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  • Solving 2D Collision Detection Issues with Relative Velocities

    - by Jengerer
    Imagine you have a situation where two objects are moving parallel to one-another and are both within range to collide with a static wall, like this: A common method used in dynamic collision detection is to loop through all objects in arbitrary order, solve for pair-wise collision detection using relative velocities, and then move the object to the nearest collision, if any. However, in this case, if the red object is checked first against the blue one, it would see that the relative velocity to the blue object is -20 m/s (and would thereby not collide this time frame). Then it would see that the red object would collide with the static wall, and the solution would be: And the red object passes through the blue one. So it appears to be a matter of choosing the right order in which you check collisions; but how can you determine which order is correct? How can this passing through of objects be avoided? Is ignoring relative velocity and considering every object as static during pair-wise checks a better idea for this reason?

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  • Collision Detection fails with AI cars

    - by amit.r007
    I am making a car parking game in flash and AS3 wherein I drive my car along with other AI traffic cars moving along a specified path using Guidelines. I am using CDK for collision detection. The collision detection works fine with few AI cars, but doesn't seems to be working as required for few AI cars. When an AI car is moving on a path in a straight line it works fine.... but when the AI Car turns at 90 degress..... my car goes into the AI car (Overlapping) and it hits at the center of that AI car and then collision is Detected.... ..... I made a New path and used a new Sprite for AI car... but still the problem pursues....

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  • 3D Collision help

    - by Taylor
    I'm having difficulties with my project. I'm quite new in XNA. Anyway, I'm trying to make 3D game and I'm already stuck on one basic thing. I have terrain made from a heightmap, and an avatar model. I want to set up some collisions for game so the player won't go through the ground. But I just don't know how to detect collisions for so complex an object. I could just make a simple box collision for my avatar, but what about the ground? I already implemented the JigLibX physics engine in my project and I know that I can make a collision map with heightmap, but I can't find any tutorials or help with this. So how can I set proper collision for complex objects? How can I detect heightmap collisions in JigLibX? Just some links to tutorials would be enough. Thanks in advance!

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  • Making an efficient collision detection system

    - by Sri Harsha Chilakapati
    I'm very new to game development (just started 3 months ago) and I'm learning through creating a game engine. It's located here. In terms of collision, I know only brute-force detection, in which case, the game slows down if there are a number of objects. So my question is How should I program the collisions? I want them to happen automatically for every object and call the object's collision(GObject other) method on each collision. Are there any new algorithms which can make this fast? If so, can anybody shed some light on this topic?

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  • Making a collision detection system

    - by Sri Harsha Chilakapati
    I'm very new to game development (just started 3 months ago) and I've learning through creating a game engine. It's located here. In terms of collision, I know only brutefoce detection, in which case, the game slows down if there are a number of objects. So my question is How should I program the collisions? I want them to happen automatically for every object and call the object's collision(GObject other) method on each collision. Are there any new algorithms which can make this fast? If so, can anybody6 sh6ed some light on this topic? And I think of making it like the game maker Thanks

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  • Who should respond to collision: Unit or projectile?

    - by aleguna
    In an RTS if a projectile hits a unit. Who should handle the collision? If projectile handles the collision, it must be aware of all possible types of units, to know what damage to inflict. For example a bullet will likely kill a human, but it will do nothing to a tank. The same goes if unit handles a collision. So either way one of them should be aware of all possible types of the other. Of course the 'true' way would be to do full physics simulation, but that's not an option for an RTS with 1000s of units and projectiles... So what are the common practicies in this regards?

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  • How to determine collision direction between two rectangles?

    - by Jon
    I am trying to figure out how to determine the direction a collision occurs between two rectangles. One rectangle does not move. The other rectangle has a velocity in any direction. When a collision occurs, I want to be able to set the position of the moving rectangle to the point of impact. I seem to be stuck in determining from what direction the impact occurs. If I am moving strictly vertically or horizontally I manage great detection. But when moving in both directions at the same time, strange things happen. What is the best way to determine what direction a collision occurs between two rectangles?

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  • XNA 2D Rotated Rectangle Collision Response

    - by Kyle Uithoven
    I am using Rotated Rectangles which collide using the Separating Axis Theorem and they work perfectly fine for collision detection using Intersects and Contains. However, I am starting to use faster objects in my game now and there is the issue of the two object overlapping during collision due to their higher velocities. I would like to do a collision response where I find out how much they are overlapping in the X and Y and put position them outside of each other. I would like to use something like this: http://go.colorize.net/xna/2d_collision_response_xna/index.html. But I am having some issues trying to adapt this to handle the rotation of the bounds. Is this possible? Are there any resources out there that I can look at?

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  • Collision for mobile game

    - by zemiguel12
    I'm writing a little game in as3 using Starling, and I need to check collision between 2 boats that can rotate. I don't need the pixel perfect collision, but bounds collision is not enough too. The boat look more or less like this: I was thinking about create one square on the back of the boat and a triangle on the front, than for each boat, check if the square collide with the other boat square or triangle, and the same for the triangle. I just don't know how to do that, I don't know if it's possible with the Shape.hitTest, or if it's the best way to do that. What can I do?

