2d

What are some good data structures for keeping track of agents in a two-dimensional, spatial simulation? I've seen some references to quadtrees (which I understand) and kd-trees (which I don't understand very well). I'm looking for something through which an agent can efficiently say, "I know my location, and I would like to know which agents are near me (within a certain radius of myself)." Examples (pseudo-code is fine) would be greatly appreciated. I'm working in Java. Well, I'm not sure exactly how it is implemented, but the MASON toolkit uses a discretization algorithm that places agents

I'm going to start programming a 2D tile-based game in Qt and read about the QGraphicsScene and QGraphicsView classes which are intended for displaying and handling lots of 2D objects. My question is that will it be feasible to create a world with lots of tiles using QGraphicsScene? Can I add the whole world at once tile-by-tile or should I try to implement something to restrict the area a bit? I've read that QGraphicsScene can handle "thousands of items" but a 2D tile map can easily get really, really big (200x200 tiles? not that many, but that's already 40,000 objects which is a lot). The

First read Taig's question Taig said: When calling Matrix.postScale( sx, sy, px, py ); the matrix gets scaled and also translated (depending on the given point x, y). That predestines this method to be used for zooming into images because I can easily focus one specific point. The android doc describes the method like this: Postconcats the matrix with the specified scale. M' = S(sx, sy, px, py) * M At a first glance this seems ridiculous because M is supposed to be a 3x3-Matrix. Digging around I've found out that android uses a 4x4-Matrix for its computations (while only providing 3x3 on its

I'm implementing a color picker. There is problem with the rendering. When I call c.fillRect(0, 0, 100, 80); the size of that rectangle is 103x42 px instead of 100x80. What is wrong here? Also, rectangles are antialiased. Do I need offset the position by (0.5, 0.5) to avoid AA? I didn't use any kind of the coordinate system transformations. colorSlider = function($e, color) { this._$canvas = $('<canvas></canvas>'); this._c = this._$canvas[0].getContext('2d'); this._color = color || { r: 0, g: 0, b: 0 }; this._$canvas.width('310px'); this._$canvas.height('80px'); $e.append(this._$canvas); this.

I have a cloud of points scattered in a 2D Euclidean space. I would like to calculate the area inside the polygon linking the most extreme (=peripheral) points of the cloud. In other words, I would like to estimate the area covered by the cloud in this space. Is there a formula in R? Thanks a lot for any response Julien This is called the convex-hull problem; R built-in chull function should do the work. To count area, you may use a formula from here . EDIT: Even better; splancs package has areapl function. So the function solving your problem should look like this: cha<-function(x,y){ chull(x

I'm designing a collision detection game tutorial for young adults, so I want this to be as simple as possible to make it easier to explain. The requirements are very simple. The world is 2D and contains only rectangles (of arbitrary sizes). BSP and even quadtrees seems like it would be overkill (again, the emphasis is on simplicity) but I would like something more efficient than brute forcing through all n(n-1)/2 possible collisions. 2D, rectangles only, and simple. Can anyone point to an algorithm I can look up? Is a quadtree algorithm what I'm looking for? EDIT: Also, the rectangles will