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• How do I run my XBOX XNA game without a network connection?

  - by Hugh

  I need to demo my XBOX XNA game in college. The college doesn't allow this type of device to connect to the network. I deployed my game to the Xbox and it is sitting in the games list along with my other games. It runs fine with a network connection but when its offline it comes up with an error message saying its needs a connection to run the game. This makes no sense, the game is deployed on the Xbox memory, it must be some security policy or something! Is there any way around this? The demo is on monday!

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• Question about mipmaps + anisotropic filtering

  - by Telanor

  I'm a bit confused here and maybe someone can explain this to me. I created a simple test texture for my terrain which is nothing more than a solid green color with a black grid overlayed on top of it. If I look at the terrain in the distance with mipmapping on and linear filtering, the grid lines become blurry fairly quickly and further back the grid is pretty much invisible. With these settings, I don't get any moire patterns at all. If I turn on anisotropic filtering, however, the higher the anisotropic level, the more the terrain looks like it did with without mipmapping. The lines are much crisper nearby but in the distance I start to see terrible moire patterns. My understanding was that mipmapping is supposed to get rid of moire patterns. I've always had anisotropic filtering on in every game I play and I've never noticed any moire patterns as a result, so I don't understand why it's happening in my game. I am using logarithmic depth however, could that be causing any problems? And if it is, how do I resolve it? I've created my sampler state like so (I'm using slimdx): ssa = SamplerState.FromDescription(Engine.Device, new SamplerDescription { AddressU = TextureAddressMode.Clamp, AddressV = TextureAddressMode.Clamp, AddressW = TextureAddressMode.Clamp, Filter = Filter.Anisotropic, MaximumAnisotropy = anisotropicLevel, MinimumLod = 0, MaximumLod = float.MaxValue });

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• Rotate an image in a scaled context

  - by nathan

  Here is my working piece of code to rotate an image toward a point (in my case, the mouse cursor). float dx = newx - ploc.x; float dy = newy - ploc.y; float angle = (float) Math.toDegrees(Math.atan2(dy, dx)); Where ploc is the location of the image i'm rotating. And here is the rendering code: g.rotate(loc.x + width / 2, loc.y + height / 2, angle); g.drawImage(frame, loc.x, loc.y); Where loc is the location of the image and "width" and "height" are respectively the width and height of the image. What changes are needed to make it works on a scaled context? e.g make it works with something like g.scale(sx, sy).

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• Using orientation to calculate position on Windows Phone 7

  - by Lavinski

  I'm using the motion API and I'm trying to figure out a control scheme for the game I'm currently developing. What I'm trying to achive is for a orienation of the device to correlate directly to a position. Such that tilting the phone forward and to the left represents the top left position and back to the right would be the bottom right position. Photos to make it clearer (the red dot would be the calculated position). Forward and Left Back and Right Now for the tricky bit. I also have to make sure that the values take into account left landscape and right landscape device orientations (portrait is the default so no calculations would be needed for it). Has anyone done anything like this? Notes: I've tried using the yaw, pitch, roll and Quaternion readings. Sample: // Get device facing vector public static Vector3 GetState() { lock (lockable) { var down = Vector3.Forward; var direction = Vector3.Transform(down, state); switch (Orientation) { case Orientation.LandscapeLeft: return Vector3.TransformNormal(direction, Matrix.CreateRotationZ(-rightAngle)); case Orientation.LandscapeRight: return Vector3.TransformNormal(direction, Matrix.CreateRotationZ(rightAngle)); } return direction; } }

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• Platformer Starter Kit - Collision Issues

