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• What kind of physics to choose for our arcade 3D MMO?

  - by Nick

  We're creating an action MMO using Three.js (WebGL) with an arcadish feel, and implementing physics for it has been a pain in the butt. Our game has a terrain where the character will walk on, and in the future 3D objects (a house, a tree, etc) that will have collisions. In terms of complexity, the physics engine should be like World of Warcraft. We don't need friction, bouncing behaviour or anything more complex like joints, etc. Just gravity. I have managed to implement terrain physics so far by casting a ray downwards, but it does not take into account possible 3D objects. Note that these 3D objects need to have convex collisions, so our artists create a 3D house and the player can walk inside but can't walk through the walls. How do I implement proper collision detection with 3D objects like in World of Warcraft? Do I need an advanced physics engine? I read about Physijs which looks cool, but I fear that it may be overkill to implement that for our game. Also, how does WoW do it? Do they have a separate raycasting system for the terrain? Or do they treat the terrain like any other convex mesh? A screenshot of our game so far:

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• LWJGL Java 2D collision when lagging

  - by user1990950

  I'm using a tile based collision, but when the game is lagging (the lag isn't the problem) the collision fails and the player falls through tiles. This is the movement/collision detection code of my Player class: gravity.y = gspeed; speed.y+=gravity.y; position.set(position.x + direction.x * speed.x * deltaSeconds, position.y + direction.y * speed.y * deltaSeconds); for (int i = (int) Math.round(position.x / 32) - 2 * t; i < (int) Math.round(position.x / 32) + 3 * t; i++) { for (int j = (int) Math.round(position.y / 32); j < (int) Math.round((position.y + height + 64) / 32); j++) { checkCollision(i, j, deltaSeconds); } } public void checkCollision(int i, int j, float deltaSeconds) { bbox.setBounds((int) position.x, (int) position.y, (int) width, (int) height); Tile t = null; t = Map.getTile(i, j); if (t != null) { if (t.isSolid()) { if (t.getTop().intersects(bbox)) { if (position.y + height < t.y * 32 + 32) { if (speed.y >= 0) { position.y = t.y * 32 - height; speed.y = 0; gravity.y = 0; jumpState = 0; } } } if (t.getBottom().intersects(bbox)) { if (position.y < t.y * 32 + 32) { position.y = t.y * 32 + 32; speed.y = 0; } } else { if (t.getLeft().intersects(bbox)) { if (position.x + width > t.x * 32) { position.x = t.x * 32 - width; speed.x = 0; } } if (t.getRight().intersects(bbox)) { if (position.x < t.x * 32 + 32) { position.x = t.x * 32 + 32; speed.x = 0; } } } } } } Is it possible to fix my code, if yes how? Or is it possible to tell if the game is lagging?

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• Boolean checks with a single quadtree, or multiple quadtrees?

  - by Djentleman

  I'm currently developing a 2D sidescrolling shooter game for PC (think metroidvania but with a lot more happening at once). Using XNA. I'm utilising quadtrees for my spatial partitioning system. All objects will be encompassed by standard bounding geometry (box or sphere) with possible pixel-perfect collision detection implemented after geometry collision (depends on how optimised I can get it). These are my collision scenarios, with < representing object overlap (multiplayer co-op is the reason for the player<player scenario): Collision scenarios (true = collision occurs): Player <> Player = false Enemy <> Enemy = false Player <> Enemy = true PlayerBullet <> Enemy = true PlayerBullet <> Player = false PlayerBullet <> EnemyBullet = true PlayerBullet <> PlayerBullet = false EnemyBullet <> Player = true EnemyBullet <> Enemy = false EnemyBullet <> EnemyBullet = false Player <> Environment = true Enemy <> Environment = true PlayerBullet <> Environment = true EnemyBullet <> Environment = true Going off this information and the fact that were will likely be several hundred objects rendering on-screen at any given time, my question is as follows: Which method is likely to be the most efficient/optimised and why: Using a single quadtree with boolean checks for collision between the different types of objects. Using three quadtrees at once (player, enemy, environment), only testing the player and enemy trees against each other while testing both the player and enemy trees against the environment tree.

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• Platform game collisions with Block

  - by Sri Harsha Chilakapati

  I am trying to create a platform game and doing wrong collision detection with the blocks. Here's my code // Variables GTimer jump = new GTimer(1000); boolean onground = true; // The update method public void update(long elapsedTime){ MapView.follow(this); // Add the gravity if (!onground && !jump.active){ setVelocityY(4); } // Jumping if (isPressed(VK_SPACE) && onground){ jump.start(); setVelocityY(-4); onground = false; } if (jump.action(elapsedTime)){ // jump expired jump.stop(); } // Horizontal movement setVelocityX(0); if (isPressed(VK_LEFT)){ setVelocityX(-4); } if (isPressed(VK_RIGHT)){ setVelocityX(4); } } // The collision method public void collision(GObject other){ if (other instanceof Block){ // Determine the horizontal distance between centers float h_dist = Math.abs((other.getX() + other.getWidth()/2) - (getX() + getWidth()/2)); // Now the vertical distance float v_dist = Math.abs((other.getY() + other.getHeight()/2) - (getY() + getHeight()/2)); // If h_dist > v_dist horizontal collision else vertical collision if (h_dist > v_dist){ // Are we moving right? if (getX()<other.getX()){ setX(other.getX()-getWidth()); } // Are we moving left? else if (getX()>other.getX()){ setX(other.getX()+other.getWidth()); } } else { // Are we moving up? if (jump.active){ jump.stop(); } // We are moving down else { setY(other.getY()-getHeight()); setVelocityY(0); onground = true; } } } } The problem is that the object jumps well but does not fall when moved out of platform. Here's an image describing the problem. I know I'm not checking underneath the object but I don't know how. The map is a list of objects and should I have to iterate over all the objects??? Thanks

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• Why does my player stop when stepping onto a new tile?

  - by user220631

  Me and my friend are creating a game from scratch. He is in charge of art design and I am in charge of coding. I have done well so far with the code, but I have a collision detection problem when the character moves right: Once the player moves right, whenever a new block is encountered, the player stops. I don't know if this is a problem with collision or the player but I can't work around it. Here is the collision code: this.IsColliding = function(obj) { if(this.X > obj.X + obj.Width) return false; else if(this.X + this.Width < obj.X) return false; else if(this.Y > obj.Y + obj.Height) return false; else if(this.Y + this.Height < obj.Y) return false; else return true; } I also wanted to see if there as a way to make the player collide with the bottom of the block and the right side of the block instead of running through it.