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  • Collision Detection for Actionscript 3

    - by M28
    Well, I was searching for a simple collision detection function for as3, I found Collision Detection Kit, but it is too complicated, I just want a damn function that I give 2 objects as paramenters and that's it. I would like to know where can I find a pixel-perfect collision detection function (The faster, the better)

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  • Getting 2D Platformer entity collision Response Correct (side-to-side + jumping/landing on heads)

    - by jbrennan
    I've been working on a 2D (tile based) 2D platformer for iOS and I've got basic entity collision detection working, but there's just something not right about it and I can't quite figure out how to solve it. There are 2 forms of collision between player entities as I can tell, either the two players (human controlled) are hitting each other side-to-side (i. e. pushing against one another), or one player has jumped on the head of the other player (naturally, if I wanted to expand this to player vs enemy, the effects would be different, but the types of collisions would be identical, just the reaction should be a little different). In my code I believe I've got the side-to-side code working: If two entities press against one another, then they are both moved back on either side of the intersection rectangle so that they are just pushing on each other. I also have the "landed on the other player's head" part working. The real problem is, if the two players are currently pushing up against each other, and one player jumps, then at one point as they're jumping, the height-difference threshold that counts as a "land on head" is passed and then it registers as a jump. As a life-long player of 2D Mario Bros style games, this feels incorrect to me, but I can't quite figure out how to solve it. My code: (it's really Objective-C but I've put it in pseudo C-style code just to be simpler for non ObjC readers) void checkCollisions() { // For each entity in the scene, compare it with all other entities (but not with one it's already compared against) for (int i = 0; i < _allGameObjects.count(); i++) { // GameObject is an Entity GEGameObject *firstGameObject = _allGameObjects.objectAtIndex(i); // Don't check against yourself or any previous entity for (int j = i+1; j < _allGameObjects.count(); j++) { GEGameObject *secondGameObject = _allGameObjects.objectAtIndex(j); // Get the collision bounds for both entities, then see if they intersect // CGRect is a C-struct with an origin Point (x, y) and a Size (w, h) CGRect firstRect = firstGameObject.collisionBounds(); CGRect secondRect = secondGameObject.collisionBounds(); // Collision of any sort if (CGRectIntersectsRect(firstRect, secondRect)) { //////////////////////////////// // // // Check for jumping first (???) // // //////////////////////////////// if (firstRect.origin.y > (secondRect.origin.y + (secondRect.size.height * 0.7))) { // the top entity could be pretty far down/in to the bottom entity.... firstGameObject.didLandOnEntity(secondGameObject); } else if (secondRect.origin.y > (firstRect.origin.y + (firstRect.size.height * 0.7))) { // second entity was actually on top.... secondGameObject.didLandOnEntity.(firstGameObject); } else if (firstRect.origin.x > secondRect.origin.x && firstRect.origin.x < (secondRect.origin.x + secondRect.size.width)) { // Hit from the RIGHT CGRect intersection = CGRectIntersection(firstRect, secondRect); // The NUDGE just offsets either object back to the left or right // After the nudging, they are exactly pressing against each other with no intersection firstGameObject.nudgeToRightOfIntersection(intersection); secondGameObject.nudgeToLeftOfIntersection(intersection); } else if ((firstRect.origin.x + firstRect.size.width) > secondRect.origin.x) { // hit from the LEFT CGRect intersection = CGRectIntersection(firstRect, secondRect); secondGameObject.nudgeToRightOfIntersection(intersection); firstGameObject.nudgeToLeftOfIntersection(intersection); } } } } } I think my collision detection code is pretty close, but obviously I'm doing something a little wrong. I really think it's to do with the way my jumps are checked (I wanted to make sure that a jump could happen from an angle (instead of if the falling player had been at a right angle to the player below). Can someone please help me here? I haven't been able to find many resources on how to do this properly (and thinking like a game developer is new for me). Thanks in advance!

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  • Collision detection - Smooth wall sliding, no bounce effect

    - by Joey
    I'm working on a basic collision detection system that provides point - OBB collision detection. I have around 200 cubes in my environment and I check (for now) each of them in turn and see if it collides. If it does I return the colliding face's normal, save the old player position and do some trigonometry to return a new player position for my wall sliding. edit I'll define my meaning of wall sliding: If a player walks in a vertical slope and has a slight horizontal rotation to the left or the right and keeps walking forward in the wall the player should slide a little to the right/left while continually walking towards the wall till he left the wall. Thus, sliding along the wall. Everything works fine and with multiple objects as well but I still have one problem I can't seem to figure out: smooth wall sliding. In my current implementation sliding along the walls make my player bounce like a mad man (especially noticable with gravity on and moving forward). I have a velocity/direction vector, a normal vector from the collided plane and an old and new player position. First I negate the normal vector and get my new velocity vector by substracting the inverted normal from my direction vector (which is the vector to slide along the wall) and I add this vector to my new Player position and recalculate the direction vector (in case I have multiple collisions). I know I am missing some step but I can't seem to figure it out. Here is my code for the collision detection (run every frame): Vector direction; Vector newPos(camera.GetOriginX(), camera.GetOriginY(), camera.GetOriginZ()); direction = newPos - oldPos; // Direction vector // Check for collision with new position for(int i = 0; i < NUM_OBJECTS; i++) { Vector normal = objects[i].CheckCollision(newPos.x, newPos.y, newPos.z, direction.x, direction.y, direction.z); if(normal != Vector::NullVector()) { // Get inverse normal (direction STRAIGHT INTO wall) Vector invNormal = normal.Negative(); Vector wallDir = direction - invNormal; // We know INTO wall, and DIRECTION to wall. Substract these and you got slide WALL direction newPos = oldPos + wallDir; direction = newPos - oldPos; } } Any help would be greatly appreciated! FIX I eventually got things up and running how they should thanks to Krazy, I'll post the updated code listing in case someone else comes upon this problem! for(int i = 0; i < NUM_OBJECTS; i++) { Vector normal = objects[i].CheckCollision(newPos.x, newPos.y, newPos.z, direction.x, direction.y, direction.z); if(normal != Vector::NullVector()) { Vector invNormal = normal.Negative(); invNormal = invNormal * (direction * normal).Length(); // Change normal to direction's length and normal's axis Vector wallDir = direction - invNormal; newPos = oldPos + wallDir; direction = newPos - oldPos; } }

