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  • Color based collision detection

    - by user1486826
    I am making a game where you fly a ship around some randomly generated planets. Since I am using a for loop to draw over 5000 planets, using the rectangle class or an oval-type class for this is not an option, since creating many objects will severely affect performance. Bitmasking each planet will likely result in performance issues too, so the only candidate is color based collision detection, because I don't need to apply some sort of object to everything I want to check for collisions. Is any way to check the perimeter around the ship for a certain color?

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  • Beat detection, weird detection

    - by Quincy
    I made this soundanalyzer class to detect beats in songs : // put it on pastebin for the big size, will put it here if people rather want that. pastebin.com/8PdgZPP3 but for some reason its only detecting beats from 637 sec to around 641(sec) and I have no idea why. I know the beats are being inserted from multiple bands since I am finding duplicates and it seems as its assigning a beat to each instant energy value in between those values. Its modeled after this : http://www.flipcode.com/misc/BeatDetectionAlgorithms.pdf So why won't the beats properly register ?

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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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  • Per Pixel Collision Detection

    - by CJ Cohorst
    Just a quick question, I have this collision detection code: public bool PerPixelCollision(Player player, Game1 dog) { Matrix atob = player.Transform * Matrix.Invert(dog.Transform); Vector2 stepX = Vector2.TransformNormal(Vector2.UnitX, atob); Vector2 stepY = Vector2.TransformNormal(Vector2.UnitY, atob); Vector2 iBPos = Vector2.Transform(Vector2.Zero, atob); for(int deltax = 0; deltax < player.playerTexture.Width; deltax++) { Vector2 bpos = iBPos; for (int deltay = 0; deltay < player.playerTexture.Height; deltay++) { int bx = (int)bpos.X; int by = (int)bpos.Y; if (bx >= 0 && bx < dog.dogTexture.Width && by >= 0 && by < dog.dogTexture.Height) { if (player.TextureData[deltax + deltay * player.playerTexture.Width].A > 150 && dog.TextureData[bx + by * dog.Texture.Width].A > 150) { return true; } } bpos += stepY; } iBPos += stepX; } return false; } What I want to know is where to put in the code where something happens. For example, I want to put in player.playerPosition.X -= 200 just as a test, but I don't know where to put it. I tried putting it under the return true and above it, but under it, it said unreachable code, and above it nothing happened. I also tried putting it by bpos += stepY; but that didn't work either. Where do I put the code? Any help is appreciated. Thanks in advance!

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  • Space-efficient data structures for broad-phase collision detection

    - by Marian Ivanov
    As far as I know, these are three types of data structures that can be used for collision detection broadphase: Unsorted arrays: Check every object againist every object - O(n^2) time; O(log n) space. It's so slow, it's useless if n isn't really small. for (i=1;i<objects;i++){ for(j=0;j<i;j++) narrowPhase(i,j); }; Sorted arrays: Sort the objects, so that you get O(n^(2-1/k)) for k dimensions O(n^1.5) for 2d and O(n^1.67) for 3d and O(n) space. Assuming the space is 2D and sortedArray is sorted so that if the object begins in sortedArray[i] and another object ends at sortedArray[i-1]; they don't collide Heaps of stacks: Divide the objects between a heap of stacks, so that you only have to check the bucket, its children and its parents - O(n log n) time, but O(n^2) space. This is probably the most frequently used approach. Is there a way of having O(n log n) time with less space? When is it more efficient to use sorted arrays over heaps and vice versa?

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  • Collision detection, stop gravity

    - by Scott Beeson
    I just started using Gamemaker Studio and so far it seems fairly intuitive. However, I set a room to "Room is Physics World" and set gravity to 10. I then enabled physics on my player object and created a block object to match a platform on my background sprite. I set up a Collision Detection event for the player and the block objects that sets the gravity to 0 (and even sets the vspeed to 0). I also put a notification in the collision event and I don't get that either. I have my key down and key up events working well, moving the player left and right and changing the sprites appropriately, so I think I understand the event system. I must just be missing something simple with the physics. I've tried making both and neither of the objects "solid". Pretty frustrating since it looks so easy. The player starting point is directly above the block object in the grid and the player does fall through the block. I even made the block sprite solid red so I could see it (initially it was invisible, obviously).

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  • Circle collision detection and Vector math: HELP?

    - by Griffin
    Hey so i'm currently going through the wildbunny blog to learn about collision detection, but i'm a bit confused on how the vectors he's talking about come into play QUOTED BLOG: p = ||A-B|| – (r1+r2) The two spheres are penetrating by distance p. We would also like the penetration vector so that we can correct the penetration once we discover it. This is the vector that moves both circles to the point where they just touch, correcting the penetration. Importantly it is not only just a vector that does this, it is the only vector which corrects the penetration by moving the minimum amount. This is important because we only want to correct the error, not introduce more by moving too much when we correct, or too little. N = (A-B) / ||A-B|| P = N*p Here we have calculated the normalised vector N between the two centres and the penetration vector P by multiplying our unit direction by the penetration distance. Ok so i understand that p is the distance each circle is penetrating each other, but i don't get what exactly N and P is. it seems to me N is just the coordinates of the 3rd point of the right trianlge formed by point A and B (A-B) then being divided by the hypotenuse of that triangle or distance between A and B (||A-B||) Whats the significance of this? Also, what is the penetration vector used for? It seems to me like a movement that one of the circles would perform to get un-penetrated.