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• Normalizing the direction to check if able to move

  - by spartan2417

  i have a a room with 4 walls along the x and z axis respectively. My player who is in first person (therefore the camera) should have collision detection with these walls. I'm relatively new to this so please bare with me. I believe the way to do this is to calculate the direction and distance to the wall from the camera and then normalize the directions. However i can only get this far before i dont know what to do. I think you should work out the angle and direction your facing? where _dx and _dz is the small buffer in front of the camera. float CalcDirection(float Cam_x, float Cam_z, float Wall_x, float Wall_z) { //Calculate direction and distance to obstacle. float ob_dirx = Cam_x + _dx - Wall_x; float ob_dirz = Cam_z + _dz - Wall_z; float ob_dist = sqrt(ob_dirx*ob_dirx + ob_dirz*ob_dirz); //Normalise directions float ob_norm = sqrt(ob_dirx*ob_dirx + ob_dirz*ob_dirz); ob_dirx = (ob_dirx)/ob_norm; ob_dirz = (ob_dirz)/ob_norm; can anyone explain in laymen's terms how i work out the angle?

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• BoundingSpheres move when they should not

  - by NDraskovic

  I have a XNA 4.0 project in which I load a file that contains type and coordinates of items I need to draw to the screen. Also I need to check if one particular type (the only movable one) is passing in front or trough other items. This is the code I use to load the configuration: if (ks.IsKeyDown(Microsoft.Xna.Framework.Input.Keys.L)) { this.GraphicsDevice.Clear(Color.CornflowerBlue); Otvaranje.ShowDialog(); try { using (StreamReader sr = new StreamReader(Otvaranje.FileName)) { String linija; while ((linija = sr.ReadLine()) != null) { red = linija.Split(','); model = red[0]; x = red[1]; y = red[2]; z = red[3]; elementi.Add(Convert.ToInt32(model)); podatci.Add(new Vector3(Convert.ToSingle(x), Convert.ToSingle(y), Convert.ToSingle(z))); sfere.Add(new BoundingSphere(new Vector3(Convert.ToSingle(x), Convert.ToSingle(y), Convert.ToSingle(z)), 1f)); } } } catch (Exception ex) { Window.Title = ex.ToString(); } } The "Otvaranje" is an OpenFileDialog object, "elementi" is a List (determines the type of item that would be drawn), podatci is a List (determines the location where the items will be drawn) and sfere is a List. Now I solved the picking algorithm (checking for ray and bounding sphere intersection) and it works fine, but the collision detection does not. I noticed, while using picking, that BoundingSphere's move even though the objects that they correspond to do not. The movable object is drawn to the world1 Matrix, and the static objects are drawn into the world2 Matrix (world1 and world2 have the same values, I just separated them so that the static elements would not move when the movable one does). The problem is that when I move the item I want, all boundingSpheres move accordingly. How can I move only the boundingSphere that corresponds to that particular item, and leave the rest where they are?

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• Point in Polygon, Ray Method: ending infinite line

  - by user2878528

  Having a bit of trouble with point in polygon collision detection using the ray method i.e. http://en.wikipedia.org/wiki/Point_in_polygon My problem is I need to give an end to the infinite line created. As with this infinite line I always get an even number of intersections and hence an invalid result. i.e. ignore or intersection to the right of the point being checked what I have what I want My current code based of Mecki awesome response for (int side = 0; side < vertices.Length; side++) { // Test if current side intersects with ray. // create infinite line // See: http://en.wikipedia.org/wiki/Linear_equation a = end_point.Y - start_point.Y; b = start_point.X - end_point.X; c = end_point.X * start_point.Y - start_point.X * end_point.Y; //insert points of vector d2 = a * vertices[side].Position.X + b * vertices[side].Position.Y + c; if (side - 1 < 0) d1 = a * vertices[vertices.Length - 1].Position.X + b * vertices[vertices.Length - 1].Position.Y + c; else d1 = a * vertices[side-1].Position.X + b * vertices[side-1].Position.Y + c; // If points have opposite sides, intersections++; if (d1 > 0 && d2 < 0 ) intersections++; if (d1 < 0 && d2 > 0 ) intersections++; } //if intersections odd inside = true if ((intersections % 2) == 1) inside = true; else inside = false;

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• how get collision callback of two specific objects using bullet physics?

  - by sebap123

  I have got problem implementing collision callback into my project. I would like to have detection between two specific objects. I have got normall collision but I want one object to stop or change color or whatever when colides with another. I wrote code from bullet wiki: int numManifolds = dynamicsWorld->getDispatcher()->getNumManifolds(); for (int i=0;i<numManifolds;i++) { btPersistentManifold* contactManifold = dynamicsWorld->getDispatcher()->getManifoldByIndexInternal(i); btCollisionObject* obA = static_cast<btCollisionObject*>(contactManifold->getBody0()); btCollisionObject* obB = static_cast<btCollisionObject*>(contactManifold->getBody1()); int numContacts = contactManifold->getNumContacts(); for (int j=0;j<numContacts;j++) { btManifoldPoint& pt = contactManifold->getContactPoint(j); if (pt.getDistance()<0.f) { const btVector3& ptA = pt.getPositionWorldOnA(); const btVector3& ptB = pt.getPositionWorldOnB(); const btVector3& normalOnB = pt.m_normalWorldOnB; bool x = (ContactProcessedCallback)(pt,fallRigidBody,earthRigidBody); if(x) printf("collision\n"); } } } where fallRigidBody is a dynamic body - a sphere and earthRigiBody is static body - StaticPlaneShape and sphere isn't touching earthRigidBody all the time. I have got also other objects that are colliding with sphere and it works fine. But the program detects collision all the time. It doesn't matter if the objects are or aren't colliding. I have also added after declarations of rigid body: earthRigidBody->setCollisionFlags(earthRigidBody->getCollisionFlags() | btCollisionObject::CF_CUSTOM_MATERIAL_CALLBACK); fallRigidBody->setCollisionFlags(fallRigidBody->getCollisionFlags() | btCollisionObject::CF_CUSTOM_MATERIAL_CALLBACK); So can someone tell me what I am doing wrong? Maybe it is something simple?

