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  • Making a game with responsive resolution

    - by alexandervrs
    I am making a game, however I wish for it to be resolution agnostic. My target resolution i.e. where things look as intended is 1600 x 900. My ideas are: Make the HUD stay fixed to the sides no matter what resolution, use different size for HUD graphics under a certain resolution and another under a certain large one. Use large HD sprites/backgrounds which are a power of 2, so they scale nicely. Use the player's native resolution. Scale the game area (not the HUD) to fit (resulting zooming in some and cropping the game area sides if necessary for widescreen, no stretch), but always fill the screen. Have a min and max resolution limit for small and very large displays where you will just change the resolution(?) or scale up/down to fit. What I am a bit confused though is what math formula I would use to scale the game area correctly based on the resolution no matter the aspect ratio, fully fit in a square screen and with some clip to the sides for widescreen. Pseudocode would help as well. :)

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  • Collision library for bullet hell in Python

    - by darkfeline
    I am making a bullet hell game in Python and am looking for a suitable collision library, taking the following into consideration: The library should do 2D polygon collision. It should be very fast. As a bullet hell game, I expect to do collision checks between hundreds, likely thousands of objects every frame at a consistent 60fps. Good documentation Permissive license (like MIT, not GPL) I am also considering writing my own library in C/C++ and wrapping with python ctypes in the event that no such library exists, though I do not have experience with collision detection algorithms, so I am not sure if this would be more trouble than it's worth. Could someone provide some guidance on this matter?

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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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  • checking for collision detection

    - by bill
    I am trying to create a game where you have a player and you can move right,left, and jump. kind of like mario but its not a side scroller. also i want to use 2d array to make a tile map. my big problem is that i dont understand how to check for collision. i spend about 2 week thinking about this and i came up with 2 solution but they both have problems. let say my map is: 0 = sky 1 = player 2 = ground 00000 10002 22022 Solution 1: move the '1'(player) and update the map less say player wants to move right, then x+=grid[x+1][y] this make the collision easy bc you can just check if if(grid[x][y+1] == 2){ //player is standing on top of ground } problem with this when u hit right key player will move (x*Titlewidth) to right. and as you can see the animation wont look smooth. Solution 2: move player and dont update map player_x += 2 this will make the animation more smoother bc i am just moving 2 pixels. problem1: i cant update map bc if player some times will be middle of int(2d array). but thats ok sinces its not a side scroller so updating the map is not a big deal. problem2: only way to check for collision is to use java intersection method. but then player have to be atleast 1 or 2 pixel in ground in order to check for collision. and as you can see that wont look good too. plz note this is my first collision game in java. so plz try to explain alot otherwise i wont understand it.

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  • Pixel Collision - Detecting corners

    - by Milkboat
    How would I go about detecting the corners of a texture when I use pixel collision detection? I read about corner collision with rectangles, but I am unsure how to adapt it to my situation. Right now my map is tile based and I do rectangular collision until the player is intersecting with a blocked tile, then I switch to pixel collision. The effect I would like to achieve is when the player hits the corner of an object to push him around the side so he doesn't just hit the edge and stop. Any ideas?

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  • 2D Rectangle Collision Response with Multiple Rectangles

    - by Justin Skiles
    Similar to: Collision rectangle response I have a level made up of tiles where the edges of the level are made up of collidable rectangles. The player's collision box is represented by a rectangle as well. The player can move in 8 directions. The player's velocity is equal in X and Y directions and constant. Each update, I am checking the player's collision against all tiles that are a certain distance away. When the player collides with a rectangle, I am finding the intersection depth and resolving along the most shallow axis followed by the other axis. This resolution happens for both axes simultaneously. See below for two examples of situations where I am having trouble. Moving up-left against the left wall In the scenario below, the player is colliding with two tiles. The tile intersection depth is equal on both axes for the top tile and more shallow in the X axis for the middle tile. Because the player is moving up the wall, the player should slide in an upward direction along the wall. This works properly as long as the rectangle with the more shallow depth is evaluated first. If the equal intersection depth rectangle is evaluated first, there is a chance the player becomes stuck. Moving up-left against the top wall Here is an identical scenario with the exception that the collision is with the top wall. The same problem occurs at the corners when intersection depth is equal for both axes. I guess my overall question is: How can I ensure that collision response occurs on tiles that have non-equal intersection depth before tiles that have equal intersection depth in order to get around the weirdness that occurs at these corners. Sean's answer in the linked question was good, but his solution required having different velocity components in a certain direction. My situation has equal velocities, so there's no good way to tell which direction to resolve at corners. I hope I have made my explanation clear.

