Hash collisions are correctly handled by Dictionary<> – in that so long as an object implements GetHashCode() and Equals() correctly, the appropriate instance will be returned from the dictionary. First, you shouldn’t make any assumptions about how Dictionary<> works internally – that’s an implementation detail that is likely to change over time. Having said that…. … Read more
Visit this table of geometric intersection algorithms courtesy of realtimerendering.com, look at the entry for triangle/triangle intersections, and follow the references, for example to Christer Ericson, Real-Time Collision Detection, page 172. (A book which I recommend highly.) The basic idea is straightforward. If two triangles intersect, then either two edges of one triangle intersect the … Read more
The simple way is don’t test Object vs Object collisions, populate an array with the center point of each ball. Then, from each center scan a a square of size 4*radius centered on that point (you can optimize this a bit by not using a square, at the expense of making the code more complex). … Read more
Collision between circles is easy. Imagine there are two circles: C1 with center (x1,y1) and radius r1; C2 with center (x2,y2) and radius r2. Imagine there is a line running between those two center points. The distance from the center points to the edge of either circle is, by definition, equal to their respective radii. … Read more
In PyGame, collision detection is done using pygame.Rect objects. The Rect object offers various methods for detecting collisions between objects. Even the collision between a rectangular and circular object such as a paddle and a ball can be detected by a collision between two rectangular objects, the paddle and the bounding rectangle of the ball. … Read more
Great question. You basically have a complex trade-off between: Speed of a complete collision detection phase Overhead of updating / maintaining the data structure as objects move around The bad news is that there is no “perfect” answer because of this – it will genuinely depend on lots of different factors unique to your situation. … Read more
I’m trying to set up some elastic collisions using Sprite Kit I think you’re misunderstanding the physics in play here. An elastic collision is an oversimplification of a collision. In reality, no collision results in a perfect transfer of energy. I’ve explained the physics here in an answer to the related question you linked to. … Read more
// returns true if the line from (a,b)->(c,d) intersects with (p,q)->(r,s) function intersects(a,b,c,d,p,q,r,s) { var det, gamma, lambda; det = (c – a) * (s – q) – (r – p) * (d – b); if (det === 0) { return false; } else { lambda = ((s – q) * (r – a) + … Read more
There are “spatial index” data-structures for storing your circles for quick comparison later; Quadtree, r-tree and kd-tree are examples. Solution 1 seems to be a spatial index, and solution 2 would benefit from a spatial index every time you recalculate your pairs. To complicate matters, your objects are moving – they have velocity. It is … Read more
Here’s a very simple bounding rectangle routine. It expects both a and b to be objects with x, y, width and height properties: function isCollide(a, b) { return !( ((a.y + a.height) < (b.y)) || (a.y > (b.y + b.height)) || ((a.x + a.width) < b.x) || (a.x > (b.x + b.width)) ); } To … Read more