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• How do 2D physics engines solve the problem of resolving collisions along tiled walls/floors in non-grid-based worlds?

  - by ssb

  I've been working on implementing my SAT algorithm which has been coming along well, but I've found that I'm at a wall when it comes to its actual use. There are plenty of questions regarding this issue on this site, but most of them either have no clear, good answer or have a solution based on checking grid positions. To restate the problem that I and many others are having, if you have a tiled surface, like a wall or a floor, consisting of several smaller component rectangles, and you traverse along them with another rectangle with force being applied into that structure, there are cases where the object gets caught on a false collision on an edge that faces the inside of the shape. I have spent a lot of time thinking about how I could possibly solve this without having to resort to a grid-based system, and I realized that physics engines do this properly. What I want to know is how they do this. What do physics engines do beyond basic SAT that allows this kind of proper collision resolution in complex environments? I've been looking through the source code to Box2D trying to find out how they do it but it's not quite as easy as looking at a Collision() method. I think I'm not good enough at physics to know what they're doing mathematically and not good enough at programming to know what they're doing programmatically. This is what I aim to fix.

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• Simple (and fast) dices physics

  - by Markus von Broady

  I'm programming a throw of 5 dices in Actionscript 3 + AwayPhysics (BulletPhysics port). I had a lot of fun tweaking frictions, masses etc. and in the end I found best results with more physics ticks per frame. Currently I use 10 ticks per frame (1/60 s) and it's OK, though I see a difference in plus for 20 ticks. Even though it's only 5 cubes (dices) in a box (or a floor with 3 walls really) I can't simulate 20 ticks in a frame and keep FPS at 60 on a medium-aged PC. That's why I decided to precompute frames for animation, finishing it in around 1700 ticks in 2 seconds. The flash player is freezed for these 2 seconds, and I'm afraid that this result will be more of a 5 seconds or even more, if I'll simulate multi-threading and compute frames in background of some other heavy processes and CPU drawing (dices is only a part of this game). Because I want both players to see dices roll in same way, I can't compute physics when having free resources, and build a buffer for at least one throw of each type (where type is number of dices thrown). I'm afraid players will see a "preparing dices........." message too often and for too long. I think the only solution to this problem is replacing PhysicsEngine with something simpler, or creating own physicsEngine. Do You have any formulas for cube-cube and cube-wall collision detection, and for calculating how their angular and linear velocities should change after a collision occurs?

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• creating objects from trivial graph format text file. java. dijkstra algorithm.

  - by user560084

  i want to create objects, vertex and edge, from trivial graph format txt file. one of programmers here suggested that i use trivial graph format to store data for dijkstra algorithm. the problem is that at the moment all the information, e.g., weight, links, is in the sourcecode. i want to have a separate text file for that and read it into the program. i thought about using a code for scanning through the text file by using scanner. but i am not quite sure how to create different objects from the same file. could i have some help please? the file is v0 Harrisburg v1 Baltimore v2 Washington v3 Philadelphia v4 Binghamton v5 Allentown v6 New York # v0 v1 79.83 v0 v5 81.15 v1 v0 79.75 v1 v2 39.42 v1 v3 103.00 v2 v1 38.65 v3 v1 102.53 v3 v5 61.44 v3 v6 96.79 v4 v5 133.04 v5 v0 81.77 v5 v3 62.05 v5 v4 134.47 v5 v6 91.63 v6 v3 97.24 v6 v5 87.94 and the dijkstra algorithm code is Downloaded from: http://en.literateprograms.org/Special:Downloadcode/Dijkstra%27s_algorithm_%28Java%29 */ import java.util.PriorityQueue; import java.util.List; import java.util.ArrayList; import java.util.Collections; class Vertex implements Comparable<Vertex> { public final String name; public Edge[] adjacencies; public double minDistance = Double.POSITIVE_INFINITY; public Vertex previous; public Vertex(String argName) { name = argName; } public String toString() { return name; } public int compareTo(Vertex other) { return Double.compare(minDistance, other.minDistance); } } class Edge { public final Vertex target; public final double weight; public Edge(Vertex argTarget, double argWeight) { target = argTarget; weight = argWeight; } } public class Dijkstra { public static void computePaths(Vertex source) { source.minDistance = 0.; PriorityQueue<Vertex> vertexQueue = new PriorityQueue<Vertex>(); vertexQueue.add(source); while (!vertexQueue.isEmpty()) { Vertex u = vertexQueue.poll(); // Visit each edge exiting u for (Edge e : u.adjacencies) { Vertex v = e.target; double weight = e.weight; double distanceThroughU = u.minDistance + weight; if (distanceThroughU < v.minDistance) { vertexQueue.remove(v); v.minDistance = distanceThroughU ; v.previous = u; vertexQueue.add(v); } } } } public static List<Vertex> getShortestPathTo(Vertex target) { List<Vertex> path = new ArrayList<Vertex>(); for (Vertex vertex = target; vertex != null; vertex = vertex.previous) path.add(vertex); Collections.reverse(path); return path; } public static void main(String[] args) { Vertex v0 = new Vertex("Nottinghill_Gate"); Vertex v1 = new Vertex("High_Street_kensignton"); Vertex v2 = new Vertex("Glouchester_Road"); Vertex v3 = new Vertex("South_Kensignton"); Vertex v4 = new Vertex("Sloane_Square"); Vertex v5 = new Vertex("Victoria"); Vertex v6 = new Vertex("Westminster"); v0.adjacencies = new Edge[]{new Edge(v1, 79.83), new Edge(v6, 97.24)}; v1.adjacencies = new Edge[]{new Edge(v2, 39.42), new Edge(v0, 79.83)}; v2.adjacencies = new Edge[]{new Edge(v3, 38.65), new Edge(v1, 39.42)}; v3.adjacencies = new Edge[]{new Edge(v4, 102.53), new Edge(v2, 38.65)}; v4.adjacencies = new Edge[]{new Edge(v5, 133.04), new Edge(v3, 102.53)}; v5.adjacencies = new Edge[]{new Edge(v6, 81.77), new Edge(v4, 133.04)}; v6.adjacencies = new Edge[]{new Edge(v0, 97.24), new Edge(v5, 81.77)}; Vertex[] vertices = { v0, v1, v2, v3, v4, v5, v6 }; computePaths(v0); for (Vertex v : vertices) { System.out.println("Distance to " + v + ": " + v.minDistance); List<Vertex> path = getShortestPathTo(v); System.out.println("Path: " + path); } } } and the code for scanning file is import java.util.Scanner; import java.io.File; import java.io.FileNotFoundException; public class DataScanner1 { //private int total = 0; //private int distance = 0; private String vector; private String stations; private double [] Edge = new double []; /*public int getTotal(){ return total; } */ /* public void getMenuInput(){ KeyboardInput in = new KeyboardInput; System.out.println("Enter the destination? "); String val = in.readString(); return val; } */ public void readFile(String fileName) { try { Scanner scanner = new Scanner(new File(fileName)); scanner.useDelimiter (System.getProperty("line.separator")); while (scanner.hasNext()) { parseLine(scanner.next()); } scanner.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } } public void parseLine(String line) { Scanner lineScanner = new Scanner(line); lineScanner.useDelimiter("\\s*,\\s*"); vector = lineScanner.next(); stations = lineScanner.next(); System.out.println("The current station is " + vector + " and the destination to the next station is " + stations + "."); //total += distance; //System.out.println("The total distance is " + total); } public static void main(String[] args) { /* if (args.length != 1) { System.err.println("usage: java TextScanner2" + "file location"); System.exit(0); } */ DataScanner1 scanner = new DataScanner1(); scanner.readFile(args[0]); //int total =+ distance; //System.out.println(""); //System.out.println("The total distance is " + scanner.getTotal()); } }