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  • Collision within a poly

    - by G1i1ch
    For an html5 engine I'm making, for speed I'm using a path poly. I'm having trouble trying to find ways to get collision with the walls of the poly. To make it simple I just have a vector for the object and an array of vectors for the poly. I'm using Cartesian vectors and they're 2d. Say poly = [[550,0],[169,523],[-444,323],[-444,-323],[169,-523]], it's just a pentagon I generated. The object that will collide is object, object.pos is it's position and object.vel is it's velocity. They're both 2d vectors too. I've had some success to get it to find a collision, but it's just black box code I ripped from a c++ example. It's very obscure inside and all it does though is return true/false and doesn't return what vertices are collided or collision point, I'd really like to be able to understand this and make my own so I can have more meaningful collision. I'll tackle that later though. Again the question is just how does one find a collision to walls of a poly given you know the poly vertices and the object's position + velocity? If more info is needed please let me know. And if all anyone can do is point me to the right direction that's great.

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  • Circle-Line Collision Detection Problem

    - by jazzdawg
    I am currently developing a breakout clone and I have hit a roadblock in getting collision detection between a ball (circle) and a brick (convex polygon) working correctly. I am using a Circle-Line collision detection test where each line represents and edge on the convex polygon brick. For the majority of the time the Circle-Line test works properly and the points of collision are resolved correctly. Collision detection working correctly. However, occasionally my collision detection code returns false due to a negative discriminant when the ball is actually intersecting the brick. Collision detection failing. I am aware of the inefficiency with this method and I am using axis aligned bounding boxes to cut down on the number of bricks tested. My main concern is if there are any mathematical bugs in my code below. /* * from and to are points at the start and end of the convex polygons edge. * This function is called for every edge in the convex polygon until a * collision is detected. */ bool circleLineCollision(Vec2f from, Vec2f to) { Vec2f lFrom, lTo, lLine; Vec2f line, normal; Vec2f intersectPt1, intersectPt2; float a, b, c, disc, sqrt_disc, u, v, nn, vn; bool one = false, two = false; // set line vectors lFrom = from - ball.circle.centre; // localised lTo = to - ball.circle.centre; // localised lLine = lFrom - lTo; // localised line = from - to; // calculate a, b & c values a = lLine.dot(lLine); b = 2 * (lLine.dot(lFrom)); c = (lFrom.dot(lFrom)) - (ball.circle.radius * ball.circle.radius); // discriminant disc = (b * b) - (4 * a * c); if (disc < 0.0f) { // no intersections return false; } else if (disc == 0.0f) { // one intersection u = -b / (2 * a); intersectPt1 = from + (lLine.scale(u)); one = pointOnLine(intersectPt1, from, to); if (!one) return false; return true; } else { // two intersections sqrt_disc = sqrt(disc); u = (-b + sqrt_disc) / (2 * a); v = (-b - sqrt_disc) / (2 * a); intersectPt1 = from + (lLine.scale(u)); intersectPt2 = from + (lLine.scale(v)); one = pointOnLine(intersectPt1, from, to); two = pointOnLine(intersectPt2, from, to); if (!one && !two) return false; return true; } } bool pointOnLine(Vec2f p, Vec2f from, Vec2f to) { if (p.x >= min(from.x, to.x) && p.x <= max(from.x, to.x) && p.y >= min(from.y, to.y) && p.y <= max(from.y, to.y)) return true; return false; }

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  • Moving objects colliding when using unalligned collision avoidance (steering)

    - by James Bedford
    I'm having trouble with unaligned collision avoidance for what I think is a rare case. I have set two objects to move towards each other but with a slight offset, so one of the objects is moving slightly upwards, and one of the objects is moving slightly downwards. In my unaligned collision avoidance steering algorithm I'm finding the points on the object's forward line and the other object's forward line where these two lines are the closest. If these closest points are within a collision avoidance distance, and if the distance between them is smaller than the two radii of the two object's bounding spheres, then the objects should steer away in the appropriate direction. The problem is that for my case, the closest points on the lines are calculated to be really far away from the actual collision point. This is because the two forward lines for each object are moving away from each other as the objects pass. The problem is that because of this, no steering takes place, and the two objects partially collide. Does anyone have any suggestions as to how I can correctly calculate the point of collision? Perhaps by somehow taking into account the size of the two objects?

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  • Changing direction after collision

    - by Balint
    In the first tutorial for GameMaker (catch the clown), I want to set the direction of the clown after the collision with the wall. I want to do it by pressing the wall object with the mouse (before the collision, to set the angle parameter). For example by pressing only once the wall object it would change the clown's direction after collision by 45 degrees, twice by 90 degrees, and so on. How can I do that?

