What is the graph or plot called which: - is an equilateral triangle - has three axes - each axes is perpendicular to a side of the triangle? [more inside]
posted by Peter Petridish on Oct 28, 2009 - 10 answers

Geometry Wars Filter: Help configure Nyko Airflo PC game controller for Geometry Wars Retro Evolved (PC) [more inside]
posted by FusiveResonance on Sep 18, 2009 - 2 answers

Photoshop Question: is there a way to get a count of pixels contained within any (irregularly shaped) selection/layer? [more inside]
posted by unmake on Sep 10, 2009 - 2 answers

How can I estimate the time that a photo was taken? [more inside]
posted by zvs on Aug 5, 2009 - 11 answers

What software can I use to make a photo collage using non-rectangular photos? [more inside]
posted by soelo on Jun 9, 2009 - 3 answers

Is there an equation that defines the change in apparent size as a function of distance from the viewer? Basically, if I'm looking at a set of railroad tracks head on, if one plank is like 10 ft away, it appears to be one size. The same plank 20 ft away appears smaller. What is the relative size difference? Put another way, how big does a 1ft line appear to be at 10 ft, at 20 ft, etc.? [more inside]
posted by miasma on May 16, 2009 - 15 answers

I've got a polygon of n points. How can I simplify out noisy edges? [more inside]
posted by soma lkzx on Mar 31, 2009 - 12 answers

Hi I'm trying to find a piece of art - a series of lights attached to wooden arms whose tips trace some sort of toroidal geometry. At high speeds the armature disappears and the lights form volumes as luminous wireframes, like synchronised mechanical sparklers. [more inside]
posted by doobiedoo on Mar 5, 2009 - 5 answers

can you help me compute the area of a triangle on the sphere? [more inside]
posted by klanawa on Feb 4, 2009 - 20 answers

3-D folks, Mathematicians, and Artists: Trying to create my own Trompe-l'œil / forced perspective illusionary image to hang on my wall (e.g. the awesome parking garage signage everyone's already seen... more examples here, and here). I'm having trouble faking it with 2-D programs, and the math is puzzling me. [more inside]
posted by jjjjjjjijjjjjjj on Jan 9, 2009 - 34 answers

Math filter: How many equally sized rectangles will fit into a circle, and how should I arrange them in order to make the best-looking approximation? [more inside]
posted by brandnew on Aug 17, 2008 - 9 answers

How can I tile a sphere using the minimum number of differently shaped units? I have a 3 meter diameter sphere and I need to tile it using units that are each about 400 square cm (ie like a 20 x 20cm square). The units must be flat (ie, not spherical triangles). [more inside]
posted by silence on Jun 2, 2008 - 14 answers

How far would I need to travel from a tower 100 feet high before the sight of it would become obscured by the horizon? [more inside]
posted by grrlaction on May 4, 2008 - 20 answers

I read a book sometime in elementary school (early/mid 90's) that I've been trying to find. It had to do with geometry and math and platonic solids and origami (I believe there were several nods to Flatland). The plot had something about evil army men toys and a boy having a fever dream. I think the cover had a picture of the boy riding a manta ray. [more inside]
posted by rivenwanderer on Mar 31, 2008 - 3 answers

My geometry teacher in high school in 1984 showed us this puzzle. I was only half paying attention, but I believe the goal was to draw a line that intersected each segment only once. [more inside]
posted by mecran01 on Jan 6, 2008 - 15 answers

Does anyone teach a course in Synergetic Geometry in Los Angeles??? In the U.S.???? [more inside]
posted by goalyeehah on Aug 27, 2007 - 1 answer

Packing efficiency of 9" balloons? [more inside]
posted by nilihm on Jul 17, 2007 - 13 answers

Help me with the math of two spheres colliding [more inside]
posted by RobotHero on Jun 10, 2007 - 8 answers

3D Trig question: I have a 2D square in 3D space (a Face). I know the positions of the four corner vertices in form x,y,z. How do I calculate the rotation in degrees (Euler angles) as relative from the center of the face? I want to end up with degrees of rotations around x-axis,y-axis,z-axis. Bonus if you can write it in pseudocode.
posted by pooya on May 9, 2007 - 7 answers

How can I work out if a point x,y,z is contained by a cone ? [more inside]
posted by matholio on Jan 14, 2007 - 15 answers

Vector Geometry Filter: I'm working in matlab and need to transform a surface to match an arbitrary angle. I have the unit vector of the new normal (and the original normal is in the Z axis (0 0 1))...however i'm not sure how to rotate one normal to another (i know, i know, it sounds very simple really...) [more inside]
posted by NGnerd on Oct 23, 2006 - 5 answers

Does anybody remember those circular templates that makes infinite radial patterns with colored ball pens? They had concentric holes for which to anchor a ballpoint against an outer axle, and then you change colors corresponding with the holes? What do you call those? Is it called anything at all?
posted by azul on Sep 18, 2006 - 21 answers

Do the curved triangular shapes made when cars (or even pedestrians) take "shortcuts" at T-junctions (seen here near my house and here in Western Sahara, although this seems like a deliberate one) have a name? What's the mathematics behind them? The psychology?
posted by Jimbob on Aug 25, 2006 - 23 answers

Is there a geometric name for the "bulging rectangle" shape, most commonly found as the front-profile outline of classic (CRT-type) TV tubes? [more inside]
posted by skyboy on Aug 2, 2006 - 13 answers

My daughter wants to decorate a sphere in a football pattern. How do we determine the correct side length for the pentagons and hexagons, given a sphere of diameter n?
posted by i_am_joe's_spleen on Jun 9, 2006 - 11 answers

given a set of points from an n dimensional metric space, construct a surface of minimal volume which contains these points. [more inside]
posted by paradroid on Jun 2, 2006 - 13 answers