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• IPhone sdk, more accurate collision detection and set the frame/bounds of UIImageView...

  - by Harry

  Hey, Im having a big problem with my app at the moment, its all too inaccurate. I have a image of a ballooon, https://dl.dropbox.com/u/2578642/Balloonedit.png And i have a dart which if it collides into the balloon the game ends. At the moment i am populating the image of the balloon with 8 UIImageViews. and i am detecting if the dart hits them, this was suppose to make it really accurate but its not, the dart pretty much passes through the balloon when its meant to collide, so i have a plan, is there any way to detect when the dart hits the actual image of the balloon not the UIImageView, or is there any way to draw a border around the balloon and detect if it hits that? currently i am using this code to detect the collision: if (CGRectIntersectsRect(pinend.frame, balloonbit1.frame)){ [maintimer invalidate]; accelManeger.delegate = nil; [ball setImage:img]; [UIImageView beginAnimations:nil context:NULL]; [UIImageView setAnimationDuration:0.3]; ball.transform = CGAffineTransformMakeScale(2, 2); [UIImageView commitAnimations]; } So in one method there are 40 of these bits of code and as you can imagine it is not very accurate/fast to respond. So like i said is there a way to draw a border or something around the balloon and detect the collision between the border and dart? Because then i would imagine it would run a lot smother because it would only have to process 5 bits of code. Thanks for any help. This is a big Question so if you can answer it i will buy your app :) Cheers, Harry :/

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• how to do collision detection for hollow(?) movieclips in flash AS3?

  - by Pieter888

  Hey everyone, I'm making small interactive games in flash to learn AS3, now I ran into a problem that I need some help with. I need to check the collision between the player and the wall which is normally simple using the hitTestObject function. But now I made a wall object totally surrounding the player with corridors and turn, a collision playground so to speak. Now when I use the hitTestObject function to check whether the player is in collision with the wall it tells me it always collides supposedly because the player object is within the bounds of the wall object. So assuming that I'm correct about the error: How can I prevent getting a collision when I'm inside the bounds of the wall object but not touching the actual walls in that object?

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• ray collision with rectangle and floating point accuracy

  - by phq

  I'm trying to solve a problem with a ray bouncing on a box. Actually it is a sphere but for simplicity the box dimensions are expanded by the sphere radius when doing the collision test making the sphere a single ray. It is done by projecting the ray onto all faces of the box and pick the one that is closest. However because I'm using floating point variables I fear that the projected point onto the surface might be interpreted as being below in the next iteration, also I will later allow the sphere to move which might make that scenario more likely. Also the bounce coefficient might be as low as zero, making the sphere continue along the surface. So my naive solution is to project not only forwards but backwards to catch those cases. That is where I got into problems shown in the figure: In the first iteration the first black arrow is calculated and we end up at a point on the surface of the box. In the second iteration the "back projection" hits the other surface making the second black arrow bounce on the wrong surface. If there are several boxes close to each other this has further consequences making the sphere fall through them all. So my main question is how to handle possible floating point accuracy when placing the sphere on the box surface so it does not fall through. In writing this question I got the idea to have a threshold to only accept back projections a certain amount much smaller than the box but larger than the possible accuracy limitation, this would only cause the "false" back projection when the sphere hit the box on an edge which would appear naturally. To clarify my original approach, the arrows shown in the image is not only the path the sphere travels but is also representing a single time step in the simulation. In reality the time step is much smaller about 0.05 of the box size. The path traveled is projected onto possible sides to avoid traveling past a thinner object at higher speeds. In normal situations the floating point accuracy is not an issue but there are two situations where I have the concern. When the new position at the end of the time step is located very close to the surface, very unlikely though. When using a bounce factor of 0, here it happens every time the sphere hit a box. To add some loss of accuracy, the motivation for my concern, is that the sphere and box are in different coordinate systems and thus the sphere location is transformed for every test. This last one is why I'm not willing to stand on luck that one floating point value lying on top of the box always will be interpreted the same. I did not know voronoi regions by name, but looking at it I'm not sure how it would be used in a projection scenario that I'm using here.

