# Questions tagged [computational-geometry]

Computer geometry is a branch of computer science devoted to the study of algorithms which can be stated in terms of geometry.

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### Cubic “bezier” curve of grade n

This is code I wrote for calculating bezier curves as quickly and RAM efficiently as possible. I would like to know if there are faster ways to optimize anything, because I am very new to C++ and ...
174 views

### Graphical editor with geometric intersection

If it is possible I would like some comments on the overall style of the program. It feels like I am writing the whole program as one big script and I'm not sure how to break it down into several ...
352 views

This checks the intersection between a Ray and a Plane and between a Ray and a ...
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### Haversine formula in SQL

This is an implementation of the Haversine formula in Microsoft Transact SQL. How can I simplify the function? ...
278 views

### Quaternion rotations and preparing matrices for a shader

I am implementing an OpenGL ES 2.0 renderer in c. I want to use quaternions for rotations. Please take a look at the way I am implementing the rotation math. Everything looks as expected when the ...
105 views

### 'Tis the season for gift-wrapping

When reviewing a Graham scan convex hull algorithm implementation, I wrote the following function in an answer: ...
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### Checking for intersection points

The aim of the program is to find those points which comes under the intersection of at least 2 circles.(space is a 1000x1000 matrix) ...
4k views

### Jarvis's March Convex Hull

I'm more concerned about the coding best practices and how it's written here than the actual algorithm and math. I'm concerned about stack constraints, passing arguments,..etc. If there is anything ...
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### Generate sample coordinates inside a Polygon

I have a Polygon named as poly. I attempted to randomly select 5 coordinate points that lies inside the polygon. ...
381 views

### 2D Convex hull exercise

I'm reading Real World Haskell, and this is my first try with the language. This is the result of the exercises of chapter 3: Consider three two-dimensional points a, b, and c. If we look at ...
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### Optimize QuadTree to find K Nearest Neighbors

I'm looking a way to make my k nearest neighbors search more efficient. The context of the question is that I'm given a list of topics that have a unique ID (integer) and a (x,y) coordinate (floats) ...
244 views

### Calculating the distance squared between all vertex-pairs of a number of 2D polygons

I have implemented my code using Cython. It is the current bottleneck in my computations. There are two non-numpy functions involved: calculate_2D_dist_squared ...
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### CodeEval's SkyScrapers challenge

This is a solution to CodeEval's SkyScrapers challenge. You are given a list of triples $(l, h, r)$. Each triple represents an axis-aligned rectangle, with top-left corner at $(l, h)$ and bottom-...
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### Custom mathematical vector class

My first bigger C++ project: a vector class for personal use and statistical computation. ...
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### Custom 2D/3D Graphics Vector Classes vs SFML's

I don't really like SFML's Vector Classes so I tried making my own. Any criticism is welcome. ...
23k views

### C++ 3D Vector Implementation

I have been learning C++ now for 2 months and this week I started reading a book on 3D graphics. I like coding whatever mathematical stuff I learn so I can understand it better, so when I learnt about ...
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### 3D matrix rotation in homogeneous coordinate space

Assuming that the framework is in place to handle the difference between row and column major matrices, I am curious to know if in a header based library such implementation is semantically and ...
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### Neighbours from point connections

I am working with a mesh of triangles (in 3D, although I doubt it makes a difference). The mesh is given as list of lists, each list containing the indices of the three vertices of a triangle in said ...
153 views

### Isometric Projection and Culling

I'm working on a small isometric drawing system in JavaScript. After much help from the Gamedev section, reading old questions, I've got something working. However, it's still a little hacky. I need ...
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### Detecting two intersecting circles with editable x, y, and radius in JavaFX

I was actually pretty proud of this programming project that I came across in this book I'm working through. I only really had problems figuring out the formula for detecting whether or not the two ...
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### Finding largest subset of line segments that don't intersect

I completed a challenge of codeeval called BayBridges. It can be found here. I have uploaded my code on GitHub here. In summary, the challenge is to take a list of line segments, each specified by ...
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### Finding the nearest polygon

Finding the nearest polygon out of a list of polygons seems to be quite a challenge on performance, due to lack of optimization. Consider the following image: I'll give the concept behind this. The "...
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### Calculating the distance between one point, and many others

In my program, I have entities that I call "blobs", because they have a blobby shape. Blobs are polygons. If I have two blobs, then their information array would look like: ...
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### Checking if a list of coordinates defines a closed, exact rectangle