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  • Help with Collision of spawned object(postion fixed) with objects that there are translating on screen

    - by Amrutha
    Hey guys I am creating a game using Corona SDK and so coding it in Lua. So there are 2 separate functions, To translate the hit objects and change their color when they are tapped The link below is the code I am using to for the first function http://developer.anscamobile.com/sample-code/fishies Spawn objects that will hit the translating objects on collision. Alos on collision the spawned object disappears and the translating object bears a color(indicating the collision). In addition the size of this spawned object is dependent on i/p volume level. The function I have written is as follows: --VOICE INPUT CODE local r = media.newRecording() r:startRecording() r:startTuner() --local function newBar() -- local bar = display.newLine( 0, 0, 1, 0 ) -- bar:setColor( 0, 55, 100, 20 ) -- bar.width = 5 -- bar.y=400 -- bar.x=20 -- return bar --end local c1 = display.newImage("str-minion-small.png") c1.isVisible=false local c2 = display.newImage("str-minion-mid.png") c2.isVisible=false local c3 = display.newImage("str-minion-big.png") c3.isVisible=false --SPAWNING local function spawnDisk( event ) local phase = event.phase local volumeBar = display.newLine( 0, 0, 1, 0 ) volumeBar.y = 400 volumeBar.x = 20 --volumeBar.isVisible=false local v = 20*math.log(r:getTunerVolume()) local MINTHRESH = 30 local LEFTMARGIN = 20 local v2 = MINTHRESH + math.max (v, -MINTHRESH) v2 = (display.contentWidth - 1 * LEFTMARGIN ) * v2 / MINTHRESH volumeBar.xScale = math.max ( 20, v2 ) local l = volumeBar.xScale local cnt1 = 0 local cnt2 = 0 local cnt3 = 0 local ONE =1 local val = event.numTaps --local px=event.x --local py=event.y if "ended" == phase then --audio.play( popSound ) --myLabel.isVisible = false if l > 50 and l <=150 then --c1:setFillColor(10,105,0) --c1.isVisible=false c1.x=math.random( 10, 450 ) c1.y=math.random( 10, 300 ) physics.addBody( c1, { density=1, radius=10.0 } ) c1.isVisible=true cnt1= cnt1+ ONE return c1 elseif l > 100 and l <=250 then --c2:setFillColor(200,10,0) c2.x=math.random( 10, 450 ) c2.y=math.random( 10, 300 ) physics.addBody( c2, { density=2, radius=9000.0 } ) c2.isVisible=true cnt2= cnt2+ ONE return c2 elseif l >=250 then c3.x=math.random( 40, 450 ) c3.y=math.random( 40, 300 ) physics.addBody( c3, { density=2, radius=7000.0 , bounce=0.0 } ) c3.isVisible=true cnt3= cnt3+ ONE return c3 end end end buzzR:addEventListener( "touch", spawnDisk ) -- touch the screen to create disks Now both functions work fine independently but there is no collision happening. Its almost as if the translating object and the spawn object are on different layers. The translating object passes through the spawn object freely. Can anyone please tell me how to resolve this problem. And how can I get them to collide. Its my first attempt at game development, that too for a mobile platform so would appreciate all help. Also if I have not been specific do let me know. I'll try to frame the query better :). Thanks in advance.

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  • Help with Collision of spawned object(postion fixed) with objects that there are translating on screen

