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  • Quick 2D sight area calculation algorithm?

    - by Rogach
    I have a matrix of tiles, on some of that tiles there are objects. I want to calculate which tiles are visible to player, and which are not, and I need to do it quite efficiently (so it would compute fast enough even when I have a big matrices (100x100) and lots of objects). I tried to do it with Besenham's algorithm, but it was slow. Also, it gave me some errors: ----XXX- ----X**- ----XXX- -@------ -@------ -@------ ----XXX- ----X**- ----XXX- (raw version) (Besenham) (correct, since tunnel walls are still visible at distance) (@ is the player, X is obstacle, * is invisible, - is visible) I'm sure this can be done - after all, we have NetHack, Zangband, and they all dealt with this problem somehow :) What algorithm can you recommend for this? EDIT: Definition of visible (in my opinion): tile is visible when at least a part (e.g. corner) of the tile can be connected to center of player tile with a straight line which does not intersect any of obstacles.

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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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  • Trying to Draw a 2D Triangle in OpenGL ES 2.0

    - by Nathan Campos
    I'm trying to convert a code from OpenGL to OpenGL ES 2.0 (for the BlackBerry PlayBook). So far what I got is this (just the part of the code that should draw the triangle): void setupScene() { glClearColor(250, 250, 250, 1); glViewport(0, 0, 600, 1024); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); } void drawScene() { setupScene(); glColorMask(0, 0, 0, 1); const GLfloat triangleVertices[] = { 100, 100, 150, 0, 200, 100 }; glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, triangleVertices); glEnableVertexAttribArray(0); glDrawArrays(GL_TRIANGLES, 0, 2); } void render() { drawScene(); bbutil_swap(); } The problem is that when I launch the app instead of showing me the triangle the screen just flickers (very fast) from white to gray. Any idea what I'm doing wrong? Also, here is the entire code if you need: Full source code

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  • Game Physics With RK4 Implementation For A 2D Platformer

    - by oscar.rpr
    I been reading about RK4 for physics implementation in a game, so I read in some pages and all people recommend me this page: http://gafferongames.com/game-physics/fix-your-timestep/ This page shows clearly how this one works, but I can't figure out how to implement in my game, maybe I don't understand that good but I find some things that are not really clearly to me. In my game, the player decides when change direction in the X-Axis but I can't figure out how with this RK4 implementation change the direction of the object, in the example the point goes side to side but I don't understand how I can control when he goes right or left. So if anyone can give a little bit of clarity in this implementation and my problem which I do not understand I will be really grateful. Thanks beforehand

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  • 2D animation example in pyglet (python) looping through 2 images/sprites every x seconds

    - by Bentley4
    Suppose you have two images: step1.png and step2.png . Can anyone show me a very simple example in pyglet how to loop through those 2 images say every 0.5 seconds? The character doesn't have to move, just a simple black screen with a fixed region wherein the two images continually change every 0.5 secs. I know how to make a character move, shoot projectiles etc. but I just can't figure out how to control the looping speed of the images.

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  • Drawing territories border in 2d map

    - by Gabriel A. Zorrilla
    I'm programming a little web strategy game. In the country map I pretend to display each country with a national color. The issue is how to render the borders in a simple and efficient way. Right now I'm planning to set a field to each tile called "border" with values from 0 to 8. The algorithm would check for EVERY tile is its adjacent has a different "owner". If the tile is inside the territory, the border value would be 0, because would not have adjacent any tile with different owner, if not, would vary between 1 (north) clockwise to 9 (north-west) and then draw the border. I find this simple but too processor-intensive. Are there any other "pro" choices to render territories borders?

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  • How do I build a 2D physics engine?

    - by Vish
    The most advanced games I've made are a 8-ball pool game made with the physics engine Box2dFlashAS3 and a platform game with levels. When I did platform games, I've always wished to know how to make an engine, so that I could re-use it. When I see games that have slopes, curved slopes, perfect gravity and real-life physics, I've always wished I knew how to code the engine. Please suggest techniques and articles for whatever relevant knowledge-base is necessary.

