# Tagged Questions

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### Applying drag to a collision prediction formula

I feel like this question might be below the minds of Math StackExchange, but I'll try anyway. (I can understand Math generally, but I'm probably not the caliber of people here.) I've been working on ...
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### Convex shape in ellipsoid containment test

Supposed you to want find out if an ellipsoid fully contains a convex shape. In the picture below I have drawn two situations. The left shape is overlapping with the ellipsoid, and the right shape is ...
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### Scaling intersecting circles that are locked to individual rays

I have two circles that intersect and I need to find the scalar value where they are only touching at one point. Each circle is locked to a point on it's circumference and can only scale relative to ...
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### Intersection of cubes in 3D space

There are two cubes cubeA and cubeB. cubeA has 8 points and cubeB has 8 points. How do I check if the cubes are intersecting. Cubes are not aligned along any axis and they have different rotations.
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### How to find the zeros of a fourth degree polynomial without integer coefficient

I am currently programming a simulation for a pinball game and want to calculate the time when the ball hits a circle (if they collide at some point). For the calculation part, i'm adding the radius ...
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### Determine if Objects are moving towards each other

If I have an object-1 at $p_1$ with velocity $v_1$ and object-2 at $p_2$ with velocity $v_2$. How would you determine if the objects are moving towards each other? The requirement is that it must be ...
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### How can I use the Bullet-Physics's ray-cast normal to calculate angles for a object to lay on a surface?

[Give the normal of a surface in XYZ format, how do I calculate rotations (also in XYZ format) needed to set an object parallel to the surface?] I have a collision library that uses the bullet ...
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### Sphere intersecting a triangle

I'm studying "game physics" programming, and in this article, at page 14, I don't understand how is the author right. ... if the sphere does indeed collide with the inside of the triangle then a ...
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### Shared Volume of Overlapping 3D Cubes/Rectangles

Good afternoon, I have been looking for an approach to figure out the volume where two cubes/rectangles overlap, meaning, I know when they do, I just don't know the coordinates of the volume in which ...
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### Algorithm to find a line segment is passing through a circle or not?

I have a line segment between two points P1 (X1,Y1) and P2 (X2,Y2). And I have a circle at point Q(Xq , Yq) with radius R . Can I have an equation in which I can put these values and the result shows ...
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### What is the optimal way to detect a collision between an AABB figure and a non-AABB figure?

Background I'm looking to do this programmatically in Java, but if desired you can post solutions in C/C++ or plain English instructions if you're not a programmer, but I would appreciate an ...
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### How to calculate solid angle of a rectangular detector of 20cm x 10cm?

I have an detector of $20\mathrm{cm}\times 10\mathrm{cm}$, how can I calculate the solid angle subtended by the detector if the detector is placed at $30\ \mathrm{cm}$ apart? Because directly I can ...
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### How do I find the Intersection of two 3D triangles?

I've got a rather complicated geometry problem that I'm trying to solve - how to find the intersection between two triangles in 3D space. I've looked around at other questions and answers on this site ...
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### Hashing Probability

I have just started to learn about the topic of hashing. I understand how it works and the difference between closed address and open address, but do not know how to calculate the probability of a ...
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### Calculate intercept location and time

I want to calculate the coordinates and time where object B2 can intercept object B1. Asuming the following: All coordinates are in pixels B1: Moves from coordinates A1 to A2, it has a speed of 2 ...
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### How do you determine if two triangles are intersecting for collision detection?

I've been scouring the internet for things about intersecting triangles. I haven't been able to find something that just gives me the math and what all the variables are equal to. I would love the ...
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### Simulating elastic collision

I wrote a simple program where i can move around some objects. Every object has a bounding box and I use hooke's law to apply forces to the colliding objects. On every tick, I calculate the forces, ...
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### How to find initial direction and angle of collision of a ball with a vertical wall?

I have a problem in my game. I have a wall where a ball hit to a wall from anywhere. I need to give it to the direction according to the collision law. Let suppose if a ball thrown from $(0, 0)$ and ...
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### How do I detect if two polygons overlap each other or not?