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  • Fixing a collision detection bug in Slick2D

    - by Jesse Prescott
    My game has a bug with collision detection. If you go against the wall and tap forward/back sometimes the game thinks the speed you travelled at is 0 and the game doesn't know how to get you out of the wall. My collision detection works by getting the speed you hit the wall at and if it is positive it moves you back, if it is negative it moves you forward. It might help if you download it: https://rapidshare.com/files/1550046269/game.zip Sorry if I explained badly, it's hard to explain. float maxSpeed = 0.3f; float minSpeed = -0.2f; float acceleration = 0.002f; float deacceleration = 0.001f; float slowdownSpeed = 0.002f; float rotateSpeed = 0.08f; static float currentSpeed = 0; boolean up = false; boolean down = false; boolean noKey = false; static float rotate = 0; //Image effect system static String locationCarNormal; static String locationCarFront; static String locationCarBack; static String locationCarBoth; static boolean carFront = false; static boolean carBack = false; static String imageRef; boolean collision = false; public ComponentPlayerMovement(String id, String ScarNormal, String ScarFront, String ScarBack, String ScarBoth) { this.id = id; playerBody = new Rectangle(900/2-16, 700/2-16, 32, 32); locationCarNormal = ScarNormal; locationCarFront = ScarFront; locationCarBack = ScarBack; locationCarBoth = ScarBoth; imageRef = locationCarNormal; } @Override public void update(GameContainer gc, StateBasedGame sbg, int delta) throws SlickException { Input input = gc.getInput(); playerBody.transform(Transform.createRotateTransform(2)); float hip = currentSpeed * delta; float unstuckspeed = 0.05f * delta; if(carBack && !carFront) { imageRef = locationCarBack; ComponentImageRender.updateImage(); } else if(carFront && !carBack) { imageRef = locationCarFront; ComponentImageRender.updateImage(); } else if(carFront && carBack) { imageRef = locationCarBoth; ComponentImageRender.updateImage(); } if(input.isKeyDown(Input.KEY_RIGHT)) { rotate += rotateSpeed * delta; owner.setRotation(rotate); } if(input.isKeyDown(Input.KEY_LEFT)) { rotate -= rotateSpeed * delta; owner.setRotation(rotate); } if(input.isKeyDown(Input.KEY_UP)) { if(!collision) { up = true; noKey = false; if(currentSpeed < maxSpeed) { currentSpeed += acceleration; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } else { currentSpeed = 1; } } else if(input.isKeyDown(Input.KEY_DOWN) && !collision) { down = true; noKey = false; if(currentSpeed > minSpeed) { currentSpeed -= slowdownSpeed; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } else { noKey = true; if(currentSpeed > 0) { currentSpeed -= deacceleration; } else if(currentSpeed < 0) { currentSpeed += acceleration; } MapCoordStorage.mapX += hip * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= hip * Math.cos(Math.toRadians(rotate)); } if(entityCollisionWith()) { collision = true; if(currentSpeed > 0 || up) { up = true; currentSpeed = 0; carFront = true; MapCoordStorage.mapX += unstuckspeed * Math.sin(Math.toRadians(rotate-180)); MapCoordStorage.mapY -= unstuckspeed * Math.cos(Math.toRadians(rotate-180)); } else if(currentSpeed < 0 || down) { down = true; currentSpeed = 0; carBack = true; MapCoordStorage.mapX += unstuckspeed * Math.sin(Math.toRadians(rotate)); MapCoordStorage.mapY -= unstuckspeed * Math.cos(Math.toRadians(rotate)); } else { currentSpeed = 0; } } else { collision = false; up = false; down = false; } if(currentSpeed >= -0.01f && currentSpeed <= 0.01f && noKey && !collision) { currentSpeed = 0; } } public static boolean entityCollisionWith() throws SlickException { for (int i = 0; i < BlockMap.entities.size(); i++) { Block entity1 = (Block) BlockMap.entities.get(i); if (playerBody.intersects(entity1.poly)) { return true; } } return false; } }

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  • Collision Systems Implementation

    - by hrr4
    Just curious what might be a good way to implement a decent collision system. As a class inherited by a base Entity class? Currently I'm stuck and could just use a couple better ideas than my own. Any help is appreciated! Edit: Sorry, it's 2D Collisioning but honestly, I'm not looking for specific collision methods. I'm looking more about the lines of implementation. Just curious of some of the common methods of how to implement collision systems such as: Should the entire collision system be it's own class? What, if anything, should be inheritable? These are some of my questions. Sorry for the confusion.

