipilab Owned by:
Priority: major Milestone: sage-8.3
Component: geometry Keywords: days93, polytope, thursdaysbdx, IMA-PolyGeom
Cc: vdelecroix, moritz, mkoeppe, chapoton Merged in:
Authors: Jean-Philippe Labbé Reviewers: Frédéric Chapoton, Vincent Delecroix
Report Upstream: N/A Work issues:
Branch: 2d78b87 (Commits) Commit: 2d78b8760d4e3ee5ffe1634bc763b3889818e314
Dependencies: Stopgaps:

Description (last modified by jipilab)

The one-point suspension of a vertex v of a polyhedron P of dimension d is obtained by placing P in a dimension d+1 vector space where the last coordinate is 0, then placing a vertex "over" v and a vertex "below" v in the last coordinate and taking the convex hull.

One can do a similar construction for faces of polyhedron by placing the two vertices relative to the center of the face. This way we get the face split of P.

On the way, the center function also got modified in the case when it is only a vertex so that it returns the vertex. This was necessary to make the one-point suspension consistent.

Change History (13)

comment:1 Changed 2 years ago by jipilab

  • Branch set to u/jipilab/24886
  • Commit set to 2dacbe12bf10300d8113ea4c4f709bc742eeb2df

New commits:

32f0e86first version of ops
eeee559Second version of ops
2dacbe1whitespaces

comment:2 Changed 2 years ago by jipilab

  • Status changed from new to needs_review

comment:3 Changed 2 years ago by git

  • Commit changed from 2dacbe12bf10300d8113ea4c4f709bc742eeb2df to 02fa0d96b88f24a5c54e2c97f49ad70a29c432f4

Branch pushed to git repo; I updated commit sha1. New commits:

02fa0d9Merge branch 'sage8.2.b7' into onepointsus

comment:4 Changed 2 years ago by vdelecroix

typo: the face splitting the face ``face``

comment:5 Changed 2 years ago by vdelecroix

You should check that you obtain the same answer using a proper vertex or a face of dimension 0

sage: C = polytopes.cube()
sage: C.faces(0)    # dimension 0 faces
(<0>, <1>, <2>, <3>, <4>, <5>, <6>, <7>)
sage: C.vertices()  # proper vertices
(A vertex at (-1, -1, -1),
 A vertex at (-1, -1, 1),
...
 A vertex at (1, 1, 1))

comment:6 Changed 2 years ago by vdelecroix

The documentation would also be nicer with:

  • a proper definition of bypiramid
  • specification that the newly added vertices will be at height -1 and 1

comment:7 Changed 2 years ago by vdelecroix

  • Keywords thursdaysbdx added
  • Status changed from needs_review to needs_work

comment:8 Changed 2 years ago by git

  • Commit changed from 02fa0d96b88f24a5c54e2c97f49ad70a29c432f4 to eef860f63f2d6b16348ea71f08035240ad02d575

Branch pushed to git repo; I updated commit sha1. Last 10 new commits:

7f5e125fixed typos in polyhedra_quickref.rst
bd6c356LateX -> LaTeX in polytope_tikz.rst
b1ce45bSeveral other corrections
d526f70renamed tutorial files
d7896f8Merge branch 'develop' into 22572
597b802Merge branch sage8.2.rc1 into 22572
eee533aCorrections from review
b74ae85Made tests pass
1c9a654Merge branch thematic tutorial into onepointsus
eef860fApplied review suggestions

comment:9 Changed 2 years ago by jipilab

  • Keywords IMA-PolyGeom added
  • Status changed from needs_work to needs_review

Hi,

Thanks Vincent for your review. I made the suggested changes (along with merging the tutorial).

I realized while making a test that the method center was changing the base ring when it was taken over a vertex, I fixed that small thing on the way too.

comment:10 Changed 2 years ago by git

  • Commit changed from eef860f63f2d6b16348ea71f08035240ad02d575 to 2d78b8760d4e3ee5ffe1634bc763b3889818e314

Branch pushed to git repo; I updated commit sha1. New commits:

2d78b87whitespaces

comment:11 Changed 2 years ago by jipilab

  • Description modified (diff)
  • Summary changed from Implement one point suspension and face split of polyhedron to Implement one-point suspension and face split of polyhedron

comment:12 Changed 22 months ago by chapoton

  • Milestone changed from sage-8.2 to sage-8.3
  • Reviewers set to Frédéric Chapoton, Vincent Delecroix
  • Status changed from needs_review to positive_review

ok, let it be too

comment:13 Changed 22 months ago by vbraun

  • Branch changed from u/jipilab/24886 to 2d78b8760d4e3ee5ffe1634bc763b3889818e314
  • Resolution set to fixed
  • Status changed from positive_review to closed
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