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• How to detect which edges of a rectange touch when they collide in iOS

  - by Mike King

  I'm creating a basic "game" in iOS 4.1. The premise is simple, there is a green rectangle ("disk") that moves/bounces around the screen, and red rectangle ("bump") that is stationary. The user can move the red "bump" by touching another coordinate on the screen, but that's irrelevant to this question. Each rectangle is a UIImageView (I will replace them with some kind of image/icon once I get the mechanics down). I've gotten as far as detecting when the rectangles collide, and I'm able to reverse the direction of the green "disk" on the Y axis if they do. This works well when the green "disk" approaches the red "bump" from top or bottom, it bounces off in the other direction. But when it approaches from the side, the bounce is incorrect; I need to reverse the X direction instead. Here's the timer I setup: - (void)viewDidLoad { xSpeed = 3; ySpeed = -3; gameTimer = [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(mainGameLoop:) userInfo:nil repeats:YES]; [super viewDidLoad]; } Here's the main game loop: - (void) mainGameLoop:(NSTimer *)theTimer { disk.center = CGPointMake(disk.center.x + xSpeed, disk.center.y + ySpeed); // make sure the disk does not travel off the edges of the screen // magic number values based on size of disk's frame // startAnimating causes the image to "pulse" if (disk.center.x < 55 || disk.center.x > 265) { xSpeed = xSpeed * -1; [disk startAnimating]; } if (disk.center.y < 55 || disk.center.y > 360) { ySpeed = ySpeed * -1; [disk startAnimating]; } // check to see if the disk collides with the bump if (CGRectIntersectsRect(disk.frame, bump.frame)) { NSLog(@"Collision detected..."); if (! [disk isAnimating]) { ySpeed = ySpeed * -1; [disk startAnimating]; } } } So my question is: how can I detect whether I need to flip the X speed or the Y speed? ie: how can I calculate which edge of the bump was collided with?

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• Question about BoundingSpheres and Ray intersections

  - by NDraskovic

  I'm working on a XNA project (not really a game) and I'm having some trouble with picking algorithm. I have a few types of 3D models that I draw to the screen, and one of them is a switch. So I'm trying to make a picking algorithm that would enable the user to click on the switch and that would trigger some other function. The problem is that the BoundingSphere.Intersect() method always returns null as result. This is the code I'm using: In the declaration section: ` //Basic matrices private Matrix world = Matrix.CreateTranslation(new Vector3(0, 0, 0)); private Matrix view = Matrix.CreateLookAt(new Vector3(10, 10, 10), new Vector3(0, 0, 0), Vector3.UnitY); private Matrix projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45), 800f / 600f, 0.01f, 100f); //Collision detection variables Viewport mainViewport; List<BoundingSphere> spheres = new List<BoundingSphere>(); Ray ControlRay; Vector3 nearPoint, farPoint, nearPlane, farPlane, direction; ` And then in the Update method: ` nearPlane = new Vector3((float)Mouse.GetState().X, (float)Mouse.GetState().Y, 0.0f); farPlane = new Vector3((float)Mouse.GetState().X, (float)Mouse.GetState().Y, 10.0f); nearPoint = GraphicsDevice.Viewport.Unproject(nearPlane, projection, view, world); farPoint = GraphicsDevice.Viewport.Unproject(farPlane, projection, view, world); direction = farPoint - nearPoint; direction.Normalize(); ControlRay = new Ray(nearPoint, direction); if (spheres.Count != 0) { for (int i = 0; i < spheres.Count; i++) { if (spheres[i].Intersects(ControlRay) != null) { Window.Title = spheres[i].Center.ToString(); } else { Window.Title = "Empty"; } } ` The "spheres" list gets filled when the 3D object data gets loaded (I read it from a .txt file). For every object marked as switch (I use simple numbers to determine which object is to be drawn), a BoundingSphere is created (center is on the coordinates of the 3D object, and the diameter is always the same), and added to the list. The objects are drawn normally (and spheres.Count is not 0), I can see them on the screen, but the Window title always says "Empty" (of course this is just for testing purposes, I will add the real function when I get positive results) meaning that there is no intersection between the ControlRay and any of the bounding spheres. I think that my basic matrices (world, view and projection) are making some problems, but I cant figure out what. Please help.

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• Circle-Rectangle collision in a tile map game

  - by furiousd

  I am making a 2D tile map based putt-putt game. I have collision detection working between the ball and the walls of the map, although when the ball collides at the meeting point between 2 tiles I offset it by 0.5 so that it doesn't get stuck in the wall. This aint a huge issue though. if(y % 20 == 0) { y+=0.5; } if(x % 20 == 0) { x+=0.5; } Collisions work as follows Find the closest point between each tile and the center of the ball If distance(ball_x, ball_y, close_x, close_y) <= ball_radius and the closest point belongs to a solid object, collision has occured Invert X/Y speed according to side of object collided with The next thing I tried to do was implement floating blocks in the middle of the map for the ball to bounce off of. When a ball collides with a corner of the block, it gets stuck in it. So I changed my determineRebound() function to treat corners as if they were circles. Here's that functon: `i and j are indexes of the solid object in the 2d map array. x & y are centre point of ball.` void determineRebound(int _i, int _j) { if(y > _i*tile_w && y < _i*tile_w + tile_w) { //Not a corner xs*=-1; } else if(x > _j*tile_w && x < _j*tile_w + tile_w) { //Not a corner ys*=-1; } else { //Corner float nx = x - close_x; float ny = y - close_y; float len = sqrt(nx * nx + ny * ny); nx /= len; ny /= len; float projection = xs * nx + ys * ny; xs -= 2 * projection * nx; ys -= 2 * projection * ny; } } This is where things have gotten messy. Collisions with 'floating' corners work fine, but now when the ball collides near the meeting point of 2 tiles, it detects a corner collision and does not rebound as expected. I'm a bit in over my head at this point. I guess I'm wondering if I'm going about making this sort of game in the right way. Is a 2d tile map the way to go? If so, is there a problem with my collision logic and where am I going wrong? Any advice/feedback would be great.