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  • 2D Tile Collision free movement

    - by andrepcg
    I'm coding a 3D game for a project using OpenGL and I'm trying to do tile collision on a surface. The surface plane is split into a grid of 64x64 pixels and I can simply check if the (x,y) tile is empty or not. Besides having a grid for collision, there's still free movement inside a tile. For each entity, in the end of the update function I simply increase the position by the velocity: pos.x += v.x; pos.y += v.y; I already have a collision grid created but my collide function is not great, i'm not sure how to handle it. I can check if the collision occurs but the way I handle is terrible. int leftTile = repelBox.x / grid->cellSize; int topTile = repelBox.y / grid->cellSize; int rightTile = (repelBox.x + repelBox.w) / grid->cellSize; int bottomTile = (repelBox.y + repelBox.h) / grid->cellSize; for (int y = topTile; y <= bottomTile; ++y) { for (int x = leftTile; x <= rightTile; ++x) { if (grid->getCell(x, y) == BLOCKED){ Rect colBox = grid->getCellRectXY(x, y); Rect xAxis = Rect(pos.x - 20 / 2.0f, pos.y - 20 / 4.0f, 20, 10); Rect yAxis = Rect(pos.x - 20 / 4.0f, pos.y - 20 / 2.0f, 10, 20); if (colBox.Intersects(xAxis)) v.x *= -1; if (colBox.Intersects(yAxis)) v.y *= -1; } } } If instead of reversing the direction I set it to false then when the entity tries to get away from the wall it's still intersecting the tile and gets stuck on that position. EDIT: I've worked with Flashpunk and it has a great function for movement and collision called moveBy. Are there any simplified implementations out there so I can check them out?

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  • Fast, accurate 2d collision

    - by Neophyte
    I'm working on a 2d topdown shooter, and now need to go beyond my basic rectangle bounding box collision system. I have large levels with many different sprites, all of which are different shapes and sizes. The textures for the sprites are all square png files with transparent backgrounds, so I also need a way to only have a collision when the player walks into the coloured part of the texture, and not the transparent background. I plan to handle collision as follows: Check if any sprites are in range of the player Do a rect bounding box collision test Do an accurate collision (Where I need help) I don't mind advanced techniques, as I want to get this right with all my requirements in mind, but I'm not sure how to approach this. What techniques or even libraries to try. I know that I will probably need to create and store some kind of shape that accurately represents each sprite minus the transparent background. I've read that per pixel is slow, so given my large levels and number of objects I don't think that would be suitable. I've also looked at Box2d, but haven't been able to find much documentation, or any examples of how to get it up and running with SFML.

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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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  • Using 2d collision with 3d objects

    - by Lyise
    I'm planning to write a fairly basic scrolling shoot 'em up, however, I have run into a query with regards to checking for collision. I plan to have a fixed top down view, where the player and enemies are all 3d objects on a fixed plane, and when the enemy or player fires at the other, their shots will also be along this fixed plane. In order to handle the collision, I have read up a bit on collision detection in 3d, as it is not something I have looked into previously, but I'm not sure what would be ideal for this situation. My options appear to be: Sphere collision, however, this lacks the pixel precision I would like Detection using all vertexes and planes of each object, but this seems overly convoluted for a fixed plane of play Rendering the play screen in black and white (where white is an object, black is empty space), once for enemies and once for the player, and checking for collisions that way (if a pixel is white on both, there is a collision) Which of these would be the best approach, or is there another option that I am missing? I have done this previously using 2d sprites, however I can't use the same thinking here as I don't have the image to refer to.

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  • Why Is Vertical Resolution Monitor Resolution so Often a Multiple of 360?