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  • 2D Physics Engine to Handle Shapes Composed of Multiple Densities XNA

    - by Stupac
    The game I'm working on involves shapes that might be composed of multiple materials in a variety of ways. Let's just take for example a wooden rod with and sizable tip of iron or say a block composed of a couple triangles of stone and aluminum and small nugget of gold. The shapes and compositions will change from time to time, so I was wondering what engine I should use and how I might implement this feature? I've looked at Farseer 3, but I'm still trying to decipher the library by reading the source and the samples and wasn't sure if I was barking up the wrong tree. Thanks!

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  • How can I make an object's hitbox rotate with its texture?

    - by Matthew Optional Meehan
    In XNA, when you have a rectangular sprite that doesnt rotate, it's easy to get its four corners to make a hitbox. However, when you do a rotation, the points get moved and I assume there is some kind of math that I can use to aquire them. I am using the four points to draw a rectangle that visually represents the hitboxes. I have seen some per-pixel collision examples, but I can forsee they would be hard to draw a box/'convex hull' around. I have also seen physics like farseer but I'm not sure if there is a quick tutorial to do what I want.

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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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  • Axis-Aligned Bounding Boxes vs Bounding Ellipse

    - by Griffin
    Why is it that most, if not all collision detection algorithms today require each body to have an AABB for the use in the broad phase only? It seems to me like simply placing a circle at the body's centroid, and extending the radius to where the circle encompasses the entire body would be optimal. This would not need to be updated after the body rotates and broad overlap-calculation would be faster to. Correct? Bonus: Would a bounding ellipse be practical for broad phase calculations also, since it would better represent long, skinny shapes? Or would it require extensive calculations, defeating the purpose of broad-phase?

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  • Resolution independent physics

    - by user46877
    I'm making a game like Doodlejump but don't know how to make the physics scale on multiple resolutions. I also can't find anything related to this on Google. Right now I'm scaling the game using letterboxing and tested scaling the jump height with this code: gravity = graphics.getHeight() * 0.001f; jumpVel = graphics.getHeight() * -0.04f; ... velY += gravity; y += velY; But if I test this on my smartphone or emulator with different resolutions, I always get a slightly different jump height. I know that Farseer is resolution independent. How can I replicate this in my game? Thanks in advance.

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  • Box2D Platform body not moving player body along with it

    - by onedayitwillmake
    I am creating a game using Box2D (Javascript implementation) - and I added the ability to have a static platform, that is moved along an axis as a function of a sine. My problem is when the player lands on the platform, as the platform moves along the X axis - the player is not moved along with it, as you visually would expect. The player can land on the object, and if it hits the side of the object, it does colide with it and is pushed. This image might explain better than I did: After jumping on to the red platform the player character will fall off as the platform moves to the right UPDATE: Here is a live demo showing the problem: http://onedayitwillmake.com/ChuClone/slideexample.php

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  • Best way to go about sorting 2D sprites in a "RPG Maker" styled RPG

    - by Aaron Stewart
    I am trying to come up with the best way to create overlapping sprites without having any issues. I was thinking of having a SortedDictionary and setting the Entity's key to it's Y position relative to the max bound of the simulation, aka the Z value. I'd update the "Z" value in the update method each frame, if the entity's position has changed at all. For those who don't know what I mean, I want characters who are standing closer in front of another character to be drawn on top, and if they are behind the character, they are drawn behind. I'm leery of using SpriteBatch back to front or front to back, I've been doing some searching and have been under the impression they are a bad idea. and want to know exactly how other people are dealing with their depth sorting. Just ultimately trying to come up with the best method of sorting for good practice before I get too far in to refactor the system effectively.