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  • 2D Side scroller collision detection

    - by Shanon Simmonds
    I am trying to do some collision detection between objects and tiles, but the tiles do not have there own x and y position, they are just rendered to the x and y position given, there is an array of integers which has the ids of the tiles to use(which are given from an image and all the different colors are assigned different tiles) int x0 = camera.x / 16; int y0 = camera.y / 16; int x1 = (camera.x + screen.width) / 16; int y1 = (camera.y + screen.height) / 16; for(int y = y0; y < y1; y++) { if(y < 0 || y >= height) continue; // height is the height of the level for(int x = x0; x < x1; x++) { if(x < 0 || x >= width) continue; // width is the width of the level getTile(x, y).render(screen, x * 16, y * 16); } } I tried using the levels getTile method to see if the tile that the object was going to advance to, to see if it was a certain tile, but, it seems to only work in some directions. Any ideas on what I'm doing wrong and fixes would be greatly appreciated. What's wrong is that it doesn't collide properly in every direction and also this is how I tested for a collision in the objects class if(!level.getTile((x + xa) / 16, (y + ya) / 16).isSolid()) { x += xa; y += ya; } EDIT: xa and ya represent the direction as well as the movement, if xa is negative it means the object is moving left, if its positive it is moving right, and same with ya except negative for up, positive for down.

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  • libgdx collision detection / bounding the object

    - by johnny-b
    i am trying to get collision detection so i am drawing a red rectangle to see if it is working, and when i do the code below in the update method. to check if it is going to work. the position is not in the right place. the red rectangle starts from the middle and not at the x and y point?Huh so it draws it wrong. i also have a getter method so nothing wrong there. bullet.set(getX(), getY(), getOriginX(), getOriginY()); this is for the render shapeRenderer.begin(ShapeType.Filled); shapeRenderer.setColor(Color.RED); shapeRenderer.rect(bullet.getX(), bullet.getY(), bullet.getOriginX(), bullet.getOriginY(), 15, 5, bullet.getRotation()); shapeRenderer.end(); i have tried to do it with a circle but the circle draws in the middle and i want it to be at the tip of the bullet. at the front of the bullet. x, y point. boundingCircle.set(getX() + getOriginX(), getY() + getOriginY(), 4.0f); shapeRenderer.begin(ShapeType.Filled); shapeRenderer.setColor(Color.RED); shapeRenderer.circle(bullet.getBoundingCircle().x, bullet.getBoundingCircle().y, bullet.getBoundingCircle().radius); shapeRenderer.end(); thank you need it to be of the x and y as the bullet is in the middle of the sprite when drawn originally via paint.

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  • Collision detection - player gets stuck in platform when jumping

    - by Sun
    So I'm having some problems with my collision detection with my platformer. Take the image below as an example. When I'm running right I am unable to go through the platform, but when I hold my right key and jump, I end up going through the object as shown in the image, below is the code im using: if(shapePlatform.intersects(player.getCollisionShape())){ Vector2f vectorSide = new Vector2f(shapePlatform.getCenter()[0] - player.getCollisionShape().getCenter()[0], shapePlatform.getCenter()[1] - player.getCollisionShape().getCenter()[1]); player.setVerticleSpeed(0f); player.setJumping(false); if(vectorSide.x > 0 && !(vectorSide.y > 0)){ player.getPosition().set(player.getPosition().x-3, player.getPosition().y); }else if(vectorSide.y > 0){ player.getPosition().set(player.getPosition().x, player.getPosition().y); }else if(vectorSide.x < 0 && !(vectorSide.y > 0)){ player.getPosition().set(player.getPosition().x+3, player.getPosition().y); } } I'm basically getting the difference between the centre of the player and the centre of the colliding platform to determine which side the player is colliding with. When my player jumps and walks right on the platform he goes right through. The same can also be observed when I jump on the actual platform, should I be resetting the players y in this situation?

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  • Collision detection between a sprite and rectangle in canvas

    - by Andy
    I'm building a Javascript + canvas game which is essentially a platformer. I have the player all set up and he's running, jumping and falling, but I'm having trouble with the collision detection between the player and blocks (the blocks will essentially be the platforms that the player moves on). The blocks are stored in an array like this: var blockList = [[50, 400, 100, 100]]; And drawn to the canvas using this: this.draw = function() { c.fillRect(blockList[0][0], blockList[0][1], 100, 100); } I'm checking for collisions using something along these lines in the player object: this.update = function() { // Check for collitions with blocks for(var i = 0; i < blockList.length; i++) { if((player.xpos + 34) > blockList[i][0] && player.ypos > blockList[i][1]) { player.xpos = blockList[i][0] - 28; return false; } } // Other code to move the player based on keyboard input etc } The idea is if the player will collide with a block in the next game update (the game uses a main loop running at 60Htz), the function will return false and exit, thus meaning the player won't move. Unfortunately, that only works when the player hits the left side of the block, and I can't work out how to make it so the player stops if it hits any side of the block. I have the properties player.xpos and player.ypos to help here.

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  • How does this circle collision detection math work?