My room has an angled ceiling. I have measured its height at the highest and lowest points, and I have the dimensions of the room. Help me determine what height the ceiling is at a particular point on the floor, and where exactly the skylight is. [more inside]
posted by xo on May 23, 2006 - 11 answers

Attention geometry wizards, Explain this picture
posted by Crotalus on May 18, 2006 - 14 answers

Let's say I have an array of 100 adjoining hexagons, 10 hexagons per side. Let's also say I also have an array of 100 adjoining squares, 10 squares per side. Each single hexagon and each square encloses the same area. Is the perimeter of the array of 100 hexagons longer than the perimeter of the array of 100 squares? [more inside]
posted by Rumple on Apr 25, 2006 - 17 answers

Say I have 5 points: a,b,c,d,e. I know the position of each one at t=0: pa₀,pb₀ etc. Now say that at t=1, the distance between each one changes, so I know Dab₁,Dac₁...Dde₁. Is there an equation or algorithm which will allow me to know (or aproximate) the positions at t=1 : pa₁...pe₁? [more inside]
posted by skree on Mar 23, 2006 - 33 answers

If April 6 and September 10 are the same length from sunrise to sunset, does the sun take the same path across the sky on both days? [more inside]
posted by squirrel on Mar 15, 2006 - 6 answers

What are these structures? And why are they hexagonal/circular?
posted by provolot on Mar 11, 2006 - 13 answers

I want a true vector-based (i.e., not merely a series of thousands of line segments) Postscript or Illustrator file of an epicycloid where a=5, b=2. [more inside]
posted by dmd on Feb 19, 2006 - 25 answers

Programming/geometry: in a Flash program (you don't need to know Flash to answer this), I'm trying to place rectangular images at random positions on the screen. There are already images on the screen. I need to make sure that the new, randomly-placed images don't obscure the images already there. [more inside]
posted by grumblebee on Sep 29, 2005 - 25 answers

Is there a specific name for a rectangle which, if you divide it in half, the two halves have the same proportions as the original rectangle? [more inside]
posted by e-man on Sep 27, 2005 - 12 answers

How can I get a Penrose tiling installed on my bathroom floor? Would Penrose sue me if I did it myself? And where the heck can you buy the tiles from? [more inside]
posted by sandking on Jul 19, 2005 - 12 answers

Remember the Spirograph? [more inside]
posted by lorbus on Jul 11, 2005 - 13 answers

Unsettled bar question: what is the shape of a Zulu Shield called? [more inside]
posted by hellbient on Mar 29, 2005 - 16 answers

Why is a rectangle not called a quadrangle?
posted by punkfloyd on Mar 10, 2005 - 12 answers

I have a circular patio table with four legs. The paving stones are uneven, so it has always been difficult to set the table in place so it doesn't wobble. I move it regularly, since the shadows from the trees change, and sometimes I want shade, other times sun. I used to mark small dots on the stones so I could set it down quickly. Then I discovered something very interesting--no matter where I put the table, if I simply rotate it around its center, I can very quickly find a steady configuration. But move it from place to place, and it takes all day. This is like the four color map theorem. It works every time, but I haven't figured out why. It might even be tricky to put this into a mathematical format. The table doesn't need to be level, and all four legs needn't be the same height or "at" the same height. The table just can't wobble. Go geeks.
posted by weapons-grade pandemonium on Mar 10, 2005 - 10 answers

Are equilateral triangles also isosceles? [more inside]
posted by i_am_joe's_spleen on Mar 3, 2005 - 25 answers

Given the latitude and longitude of three points, how can I find the coordinates of the point that is equidistant from them? [mi] [more inside]
posted by obiwanwasabi on Feb 6, 2005 - 21 answers

What do you call those three-dimensional geometric novelties, consisting of eight cubes, joined to each other at one edge to form one large cube, whose pieces can be flipped around to display different images on the exterior of the large cube? What is the history of this delightful object? What are the geometric priniciples behind it?
posted by Faze on Jan 20, 2005 - 15 answers

I read Edwin A. Abbott's Flatland this weekend and really enjoyed its fiction and speculative geometry/mathematics. I guess the logical next step would be to read the unofficial sequel, Flatterland, but can any of you recommend other books that similarly twist math and fiction, or just books that explain mathematical concepts or theories to laymen such as myself in ways that are entertaining to read?
posted by Evstar on Jan 3, 2005 - 28 answers

I'm currently a junior in college majoring in computer science. Like most geeks I slacked off during high school and now find that I don't know a lot of very basic math (my geometry is horrible, my algebra skills could be much better). This is very embarrassing and I would like to get caught up with this material as quickly as possible. I have two questions:

1) Are there any math audio books? A google search didn't show any, but this would be the best for me.

2) Are there any books aimed at adults for personal study?

I'd like to understand the theory behind the math more than the math itself. Anyways, any help is appreciated.
posted by anonymous on Nov 17, 2004 - 18 answers

I am working on a project involving some 3d programming (in AutoLisp), and have managed to muddle through with what I remember of university geometry. I run into basic geometry problems (i.a.: find the 3d point where 2 lines intersect, given only the start points, angles and slope of the lines) which I manage to laboriously and clumsily solve. I'm sure most of these problems have 'canonical' solutions, worked out by graphic programmers. Is there any online resource for algorithms and formulas for typical 3d programming problems?
A good, simple explanation of the theory (and application in 3d graphics) of transformation matrixes would be nice, too.
posted by signal on Sep 3, 2004 - 6 answers

Do you know of any 3D interactive geometry software? I would like to have the power of Cabri / Geometer's Sketchpad in 3D.
posted by MzB on Feb 3, 2004 - 0 answers