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• Java 2D Tile Collision

  - by opiop65

  I have been working on a way to do collision detection forever, and just can't figure it out. Here's my simple 2D array: for (int x = 0; x < 16; x++) { for (int y = 0; y < 16; y++) { map[x][y] = AIR; if(map[x][y] == AIR) { air.draw(x * tilesize, y * tilesize); } } } for (int x = 0; x < 16; x++) { for (int y = 6; y < 16; y++) { map[x][y] = GRASS; if(map[x][y] == GRASS) { grass.draw(x * tilesize, y * tilesize); } } } for (int x = 0; x < 16; x++) { for (int y = 8; y < 16; y++) { map[x][y] = STONE; if(map[x][y] == STONE) { stone.draw(x * tilesize, y * tilesize); } } } I want to do it with rectangles, and using the intersect() method, but how would I go about adding rectangles to all the tiles? Edit: My player moves like this: if(input.isKeyDown(Input.KEY_W)) { shiftY -= delta * speed; idY = (int) shiftY; if(shift == true) { shiftY -= delta * runspeed; } if(isColliding == true) { shiftY += delta * speed; } } if(input.isKeyDown(Input.KEY_S)) { shiftY += delta * speed; idY = (int) shiftY; if(shift == true) { shiftY += delta * runspeed; } if(isColliding == true) { shiftY -= delta * speed; } } if (input.isKeyDown(Input.KEY_A)) { steve = left; shiftX -= delta * speed; idX = (int) shiftX; if(shift == true) { shiftX -= delta * runspeed; } if(isColliding == true) { shiftX += delta * speed; } } if (input.isKeyDown(Input.KEY_D)) { steve = right; shiftX += delta * speed; idX = (int) shiftX; if(shift == true) { shiftX += delta * runspeed; } if(isColliding == true) { shiftX -= delta * speed; } } (I have tried my own collision code, but its horrible. Doesn't work in the slightest)

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• Platformer Collision Error [closed]

  - by Connor

  I am currently working on a relatively simple platform game that has an odd bug.You start the game by falling onto the ground (you spawn a few blocks above the ground), but when you land your feet get stuck INSIDE the world and you can't move until you jump. Here's what I mean: The player's feet are a few pixels below the ground level. However, this problem only occurs in 3 places throughout the map and only in those 3 select places. I'm assuming that the problem lies within my collision detection code but I'm not entirely sure, as I don't get an error when it happens. public boolean isCollidingWithBlock(Point pt1, Point pt2) { //Checks x for(int x = (int) (this.x / Tile.tileSize); x < (int) (this.x / Tile.tileSize + 4); x++) { //Checks y for(int y = (int) (this.y / Tile.tileSize); y < (int) (this.y / Tile.tileSize + 4); y++) { if(x >= 0 && y >= 0 && x < Component.dungeon.block.length && y < Component.dungeon.block[0].length) { //If the block is not air if(Component.dungeon.block[x][y].id != Tile.air) { //If the player is in contact with point one or two on the block if(Component.dungeon.block[x][y].contains(pt1) || Component.dungeon.block[x][y].contains(pt2)) { //Checks for specific blocks if(Component.dungeon.block[x][y].id == Tile.portalBlock) { Component.isLevelDone = true; } if(Component.dungeon.block[x][y].id == Tile.spike) { Health.health -= 1; Component.isJumping = true; if(Health.health == 0) { Component.isDead = true; } } return true; } } } } } return false; } What I'm asking is how I would fix the problem. I've looked over my code for quite a while and I'm not sure what's wrong with it. Also, if there's a more efficient way to do my collision checking then please let me know! I hope that is enough information, if it's not just tell me what you need and I'll be sure to add it. Thank you! [EDIT] Jump code: if(!isJumping && !isCollidingWithBlock(new Point((int) x + 2, (int) (y + height)), new Point((int) (x + width + 2), (int) (y + height)))) { y += fallSpeed; //sY is the screen's Y. The game is a side-scroller Component.sY += fallSpeed; } else { if(Component.isJumping) { isJumping = true; } } if(isJumping) { if(!isCollidingWithBlock(new Point((int) x + 2, (int) y), new Point((int) (x + width + 2), (int) y))) { if(jumpCount >= jumpHeight) { isJumping = false; jumpCount = 0; } else { y -= jumpSpeed; Component.sY -= jumpSpeed; jumpCount += 1; } } else { isJumping = false; jumpCount = 0; } }

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• BFS Shortest Path: Edge weight either 1 or 2

  - by Hackster

  I am trying to implement a shortest path algorithm using BFS. That is I am trying to find the shortest path from a specified vertex to every other vertex. However, its a special case where all edge weights are either 1 or 2. I know it could be done with Dijkstra's algorithm but I must use Breadth First Search. So far I have a working version of BFS that searches first for a vertex connected with an edge of weight 1. If it cannot find it, then returns a vertex connected with an edge of weight 2. After thinking about it, this is not the correct way to find the shortest path. The problem is I cannot think of any reasoning why BFS would work with weights 1 or 2, as opposed to any weight. Here is the code: public void addEdge(int start, int end, int weight) { adjMat[start][end] = 1; adjMat[end][start] = 1; edge_weight[start][end] = weight; edge_weight[end][start] = weight; } // ------------------------------------------------------------- public void bfs() // breadth-first search { // begin at vertex 0 vertexList[0].wasVisited = true; // mark it displayVertex(0); // display it theQueue.insert(0); // insert at tail int v2; while( !theQueue.isEmpty() ) // until queue empty, { int v1 = theQueue.remove(); // remove vertex at head // until it has no unvisited neighbors while( (v2=getAdjUnvisitedVertex(v1)) != -1 ){// get one, vertexList[v2].wasVisited = true; // mark it displayVertex(v2); // display it theQueue.insert(v2); // insert it } } // end while(queue not empty) // queue is empty, so we're done for(int j=0; j<nVerts; j++) // reset flags vertexList[j].wasVisited = false; } // end bfs() // ------------------------------------------------------------- // returns an unvisited vertex adj to v -- ****WITH WEIGHT 1**** public int getAdjUnvisitedVertex(int v) { for (int j = 0; j < nVerts; j++) if (adjMat[v][j] == 1 && vertexList[j].wasVisited == false && edge_weight[v][j] == 1){ //System.out.println("Vertex found with 1:"+ vertexList[j].label); return j; } for (int k = 0; k < nVerts; k++) if (adjMat[v][k] == 1 && vertexList[k].wasVisited == false && edge_weight[v][k] == 2){ //System.out.println("Vertex found with 2:"+vertexList[k].label); return k; } return -1; } // end getAdjUnvisitedVertex() // ------------------------------------------------------------- } //////////////////////////////////////////////////////////////// public class BFS{ public static void main(String[] args) { Graph theGraph = new Graph(); theGraph.addVertex('A'); // 0 (start for bfs) theGraph.addVertex('B'); // 1 theGraph.addVertex('C'); // 2 theGraph.addEdge(0, 1,2); // AB theGraph.addEdge(1, 2,1); // BC theGraph.addEdge(2, 0,1); // AD System.out.print("Visits: "); theGraph.bfs(); // breadth-first search System.out.println(); } // end main() } The problem then is, that I don't know why BFS can work for the shortest path problem with edges of weight 1 or 2 as opposed to any edges of any weight. Any help is appreciated. Thanks!