    - by Griffin
    I'm going through the wildbunny blog to learn about collision detection. I'm confused about how the vectors he's talking about come into play. Here's the part that confuses me: p = ||A-B|| – (r1+r2) The two spheres are penetrating by distance p. We would also like the penetration vector so that we can correct the penetration once we discover it. This is the vector that moves both circles to the point where they just touch, correcting the penetration. Importantly it is not only just a vector that does this, it is the only vector which corrects the penetration by moving the minimum amount. This is important because we only want to correct the error, not introduce more by moving too much when we correct, or too little. N = (A-B) / ||A-B|| P = N*p Here we have calculated the normalised vector N between the two centres and the penetration vector P by multiplying our unit direction by the penetration distance. I understand that p is the distance by which the circles penetrate, but I don't get what exactly N and P are. It seems to me N is just the coordinates of the 3rd point of the right trianlge formed by point A and B (A-B) then being divided by the hypotenuse of that triangle or distance between A and B (||A-B||). What's the significance of this? Also, what is the penetration vector used for? It seems to me like a movement that one of the circles would perform to get un-penetrated.

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  • Hit Detection When rotating the camera

    - by SD1990
    This bug/feature has been plaguing me for a while and i want to know the best way to fix it. I'm testing simple hit detection with a wall, like: if (Forward button) if(Inv.w.z < -49 || Inv.w.z > 49) pos.z = 0.0f; else if(Inv.w.x < -49 || Inv.w.x > 49) pos.z = 0.0f; else pos.z = +1.0f; where Inv.w. is the camera positions. Now obviously when i now hit that certain point i can no longer move away from the wall or anywhere in fact. How can i change this code to allow for the camera to be turned away from the wall so therefore i should be allowed to move? for example, the player hits the wall and i cant move until i turn around or to the side? I know its something to do with velocity but im pretty new to this so please bare with me if this is easy.

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  • Help with collision detection method [on hold]

    - by derek jones
    I was wondering if any of you could spare me some time to go over some collision detection on my platform engine. i tried XNA a few years back but for reasons i wont go into online could not continue, my health is now at a state where i am ready to try again but due to my current circumstances (and age) schooling is out of the question so i turn to you guys for help. Whilst i can adapt the MS sample ok and have some great features, you will agree modifying code is not really learning. So i have spent the last couple of week going over my old MS code and lots of stuff online and decided on what i want and have ported most of it over to code that i understand 90% of. I have my player class that moves about, jumps with gravity, has animations and a bounding box that follows it around. I have my map & basic level class to load levels from text files. Its just how i handle the collisions that i am struggling with as i will want per pixel collision on some tiles(i have code for this in a pong game i made so that should be ok). I'm pretty clear in my mind on what i need to do its just putting it in code and in the right place, here's what i was thinking. I was going to do it all in layers, have a tile layer, a collision layer & an item layer this way i could make a nice map editor in Win Forms at some point. Anyway i need to read in the collision layer the assign each tile a rectangle and collision property, and this is where i get me. Would any of you be able to spare some time and go over this with me ? I will post some code later Regards Del

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  • Tile-based 2D collision detection problems

    - by Vee
    I'm trying to follow this tutorial http://www.tonypa.pri.ee/tbw/tut05.html to implement real-time collisions in a tile-based world. I find the center coordinates of my entities thanks to these properties: public float CenterX { get { return X + Width / 2f; } set { X = value - Width / 2f; } } public float CenterY { get { return Y + Height / 2f; } set { Y = value - Height / 2f; } } Then in my update method, in the player class, which is called every frame, I have this code: public override void Update() { base.Update(); int downY = (int)Math.Floor((CenterY + Height / 2f - 1) / 16f); int upY = (int)Math.Floor((CenterY - Height / 2f) / 16f); int leftX = (int)Math.Floor((CenterX + Speed * NextX - Width / 2f) / 16f); int rightX = (int)Math.Floor((CenterX + Speed * NextX + Width / 2f - 1) / 16f); bool upleft = Game.CurrentMap[leftX, upY] != 1; bool downleft = Game.CurrentMap[leftX, downY] != 1; bool upright = Game.CurrentMap[rightX, upY] != 1; bool downright = Game.CurrentMap[rightX, downY] != 1; if(NextX == 1) { if (upright && downright) CenterX += Speed; else CenterX = (Game.GetCellX(CenterX) + 1)*16 - Width / 2f; } } downY, upY, leftX and rightX should respectively find the lowest Y position, the highest Y position, the leftmost X position and the rightmost X position. I add + Speed * NextX because in the tutorial the getMyCorners function is called with these parameters: getMyCorners (ob.x+ob.speed*dirx, ob.y, ob); The GetCellX and GetCellY methods: public int GetCellX(float mX) { return (int)Math.Floor(mX / SGame.Camera.TileSize); } public int GetCellY(float mY) { return (int)Math.Floor(mY / SGame.Camera.TileSize); } The problem is that the player "flickers" while hitting a wall, and the corner detection doesn't even work correctly since it can overlap walls that only hit one of the corners. I do not understand what is wrong. In the tutorial the ob.x and ob.y fields should be the same as my CenterX and CenterY properties, and the ob.width and ob.height should be the same as Width / 2f and Height / 2f. However it still doesn't work. Thanks for your help.