I'm developing a game engine. Currently I'm writing the collision detection part. I have to write down an algorithm which detects if two given polygons are overlapping each other or they are separated ...
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### Find the plane a triangle lies on

I am trying to determine if the plane on which two triangles lie intersects for a collision-detection implementation. Unfortunately, I'm stuck at step one, which is finding the plane on which a ...
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### Collision Detection in Finite but Limitless Space

Doing collision detection on two arbitrary rectangles is easy, given their coordinates and dimensions. In regular 2d-space, that is. But what about "finite but limitless" space, say a screen area ...
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### Probability of 8 or 9 digit sequence colliding in the same place in two 65 digit numbers

I have two numbers: 3032643431333337636238613038343231383364303731376566303037663231 3861663464383131656131653461343961343364303737663565356561653361 36430373 ...
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### Assuming a ray defined by a starting point and a direction. How can I tell if a plane is behind it or in front of it?

If I have a ray defined by a starting point and a direction, and a plane defined by its normal and its distance from the origin, how can I tell if the plane is in front versus behind the ray? By ...
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### How to find the intersection point of two moving circles?

I'm trying to develop a simulation in C#, and I have to find the intersection (or collision) point of two moving circles, in 2D space. Actually one of my circles will be stationary, so only one of ...
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### Optimized collision check for all pairs using bounding volume hierarchy

I am working on broad-phase collision detection. I understood how to build a bounding volume hierarchy using AABB's as bounding volumes. I also understood how to check all collisions of a single AABB ...
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### Repeated Random Number Selection Until No Collisions - Number of Repetitions

I have a problem that has to do with my research that troubles me for a while and I could not find a solution either by myself or online. Suppose you have $n$ people in one room. Everyone picks a ...
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### Collision detection between two accelerating spheres with no initial velocity?

We have two non-touching spheres of radii r1 & r2 are lying in space at rest. Both of them are then given accelerations a1 & a2 respectively at time t=0. Find whether they will ever come in ...
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### What's the shortest distance between two cubic Bézier curves?

This question comes from TeX.SX http://tex.stackexchange.com/questions/183123/whats-the-minimum-distance-between-two-bezier-curves (From typography; TeX) We are trying to find minimum distance ...
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### N points in a circle around a point on a sphere.

Consider a 3D sphere: $(x_{c}, y_{c}, z_{c})$ : cartesian coordinates of the center $r$ : the radius Consider a random point on the surface of this sphere of coordinates : $(x_{0}, y_{0}, z_{0})$...
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### 2D elastic collision using Matlab

I recently started using Matlab and am modeling hard spheres in 2D. I have n particles, their positions are given by two arrays x(n,1) and y(n,1). The simulation has N time steps. I set up a distance ...
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### Collision of two moving lines (3D)

I have two lines / edges moving with linear velocity in timesteps. How do I determine whether the lines collide / intersect in the intervening period? My lines are (P1,Q1) and (P2,Q2). The endpoints ...
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### Find all the intersection points of a vector parabola (in R3) and a sphere

Given that I have a vector in R3 (7t, 10t - 2t^2, 5t) | (These numbers are arbitrary for the sake of the process) A sphere centered at the point ( 15, 25, 10) with a radius of 20 There is a ...
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### Resolve A Circle to Rectangle Collision

In 2D, I have a circle and a rectangle, the circle has properties: density: 0.7, velx: 2, vely: 3, rad: 20, centx: 20, centy: 10 and the rectangle has properties: topx: 200, topy: 300, width: 500, ...
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### Moving segments colliding

I need to check if the edges of two triangles will collide. I do an edge-edge check for each pair. One segment is stationary, while the other moves with constant velocity. The segments are not ...
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### Crash and Collision - Kinematics Question?

Vancouver is 300 km away from Seattle. Two friends, one leaving from each city on a bike want to find a campsite between the two cities. One cyclist starts from vancouver at 25 km/h. His friend will ...
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### Closest point out of collision

I am tackling IMO very hard problem from geometry "How to find closest point out of collision". To explain it better I've drawn an image explaining it. Basically: given a point on 2D plane( yellow ...
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### How to compute characteristic polynominal of two conics

If I have two conics defined as $A: XAX^T$ and $B: XBX^T$ how can I expand characteristic polynomial $f(\lambda) = det(\lambda A + B)$ so that it can be computed by a computer program or Matlab?
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### Avoiding collision with a plane

I am developing the software to control a common fly's flight in Opensim simulator, although I am facing some troubles determining when the fly must maneuver to avoid hitting a wall. Questions How ...
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### Sphere-Sphere intersection c#, 3D coordinates of collision points

Ive had a look over numerous 3D sphere-sphere intersection questions and unfortunately they are either too far ahead of my ability to comprehend or not tailored to what I am looking for. This is ...
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### Finding coordinates of a path

I am trying to find out whether to geometrical shapes overlap. This is based on an SVG-file. The following is an example: Group 1: ...