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  • Game physics / 2D Collision detection AS3

    - by Jery
    I know there are some methods you can use like hittestPoint and so on, but I want to see where my movieclip colliedes with another another movieclip. Any other methods I can use? by any chance does somebody know some a good introduction to game physics? Im asking because I coded a small engine and pretty much the whole code is spagetti code thats why I would like to know how you can setup something like this properly

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  • Making an interactive 2D map

    - by Chad
    So recently I have been working on a Legend of Zelda: A Link to the Past clone, and I am wondering how I could handle certain map interactions (like cutting grass, lifting rocks, etc). The way I am currently doing the tilemap is with 2 PNGs. The first is the "tilemap" where each pixel represents a 16x16 tile and the (red, green) values are the (x, y) coords for the tile in the second PNG (the "tileset"). I am then using the blue channel to store collision data. Each tile is split into 4 8x8 tiles and represented by a 2 bit value (0 = empty, 1 = Jumpdown point, 2 = unused right now, 3 = blocking). 4 of these 2 bit values make up the full blue channel (1 byte). So collisions work great, and I am moving on to putting interactive units on the level; but I am not sure what a good way is to do it. I have experimented with spawning an entity for each grass and rock, but there are just WAY to many; FPS just dies even if I confine it to the current "zone" the user is in (for those who remember LTTP it had zones you moved between). It does make a difference that this is a browser-based JavaScript game. tl;dr: What is a good way to have an interactive map without using full blown entities for each interactive item?

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  • Good book or tutorial for learning how to apply integration methods

    - by Cumatru
    I'm looking to animate a graph layout using edges as springs and nodes as weights ( a node with more links will have a bigger weight ). I'm not capable of wrapping my head around the usage of mathematical and physics relations in my application. As far as i read, Runge Kutta 4 ( preferably ) or Verlet will be a good choice, but i have problems with understanding how they really work, and what physics equations should i apply. If i can't understand them, i can't use them. I'm looking for a book or a tutorial which describe the things that i need.

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  • Grid-Based 2D Lighting Problems

    - by Lemoncreme
    I am aware this question has been asked before, but unfortunately I am new to the language, so the complicated explanations I've found do not help me in the least. I need a lighting engine for my game, and I've tried some procedural lighting systems. This method works the best: if (light[xx - 1, yy] > light[xx, yy]) light[xx, yy] = light[xx - 1, yy] - lightPass; if (light[xx, yy - 1] > light[xx, yy]) light[xx, yy] = light[xx, yy - 1] - lightPass; if (light[xx + 1, yy] > light[xx, yy]) light[xx, yy] = light[xx + 1, yy] - lightPass; if (light[xx, yy + 1] > light[xx, yy]) light[xx, yy] = light[xx, yy + 1] - lightPass; (Subtracts adjacent values by 'lightPass' variable if they are more bright) (It's in a for() loop) This is all fine and dandy except for a an obvious reason: The system favors whatever comes first in the for() loop This is what the above code looks like applied to my game: If I could get some help on creating a new procedural or otherwise lighting system I would really appreciate it!

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  • How can I convert a 2D bitmap (Used for terrain) to a 2D polygon mesh for collision?