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  • My grid based collision detection is slow

    - by Fibericon
    Something about my implementation of a basic 2x4 grid for collision detection is slow - so slow in fact, that it's actually faster to simply check every bullet from every enemy to see if the BoundingSphere intersects with that of my ship. It becomes noticeably slow when I have approximately 1000 bullets on the screen (36 enemies shooting 3 bullets every .5 seconds). By commenting it out bit by bit, I've determined that the code used to add them to the grid is what's slowest. Here's how I add them to the grid: for (int i = 0; i < enemy[x].gun.NumBullets; i++) { if (enemy[x].gun.bulletList[i].isActive) { enemy[x].gun.bulletList[i].Update(timeDelta); int bulletPosition = 0; if (enemy[x].gun.bulletList[i].position.Y < 0) { bulletPosition = (int)Math.Floor((enemy[x].gun.bulletList[i].position.X + 900) / 450); } else { bulletPosition = (int)Math.Floor((enemy[x].gun.bulletList[i].position.X + 900) / 450) + 4; } GridItem bulletItem = new GridItem(); bulletItem.index = i; bulletItem.type = 5; bulletItem.parentIndex = x; if (bulletPosition > -1 && bulletPosition < 8) { if (!grid[bulletPosition].Contains(bulletItem)) { for (int j = 0; j < grid.Length; j++) { grid[j].Remove(bulletItem); } grid[bulletPosition].Add(bulletItem); } } } } And here's how I check if it collides with the ship: if (ship.isActive && !ship.invincible) { BoundingSphere shipSphere = new BoundingSphere( ship.Position, ship.Model.Meshes[0].BoundingSphere.Radius * 9.0f); for (int i = 0; i < grid.Length; i++) { if (grid[i].Contains(shipItem)) { for (int j = 0; j < grid[i].Count; j++) { //Other collision types omitted else if (grid[i][j].type == 5) { if (enemy[grid[i][j].parentIndex].gun.bulletList[grid[i][j].index].isActive) { BoundingSphere bulletSphere = new BoundingSphere(enemy[grid[i][j].parentIndex].gun.bulletList[grid[i][j].index].position, enemy[grid[i][j].parentIndex].gun.bulletModel.Meshes[0].BoundingSphere.Radius); if (shipSphere.Intersects(bulletSphere)) { ship.health -= enemy[grid[i][j].parentIndex].gun.damage; enemy[grid[i][j].parentIndex].gun.bulletList[grid[i][j].index].isActive = false; grid[i].RemoveAt(j); break; //no need to check other bullets } } else { grid[i].RemoveAt(j); } } What am I doing wrong here? I thought a grid implementation would be faster than checking each one.

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  • Collision detection via adjacent tiles - sprite too big

    - by BlackMamba
    I have managed to create a collision detection system for my tile-based jump'n'run game (written in C++/SFML), where I check on each update what values the surrounding tiles of the player contain and then I let the player move accordingly (i. e. move left when there is an obstacle on the right side). This works fine when the player sprite is not too big: Given a tile size of 5x5 pixels, my solution worked quite fine with a spritesize of 3x4 and 5x5 pixels. My problem is that I actually need the player to be quite gigantic (34x70 pixels given the same tilesize). When I try this, there seems to be an invisible, notably smaller boundingbox where the player collides with obstacles, the player also seems to shake strongly. Here some images to explain what I mean: Works: http://tinypic.com/r/207lvfr/8 Doesn't work: http://tinypic.com/r/2yuk02q/8 Another example of non-functioning: http://tinypic.com/r/kexbwl/8 (the player isn't falling, he stays there in the corner) My code for getting the surrounding tiles looks like this (I removed some parts to make it better readable): std::vector<std::map<std::string, int> > Game::getSurroundingTiles(sf::Vector2f position) { // converting the pixel coordinates to tilemap coordinates sf::Vector2u pPos(static_cast<int>(position.x/tileSize.x), static_cast<int>(position.y/tileSize.y)); std::vector<std::map<std::string, int> > surroundingTiles; for(int i = 0; i < 9; ++i) { // calculating the relative position of the surrounding tile(s) int c = i % 3; int r = static_cast<int>(i/3); // we subtract 1 to place the player in the middle of the 3x3 grid sf::Vector2u tilePos(pPos.x + (c - 1), pPos.y + (r - 1)); // this tells us what kind of block this tile is int tGid = levelMap[tilePos.y][tilePos.x]; // converts the coords from tile to world coords sf::Vector2u tileRect(tilePos.x*5, tilePos.y*5); // storing all the information std::map<std::string, int> tileDict; tileDict.insert(std::make_pair("gid", tGid)); tileDict.insert(std::make_pair("x", tileRect.x)); tileDict.insert(std::make_pair("y", tileRect.y)); // adding the stored information to our vector surroundingTiles.push_back(tileDict); } // I organise the map so that it is arranged like the following: /* * 4 | 1 | 5 * -- -- -- * 2 | / | 3 * -- -- -- * 6 | 0 | 7 * */ return surroundingTiles; } I then check in a loop through the surrounding tiles, if there is a 1 as gid (indicates obstacle) and then check for intersections with that adjacent tile. The problem I just can't overcome is that I think that I need to store the values of all the adjacent tiles and then check for them. How? And may there be a better solution? Any help is appreciated. P.S.: My implementation derives from this blog entry, I mostly just translated it from Objective-C/Cocos2d.

