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Questions tagged [geometry]

Data structures and algorithms related to geometry.

Data structures and algorithms related to geometry, a branch of mathematics concerned with questions of shape, figures, and dimensions in space.

See also Wikipedia

12992 questions
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Easier way to create circle div than using an image?

I'm wondering if there's an easier way to create circular divs than what I'm doing now. Currently, I am just making an image for each different size, but it's annoying to do this. Is there anyway using CSS to make divs which are circular and I can…
bmaster
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2 answers

Why are my balls disappearing?

Pardon the funny title. I've created a little graphic demo of 200 balls bouncing and colliding, both against the walls and each other. You can see what I have currently here: http://www.exeneva.com/html5/multipleBallsBouncingAndColliding/ The…
Yang Pulse
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18 answers

Evenly distributing n points on a sphere

I need an algorithm that can give me positions around a sphere for N points (less than 20, probably) that vaguely spreads them out. There's no need for "perfection", but I just need it so none of them are bunched together. This question provided…
Befall
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190
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11 answers

How can I find the smallest difference between two angles around a point?

Given a 2D circle with 2 angles in the range -PI -> PI around a coordinate, what is the value of the smallest angle between them? Taking into account that the difference between PI and -PI is not 2 PI but zero. An Example: Imagine a circle, with 2…
Tom J Nowell
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183
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8 answers

Sort points in clockwise order?

Given an array of x,y points, how do I sort the points of this array in clockwise order (around their overall average center point)? My goal is to pass the points to a line-creation function to end up with something looking rather "solid", as convex…
Philipp Lenssen
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Circle drawing with SVG's arc path

Using SVG path, we can draw 99.99% of a circle and it shows up, but when it is 99.99999999% of a circle, then the circle won't show up. How can it be fixed? The following SVG path can draw 99.99% of a circle: var paper = Raphael(0, 0, 300,…
nonopolarity
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How to tell whether a point is to the right or left side of a line

I have a set of points. I want to separate them into 2 distinct sets. To do this, I choose two points (a and b) and draw an imaginary line between them. Now I want to have all points that are left from this line in one set and those that are right…
Aaginor
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How do you calculate the average of a set of circular data?

I want to calculate the average of a set of circular data. For example, I might have several samples from the reading of a compass. The problem of course is how to deal with the wraparound. The same algorithm might be useful for a clockface. The…
Nick Fortescue
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How can I check if two segments intersect?

How can I check if 2 segments intersect? I've the following data: Segment1 [ {x1,y1}, {x2,y2} ] Segment2 [ {x1,y1}, {x2,y2} ] I need to write a small algorithm in Python to detect if the 2 lines are intersecting.
aneuryzm
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Simple calculations for working with lat/lon and km distance?

Is there a simple calculation I can do which will convert km into a value which I can add to a lat or lon float to calculate a bounding box for searches? It doesn't need to be completely accurate. For instance: if I were given a lat/lon for London,…
Phillip B Oldham
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148
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Algorithm to detect intersection of two rectangles?

I'm looking for an algorithm to detect if two rectangles intersect (one at an arbitrary angle, the other with only vertical/horizontal lines). Testing if a corner of one is in the other ALMOST works. It fails if the rectangles form a cross-like…
user20493
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How to draw circle in html page?

How do you draw a circle using HTML5 and CSS3? Is it also possible to put text inside?
Sergey Metlov
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139
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10 answers

How to create circle with Bézier curves?

We have a start point (x, y) and a circle radius. There also exists an engine that can create a path from Bézier curve points. How can I create a circle using Bézier curves?
Rella
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Postgis installation: type "geometry" does not exist

I am trying to create table with Postgis. I do it by this page. But when I import postgis.sql file, I get a lot of errors: ERROR: type "geometry" does not exist Does anybody know how can I fix it?
yetty
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Converting from longitude\latitude to Cartesian coordinates

I have some earth-centered coordinate points given as latitude and longitude (WGS-84). How can i convert them to Cartesian coordinates (x,y,z) with the origin at the center of the earth?
daphshez
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