    - by Jason Fitzpatrick
    Stare at a list of monitor resolutions long enough and you might notice a pattern: many of the vertical resolutions, especially those of gaming or multimedia displays, are multiples of 360 (720, 1080, 1440, etc.) But why exactly is this the case? Is it arbitrary or is there something more at work? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. The Question SuperUser reader Trojandestroy recently noticed something about his display interface and needs answers: YouTube recently added 1440p functionality, and for the first time I realized that all (most?) vertical resolutions are multiples of 360. Is this just because the smallest common resolution is 480×360, and it’s convenient to use multiples? (Not doubting that multiples are convenient.) And/or was that the first viewable/conveniently sized resolution, so hardware (TVs, monitors, etc) grew with 360 in mind? Taking it further, why not have a square resolution? Or something else unusual? (Assuming it’s usual enough that it’s viewable). Is it merely a pleasing-the-eye situation? So why have the display be a multiple of 360? The Answer SuperUser contributor User26129 offers us not just an answer as to why the numerical pattern exists but a history of screen design in the process: Alright, there are a couple of questions and a lot of factors here. Resolutions are a really interesting field of psychooptics meeting marketing. First of all, why are the vertical resolutions on youtube multiples of 360. This is of course just arbitrary, there is no real reason this is the case. The reason is that resolution here is not the limiting factor for Youtube videos – bandwidth is. Youtube has to re-encode every video that is uploaded a couple of times, and tries to use as little re-encoding formats/bitrates/resolutions as possible to cover all the different use cases. For low-res mobile devices they have 360×240, for higher res mobile there’s 480p, and for the computer crowd there is 360p for 2xISDN/multiuser landlines, 720p for DSL and 1080p for higher speed internet. For a while there were some other codecs than h.264, but these are slowly being phased out with h.264 having essentially ‘won’ the format war and all computers being outfitted with hardware codecs for this. Now, there is some interesting psychooptics going on as well. As I said: resolution isn’t everything. 720p with really strong compression can and will look worse than 240p at a very high bitrate. But on the other side of the spectrum: throwing more bits at a certain resolution doesn’t magically make it better beyond some point. There is an optimum here, which of course depends on both resolution and codec. In general: the optimal bitrate is actually proportional to the resolution. So the next question is: what kind of resolution steps make sense? Apparently, people need about a 2x increase in resolution to really see (and prefer) a marked difference. Anything less than that and many people will simply not bother with the higher bitrates, they’d rather use their bandwidth for other stuff. This has been researched quite a long time ago and is the big reason why we went from 720×576 (415kpix) to 1280×720 (922kpix), and then again from 1280×720 to 1920×1080 (2MP). Stuff in between is not a viable optimization target. And again, 1440P is about 3.7MP, another ~2x increase over HD. You will see a difference there. 4K is the next step after that. Next up is that magical number of 360 vertical pixels. Actually, the magic number is 120 or 128. All resolutions are some kind of multiple of 120 pixels nowadays, back in the day they used to be multiples of 128. This is something that just grew out of LCD panel industry. LCD panels use what are called line drivers, little chips that sit on the sides of your LCD screen that control how bright each subpixel is. Because historically, for reasons I don’t really know for sure, probably memory constraints, these multiple-of-128 or multiple-of-120 resolutions already existed, the industry standard line drivers became drivers with 360 line outputs (1 per subpixel). If you would tear down your 1920×1080 screen, I would be putting money on there being 16 line drivers on the top/bottom and 9 on one of the sides. Oh hey, that’s 16:9. Guess how obvious that resolution choice was back when 16:9 was ‘invented’. Then there’s the issue of aspect ratio. This is really a completely different field of psychology, but it boils down to: historically, people have believed and measured that we have a sort of wide-screen view of the world. Naturally, people believed that the most natural representation of data on a screen would be in a wide-screen view, and this is where the great anamorphic revolution of the ’60s came from when films were shot in ever wider aspect ratios. Since then, this kind of knowledge has been refined and mostly debunked. Yes, we do have a wide-angle view, but the area where we can actually see sharply – the center of our vision – is fairly round. Slightly elliptical and squashed, but not really more than about 4:3 or 3:2. So for detailed viewing, for instance for reading text on a screen, you can utilize most of your detail vision by employing an almost-square screen, a bit like the screens up to the mid-2000s. However, again this is not how marketing took it. Computers in ye olden days were used mostly for productivity and detailed work, but as they commoditized and as the computer as media consumption device evolved, people didn’t necessarily use their computer for work most of the time. They used it to watch media content: movies, television series and photos. And for that kind of viewing, you get the most ‘immersion factor’ if the screen fills as much of your vision (including your peripheral vision) as possible. Which means widescreen. But there’s more marketing still. When detail work was still an important factor, people cared about resolution. As many pixels as possible on the screen. SGI was selling almost-4K CRTs! The most optimal way to get the maximum amount of pixels out of a glass substrate is to cut it as square as possible. 1:1 or 4:3 screens have the most pixels per diagonal inch. But with displays becoming more consumery, inch-size became more important, not amount of pixels. And this is a completely different optimization target. To get the most diagonal inches out of a substrate, you want to make the screen as wide as possible. First we got 16:10, then 16:9 and there have been moderately successful panel manufacturers making 22:9 and 2:1 screens (like Philips). Even though pixel density and absolute resolution went down for a couple of years, inch-sizes went up and that’s what sold. Why buy a 19″ 1280×1024 when you can buy a 21″ 1366×768? Eh… I think that about covers all the major aspects here. There’s more of course; bandwidth limits of HDMI, DVI, DP and of course VGA played a role, and if you go back to the pre-2000s, graphics memory, in-computer bandwdith and simply the limits of commercially available RAMDACs played an important role. But for today’s considerations, this is about all you need to know. Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.     