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  • Basic collision direction detection on 2d objects

    - by Osso Buko
    I am trying to develop a platform game for Android by using ANdroid GL Engine (ANGLE). And I am having trouble with collision detection. I have two objects which is shaped as rectangular. And no change in rotation. Here is a scheme of attributes of objects. What i am trying to do is when objects collide they block each other's movement on that direction. Every object has 4 boolean (bTop, bBottom, bRight, bLeft). For example when bBottom is true object can't advance on that direction. I came up with a solution but it seems it only works on one dimensional. Bottom and top or right and left. public void collisionPlatform (MyObject a, MyObject b) { // first obj is player and second is a wall or a platform Vector p1 = a.mPosition; // p1 = middle point of first object Vector d1 = a.mPosition2; // width(mX) and height of first object Vector mSpeed1 = a.mSpeed; // speed vector of first object Vector p2 = b.mPosition; // p1 = middle point of second object Vector d2 = b.mPosition2; // width(mX) and height of second object Vector mSpeed2 = b.mSpeed; // speed vector of second object float xDist, yDist; // distant between middle of two object float width , height; // this is average of two objects measurements width=(width1+width2)/2 xDist=(p1.mX - p2.mX); // calculate distance // if positive first object is at the right yDist=(p1.mY - p2.mY); // if positive first object is below width = d1.mX + d2.mX; // average measurements calculate height = d1.mY + d2.mY; width/=2; height/=2; if (Math.abs(xDist) < width && Math.abs(yDist) < height) { // Two object is collided if(p1.mY>p2.mY) { // first object is below second one a.bTop = true; if(a.mSpeed.mY<0) a.mSpeed.mY=0; b.bBottom = true; if(b.mSpeed.mY>0) b.mSpeed.mY=0; } else { a.bBottom = true; if(a.mSpeed.mY>0) a.mSpeed.mY=0; b.bTop = true; if(b.mSpeed.mY<0) b.mSpeed.mY=0; } } As seen in my code it simply will not work. when object comes from right or left it doesn't work. I tried couple of ways other than this one but none worked. I am guessing right method will include mSpeed vector. But I have no idea how to do it. I really appreciate if you could help. Sorry for my bad english.

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  • Resolving bounding box collision detection

    - by ndg
    I'm working on a simple collision detection and resolution method for a 2d tile-based bounding box system. Collision appears to work correctly, but I'm having issues with resolving a collision after it has happened. Essentially what I'm attempting to do is very similar to this approach. The problem I'm experiencing is that because objects can be traveling with both horizontal and vertical velocity, my resolution code causes the object to jump incorrectly. I've drawn the following annotation to explain my issue. In this example, because my object has both horizontal and vertical velocity, my object (which is heading upwards and collides with the bottom of a tile) has it's position altered twice: To correctly adjust it's vertical position to be beneath the tile. To incorrectly adjust it's horizontal position to be to the left of the tile. Below is my collision/resolution code in full: function intersects(x1, y1, w1, h1, x2, y2, w2, h2) { w2 += x2; w1 += x1; if (x2 > w1 || x1 > w2) return false; h2 += y2; h1 += y1; if (y2 > h1 || y1 > h2) return false; return true; } for(var y = 0; y < this.game.level.tiles.length; y++) { for(var x = 0; x < this.game.level.tiles[y].length; x++) { var tile = this.game.level.getTile(x, y); if(tile) { if( this.velocity.x > 0 && intersects(this.position.x+dx+this.size.w, this.position.y+dy, 1, this.size.h, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.x = ((x*tileSize)-this.size.w); hitSomething = true; break; } else if( this.velocity.x < 0 && intersects(this.position.x+dx, this.position.y+dy, 1, this.size.h, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.x = ((x*tileSize)+tileSize); hitSomething = true; break; } if( this.velocity.y > 0 && intersects(this.position.x+dx, this.position.y+dy+this.size.h, this.size.w, 1, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.y = ((y*tileSize)-this.size.h); hitSomething = true; break; } else if( this.velocity.y < 0 && intersects(this.position.x+dx, this.position.y+dy, this.size.w, 1, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.y = ((y*tileSize)+tileSize); hitSomething = true; break; } } } } if(hitSomething) { this.velocity.x = this.velocity.y = 0; dx = dy = 0; this.setJumping(false); }

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  • 2D OBB collision detection, resolving collisions?

    - by Milo
    I currently use OBBs and I have a vehicle that is a rigid body and some buildings. Here is my update() private void update() { camera.setPosition((vehicle.getPosition().x * camera.getScale()) - ((getWidth() ) / 2.0f), (vehicle.getPosition().y * camera.getScale()) - ((getHeight() ) / 2.0f)); //camera.move(input.getAnalogStick().getStickValueX() * 15.0f, input.getAnalogStick().getStickValueY() * 15.0f); if(input.isPressed(ControlButton.BUTTON_GAS)) { vehicle.setThrottle(1.0f, false); } if(input.isPressed(ControlButton.BUTTON_BRAKE)) { vehicle.setBrakes(1.0f); } vehicle.setSteering(input.getAnalogStick().getStickValueX()); vehicle.update(16.6666f / 1000.0f); ArrayList<Building> buildings = city.getBuildings(); for(Building b : buildings) { if(vehicle.getRect().overlaps(b.getRect())) { vehicle.update(-17.0f / 1000.0f); break; } } } The collision detection works well. What doesn't is how they are dealt with. My goal is simple. If the vehicle hits a building, it should stop, and never go into the building. When I apply negative torque to reverse the car should not feel buggy and move away from the building. I don't want this to look buggy. This is my rigid body class: class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private float mass; //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position, getWidth(), getHeight(), angle); } public Vector2D getPosition() { return getRect().getCenter(); } @Override public void update(float timeStep) { //integrate physics //linear Vector2D acceleration = Vector2D.scalarDivide(forces, mass); velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); c = Vector2D.add(getRect().getCenter(), Vector2D.scalarMultiply(velocity , timeStep)); setCenter(c.x, c.y); forces = new Vector2D(0,0); //clear forces //angular float angAcc = torque / inertia; angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { Matrix mat = new Matrix(); float[] Vector2Ds = new float[2]; Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); return new Vector2D(Vector2Ds[0], Vector2Ds[1]); } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { Matrix mat = new Matrix(); float[] Vectors = new float[2]; Vectors[0] = world.x; Vectors[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vectors); return new Vector2D(Vectors[0], Vectors[1]); } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { Vector2D tangent = new Vector2D(-worldOffset.y, worldOffset.x); return Vector2D.add( Vector2D.scalarMultiply(tangent, angularVelocity) , velocity); } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces = Vector2D.add(forces ,worldForce); //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } } Essentially, when any rigid body hits a building it should exhibit the same behavior. How is collision solving usually done? Thanks