    - by Amrutha
    Hey guys I am creating a game using Corona SDK and so coding it in Lua. So there are 2 separate functions, To translate the hit objects and change their color when they are tapped The link below is the code I am using to for the first function http://developer.anscamobile.com/sample-code/fishies Spawn objects that will hit the translating objects on collision. Alos on collision the spawned object disappears and the translating object bears a color(indicating the collision). In addition the size of this spawned object is dependent on i/p volume level. The function I have written is as follows, --VOICE INPUT CODE local r = media.newRecording() r:startRecording() r:startTuner() --local function newBar() -- local bar = display.newLine( 0, 0, 1, 0 ) -- bar:setColor( 0, 55, 100, 20 ) -- bar.width = 5 -- bar.y=400 -- bar.x=20 -- return bar --end local c1 = display.newImage("str-minion-small.png") c1.isVisible=false local c2 = display.newImage("str-minion-mid.png") c2.isVisible=false local c3 = display.newImage("str-minion-big.png") c3.isVisible=false --SPAWNING local function spawnDisk( event ) local phase = event.phase local volumeBar = display.newLine( 0, 0, 1, 0 ) volumeBar.y = 400 volumeBar.x = 20 -- volumeBar.isVisible=false local v = 20*math.log(r:getTunerVolume()) local MINTHRESH = 30 local LEFTMARGIN = 20 local v2 = MINTHRESH + math.max (v, -MINTHRESH) v2 = (display.contentWidth - 1 * LEFTMARGIN ) * v2 / MINTHRESH volumeBar.xScale = math.max ( 20, v2 ) local l = volumeBar.xScale local cnt1 = 0 local cnt2 = 0 local cnt3 = 0 local ONE =1 local val = event.numTaps --local px=event.x --local py=event.y if "ended" == phase then --audio.play( popSound ) --myLabel.isVisible = false if l > 50 and l <=150 then -- c1:setFillColor(10,105,0) -- c1.isVisible=false c1.x=math.random( 10, 450 ) c1.y=math.random( 10, 300 ) physics.addBody( c1, { density=1, radius=10.0 } ) c1.isVisible=true cnt1= cnt1+ ONE return c1 elseif l > 100 and l <=250 then --c2:setFillColor(200,10,0) c2.x=math.random( 10, 450 ) c2.y=math.random( 10, 300 ) physics.addBody( c2, { density=2, radius=9000.0 } ) c2.isVisible=true cnt2= cnt2+ ONE return c2 elseif l >=250 then c3.x=math.random( 40, 450 ) c3.y=math.random( 40, 300 ) physics.addBody( c3, { density=2, radius=7000.0 , bounce=0.0 } ) c3.isVisible=true cnt3= cnt3+ ONE return c3 end end end buzzR:addEventListener( "touch", spawnDisk ) -- touch the screen to create disks Now both functions work fine independently but there is no collision happening. Its almost as if the translating object and the spawn object are on different layers. The translating object passes through the spawn object freely. Can anyone please tell me how to resolve this problem. And how can I get them to collide. Its my first attempt at game development, that too for a mobile platform so would appreciate all help. Also if I have not been specific do let me know. I ll try to frame the query better :). Thanks in advance.

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  • 2D Collision in Canvas - Balls Overlapping When Velocity is High

    - by kushsolitary
    I am doing a simple experiment in canvas using Javascript in which some balls will be thrown on the screen with some initial velocity and then they will bounce on colliding with each other or with the walls. I managed to do the collision with walls perfectly but now the problem is with the collision with other balls. I am using the following code for it: //Check collision between two bodies function collides(b1, b2) { //Find the distance between their mid-points var dx = b1.x - b2.x, dy = b1.y - b2.y, dist = Math.round(Math.sqrt(dx*dx + dy*dy)); //Check if it is a collision if(dist <= (b1.r + b2.r)) { //Calculate the angles var angle = Math.atan2(dy, dx), sin = Math.sin(angle), cos = Math.cos(angle); //Calculate the old velocity components var v1x = b1.vx * cos, v2x = b2.vx * cos, v1y = b1.vy * sin, v2y = b2.vy * sin; //Calculate the new velocity components var vel1x = ((b1.m - b2.m) / (b1.m + b2.m)) * v1x + (2 * b2.m / (b1.m + b2.m)) * v2x, vel2x = (2 * b1.m / (b1.m + b2.m)) * v1x + ((b2.m - b1.m) / (b2.m + b1.m)) * v2x, vel1y = v1y, vel2y = v2y; //Set the new velocities b1.vx = vel1x; b2.vx = vel2x; b1.vy = vel1y; b2.vy = vel2y; } } You can see the experiment here. The problem is, some balls overlap each other and stick together while some of them rebound perfectly. I don't know what is causing this issue. Here's my balls object if that matters: function Ball() { //Random Positions this.x = 50 + Math.random() * W; this.y = 50 + Math.random() * H; //Random radii this.r = 15 + Math.random() * 30; this.m = this.r; //Random velocity components this.vx = 1 + Math.random() * 4; this.vy = 1 + Math.random() * 4; //Random shade of grey color this.c = Math.round(Math.random() * 200); this.draw = function() { ctx.beginPath(); ctx.fillStyle = "rgb(" + this.c + ", " + this.c + ", " + this.c + ")"; ctx.arc(this.x, this.y, this.r, 0, Math.PI*2, false); ctx.fill(); ctx.closePath(); } }

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  • Collision detection doesn't work for automated elements in XNA 4.0

