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Re: [geodesic 00493] Re: icosahedron..

Adrian Rossiter — Tue, 09 Feb 2010 11:58:13 GMT

Hi Gerald and Marcelo ... If the strut ends are the vertices of an icosahedron then the value is phi/2 = 81% approx. On the subject of naming, I like

Re: lines_intersection

Roger Kaufman — Sun, 07 Feb 2010 14:07:27 GMT

Hi Adrian, ... This was a bit of a panic on my part. The code works on everything unitile2d produces. But is possible to create a tiling by hand such that the

Re: lines_intersection

Alan M — Sat, 06 Feb 2010 02:03:35 GMT

Each perpendicular line segment is really the cross product of the area of the face. For example, if each face were a parallelogram, then the resulting

Re: lines_intersection

Adrian Rossiter — Fri, 05 Feb 2010 15:35:25 GMT

... That should have said prism instead of pyramid (there were no pyramids!) Adrian. -- Adrian Rossiter adrian@... http://antiprism.com/adrian

Re: lines_intersection

Adrian Rossiter — Fri, 05 Feb 2010 15:21:22 GMT

Hi Roger ... Here is an example. Three prisms are joined, each sharing an edge with the other two http://www.antiprism.com/misc/orient_choice.jpg The

Re: lines_intersection

Adrian Rossiter — Fri, 05 Feb 2010 12:46:19 GMT

Hi Roger ... If you mean regular polygon, in this case all the edges wind the same way around the centre. If you choose a point in some closed region and shoot

Re: lines_intersection

Roger Kaufman — Fri, 05 Feb 2010 02:09:53 GMT

Hi Adrian, ... I was looking at this a bit. First I didn't know that antiview did this! I've been looking at "winding number" and there seems to be algorithms

Re: Don't always believe appearances

Alan M — Fri, 05 Feb 2010 00:21:47 GMT

* GeoJourney : Messages : 2758-2761 of 3972 * "All faces now are

Re: lines_intersection

Adrian Rossiter — Thu, 04 Feb 2010 11:43:22 GMT

Hi Roger ... I thought about the how you might solve this, and you seem to be describing what I was thinking of, except the the triangle in triangle wouldn't

Re: lines_intersection

Adrian Rossiter — Thu, 04 Feb 2010 10:57:47 GMT

Hi Roger ... It depends on the winding. If you join a couple of triangles that wind in opposite directions by a bridging (double) edge then you get a zero

Re: Graphics Gems Repository

Adrian Rossiter — Thu, 04 Feb 2010 10:24:17 GMT

Hi Roger ... That is useful as the code can be used without restrictions. I have bookmarked the page and will try to make a list of the geometry related code

Re: Don't always believe appearances [2 Attachments]

Adrian Rossiter — Thu, 04 Feb 2010 09:59:45 GMT

Hi Alan ... In the first image it is possible to interpret the dodecahedron and icosahedron in two positions. If you pick a face it can be on the front side or

Don't always believe appearances

Alan Michelson — Thu, 04 Feb 2010 07:54:33 GMT

... Actually, they might not be OK 2-dimensionally. You see, I was rotating each polyhedron along its 3-fold axis, assuming 22.5°[?] increments. But Rybo has

Re: lines_intersection

Roger Kaufman — Wed, 03 Feb 2010 16:32:06 GMT

Hi Adrian, ... I have given this some more thought and the algorithm gets simpler. Redefine the problem as this. Given two triangles which intersect, the aim

Re: lines_intersection

Alan M — Wed, 03 Feb 2010 03:34:58 GMT

... Somehow, this reminds me of the discussion of the orientation of the figure-8