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  • How to implement a 2d collision detection for Android

    - by Michael Seun Araromi
    I am making a 2d space shooter using opengl ES. Can someone please show me how to implement a collision detection between the enemy ship and player ship. The code for the two classes are below: Player Ship Class: package com.proandroidgames; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.FloatBuffer; import javax.microedition.khronos.opengles.GL10; public class SSGoodGuy { public boolean isDestroyed = false; private int damage = 0; private FloatBuffer vertexBuffer; private FloatBuffer textureBuffer; private ByteBuffer indexBuffer; private float vertices[] = { 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, }; private float texture[] = { 0.0f, 0.0f, 0.25f, 0.0f, 0.25f, 0.25f, 0.0f, 0.25f, }; private byte indices[] = { 0, 1, 2, 0, 2, 3, }; public void applyDamage(){ damage++; if (damage == SSEngine.PLAYER_SHIELDS){ isDestroyed = true; } } public SSGoodGuy() { ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4); byteBuf.order(ByteOrder.nativeOrder()); vertexBuffer = byteBuf.asFloatBuffer(); vertexBuffer.put(vertices); vertexBuffer.position(0); byteBuf = ByteBuffer.allocateDirect(texture.length * 4); byteBuf.order(ByteOrder.nativeOrder()); textureBuffer = byteBuf.asFloatBuffer(); textureBuffer.put(texture); textureBuffer.position(0); indexBuffer = ByteBuffer.allocateDirect(indices.length); indexBuffer.put(indices); indexBuffer.position(0); } public void draw(GL10 gl, int[] spriteSheet) { gl.glBindTexture(GL10.GL_TEXTURE_2D, spriteSheet[0]); gl.glFrontFace(GL10.GL_CCW); gl.glEnable(GL10.GL_CULL_FACE); gl.glCullFace(GL10.GL_BACK); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer); gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer); gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_BYTE, indexBuffer); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glDisable(GL10.GL_CULL_FACE); } } Enemy Ship Class: package com.proandroidgames; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.FloatBuffer; import java.util.Random; import javax.microedition.khronos.opengles.GL10; public class SSEnemy { public float posY = 0f; public float posX = 0f; public float posT = 0f; public float incrementXToTarget = 0f; public float incrementYToTarget = 0f; public int attackDirection = 0; public boolean isDestroyed = false; private int damage = 0; public int enemyType = 0; public boolean isLockedOn = false; public float lockOnPosX = 0f; public float lockOnPosY = 0f; private Random randomPos = new Random(); private FloatBuffer vertexBuffer; private FloatBuffer textureBuffer; private ByteBuffer indexBuffer; private float vertices[] = { 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, }; private float texture[] = { 0.0f, 0.0f, 0.25f, 0.0f, 0.25f, 0.25f, 0.0f, 0.25f, }; private byte indices[] = { 0, 1, 2, 0, 2, 3, }; public void applyDamage() { damage++; switch (enemyType) { case SSEngine.TYPE_INTERCEPTOR: if (damage == SSEngine.INTERCEPTOR_SHIELDS) { isDestroyed = true; } break; case SSEngine.TYPE_SCOUT: if (damage == SSEngine.SCOUT_SHIELDS) { isDestroyed = true; } break; case SSEngine.TYPE_WARSHIP: if (damage == SSEngine.WARSHIP_SHIELDS) { isDestroyed = true; } break; } } public SSEnemy(int type, int direction) { enemyType = type; attackDirection = direction; posY = (randomPos.nextFloat() * 4) + 4; switch (attackDirection) { case SSEngine.ATTACK_LEFT: posX = 0; break; case SSEngine.ATTACK_RANDOM: posX = randomPos.nextFloat() * 3; break; case SSEngine.ATTACK_RIGHT: posX = 3; break; } posT = SSEngine.SCOUT_SPEED; ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4); byteBuf.order(ByteOrder.nativeOrder()); vertexBuffer = byteBuf.asFloatBuffer(); vertexBuffer.put(vertices); vertexBuffer.position(0); byteBuf = ByteBuffer.allocateDirect(texture.length * 4); byteBuf.order(ByteOrder.nativeOrder()); textureBuffer = byteBuf.asFloatBuffer(); textureBuffer.put(texture); textureBuffer.position(0); indexBuffer = ByteBuffer.allocateDirect(indices.length); indexBuffer.put(indices); indexBuffer.position(0); } public float getNextScoutX() { if (attackDirection == SSEngine.ATTACK_LEFT) { return (float) ((SSEngine.BEZIER_X_4 * (posT * posT * posT)) + (SSEngine.BEZIER_X_3 * 3 * (posT * posT) * (1 - posT)) + (SSEngine.BEZIER_X_2 * 3 * posT * ((1 - posT) * (1 - posT))) + (SSEngine.BEZIER_X_1 * ((1 - posT) * (1 - posT) * (1 - posT)))); } else { return (float) ((SSEngine.BEZIER_X_1 * (posT * posT * posT)) + (SSEngine.BEZIER_X_2 * 3 * (posT * posT) * (1 - posT)) + (SSEngine.BEZIER_X_3 * 3 * posT * ((1 - posT) * (1 - posT))) + (SSEngine.BEZIER_X_4 * ((1 - posT) * (1 - posT) * (1 - posT)))); } } public float getNextScoutY() { return (float) ((SSEngine.BEZIER_Y_1 * (posT * posT * posT)) + (SSEngine.BEZIER_Y_2 * 3 * (posT * posT) * (1 - posT)) + (SSEngine.BEZIER_Y_3 * 3 * posT * ((1 - posT) * (1 - posT))) + (SSEngine.BEZIER_Y_4 * ((1 - posT) * (1 - posT) * (1 - posT)))); } public void draw(GL10 gl, int[] spriteSheet) { gl.glBindTexture(GL10.GL_TEXTURE_2D, spriteSheet[0]); gl.glFrontFace(GL10.GL_CCW); gl.glEnable(GL10.GL_CULL_FACE); gl.glCullFace(GL10.GL_BACK); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer); gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer); gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_BYTE, indexBuffer); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glDisable(GL10.GL_CULL_FACE); } }