  - by Cyral

  I'm having trouble with my game that is based off the XNA Platformer starter kit. My game uses smaller tiles (16x16) then the original (32x40) which I'm thinking may be having an effect on collision (Being it needs to be more precise). Standing on the edge of a tile and jumping causes the player to move off the the tile when he lands. And 80% of the time, when the player lands, he goes flying though SOLID tiles in a diagonal fashion. This is very annoying as it is almost impossible to test other features, when spawning and jumping will result in the player landing in another part of the level or falling off the edge completely. The code is as follows: /// <summary> /// Updates the player's velocity and position based on input, gravity, etc. /// </summary> public void ApplyPhysics(GameTime gameTime) { float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; Vector2 previousPosition = Position; // Base velocity is a combination of horizontal movement control and // acceleration downward due to gravity. velocity.X += movement * MoveAcceleration * elapsed; velocity.Y = MathHelper.Clamp(velocity.Y + GravityAcceleration * elapsed, -MaxFallSpeed, MaxFallSpeed); velocity.Y = DoJump(velocity.Y, gameTime); // Apply pseudo-drag horizontally. if (IsOnGround) velocity.X *= GroundDragFactor; else velocity.X *= AirDragFactor; // Prevent the player from running faster than his top speed. velocity.X = MathHelper.Clamp(velocity.X, -MaxMoveSpeed, MaxMoveSpeed); // Apply velocity. Position += velocity * elapsed; Position = new Vector2((float)Math.Round(Position.X), (float)Math.Round(Position.Y)); // If the player is now colliding with the level, separate them. HandleCollisions(); // If the collision stopped us from moving, reset the velocity to zero. if (Position.X == previousPosition.X) velocity.X = 0; if (Position.Y == previousPosition.Y) velocity.Y = 0; } /// <summary> /// Detects and resolves all collisions between the player and his neighboring /// tiles. When a collision is detected, the player is pushed away along one /// axis to prevent overlapping. There is some special logic for the Y axis to /// handle platforms which behave differently depending on direction of movement. /// </summary> private void HandleCollisions() { // Get the player's bounding rectangle and find neighboring tiles. Rectangle bounds = BoundingRectangle; int leftTile = (int)Math.Floor((float)bounds.Left / Tile.Width); int rightTile = (int)Math.Ceiling(((float)bounds.Right / Tile.Width)) - 1; int topTile = (int)Math.Floor((float)bounds.Top / Tile.Height); int bottomTile = (int)Math.Ceiling(((float)bounds.Bottom / Tile.Height)) - 1; // Reset flag to search for ground collision. isOnGround = false; // For each potentially colliding tile, for (int y = topTile; y <= bottomTile; ++y) { for (int x = leftTile; x <= rightTile; ++x) { // If this tile is collidable, ItemCollision collision = Level.GetCollision(x, y); if (collision != ItemCollision.Passable) { // Determine collision depth (with direction) and magnitude. Rectangle tileBounds = Level.GetBounds(x, y); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if (depth != Vector2.Zero) { float absDepthX = Math.Abs(depth.X); float absDepthY = Math.Abs(depth.Y); // Resolve the collision along the shallow axis. if (absDepthY < absDepthX || collision == ItemCollision.Platform) { // If we crossed the top of a tile, we are on the ground. if (previousBottom <= tileBounds.Top) isOnGround = true; // Ignore platforms, unless we are on the ground. if (collision == ItemCollision.Impassable || IsOnGround) { // Resolve the collision along the Y axis. Position = new Vector2(Position.X, Position.Y + depth.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } else if (collision == ItemCollision.Impassable) // Ignore platforms. { // Resolve the collision along the X axis. Position = new Vector2(Position.X + depth.X, Position.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } } } } // Save the new bounds bottom. previousBottom = bounds.Bottom; } It also tends to jitter a little bit sometimes, I'm solved some of this with some fixes I found here on stackexchange, But Ive only seen one other case of the flying though blocks problem. This question seems to have a similar problem in the video, but mine is more crazy. Again this is a very annoying bug! Any help would be greatly appreciated! EDIT: Speed stuff // Constants for controling horizontal movement private const float MoveAcceleration = 13000.0f; private const float MaxMoveSpeed = 1750.0f; private const float GroundDragFactor = 0.48f; private const float AirDragFactor = 0.58f; // Constants for controlling vertical movement private const float MaxJumpTime = 0.35f; private const float JumpLaunchVelocity = -3500.0f; private const float GravityAcceleration = 3400.0f; private const float MaxFallSpeed = 550.0f; private const float JumpControlPower = 0.14f;

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• What is the benefit of triple buffering?

  - by user782220

  I read everything written in a previous question. From what I understand in double buffering the program must wait until the finished drawing is copied or swapped before starting the next drawing. In triple buffering the program has two back buffers and can immediately start drawing in the one that is not involved in such copying. But with triple buffering if you're in a situation where you can take advantage of the third buffer doesn't that suggest that you are drawing frames faster than the monitor can refresh. So then you don't actually get a higher frame rate. So what is the benefit of triple buffering then?

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• Importing a windows project into android using cocos2d-x

  - by Ef Es

  What I am trying to do today is to import a full project to Android, but no tutorials are available for that that I have seen. My approach was to create a new android project, copy all the classes and resources in the folders and calling ./build_native.sh but I get an error because most of the files are not being included in the project. I tried opening the Android.mk and I can see why "LOCAL_SRC_FILES := AppDelegate.cpp \ HelloWorldScene.cpp" are the only files linked. Should I manually modify the make file or can it be automated by some way I don't know? Thank you. UPDATE: I manually added all files and headers to the make file and I get errors linking Box2D or cocosdenshion libraries.