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• Matlab - Propagate points orthogonally on to the edge of shape boundaries

  - by Graham

  Hi I have a set of points which I want to propagate on to the edge of shape boundary defined by a binary image. The shape boundary is defined by a 1px wide white edge. I also have the coordinates of these points stored in a 2 row by n column matrix. The shape forms a concave boundary with no holes within itself made of around 2500 points. I want to cast a ray from each point from the set of points in an orthogonal direction and detect at which point it intersects the shape boundary at. What would be the best method to do this? Are there some sort of ray tracing algorithms that could be used? Or would it be a case of taking orthogonal unit vector and multiplying it by a scalar and testing after multiplication if the end point of the vector is outside the shape boundary. When the end point of the unit vector is outside the shape, just find the point of intersection? Thank you very much in advance for any help!

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• Determining Maximum Txpower a WiFi Card Supports?

  - by BigGenius

  I have a Atheros R9285 wifi card. How can i determine , what is max. Txpower it can support? biggenius@hackbook:~$ iwconfig lo no wireless extensions. wlan0 IEEE 802.11abgn ESSID:"Default" Mode:Managed Frequency:2.437 GHz Access Point: 00:08:5C:9D:4F:40 Bit Rate=2 Mb/s Tx-Power=35 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:on Link Quality=24/70 Signal level=-86 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:140 Invalid misc:247 Missed beacon:0 eth0 no wireless extensions. biggenius@hackbook:~$ iw phy0 info Wiphy phy0 Band 1: Capabilities: 0x11ce HT20/HT40 SM Power Save disabled RX HT40 SGI TX STBC RX STBC 1-stream Max AMSDU length: 3839 bytes DSSS/CCK HT40 Maximum RX AMPDU length 65535 bytes (exponent: 0x003) Minimum RX AMPDU time spacing: 8 usec (0x06) HT TX/RX MCS rate indexes supported: 0-7 Frequencies: * 2412 MHz [1] (35.0 dBm) * 2417 MHz [2] (35.0 dBm) * 2422 MHz [3] (35.0 dBm) * 2427 MHz [4] (35.0 dBm) * 2432 MHz [5] (35.0 dBm) * 2437 MHz [6] (35.0 dBm) * 2442 MHz [7] (35.0 dBm) * 2447 MHz [8] (35.0 dBm) * 2452 MHz [9] (35.0 dBm) * 2457 MHz [10] (35.0 dBm) * 2462 MHz [11] (35.0 dBm) * 2467 MHz [12] (35.0 dBm) * 2472 MHz [13] (35.0 dBm) * 2484 MHz [14] (35.0 dBm) Bitrates (non-HT): * 1.0 Mbps * 2.0 Mbps (short preamble supported) * 5.5 Mbps (short preamble supported) * 11.0 Mbps (short preamble supported) * 6.0 Mbps * 9.0 Mbps * 12.0 Mbps * 18.0 Mbps * 24.0 Mbps * 36.0 Mbps * 48.0 Mbps * 54.0 Mbps Band 2: Capabilities: 0x11ce HT20/HT40 SM Power Save disabled RX HT40 SGI TX STBC RX STBC 1-stream Max AMSDU length: 3839 bytes DSSS/CCK HT40 Maximum RX AMPDU length 65535 bytes (exponent: 0x003) Minimum RX AMPDU time spacing: 8 usec (0x06) HT TX/RX MCS rate indexes supported: 0-7 Frequencies: * 5180 MHz [36] (35.0 dBm) * 5200 MHz [40] (35.0 dBm) * 5220 MHz [44] (35.0 dBm) * 5240 MHz [48] (35.0 dBm) * 5260 MHz [52] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5280 MHz [56] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5300 MHz [60] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5320 MHz [64] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5500 MHz [100] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5520 MHz [104] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5540 MHz [108] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5560 MHz [112] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5580 MHz [116] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5600 MHz [120] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5620 MHz [124] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5640 MHz [128] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5660 MHz [132] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5680 MHz [136] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5700 MHz [140] (35.0 dBm) (passive scanning, no IBSS, radar detection) * 5745 MHz [149] (35.0 dBm) * 5765 MHz [153] (35.0 dBm) * 5785 MHz [157] (35.0 dBm) * 5805 MHz [161] (35.0 dBm) * 5825 MHz [165] (35.0 dBm) Bitrates (non-HT): * 6.0 Mbps * 9.0 Mbps * 12.0 Mbps * 18.0 Mbps * 24.0 Mbps * 36.0 Mbps * 48.0 Mbps * 54.0 Mbps max # scan SSIDs: 4 max scan IEs length: 2257 bytes Coverage class: 0 (up to 0m) Supported Ciphers: * WEP40 (00-0f-ac:1) * WEP104 (00-0f-ac:5) * TKIP (00-0f-ac:2) * CCMP (00-0f-ac:4) * CMAC (00-0f-ac:6) Available Antennas: TX 0x1 RX 0x3 Configured Antennas: TX 0x1 RX 0x3 Supported interface modes: * IBSS * managed * AP * AP/VLAN * WDS * monitor * mesh point * P2P-client * P2P-GO software interface modes (can always be added): * AP/VLAN * monitor valid interface combinations: * #{ managed, WDS, P2P-client } <= 2048, #{ AP, mesh point, P2P-GO } <= 8, total <= 2048, #channels <= 1 Supported commands: * new_interface * set_interface * new_key * new_beacon * new_station * new_mpath * set_mesh_params * set_bss * authenticate * associate * deauthenticate * disassociate * join_ibss * join_mesh * remain_on_channel * set_tx_bitrate_mask * action * frame_wait_cancel * set_wiphy_netns * set_channel * set_wds_peer * Unknown command (82) * Unknown command (81) * Unknown command (84) * Unknown command (87) * Unknown command (85) * testmode * connect * disconnect Supported TX frame types: * IBSS: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * managed: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * AP: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * AP/VLAN: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * mesh point: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * P2P-client: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 * P2P-GO: 0x0000 0x0010 0x0020 0x0030 0x0040 0x0050 0x0060 0x0070 0x0080 0x0090 0x00a0 0x00b0 0x00c0 0x00d0 0x00e0 0x00f0 Supported RX frame types: * IBSS: 0x00d0 * managed: 0x0040 0x00d0 * AP: 0x0000 0x0020 0x0040 0x00a0 0x00b0 0x00c0 0x00d0 * AP/VLAN: 0x0000 0x0020 0x0040 0x00a0 0x00b0 0x00c0 0x00d0 * mesh point: 0x00b0 0x00c0 0x00d0 * P2P-client: 0x0040 0x00d0 * P2P-GO: 0x0000 0x0020 0x0040 0x00a0 0x00b0 0x00c0 0x00d0 Device supports RSN-IBSS.