    - by NDraskovic
    I have a really weird problem. I made a 3D simulator of an "assembly line" as a part of a college project. Among other things it needs to be able to detect when a box object passes in front of sensor. I tried to solve this by making a model of a laser and checking if the box collides with it. I had some problems with BoundingSpheres of models meshes so I simply create a BoundingSphere and place it in the same place as the model. I organized them into a list of BoundingSpheres called "spheres" and for each model I create one BoundingSphere. All models except the box are static, so the box object has its own BoundingSphere (not a member of the "spheres" list). I also implemented a picking algorithm that I use to start the movement. This is the code that checks for collision: if (spheres.Count != 0) { for (int i = 1; i < spheres.Count; i++) { if (spheres[i].Intersects(PickingRay) != null && Microsoft.Xna.Framework.Input.ButtonState.Pressed == Mouse.GetState().LeftButton) { start = true; break; } if (BoxSphere.Intersects(spheres[i]) && start) { MoveBox(0, false);//The MoveBox function receives the direction (0) and a bool value that dictates whether the box should move or not (false means stop) start = false; break; } if (start /*&& Microsoft.Xna.Framework.Input.ButtonState.Pressed == Mouse.GetState().LeftButton*/ && !BoxSphere.Intersects(spheres[i])) { MoveBox(0, true); break; } } The problem is this: When I use the mouse to move the box (the commented part in the third if condition) the collision works fine (I have another part of code that I removed to simplify my question - it calculates the "address" of the box, and by that number I know that the collision is correct). But when I comment it (like in this example) the box just passes trough the lasers and does not detect the collision (the idea is that the box stops at each laser and the user passes it forth by clicking on the appropriate "switch"). Can you see the problem? Please help, and if you need more informations I will try to give them. Thanks

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  • Cocos2D - Detecting collision

    - by Grace
    I am a beginner in cocos2d and im facing a problem with detecting collision for my coins. Sometimes it works sometimes it doesn't. So basically, im creating a game which the user (ship) have to avoid the obstacles and collect coins on the way. The collision of the obstacle works well but not for the coins. I was thinking maybe the loops for creating many coins is the problem but im not sure. Can anyone help? My codes: - (void)update:(ccTime)dt{ double curTime = CACurrentMediaTime(); if (curTime > _nextBridgeSpawn) { float randSecs = [self randomValueBetween:3.0 andValue:5.0]; _nextBridgeSpawn = randSecs + curTime; float randX = [self randomValueBetween:50 andValue:500]; float randDuration = [self randomValueBetween:8.0 andValue:10.0]; CCSprite *bridge = [_bridge objectAtIndex:_nextBridge]; _nextBridge++; if (_nextBridge >= _bridge.count) _nextBridge = 0; [bridge stopAllActions]; bridge.position = ccp(winSize.width/2, winSize.height); bridge.visible = YES; [bridge runAction:[CCSequence actions: [CCMoveBy actionWithDuration:randDuration position:ccp(0, -winSize.height)], [CCCallFuncN actionWithTarget:self selector:@selector(setInvisible:)], nil]]; this is where i declare my coins (continued from the update method) int randCoin = [self randomValueBetween:0 andValue:5]; _coin = [[CCArray alloc] initWithCapacity:randCoin]; for(int i = 0; i < randCoin; ++i) { coin = [CCSprite spriteWithFile:@"coin.png"]; coin.visible = NO; [self addChild:coin]; [_coin addObject:coin]; } float randCoinX = [self randomValueBetween:winSize.width/5 andValue:winSize.width - (border.contentSize.width *2)]; float randCoinY = [self randomValueBetween:100 andValue:700]; float randCoinPlace = [self randomValueBetween:30 andValue:60]; for (int i = 0; i < _coin.count; ++i) { CCSprite *coin2 = [_coin objectAtIndex:i]; coin2.position = ccp(randCoinX, (bridge.position.y + randCoinY) + (randCoinPlace *i)); coin2.visible = YES; [coin2 runAction:[CCSequence actions: [CCMoveBy actionWithDuration:randDuration position:ccp(0, -winSize.height-2000)], [CCCallFuncN actionWithTarget:self selector:@selector(setInvisible:)], nil]]; } } this is to check for collision (also in the update method) for (CCSprite *bridge in _bridge) { if (!bridge.visible) continue; if (CGRectIntersectsRect(ship.boundingBox, bridge.boundingBox)){ bridge.visible = NO; [ship runAction:[CCBlink actionWithDuration:1.0 blinks:5]]; } } } //this is the collision for coins which only work at times for (CCSprite *coin2 in _coin) { if (!coin2.visible) continue; if (CGRectIntersectsRect(ship.boundingBox, coin2.boundingBox)) { NSLog(@"Coin collected"); coin2.visible = NO; } } } Thank you.

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  • 2D Platformer Collision Handling