I have to determine if an N sized list of coordinates defines a closed, exact rectangle. I start with the question "How do I check if a list of coordinates is in the shape of a rectangle?" The ...
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### Calculating if a point is within a polygon, or outside of it

Here is the function (along with its support functions): ...
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### Calculating “element-wise” the angles between two lists of vectors

Let's say you have two lists of vectors: v1s = [a, b, c] v2s = [d, e, f] I am interested in generating the following result:...
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### Calculate the intersection between two intervals on the same circle

I want to calculate the ratio of intersection between two intervals; the length of the intersection divided by the length of the shorter interval. If two intervals do not intersect, the ratio is 0. ...
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### Quick Hull Algorithm implementation for higher dimensions

Last version of library (performance has been improved drastically since posting). I tried to implement the Quick Hull Algorithm for computing the convex hull of a finite set of D-dimensional points. ...
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### Point in a polygon algorithm

I am implementing a Point in polygon algorithm. Inputs: M, N: size of the matrix poly: a ...
686 views

### 3D vector CUDA kernel

I designed this CUDA kernel to compute a function on a 3D domain: p and Ap are 3D vectors that are actually implemented as a ...
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### Find triangles from line

I have some lines that form triangles. I'd like to challenge the fastest way to find all triangles. In particular the code should take an ArrayList of Line2D object and return an ArrayList of ...
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### Python implementation of the Ramer-Douglas-Peucker Algorithm

I recently implemented the RDP polygon approximation algorithm in Python and I'm skeptical of whether or not I implemented it correctly of with the greatest efficiency. The algorithm runs in around 0....
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### Class Vector with Python 3

Here is a class vector in python 3, for n-dimmensional vectors. Please suggest ways to improve the code as well as fix bugs and errors. The only rule is not using: numpy, sympy, scipy and so on. Only ...
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### Implementation of SAT (Separating axis theorem)

A project I was working on required the usage of the Separating Axis Theorem to detect collisions between two convex polygons in real time. So I implemented a basic class (...
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### Optimize vector rotation

I have a trivial function that rotates 2d vectors, and a method in a class representing a polygon that rotates every point in the polygon around an origin. The code is fairly optimized as it is, but I ...
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### Algorithm to get an arbitrary perpendicular vector

Is there a more efficient/direct way to find an arbitrary perpendicular vector of another vector? ...
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### Faster computation of barycentric coordinates for many points

I'm just starting to understand the Python syntax and I created a module that does what I wanted, but really slow. Here are the stats of cProfile, top 10 ordered by ...
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### Calculating angle in isometric view

I have an angle where I need to convert a 'normal' angle to an isometric angle (116 degrees), and I came up with this function. It works, but I was wondering if the math could be optimized/simplified, ...
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### How to reduce execution time for this clustering computation?

Is there any way to reduce total execution time for the function getSilhouetteIndex? P.S. I am using weka SimpleKMeans for ...
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### Centroid of a polygon in Clojure

I am studying Clojure and functional programming. I wrote this function to compute the centroid of a polygon specified as a vector of points, e.g. ...
611 views

### Computing tangent space basis vectors for an arbitrary mesh

This is more like a share and a request than a question. I converted Eric Lengyel's code, which calculates tangents of a mesh for the purpose of texturing and normal mapping, to support SIMD. For this ...
485 views

### Refactor code to find four co-linear points

I am relatively new to Java, but have been reading up on how to improve the quality of my code. I am writing a system where I take in a series of points from a file with x and y co-ordinates and by ...
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### Move Line across Plane

I want move a Vertical line segment across a plane or another way sweep the plane, from Left to right. The figure illustrates how the segment is moving at the X-axis. When x1 >= X beginning and i ...
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### Best way to work out angle between points?

I have the following JavaScript code to work out the angle between two points (clockwise). The code I have seems a bit "hacky" to me, as I have a while loop ensuring the number is not negative (to ...
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### Complex logic that I'm certain can be simplified

This is code from a grappling hook implementation. This is specifically code that, after a block is detected between two way points, it tries to find a path around. This particular piece of the ...
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### Overlapping rectangles

I received the following question in a technical interview today (for a devops/SRE position): Write a function which returns true if the two rectangles passed to it as arguments would overlap if ...
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### Graham Scan convex hull algorithm

I'm beginning to learn Haskell. I've implemented the Graham Scan algorithm for detection of convex hull following the Real World Haskell book. I'm looking for general advice regarding the style and ...
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### Algorithm for merging overlapping rectangles

The following code is part of an application I maintain that has a VT100/Xterm style graphical user interface that is implemented using text (Think Midnight Commander. Retro, I know.) Part of the ...