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• Collision between sprites in game programming?

  - by Lyn Maxino

  I've since just started coding for an android game using eclipse. I've read Beginning Android Game Programming and various other e-books. Recently, I've encountered a problem with collision between sprites. I've used this code template for my program. package com.project.CAI_test; import java.util.Random; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Rect; public class Sprite { // direction = 0 up, 1 left, 2 down, 3 right, // animation = 3 back, 1 left, 0 front, 2 right int[] DIRECTION_TO_ANIMATION_MAP = { 3, 1, 0, 2 }; private static final int BMP_ROWS = 4; private static final int BMP_COLUMNS = 3; private static final int MAX_SPEED = 5; private GameView gameView; private Bitmap bmp; private int x = 0; private int y = 0; private int xSpeed; private int ySpeed; private int currentFrame = 0; private int width; private int height; public Sprite(GameView gameView, Bitmap bmp) { this.width = bmp.getWidth() / BMP_COLUMNS; this.height = bmp.getHeight() / BMP_ROWS; this.gameView = gameView; this.bmp = bmp; Random rnd = new Random(); x = rnd.nextInt(gameView.getWidth() - width); y = rnd.nextInt(gameView.getHeight() - height); xSpeed = rnd.nextInt(MAX_SPEED * 2) - MAX_SPEED; ySpeed = rnd.nextInt(MAX_SPEED * 2) - MAX_SPEED; } private void update() { if (x >= gameView.getWidth() - width - xSpeed || x + xSpeed <= 0) { xSpeed = -xSpeed; } x = x + xSpeed; if (y >= gameView.getHeight() - height - ySpeed || y + ySpeed <= 0) { ySpeed = -ySpeed; } y = y + ySpeed; currentFrame = ++currentFrame % BMP_COLUMNS; } public void onDraw(Canvas canvas) { update(); int srcX = currentFrame * width; int srcY = getAnimationRow() * height; Rect src = new Rect(srcX, srcY, srcX + width, srcY + height); Rect dst = new Rect(x, y, x + width, y + height); canvas.drawBitmap(bmp, src, dst, null); } private int getAnimationRow() { double dirDouble = (Math.atan2(xSpeed, ySpeed) / (Math.PI / 2) + 2); int direction = (int) Math.round(dirDouble) % BMP_ROWS; return DIRECTION_TO_ANIMATION_MAP[direction]; } public boolean isCollition(float x2, float y2) { return x2 > x && x2 < x + width && y2 > y && y2 < y + height; } } The above code only detects collision between the generated sprites and the surface border. What I want to achieve is a collision detection that is controlled by the update function without having to change much of the coding. Probably several lines placed in the update() function. Tnx for any comment/suggestion.

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• 2D Tile based Game Collision problem

  - by iNbdy

  I've been trying to program a tile based game, and I'm stuck at the collision detection. Here is my code (not the best ^^): void checkTile(Character *c, int **map) { int x1,x2,y1,y2; /* Character position in the map */ c->upY = (c->y) / TILE_SIZE; // Top left corner c->downY = (c->y + c->h) / TILE_SIZE; // Bottom left corner c->leftX = (c->x) / TILE_SIZE; // Top right corner c->rightX = (c->x + c->w) / TILE_SIZE; // Bottom right corner x1 = (c->x + 10) / TILE_SIZE; // 10px from left side point x2 = (c->x + c->w - 10) / TILE_SIZE; // 10px from right side point y1 = (c->y + 10) / TILE_SIZE; // 10px from top side point y2 = (c->y + c->h - 10) / TILE_SIZE; // 10px from bottom side point /* Top */ if (map[c->upY][x1] > 2 || map[c->upY][x2] > 2) c->topCollision = 1; else c->topCollision = 0; /* Bottom */ if ((map[c->downY][x1] > 2 || map[c->downY][x2] > 2)) c->downCollision = 1; else c->downCollision = 0; /* Left */ if (map[y1][c->leftX] > 2 || map[y2][c->leftX] > 2) c->leftCollision = 1; else c->leftCollision = 0; /* Right */ if (map[y1][c->rightX] > 2 || map[y2][c->rightX] > 2) c->rightCollision = 1; else c->rightCollision = 0; } That calculates 8 collision points My moving function is like that: void movePlayer(Character *c, int **map) { if ((c->dirX == LEFT && !c->leftCollision) || (c->dirX == RIGHT && !c->rightCollision)) c->x += c->vx; if ((c->dirY == UP && !c->topCollision) || (c->dirY == DOWN && !c->downCollision)) c->y += c->vy; checkPosition(c, map); } and the checkPosition: void checkPosition(Character *c, int **map) { checkTile(c, map); if (c->downCollision) { if (c->state != JUMPING) { c->vy = 0; c->y = (c->downY * TILE_SIZE - c->h); } } if (c->leftCollision) { c->vx = 0; c->x = (c->leftX) * TILE_SIZE + TILE_SIZE; } if (c->rightCollision) { c->vx = 0; c->x = c->rightX * TILE_SIZE - c->w; } } This works, but sometimes, when the player is landing on ground, right and left collision points become equal to 1. So it's as if there were collision coming from left or right. Does anyone know why this is doing this?

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