    - by Megadanxzero
    So I'm making an artillery type game, sort of similar to Worms with all the usual stuff like destructible terrain etc... and while I could use per-pixel collision that doesn't give me collision normals or anything like that. Converting it all to a mesh would also mean I could use an existing physics library, which would be better than anything I can make by myself. I've seen people mention doing this by using Marching Squares to get contours in the bitmap, but I can't find anything which mentions how to turn these into a mesh (Unless it refers to a 3D mesh with contour lines defining different heights, which is NOT what I want). At the moment I can get a basic Marching Squares contour which looks something like this (Where the grid-like lines in the background would be the Marching Squares 'cells'): That needs to be interpolated to get a smoother, more accurate result but that's the general idea. I had a couple ideas for how to turn this into a mesh, but many of them wouldn't work in certain cases, and the one which I thought would work perfectly has turned out to be very slow and I've not even finished it yet! Ideally I'd like whatever I end up using to be fast enough to do every frame for cases such as rapidly-firing weapons, or digging tools. I'm thinking there must be some kind of existing algorithm/technique for turning something like this into a mesh, but I can't seem to find anything. I've looked at some things like Delaunay Triangulation, but as far as I can tell that won't correctly handle concave shapes like the above example, and also wouldn't account for holes within the terrain. I'll go through the technique I came up with for comparison and I guess I'll see if anyone has a better idea. First of all interpolate the Marching Squares contour lines, creating vertices from the line ends, and getting vertices where lines cross cell edges (Important). Then, for each cell containing vertices create polygons by using 2 vertices, and a cell corner as the 3rd vertex (Probably the closest corner). Do this for each cell and I think you should have a mesh which accurately represents the original bitmap (Though there will only be polygons at the edges of the bitmap, and large filled in areas in between will be empty). The only problem with this is that it involves lopping through every pixel once for the initial Marching Squares, then looping through every cell (image height + 1 x image width + 1) at least twice, which ends up being really slow for any decently sized image...

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  • 2D object-aligned bounding-box intersection test

    - by AshleysBrain
    Hi all, I have two object-aligned bounding boxes (i.e. not axis aligned, they rotate with the object). I'd like to know if two object-aligned boxes overlap. (Edit: note - I'm using an axis-aligned bounding box test to quickly discard distant objects, so it doesn't matter if the quad routine is a little slower.) My boxes are stored as four x,y points. I've searched around for answers, but I can't make sense of the variable names and algorithms in examples to apply them to my particular case. Can someone help show me how this would be done, in a clear and simple way? Thanks. (The particular language isn't important, C-style pseudo code is OK.)

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  • 2D SAT Collision Detection not working when using certain polygons

    - by sFuller
    My SAT algorithm falsely reports that collision is occurring when using certain polygons. I believe this happens when using a polygon that does not contain a right angle. Here is a simple diagram of what is going wrong: Here is the problematic code: std::vector<vec2> axesB = polygonB->GetAxes(); //loop over axes B for(int i = 0; i < axesB.size(); i++) { float minA,minB,maxA,maxB; polygonA->Project(axesB[i],&minA,&maxA); polygonB->Project(axesB[i],&minB,&maxB); float intervalDistance = polygonA->GetIntervalDistance(minA, maxA, minB, maxB); if(intervalDistance >= 0) return false; //Collision not occurring } This function retrieves axes from the polygon: std::vector<vec2> Polygon::GetAxes() { std::vector<vec2> axes; for(int i = 0; i < verts.size(); i++) { vec2 a = verts[i]; vec2 b = verts[(i+1)%verts.size()]; vec2 edge = b-a; axes.push_back(vec2(-edge.y,edge.x).GetNormailzed()); } return axes; } This function returns the normalized vector: vec2 vec2::GetNormailzed() { float mag = sqrt( x*x + y*y ); return *this/mag; } This function projects a polygon onto an axis: void Polygon::Project(vec2* axis, float* min, float* max) { float d = axis->DotProduct(&verts[0]); float _min = d; float _max = d; for(int i = 1; i < verts.size(); i++) { d = axis->DotProduct(&verts[i]); _min = std::min(_min,d); _max = std::max(_max,d); } *min = _min; *max = _max; } This function returns the dot product of the vector with another vector. float vec2::DotProduct(vec2* other) { return (x*other->x + y*other->y); } Could anyone give me a pointer in the right direction to what could be causing this bug?