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  • How can I improve this collision detection logic?

    - by Dan
    I’m trying to make an android game and I’m having a bit of trouble getting the collision detection to work. It works sometimes but my conditions aren’t specific enough and my program gets it wrong. How could I improve the following if conditions? public boolean checkColisionWithPlayer( Player player ) { // Top Left // Top Right // Bottom Right // Bottom Left // int[][] PP = { { player.x, player.y }, { player.x + player.width, player.y }, {player.x + player.height, player.y + player.width }, { player.x, player.y + player.height } }; // TOP LEFT - PLAYER // if( ( PP[0][0] > x && PP[0][0] < x + width ) && ( PP[0][1] > y && PP[0][1] < y + height ) && ( (x - player.x) < 0 ) ) { player.isColided = true; //player.isSpinning = false; // Collision On Right if( PP[0][0] > ( x + width/2 ) && ( PP[0][1] - y < ( x + width ) - PP[0][0] ) ) { Log.i("Colision", "Top Left - Right Side"); player.x = ( x + width ) + 1; player.Vh = player.phy.getVelsoityWallColision(player.Vh, player.Cr); } // Collision On Bottom else if( PP[0][1] > ( y + height/2 ) ) { Log.i("Colision", "Top Left - Bottom Side"); player.y = ( y + height ) + 1; if( player.Vv > 0 ) player.Vv = 0; } return true; } // TOP RIGHT - PLAYER // else if( ( PP[1][0] > x && PP[1][0] < x + width ) && ( PP[1][1] > y && PP[1][1] < y + height ) && ( (x - player.x) > 0 ) ) { player.isColided = true; //player.isSpinning = false; // Collision On Left if( PP[1][0] < ( x + width/2 ) && ( PP[1][0] - x < PP[1][1] - y ) ) { Log.i("Colision", "Top Right - Left Side"); player.x = ( x ) + 1; player.Vh = player.phy.getVelsoityWallColision(player.Vh, player.Cr); } // Collision On Bottom else if( PP[1][1] > ( y + height/2 ) ) { Log.i("Colision", "Top Right - Bottom Side"); player.y = ( y + height ) + 1; if( player.Vv > 0 ) player.Vv = 0; } return true; } // BOTTOM RIGHT - PLAYER // else if( ( PP[2][0] > x && PP[2][0] < x + width ) && ( PP[2][1] > y && PP[2][1] < y + height ) ) { player.isColided = true; //player.isSpinning = false; // Collision On Left if( PP[2][0] < ( x + width/2 ) && ( PP[2][0] - x < PP[2][1] - y ) ) { Log.i("Colision", "Bottom Right - Left Side"); player.x = ( x ) + 1; player.Vh = player.phy.getVelsoityWallColision(player.Vh, player.Cr); } // Collision On Top else if( PP[2][1] < ( y + height/2 ) ) { Log.i("Colision", "Bottom Right - Top Side"); player.y = y - player.height; player.Vv = player.phy.getVelsoityWallColision(player.Vv, player.Cr); //player.Vh = -1 * ( player.phy.getVelsoityWallColision(player.Vv, player.Cr) ); int rs = x - player.x; Log.i("RS", String.format("%d", rs)); if( rs > 0 ) { player.direction = -1; player.isSpinning = true; player.Vh = -0.5 * ( player.phy.getVelsoityWallColision(player.Vv, player.Cr) ); } if( rs < 0 ) { player.direction = 1; player.isSpinning = true; player.Vh = 0.5 * ( player.phy.getVelsoityWallColision(player.Vv, player.Cr) ); } player.rotateSpeed = 1 * rs; } return true; } // BOTTOM LEFT - PLAYER // else if( ( PP[3][0] > x && PP[3][0] < x + width ) && ( PP[3][1] > y && PP[3][1] < y + height ) )//&& ( (x - player.x) > 0 ) ) { player.isColided = true; //player.isSpinning = false; // Collision On Right if( PP[3][0] > ( x + width/2 ) && ( PP[3][1] - y < ( x + width ) - PP[3][0] ) ) { Log.i("Colision", "Bottom Left - Right Side"); player.x = ( x + width ) + 1; player.Vh = player.phy.getVelsoityWallColision(player.Vh, player.Cr); } // Collision On Top else if( PP[3][1] < ( y + height/2 ) ) { Log.i("Colision", "Bottom Left - Top Side"); player.y = y - player.height; player.Vv = player.phy.getVelsoityWallColision(player.Vv, player.Cr); //player.Vh = -1 * ( player.phy.getVelsoityWallColision(player.Vv, player.Cr) ); int rs = x - player.x; //Log.i("RS", String.format("%d", rs)); //player.direction = -1; //player.isSpinning = true; if( rs > 0 ) { player.direction = -1; player.isSpinning = true; player.Vh = -1 * ( player.phy.getVelsoityWallColision(player.Vv, player.Cr) ); } if( rs < 0 ) { player.direction = 1; player.isSpinning = true; player.Vh = 1 * ( player.phy.getVelsoityWallColision(player.Vv, player.Cr) ); } player.rotateSpeed = 1 * rs; } //try { Thread.sleep(1000, 0); } //catch (InterruptedException e) {} return true; } else { player.isColided = false; player.isSpinning = true; } return false; }