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  • Trouble with AABB collision response and physics

    - by WCM
    I have been racking my brain trying to figure out a problem I am having with physics and basic AABB collision response. I am fairly close as the physics are mostly right. Gravity feels good and movement is solid. The issue I am running into is that when I land on the test block in my project, I can jump off of it most of the time. If I repeatedly jump in place, I will eventually get stuck one or two pixels below the surface of the test block. If I try to jump, I can become free of the other block, but it will happen again a few jumps later. I feel like I am missing something really obvious with this. I have two functions that support the detection and function to return a vector for the overlap of the two rectangle bounding boxes. I have a single update method that is processing the physics and collision for the entity. I feel like I am missing something very simple, like an ordering of the physics vs. collision response handling. Any thoughts or help can be appreciated. I apologize for the format of the code, tis prototype code mostly. The collision detection function: public static bool Collides(Rectangle source, Rectangle target) { if (source.Right < target.Left || source.Bottom < target.Top || source.Left > target.Right || source.Top > target.Bottom) { return false; } return true; } The overlap function: public static Vector2 GetMinimumTranslation(Rectangle source, Rectangle target) { Vector2 mtd = new Vector2(); Vector2 amin = source.Min(); Vector2 amax = source.Max(); Vector2 bmin = target.Min(); Vector2 bmax = target.Max(); float left = (bmin.X - amax.X); float right = (bmax.X - amin.X); float top = (bmin.Y - amax.Y); float bottom = (bmax.Y - amin.Y); if (left > 0 || right < 0) return Vector2.Zero; if (top > 0 || bottom < 0) return Vector2.Zero; if (Math.Abs(left) < right) mtd.X = left; else mtd.X = right; if (Math.Abs(top) < bottom) mtd.Y = top; else mtd.Y = bottom; // 0 the axis with the largest mtd value. if (Math.Abs(mtd.X) < Math.Abs(mtd.Y)) mtd.Y = 0; else mtd.X = 0; return mtd; } The update routine (gravity = 0.001f, jumpHeight = 0.35f, moveAmount = 0.15f): public void Update(GameTime gameTime) { Acceleration.Y = gravity; Position += new Vector2((float)(movement * moveAmount * gameTime.ElapsedGameTime.TotalMilliseconds), (float)(Velocity.Y * gameTime.ElapsedGameTime.TotalMilliseconds)); Velocity.Y += Acceleration.Y; Vector2 previousPosition = new Vector2((int)Position.X, (int)Position.Y); KeyboardState keyboard = Keyboard.GetState(); movement = 0; if (keyboard.IsKeyDown(Keys.Left)) { movement -= 1; } if (keyboard.IsKeyDown(Keys.Right)) { movement += 1; } if (Position.Y + 16 > GameClass.Instance.GraphicsDevice.Viewport.Height) { Velocity.Y = 0; Position = new Vector2(Position.X, GameClass.Instance.GraphicsDevice.Viewport.Height - 16); IsOnSurface = true; } if (Collision.Collides(BoundingBox, GameClass.Instance.block.BoundingBox)) { Vector2 mtd = Collision.GetMinimumTranslation(BoundingBox, GameClass.Instance.block.BoundingBox); Position += mtd; Velocity.Y = 0; IsOnSurface = true; } if (keyboard.IsKeyDown(Keys.Space) && !previousKeyboard.IsKeyDown(Keys.Space)) { if (IsOnSurface) { Velocity.Y = -jumpHeight; IsOnSurface = false; } } previousKeyboard = keyboard; } This is also a full download to the project. https://www.box.com/s/3rkdtbso3xgfgc2asawy P.S. I know that I could do this with the XNA Platformer Starter Kit algo, but it has some deep flaws that I am going to try to live without. I'd rather go the route of collision response via an overlay function. Thanks for any and all insight!