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• Rendering Unity across multiple monitors

  - by N0xus

  At the moment I am trying to get unity to run across 2 monitors. I've done some research and know that this is, strictly, possible. There is a workaround where you basically have to fluff your window size in order to get unity to render across both monitors. What I've done is create a new custom screen resolution that takes in the width of both of my monitors, as seen in the following image, its the 3840 x 1080: How ever, when I go to run my unity game exe that size isn't available. All I get is the following: My custom size should be at the very bottom, but isn't. Is there something I haven't done, or missed, that will get unity to take in my custom screen size when it comes to running my game through its exe? Oddly enough, inside the unity editor, my custom screen size is picked up and I can have it set to that in my game window: Is there something that I have forgotten to do when I build and run the game from the file menu? Has someone ever beaten this issue before?

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• Deserialize inherited classes into the same list in XNA

  - by M0rgenstern

  I am writing a Gui for a game (for what else ...). Therefor I wrote a class GuiElement which has some serializeable fields. From this class I deflect a Class "Button" which has one serializeable field more. Furthermore, I have a Class GuiWindow, which is as well deflected from "GuiElement". An Object of this Class has a Field "HandledElements" of the type "List". To know the layout of the Menues, I use XML-Files, which look like that (for example): <?xml version="1.0" encoding="utf-8" ?> <XnaContent xmlns:Generic="System.Collections.Generic"> <Asset Type="System.Collections.Generic.List[GUI.GuiWindow]"> <Item> <Position>0 0</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>true</IsActive> <Name>MainMenu</Name> <HandledElements> <Item> <Position>100 100</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>true</IsActive> <Name>Optionen</Name> <Caption>Optionen</Caption> </Item> </HandledElements> </Item> <Item> <Position>0 0</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>false</IsActive> <Name>Options</Name> <HandledElements> </HandledElements> </Item> </Asset> </XnaContent> As you can see, the first window has in its "HandledElements" List an Item with the Field . This is a field which only a Button has. The Problem is now: I can't deserialize this XML file, because GuiElement does not have this Field, it only has the few fields above. I thought it would know automatically which Class to use,but it doesn't. Do I really have to give my windows a list for each child class of GuiElement? Or can I do another workaround?

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• How to move Objects smoothly like swimming arround

  - by philipp

  I have a Box2D project that is about to create a view where the user looks from the Sky onto Water. Or perhaps on a bathtub filled with water or something like this. The Object which holds the fluid actually does not matter, what matters is the movement of the bodies, because they should move like drops of grease on a soup, or wood on water, I can even imagine the the fluid is mercurial, extreme heavy and "lazy". How can I manipulate the bodies (every frame or time by time) to make them move like this? I started with randomly manipulation their linear velocity, but I turned out that this not very smooth and looks quite hard. Is it a better idea to check their velocity and apply impulses? Is there any example? Greetings philipp

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• Which Game Engine to Use for an Angry Bird style game? [JAVA] [on hold]

  - by Arch1tect

  Our team is building an Angry Bird Style game, and we have only about ten days. The game is a little more complex than Angry Bird because there are two players, they each have a castle with pigs to protect(not destroy:)). And the goal is to destroy the other player's pigs. I wonder what Game Engine would help us finish this game most efficiently. We at least need a physics engine but I guess game engine is more helpful since it usually includes physics engine. Correct me if I'm wrong. (So I'm wondering which game engine I should use, if it's just physics engine, I'll use box2d) Networking may or may not be added later depend on time we have. Thanks in advance for any advice! EDIT: image looks small, I'll add one:

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• How to play many sounds at once in OpenAL

  - by Krom

  Hello, I'm developing an RTS game and I would like to add sounds to it. My choice has landed on OpenAL. I have plenty of units which from time to time make sounds: fSound.Play(sfx_shoot, location). Sounds often repeat, e.g. when squad of archers shoots arrows, but they are not synced with each other. My questions are: What is the common design pattern to play multiple sounds in OpenAL, when some of them are duplicate? What are the hardware limitations on sounds count and tricks to overcome them?

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• Html 5 ping pong game side collision problem

  - by Gurjit

  I am making a simple ping pong game where I am facing a side collision problem means when the ball collides with the either side of the paddle . Although I have written code for making it works but something is failing....I want plz someone to give suggestions and tell how to avoid it. Means while trying to hit the ball with side face of the paddle poses a problem.!! Here is the main part of the code causing problem function checkCollision(){ ///// This is collision detection for the upper part ///// if( cy + radius >= paddleTop && cx + radius > paddleLeft && cy + radius >= paddleTop + 5 && cx - radius <= paddleLeft + paddleWidth ) { dy = -dy; ++hits; /// On collision we are increasing the Score playSound(); } else if( cy + radius >= paddleTop && cy + radius <= paddleTop + paddleHeight && cx + radius >= paddleLeft && cy - radius <= paddleLeft - (radius + 1) ) { dx = -dx; } } here is working fiddle for it :- http://jsfiddle.net/gurjitmehta/orzpzf69/