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  • Collision detection with multiple polygons simultaneously

    - by Craig Innes
    I've written a collision system which detects/resolves collisions between a rectangular player and a convex polygon world using the Separating Axis Theorem. This scheme works fine when the player is colliding with a single polygon, but when I try to create a level made up of combinations of these shapes, the player gets "stuck" between shapes when trying to move from one polygon to the other. The reason for this seems to be that collisions are detected after the player has been pushed through the shape by its movement or gravity. When the system resolves the collision, it resolves them in an order that doesn't make sense (for example, when the player is moving from one flat rectangle to another, gravity pushes them below the ground, but the collision with the left hand side of the second block is resolved before the collision with the top of the block, meaning the player is pushed back left before being pushed back up). Other similar posts have resolved this problem by having a strict rule on which axes to resolve first. For example, always resolve the collision on the y axis, then if the object is still colliding with things, resolve on the x axis. This solution only works in the case of a completely axis oriented box world, and doesn't solve the problem if the player is stuck moving along a series of angled shapes or sliding down a wall. Does any one have any ideas of how I could alter my collision system to prevent these situations from happening?

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  • simple collision detection with box2dweb

    - by skywalker
    im beginner in box2dweb that version of box2d for javascript i wrote simple gravity system and i want to detect the collision between the box and the ground , when the falling box hit the ground execute simple function like function sucs(){alert("the box on the floor !")}; this is my code var CANVAS_WIDTH = 1024, CANVAS_HEIGHT = 700, SCALE = 30; var b2Vec2 = Box2D.Common.Math.b2Vec2 , b2BodyDef = Box2D.Dynamics.b2BodyDef , b2Body = Box2D.Dynamics.b2Body , b2FixtureDef = Box2D.Dynamics.b2FixtureDef , b2Fixture = Box2D.Dynamics.b2Fixture , b2World = Box2D.Dynamics.b2World , b2MassData = Box2D.Collision.Shapes.b2MassData , b2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape , b2CircleShape = Box2D.Collision.Shapes.b2CircleShape , b2DebugDraw = Box2D.Dynamics.b2DebugDraw; var canvas = document.getElementById("canvas"); var context = canvas.getContext("2d"); var world = new b2World(new b2Vec2(0, 8), true); var fixDef = new b2FixtureDef(); var bodyDef = new b2BodyDef(); fixDef.density = 1.0; fixDef.friction = 0.5; bodyDef.type = b2Body.b2_staticBody; fixDef.shape = new b2PolygonShape; fixDef.shape.SetAsBox(20, 2); bodyDef.position.Set(10, 400 / 30 + 1.8); world.CreateBody(bodyDef).CreateFixture(fixDef); fixDef.density = 1.0; fixDef.friction = 0.5; fixDef.restitution = 0.3; bodyDef.type = b2Body.b2_dynamicBody; bodyDef.position.Set(50 / SCALE, 0 / SCALE); //bodyDef.linearVelocity.Set((Math.random() * 12) + 2, (Math.random() * 12) + 2); fixDef.shape = new b2PolygonShape(); fixDef.shape.SetAsBox(25 / SCALE, 25 / SCALE); world.CreateBody(bodyDef).CreateFixture(fixDef); var debugDraw = new b2DebugDraw(); debugDraw.SetSprite(document.getElementById("canvas").getContext("2d")); debugDraw.SetDrawScale(30.0); debugDraw.SetFillAlpha(0.5); debugDraw.SetLineThickness(1.0); debugDraw.SetFlags(b2DebugDraw.e_shapeBit | b2DebugDraw.e_jointBit); world.SetDebugDraw(debugDraw); var image = new Image(); image.src = "image.png"; window.setInterval(gameLoop, 1000 / 60); function gameLoop() { world.Step(1 / 60, 8, 3); world.ClearForces(); context.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT); b = world.GetBodyList() var pos = b.GetPosition(); context.save(); context.translate(pos.x * SCALE, pos.y * SCALE); context.rotate(b.GetAngle()); context.drawImage(image, -25, -25); context.restore(); b = b.GetNext(); pos = b.GetPosition(); context.save(); context.translate(pos.x * SCALE, pos.y * SCALE); //b.GetAngle()++; context.rotate(b.GetAngle()); context.drawImage(image, -25, -25); context.restore(); world.DrawDebugData(); };

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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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