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  • Extrapolation breaks collision detection

    - by user22241
    Before applying extrapolation to my sprite's movement, my collision worked perfectly. However, after applying extrapolation to my sprite's movement (to smooth things out), the collision no longer works. This is how things worked before extrapolation: However, after I implement my extrapolation, the collision routine breaks. I am assuming this is because it is acting upon the new coordinate that has been produced by the extrapolation routine (which is situated in my render call ). After I apply my extrapolation How to correct this behaviour? I've tried puting an extra collision check just after extrapolation - this does seem to clear up a lot of the problems but I've ruled this out because putting logic into my rendering is out of the question. I've also tried making a copy of the spritesX position, extrapolating that and drawing using that rather than the original, thus leaving the original intact for the logic to pick up on - this seems a better option, but it still produces some weird effects when colliding with walls. I'm pretty sure this also isn't the correct way to deal with this. I've found a couple of similar questions on here but the answers haven't helped me. This is my extrapolation code: public void onDrawFrame(GL10 gl) { //Set/Re-set loop back to 0 to start counting again loops=0; while(System.currentTimeMillis() > nextGameTick && loops < maxFrameskip){ SceneManager.getInstance().getCurrentScene().updateLogic(); nextGameTick+=skipTicks; timeCorrection += (1000d/ticksPerSecond) % 1; nextGameTick+=timeCorrection; timeCorrection %=1; loops++; tics++; } extrapolation = (float)(System.currentTimeMillis() + skipTicks - nextGameTick) / (float)skipTicks; render(extrapolation); } Applying extrapolation render(float extrapolation){ //This example shows extrapolation for X axis only. Y position (spriteScreenY is assumed to be valid) extrapolatedPosX = spriteGridX+(SpriteXVelocity*dt)*extrapolation; spriteScreenPosX = extrapolationPosX * screenWidth; drawSprite(spriteScreenX, spriteScreenY); } Edit As I mentioned above, I have tried making a copy of the sprite's coordinates specifically to draw with.... this has it's own problems. Firstly, regardless of the copying, when the sprite is moving, it's super-smooth, when it stops, it's wobbling slightly left/right - as it's still extrapolating it's position based on the time. Is this normal behavior and can we 'turn it off' when the sprite stops? I've tried having flags for left / right and only extrapolating if either of these is enabled. I've also tried copying the last and current positions to see if there is any difference. However, as far as collision goes, these don't help. If the user is pressing say, the right button and the sprite is moving right, when it hits a wall, if the user continues to hold the right button down, the sprite will keep animating to the right, while being stopped by the wall (therefore not actually moving), however because the right flag is still set and also because the collision routine is constantly moving the sprite out of the wall, it still appear to the code (not the player) that the sprite is still moving, and therefore extrapolation continues. So what the player would see, is the sprite 'static' (yes, it's animating, but it's not actually moving across the screen), and every now and then it shakes violently as the extrapolation attempts to do it's thing....... Hope this help

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  • Pixel Perfect Collision Detection in Cocos2dx

    - by Happybirthday
    I am trying to port the pixel perfect collision detection in Cocos2d-x the original version was made for Cocos2D and can be found here: http://www.cocos2d-iphone.org/forums/topic/pixel-perfect-collision-detection-using-color-blending/ Here is my code for the Cocos2d-x version bool CollisionDetection::areTheSpritesColliding(cocos2d::CCSprite *spr1, cocos2d::CCSprite *spr2, bool pp, CCRenderTexture* _rt) { bool isColliding = false; CCRect intersection; CCRect r1 = spr1-boundingBox(); CCRect r2 = spr2-boundingBox(); intersection = CCRectMake(fmax(r1.getMinX(),r2.getMinX()), fmax( r1.getMinY(), r2.getMinY()) ,0,0); intersection.size.width = fmin(r1.getMaxX(), r2.getMaxX() - intersection.getMinX()); intersection.size.height = fmin(r1.getMaxY(), r2.getMaxY() - intersection.getMinY()); // Look for simple bounding box collision if ( (intersection.size.width0) && (intersection.size.height0) ) { // If we're not checking for pixel perfect collisions, return true if (!pp) { return true; } unsigned int x = intersection.origin.x; unsigned int y = intersection.origin.y; unsigned int w = intersection.size.width; unsigned int h = intersection.size.height; unsigned int numPixels = w * h; //CCLog("Intersection X and Y %d, %d", x, y); //CCLog("Number of pixels %d", numPixels); // Draw into the RenderTexture _rt-beginWithClear( 0, 0, 0, 0); // Render both sprites: first one in RED and second one in GREEN glColorMask(1, 0, 0, 1); spr1-visit(); glColorMask(0, 1, 0, 1); spr2-visit(); glColorMask(1, 1, 1, 1); // Get color values of intersection area ccColor4B *buffer = (ccColor4B *)malloc( sizeof(ccColor4B) * numPixels ); glReadPixels(x, y, w, h, GL_RGBA, GL_UNSIGNED_BYTE, buffer); _rt-end(); // Read buffer unsigned int step = 1; for(unsigned int i=0; i 0 && color.g 0) { isColliding = true; break; } } // Free buffer memory free(buffer); } return isColliding; } My code is working perfectly if I send the "pp" parameter as false. That is if I do only a bounding box collision but I am not able to get it working correctly for the case when I need Pixel Perfect collision. I think the opengl masking code is not working as I intended. Here is the code for "_rt" _rt = CCRenderTexture::create(visibleSize.width, visibleSize.height); _rt-setPosition(ccp(origin.x + visibleSize.width * 0.5f, origin.y + visibleSize.height * 0.5f)); this-addChild(_rt, 1000000); _rt-setVisible(true); //For testing I think I am making a mistake with the implementation of this CCRenderTexture Can anyone guide me with what I am doing wrong ? Thank you for your time :)

