Questions tagged [computational-geometry]
The study of computer algorithms which admit geometric descriptions, and geometric problems arising in association with such algorithms. The two major classes of problems are (a) efficient design of algorithms and data classes using geometric concepts and (b) representation and modelling of curves and surfaces.
1,263 questions
0 votes
1 answer
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I need help to understand the algorithm that tests if a point lies inside or outside a general 2D polygon
The algorithm in question is from this webpage. The complete algorithm from this webpage is as follows: ...
3 votes
1 answer
206 views
Smallest overlapping circles containing unit circles in each section - Fifth arrangement
This question is related to my previous posts about overlapping circles, like this one. Another way of overlapping 3 circles looks like this: Once again, my question is, "How can these 3 circles ...
4 votes
0 answers
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Is there an efficient algorithm to find the smallest circumscribed circle to a set of points?
I have a set of $n$ points in the plane and I want to find the smallest circumscribed circle that contains them. By circumscribed I mean that the circle must pass through $3$ of the points. Brute ...
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3 answers
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How do I find the straightest path through 3D rectangles?
I'm mainly a programmer, not a mathematician, so please bear with me. I have a sequence of rectangles in 3D space. Each one has a specified pose: position, an orientation (rotation in 3D), and a width ...
3 votes
0 answers
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Is the adaptive jamming complexity for aperture identification $O(m \log m + \log N)$?
Let $D\subset\mathbb{R}^{2}$ be a bounded, open, connected polygonal domain whose boundary decomposes (unknown to the observer) as a disjoint union $$ \partial D \;=\; U \,\sqcup\, W $$ where $U$ is ...
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Calculate the area of the union of rectangles in a plane
Given a set of $n$ rectangles $[a, b] × [c, d]$ in a cartesian coordinate plane, calculate the area of their union. My first thought of this problem is by using a simple sweep line algorithm plus a ...
3 votes
1 answer
101 views
Toric arrangements and system of polynomial equations
I am working on some problem on toric arrangements at the crossroad between topology, combinatorics and algebraic geometry. $\textbf{Setting}$ Let $m,n\geq1$ and let \begin{equation*}\mathcal{S}=\left\...
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Volume/centroid of unit cube cut by plane
I need to calculate the volume (and centroid, but techniques for both seem to be fairly similar) of the intersection between the unit cube defined by $0 \leq x,y,z \leq 1$ and the halfspace defined by ...
1 vote
2 answers
101 views
How to partition a polygon into contiguous regions with given area ratios?
I am looking for a way to divide a 2D polygon (possibly with a complex shape, like an "H". These are actually floor layouts of buildings) into several connected sub-regions, where each ...
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0 answers
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How does the existence of a second order Voronoi polyhedron imply corresponding first order Voronoi polyhedra to be adjacent?
Theorem in question: I understood the first part, I don't understand the converse. Why can we assume that for all $v \in V_{ij}$ point $w_i$ is the nearest neighbor? Can't we say that $w_i$ or $w_j$ ...
1 vote
0 answers
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Simple medial axis algorithm for convex polygons gets unexpectedly tangled up
When a polygon is convex, its medial axis a.k.a. topological skeleton is particularly simple: there are no curved parts; it looks like an undirected tree whose internal nodes are all those points in ...
1 vote
0 answers
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Found simple quantities to check if a plane quadrilateral is convex, concave or self-intersecting [closed]
I have discovered two quantities that are very easily computable from the vertex coordinates of a plane quadrilateral which allow to check directly if the quadrilateral is convex, concave, or self-...
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1 answer
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How to test if a cubic Bézier approximates a circular arc using only its control points?
Given a cubic Bézier curve with control points P0, P1, P2, P3, is there a way to determine whether it approximates a circular arc using only those four points — without evaluating the curve at ...
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0 answers
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Why does the conic combination of two points in two dimension does not contain points outside the rays formed from origin to the two points?
I know the conic combination is A set $C \subseteq \mathbb{R}^n$ is a cone if: $$x \in C \Rightarrow \lambda x \in C \quad \text{for all } \lambda \geq 0$$ Let's take two non-zero, non-colinear ...
0 votes
2 answers
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How to test if a point lies inside a spherical quadrilateral?
I have four 3D points A , B , C , D that define a quadrilateral (assumed to be convex) on the surface of a unit sphere (i.e., all points lie on the sphere centered at the origin). These points define ...