    - by defender-zone
    Hello, everyone! I am trying to create a 2D platformer (Mario-type) game and I am some having some issues with handling collisions properly. I am writing this game in C++, using SDL for input, image loading, font loading, etcetera. I am also using OpenGL via the FreeGLUT library in conjunction with SDL to display graphics. My method of collision detection is AABB (Axis-Aligned Bounding Box), which is really all I need to start with. What I need is an easy way to both detect which side the collision occurred on and handle the collisions properly. So, basically, if the player collides with the top of the platform, reposition him to the top; if there is a collision to the sides, reposition the player back to the side of the object; if there is a collision to the bottom, reposition the player under the platform. I have tried many different ways of doing this, such as trying to find the penetration depth and repositioning the player backwards by the penetration depth. Sadly, nothing I've tried seems to work correctly. Player movement ends up being very glitchy and repositions the player when I don't want it to. Part of the reason is probably because I feel like this is something so simple but I'm over-thinking it. If anyone thinks they can help, please take a look at the code below and help me try to improve on this if you can. I would like to refrain from using a library to handle this (as I want to learn on my own) or the something like the SAT (Separating Axis Theorem) if at all possible. Thank you in advance for your help! void world1Level1CollisionDetection() { for(int i; i < blocks; i++) { if (de2dCheckCollision(ball,block[i],0.0f,0.0f)==true) { int up = 0; int left = 0; int right = 0; int down = 0; if(ball.coords[0] < block[i].coords[0] && block[i].coords[0] < ball.coords[2] && ball.coords[2] < block[i].coords[2]) { left = 1; } if(block[i].coords[0] < ball.coords[0] && ball.coords[0] < block[i].coords[2] && block[i].coords[2] < ball.coords[2]) { right = 1; } if(ball.coords[1] < block[i].coords[1] && block[i].coords[1] < ball.coords[3] && ball.coords[3] < block[i].coords[3]) { up = 1; } if(block[i].coords[1] < ball.coords[1] && ball.coords[1] < block[i].coords[3] && block[i].coords[3] < ball.coords[3]) { down = 1; } cout << left << ", " << right << ", " << up << ", " << down << ", " << endl; if (left == 1) { ball.coords[0] = block[i].coords[0] - 16.0f; ball.coords[2] = block[i].coords[0] - 0.0f; } if (right == 1) { ball.coords[0] = block[i].coords[2] + 0.0f; ball.coords[2] = block[i].coords[2] + 16.0f; } if (down == 1) { ball.coords[1] = block[i].coords[3] + 0.0f; ball.coords[3] = block[i].coords[3] + 16.0f; } if (up == 1) { ball.yspeed = 0.0f; ball.gravity = 0.0f; ball.coords[1] = block[i].coords[1] - 16.0f; ball.coords[3] = block[i].coords[1] - 0.0f; } } if (de2dCheckCollision(ball,block[i],0.0f,0.0f)==false) { ball.gravity = -0.5f; } } } To explain what some of this code means: The blocks variable is basically an integer that is storing the amount of blocks, or platforms. I am checking all of the blocks using a for loop, and the number that the loop is currently on is represented by integer i. The coordinate system might seem a little weird, so that's worth explaining. coords[0] represents the x position (left) of the object (where it starts on the x axis). coords[1] represents the y position (top) of the object (where it starts on the y axis). coords[2] represents the width of the object plus coords[0] (right). coords[3] represents the height of the object plus coords[1] (bottom). de2dCheckCollision performs an AABB collision detection. Up is negative y and down is positive y, as it is in most games. Hopefully I have provided enough information for someone to help me successfully. If there is something I left out that might be crucial, let me know and I'll provide the necessary information. Finally, for anyone who can help, providing code would be very helpful and much appreciated. Thank you again for your help!

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  • Fraud Detection with the SQL Server Suite Part 1