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  • Collision detection in 3D space

    - by dreta
    I've got to write, what can be summed up as, a compelte 3D game from scratch this semester. Up untill now i have only programmed 2D games in my spare time, the transition doesn't seem tough, the game's simple. The only issue i have is collision detection. The only thing i could find was AABB, bounding spheres or recommendations of various physics engines. I have to program a submarine that's going to be moving freely inside of a cave system, AFAIK i can't use physics libraries, so none of the above solves my problem. Up untill now i was using SAT for my collision detection. Are there any similar, great algorithms, but crafted for 3D collision? I'm not talking about octrees, or other optimalizations, i'm talking about direct collision detection of one set of 3D polygons with annother set of 3D polygons. I thought about using SAT twice, project the mesh from the top and the side, but then it seems so hard to even divide 3D space into convex shapes. Also that seems like far too much computation even with octrees. How do proffessionals do it? Could somebody shed some light.

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  • Collision Detection for a 2D RPG

    - by PHMitrious
    First of all, I have done some research on this topic before asking, and I'm asking this question as a mean to get some opinions on this topic, so I don't make a decision only on my own, but taking into account other people's experience as well. I'm starting a 2D online RPG project. I am using SFML for graphics and input and I'm creating a basic game structure and all for the game, creating modules for each part of the game. Well, let me get to the point I just wanted to give you guys some context. I want to decide on how I'm going to work with collision detection. Well I'm kinda going to work on maps with a tile map divided in layers (as usual) and add an extra 2 layers - not exactly in the map - for objects. So I'll have collisions between objects and agents (players - npcs - monsters - spells etc) and agents and tiles. The seconds one can be easily solved the first one need a little bit of work. I considered both creating a basic collision test engine using polygons and a quadtree to diminish tests since I'm going to be working with big maps with lots of objects - creating both a physical and graphical world representation. And I also considered using a physics engine like Box2D for collision tests. I think the first approach would take more work on my part but the second one would have the overhead of using a whole physics engine for just collision detection and no physics. What do you guys think ?

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  • Collision Detection with SAT: False Collision for Diagonal Movement Towards Vertical Tile-Walls?

    - by Macks
    Edit: Problem solved! Big thanks to Jonathan who pointed me in the right direction. Sean describes the method I used in a different thread. Also big thanks to him! :) Here is how I solved my problem: If a collision is registered by my SAT-method, only fire the collision-event on my character if there are no neighbouring solid tiles in the direction of the returned minimum translation vector. I'm developing my first tile-based 2D-game with Javascript. To learn the basics, I decided to write my own "game engine". I have successfully implemented collision detection using the separating axis theorem, but I've run into a problem that I can't quite wrap my head around. If I press the [up] and [left] arrow-keys simultaneously, my character moves diagonally towards the upper left. If he hits a horizontal wall, he'll just keep moving in x-direction. The same goes for [up] and [left] as well as downward-diagonal movements, it works as intended: http://i.stack.imgur.com/aiZjI.png Diagonal movement works fine for horizontal walls, for both left and right-movement However: this does not work for vertical walls. Instead of keeping movement in y-direction, he'll just stop as soon as he "enters" a new tile on the y-axis. So for some reason SAT thinks my character is colliding vertically with tiles from vertical walls: http://i.stack.imgur.com/XBEKR.png My character stops because he thinks that he is colliding vertically with tiles from the wall on the right. This only occurs, when: Moving into top-right direction towards the right wall Moving into top-left direction towards the left wall Bottom-right and bottom-left movement work: the character keeps moving in y-direction as intended. Is this inherited from the way SAT works or is there a problem with my implementation? What can I do to solve my problem? Oh yeah, my character is displayed as a circle but he's actually a rectangular polygon for the collision detection. Thank you very much for your help.

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