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  • Joystick example problem for android 2D

    - by iQue
    I've searched all over the web for an answer to this, and there are simular topics but nothing works for me, and I have no Idea why. I just want to move my sprite using a joystick, since I'm useless at math when it comes to angles etc I used an example, Ill post the code here: public float initx = 50; //og 425; public float inity = 300; //og 267; public Point _touchingPoint = new Point(50, 300); //og(425, 267); public Point _pointerPosition = new Point(100, 170); private Boolean _dragging = false; private MotionEvent lastEvent; @Override public boolean onTouchEvent(MotionEvent event) { if (event == null && lastEvent == null) { return _dragging; } else if (event == null && lastEvent != null) { event = lastEvent; } else { lastEvent = event; } // drag drop if (event.getAction() == MotionEvent.ACTION_DOWN) { _dragging = true; } else if (event.getAction() == MotionEvent.ACTION_UP) { _dragging = false; } if (_dragging) { // get the pos _touchingPoint.x = (int) event.getX(); _touchingPoint.y = (int) event.getY(); // bound to a box if (_touchingPoint.x < 25) { _touchingPoint.x = 25; //og 400 } if (_touchingPoint.x > 75) { _touchingPoint.x = 75; //og 450 } if (_touchingPoint.y < 275) { _touchingPoint.y = 275; //og 240 } if (_touchingPoint.y > 325) { _touchingPoint.y = 325; //og 290 } // get the angle double angle = Math.atan2(_touchingPoint.y - inity, _touchingPoint.x - initx) / (Math.PI / 180); // Move the beetle in proportion to how far // the joystick is dragged from its center _pointerPosition.y += Math.sin(angle * (Math.PI / 180)) * (_touchingPoint.x / 70); _pointerPosition.x += Math.cos(angle * (Math.PI / 180)) * (_touchingPoint.x / 70); // stop the sprite from goin thru if (_pointerPosition.x + happy.getWidth() >= getWidth()) { _pointerPosition.x = getWidth() - happy.getWidth(); } if (_pointerPosition.x < 0) { _pointerPosition.x = 0; } if (_pointerPosition.y + happy.getHeight() >= getHeight()) { _pointerPosition.y = getHeight() - happy.getHeight(); } if (_pointerPosition.y < 0) { _pointerPosition.y = 0; } } public void render(Canvas canvas) { canvas.drawColor(Color.BLUE); canvas.drawBitmap(joystick.get_joystickBg(), initx-45, inity-45, null); canvas.drawBitmap(happy, _pointerPosition.x, _pointerPosition.y, null); canvas.drawBitmap(joystick.get_joystick(), _touchingPoint.x - 26, _touchingPoint.y - 26, null); } public void update() { this.onTouchEvent(null); } og= original position. as you can see Im trying to move the joystick, but when I do it stops working correctly, I mean it still works like a joystick but the sprite dosnt move accordingly, if I for example push the joystick down, the sprite moves up, and if I push it up it moves left. can anyone PLEASE help me, I've been stuck here for sooo long and its really frustrating.

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  • Moving a body in a specific direction using XNA with Farseer Physics

    - by Code Assasssin
    I have a custom polygon attached to a body, which looks like this: What I am trying to accomplish is getting the body to move according to wherever the tip of the body is. So far this is what I've tried: if (ks.IsKeyDown(Keys.Up)) { body.ApplyForce(new Vector2(0, -20),body.GetLocalPoint(new Vector2(0,0))); } if (ks.IsKeyDown(Keys.Left)) { body.ApplyTorque(-500); } if (ks.IsKeyDown(Keys.Right)) { body.ApplyTorque(500); } The body rotates fine - but when I try making the body accelerate according to the tip of the body - assuming I have specified the tip correctly(I am pretty sure I haven't), it just spins around, as if I have applied Torque to it. Can anyone point me in the right direction of how to fix this problem?

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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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  • 2D Platform Game Jumping

    - by Bradley Kreuger
    I'm currently writing a game in XNA for fun which uses C#. I have got my sprites loaded and when the character moves right he looks like he is running right and when he moves left he looks like he is running left. I been looking everywhere for a good coding example for how to create a jumping ability. I have read all the physics stuff that I can stand and it doesn't help when I can't figure out how to use say space bar to jump yet can't keep them from using space just jump again until they land.

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