    - by Dejan Sarka
    While working on different fraud detection projects, I developed my own approach to the solution for this problem. In my PASS Summit 2013 session I am introducing this approach. I also wrote a whitepaper on the same topic, which was generously reviewed by my friend Matija Lah. In order to spread this knowledge faster, I am starting a series of blog posts which will at the end make the whole whitepaper. Abstract With the massive usage of credit cards and web applications for banking and payment processing, the number of fraudulent transactions is growing rapidly and on a global scale. Several fraud detection algorithms are available within a variety of different products. In this paper, we focus on using the Microsoft SQL Server suite for this purpose. In addition, we will explain our original approach to solving the problem by introducing a continuous learning procedure. Our preferred type of service is mentoring; it allows us to perform the work and consulting together with transferring the knowledge onto the customer, thus making it possible for a customer to continue to learn independently. This paper is based on practical experience with different projects covering online banking and credit card usage. Introduction A fraud is a criminal or deceptive activity with the intention of achieving financial or some other gain. Fraud can appear in multiple business areas. You can find a detailed overview of the business domains where fraud can take place in Sahin Y., & Duman E. (2011), Detecting Credit Card Fraud by Decision Trees and Support Vector Machines, Proceedings of the International MultiConference of Engineers and Computer Scientists 2011 Vol 1. Hong Kong: IMECS. Dealing with frauds includes fraud prevention and fraud detection. Fraud prevention is a proactive mechanism, which tries to disable frauds by using previous knowledge. Fraud detection is a reactive mechanism with the goal of detecting suspicious behavior when a fraudster surpasses the fraud prevention mechanism. A fraud detection mechanism checks every transaction and assigns a weight in terms of probability between 0 and 1 that represents a score for evaluating whether a transaction is fraudulent or not. A fraud detection mechanism cannot detect frauds with a probability of 100%; therefore, manual transaction checking must also be available. With fraud detection, this manual part can focus on the most suspicious transactions. This way, an unchanged number of supervisors can detect significantly more frauds than could be achieved with traditional methods of selecting which transactions to check, for example with random sampling. There are two principal data mining techniques available both in general data mining as well as in specific fraud detection techniques: supervised or directed and unsupervised or undirected. Supervised techniques or data mining models use previous knowledge. Typically, existing transactions are marked with a flag denoting whether a particular transaction is fraudulent or not. Customers at some point in time do report frauds, and the transactional system should be capable of accepting such a flag. Supervised data mining algorithms try to explain the value of this flag by using different input variables. When the patterns and rules that lead to frauds are learned through the model training process, they can be used for prediction of the fraud flag on new incoming transactions. Unsupervised techniques analyze data without prior knowledge, without the fraud flag; they try to find transactions which do not resemble other transactions, i.e. outliers. In both cases, there should be more frauds in the data set selected for checking by using the data mining knowledge compared to selecting the data set with simpler methods; this is known as the lift of a model. Typically, we compare the lift with random sampling. The supervised methods typically give a much better lift than the unsupervised ones. However, we must use the unsupervised ones when we do not have any previous knowledge. Furthermore, unsupervised methods are useful for controlling whether the supervised models are still efficient. Accuracy of the predictions drops over time. Patterns of credit card usage, for example, change over time. In addition, fraudsters continuously learn as well. Therefore, it is important to check the efficiency of the predictive models with the undirected ones. When the difference between the lift of the supervised models and the lift of the unsupervised models drops, it is time to refine the supervised models. However, the unsupervised models can become obsolete as well. It is also important to measure the overall efficiency of both, supervised and unsupervised models, over time. We can compare the number of predicted frauds with the total number of frauds that include predicted and reported occurrences. For measuring behavior across time, specific analytical databases called data warehouses (DW) and on-line analytical processing (OLAP) systems can be employed. By controlling the supervised models with unsupervised ones and by using an OLAP system or DW reports to control both, a continuous learning infrastructure can be established. There are many difficulties in developing a fraud detection system. As has already been mentioned, fraudsters continuously learn, and the patterns change. The exchange of experiences and ideas can be very limited due to privacy concerns. In addition, both data sets and results might be censored, as the companies generally do not want to publically expose actual fraudulent behaviors. Therefore it can be quite difficult if not impossible to cross-evaluate the models using data from different companies and different business areas. This fact stresses the importance of continuous learning even more. Finally, the number of frauds in the total number of transactions is small, typically much less than 1% of transactions is fraudulent. Some predictive data mining algorithms do not give good results when the target state is represented with a very low frequency. Data preparation techniques like oversampling and undersampling can help overcome the shortcomings of many algorithms. SQL Server suite includes all of the software required to create, deploy any maintain a fraud detection infrastructure. The Database Engine is the relational database management system (RDBMS), which supports all activity needed for data preparation and for data warehouses. SQL Server Analysis Services (SSAS) supports OLAP and data mining (in version 2012, you need to install SSAS in multidimensional and data mining mode; this was the only mode in previous versions of SSAS, while SSAS 2012 also supports the tabular mode, which does not include data mining). Additional products from the suite can be useful as well. SQL Server Integration Services (SSIS) is a tool for developing extract transform–load (ETL) applications. SSIS is typically used for loading a DW, and in addition, it can use SSAS data mining models for building intelligent data flows. SQL Server Reporting Services (SSRS) is useful for presenting the results in a variety of reports. Data Quality Services (DQS) mitigate the occasional data cleansing process by maintaining a knowledge base. Master Data Services is an application that helps companies maintaining a central, authoritative source of their master data, i.e. the most important data to any organization. For an overview of the SQL Server business intelligence (BI) part of the suite that includes Database Engine, SSAS and SSRS, please refer to Veerman E., Lachev T., & Sarka D. (2009). MCTS Self-Paced Training Kit (Exam 70-448): Microsoft® SQL Server® 2008 Business Intelligence Development and Maintenance. MS Press. For an overview of the enterprise information management (EIM) part that includes SSIS, DQS and MDS, please refer to Sarka D., Lah M., & Jerkic G. (2012). Training Kit (Exam 70-463): Implementing a Data Warehouse with Microsoft® SQL Server® 2012. O'Reilly. For details about SSAS data mining, please refer to MacLennan J., Tang Z., & Crivat B. (2009). Data Mining with Microsoft SQL Server 2008. Wiley. SQL Server Data Mining Add-ins for Office, a free download for Office versions 2007, 2010 and 2013, bring the power of data mining to Excel, enabling advanced analytics in Excel. Together with PowerPivot for Excel, which is also freely downloadable and can be used in Excel 2010, is already included in Excel 2013. It brings OLAP functionalities directly into Excel, making it possible for an advanced analyst to build a complete learning infrastructure using a familiar tool. This way, many more people, including employees in subsidiaries, can contribute to the learning process by examining local transactions and quickly identifying new patterns.

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  • Continuous Physics Engine's Collision Detection Techniques

    - by Griffin
    I'm working on a purely continuous physics engine, and I need to choose algorithms for broad and narrow phase collision detection. "Purely continuous" means I never do intersection tests, but instead want to find ways to catch every collision before it happens, and put each into "planned collisions" stack that is ordered by TOI. Broad Phase The only continuous broad-phase method I can think of is encasing each body in a circle and testing if each circle will ever overlap another. This seems horribly inefficient however, and lacks any culling. I have no idea what continuous analogs might exist for today's discrete collision culling methods such as quad-trees either. How might I go about preventing inappropriate and pointless broad test's such as a discrete engine does? Narrow Phase I've managed to adapt the narrow SAT to a continuous check rather than discrete, but I'm sure there's other better algorithms out there in papers or sites you guys might have come across. What various fast or accurate algorithm's do you suggest I use and what are the advantages / disatvantages of each? Final Note: I say techniques and not algorithms because I have not yet decided on how I will store different polygons which might be concave, convex, round, or even have holes. I plan to make a decision on this based on what the algorithm requires (for instance if I choose an algorithm that breaks down a polygon into triangles or convex shapes I will simply store the polygon data in this form).

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  • 2D Side Scrolling game and "walk over ground" collision detection

    - by Fire-Dragon-DoL
    The question is not hard, I'm writing a game engine for 2D side scrolling games, however I'm thinking to my 2D side scrolling game and I always come up with the problem of "how should I do collision with the ground". I think I couldn't handle the collision with ground (ground for me is "where the player walk", so something heavily used) in a per-pixel way, and I can't even do it with simple shape comparison (because the ground can be tilted), so what's the correct way? I'know what tiles are and i've read about it, but how much should be big each tile to not appear like a stairs?Are there any other approach? I watched this game and is very nice how he walks on ground: http://www.youtube.com/watch?v=DmSAQwbbig8&feature=player_embedded If there are "platforms" in mid air, how should I handle them?I can walk over them but I can't pass "inside". Imagine a platform in mid air, it allows you to walk over it but limit you because you can't jump in the area she fits Sorry for my english, it's not my native language and this topic has a lot of keywords I don't know so I have to use workarounds Thanks for any answer Additional informations and suggestions: I'm doing a game course in this period and I asked them how to do this, they suggested me this approach (a QuadTree): -All map is divided into "big nodes" -Each bigger node has sub nodes, to find where the player is -You can find player's node with a ray on player position -When you find the node where the player is, you can do collision check through all pixels (which can be 100-200px nothing more) Here is an example, however i didn't show very well the bigger nodes because i'm not very good with photoshop :P How is this approach?

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  • Camera Collision inside the room model

    - by sanddy
    I am having a problem in Calculating the camera collision for my Room model which consists of sofa, tables and other models. The users shall be moving the camera front, back, rotating so i need to make sure that the camera does not collide with any of the models with in the room. I have treated all my models inside the room by BoundingBox[] and the camera by BoundingSphere. So, far i have implemented collision by looking into the tutorial from http://www.toymaker.info/Games/XNA/html/xna_model_collisions.html which was great. But, I guess the problem lies in the Transformation part. I debugged and found some points to be at Vector(-XXX,-XXX,-XXX) where X is digit. Also i found my radius of some models where too large(in thousand, i just looked into its radius value before converting to BoundingBox). Do I need to scale the model for collision??? Below are my code:- On My LoadContent(): Matrix[] transforms = new Matrix[myModel.Bones.Count]; myModel.CopyAbsoluteBoneTransformsTo(transforms); int index = 0; box = new List<BoundingBox>(); BoundingBox worldModel = Utility.CalculateBoundingBox(myModel); foreach (ModelMesh mesh in myModel.Meshes) { Vector3[] obb = new Vector3[8]; worldModel.GetCorners(obb); Vector3[] asdf = (Vector3[])obb.Clone(); Vector3.Transform(obb, ref transforms[mesh.ParentBone.Index], obb); BoundingBox worldBox = BoundingBox.CreateFromPoints(obb); box.Add(worldBox); index++; } On CameraPosition Update: BoundingSphere bs = new BoundingSphere(this.cameraPos, 5.0f); if (RoomWalkthrough.Utility.CheckCollision(bs, bb)) { // Do Something } Please Help.

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  • improve Collision detection memory usage (blocks with bullets)

    - by Eddy
    i am making a action platform 2D game, something like Megaman. I am using XNA to make it. already made player phisics,collisions, bullets, enemies and AIs, map editor, scorolling X Y camera (about 75% of game is finished ). as i progressed i noticed that my game would be more interesting to play if bullets would be destroyed on collision with regular(stationary ) map blocks, only problem is that if i use my collision detection (each bullet with each block) sometimes it begins to lag(btw if my bullet exits the screen player can see it is removed from bullet list) So how to improve my collision detection so that memory usage would be so high? :) ( on a map 300x300 blocks for example don't think that bigger map should be made); int block = 0; int bulet= 0; bool destroy_bullet = false; while (bulet < bullets.Count) { while (block < blocks.Count) { if (bullets[bulet].P_Bul_rec.Intersects( blocks[block].rect)) {//bullets and block are Lists that holds objects of bullet and block classes //P_Bul_rec just bullet rectangle destroy_bullet = true; } block++; } if (destroy_bullet) { bullets.RemoveAt(bulet); destroy_bullet = false; } else { bulet++; } block = 0; }

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  • Circle to Circle collision, checking each circle against all others

    - by user14861
    I'm currently coding a little circle to circle collision demo but I've got a little stuck. I think I currently have the code to detect collision but I'm not sure how to loop through my list of circles and check them off against one another. Collision check code: public static Vector2 GetIntersectionDepth(Circle a, Circle b) { float xValue = a.Center.X - b.Center.X; float yValue = a.Center.Y - b.Center.Y; Vector2 depth = Vector2.Zero; float distance = Vector2.Distance(a.Center, b.Center); if (a.Radius + b.Radius > distance) { float result = (a.Radius + b.Radius) - distance; depth.X = (float)Math.Cos(result); depth.Y = (float)Math.Sin(result); } return depth; } Loop through code: Vector2 depth = Vector2.Zero; for (int i = 0; i < bounds.Count; i++) for (int j = i+1; j < bounds.Count; j++) { depth = CircleToCircleIntersection.GetIntersectionDepth(bounds[i], bounds[j]); } Clearly I'm a complete newbie, wondering if anyone can give any suggestions or point out my errors, thanks in advance. :)

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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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