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• Actually utilizing relational databases for entity systems

  - by Marc Müller

  Recently I was researching several entity systems and obviously I came across T=Machine's fantastic articles on the subject. In Part 5 of the series the author uses a relational schema to explain how an entity system is built and works. Since reading this, I have been wondering whether or not actually using a compact SQL library would be fast enough for real-time usage in video games. Performance seems to be the main issue with a full blown SQL database for management of all entities and components. However, as mentioned in T=Machine's post, basically all access to data inside the SQLDB is done sequentlially by each system over each component. Additionally, using a library like SQLite, one could easily improve performance by storing the entity data exclusively in RAM to increase access speeds. Disregarding possible performance issues, using a SQL database, in my opinion, would allow for a very intuitive implementation of entity systems and bring a long certain other benefits like easy de/serialization of game states and consistency checks like the uniqueness of entity IDs. Edit for clarification: The main question was whether using a SQL database for the actual entity management (not just storing the game state on the disk) in a real-time game would still yield a framerate appropriate for a game or even if someone is aware of projects that demonstrate SQL in a video game.

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• Monogame - Input secuence game (Scripting?)

  - by user2662567

  I'm starting to program my very first game, it's a clone of DDR/Stepmania done for research purposes and learning. I (at this early stage) get most of the UI/Music/input work that should be done, but what i still can't grasp is scripting, i've read about Lua and that you shouldn't use it with XNA/Monogame as C# is capable enough, but i cannot get the utility of it. Assuming the needs of my game, ¿What would be the ideal way to implement the input secuences it needs?, i thought of XML/Json, let's say Stage 1 <game> <level id="1"> <step id="1" key="up" time="00:00:01"/> <step id="2" key="left" time="00:00:02"/> </level> </game> Is that a correct implementation? or are there better ways with more benefits?

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• How can I perform 2D side-scroller collision checks in a tile-based map?

  - by bill

  I am trying to create a game where you have a player that can move horizontally and jump. It's kind of like Mario but it isn't a side scroller. I'm using a 2D array to implement a tile map. My problem is that I don't understand how to check for collisions using this implementation. After spending about two weeks thinking about it, I've got two possible solutions, but both of them have some problems. Let's say that my map is defined by the following tiles: 0 = sky 1 = player 2 = ground The data for the map itself might look like: 00000 10002 22022 For solution 1, I'd move the player (the 1) a complete tile and update the map directly. This make the collision easy because you can check if the player is touching the ground simply by looking at the tile directly below the player: // x and y are the tile coordinates of the player. The tile origin is the upper-left. if (grid[x][y+1] == 2){ // The player is standing on top of a ground tile. } The problem with this approach is that the player moves in discrete tile steps, so the animation isn't smooth. For solution 2, I thought about moving the player via pixel coordinates and not updating the tile map. This will make the animation much smoother because I have a smaller movement unit per frame. However, this means I can't really accurately store the player in the tile map because sometimes he would logically be between two tiles. But the bigger problem here is that I think the only way to check for collision is to use Java's intersection method, which means the player would need to be at least a single pixel "into" the ground to register collision, and that won't look good. How can I solve this problem?

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• Actionscript 3.0 - Enemies do not move right in my platformer game

  - by Christian Basar

  I am making a side-scrolling platformer game in Flash (Actionscript 3.0). I have made lots of progress lately, but I have come across a new problem. I will give some background first. My game level's terrain (or 'floor') is referenced by a MovieClip variable called 'floor.' My desire is to have the Player and enemy characters walk along the terrain. I have gotten the Player character to move on the terrain just fine; he walks up/down hills and falls whenever there is no ground beneath him. Here is the code I created to allow the Player to follow the terrain correctly. Much more code is used to control the Player, but only this code deals with the Player character's following of the terrain and gravity. // If the Player's not on the ground (not touching the 'floor' MovieClip)... if (!onGround) { // Disable ducking downKeyPressed = false; // Increase the Player's 'y' position by his 'y' velocity player.y += playerYVel; } // Increase the 'playerYVel' variable so that the Player will fall // progressively faster down the screen. This code technically // runs "all the time" but in reality it only affects the player // when he's off the ground. playerYVel += gravity; // Give the Player a terminal velocity of 15 px/frame if (playerYVel > 15) { playerYVel = 15; } // If the Player has not hit the 'floor,' increase his falling //speed if (! floor.hitTestPoint(player.x, player.y, true)) { player.y += playerYVel; // The Player is not on the ground when he's not touching it onGround = false; } Since getting this code to work for the Player, I have created a 'SkullDemon' class, which is one of the planned enemies for my game. I want the 'SkullDemon' objects to move along the terrain like the Player does. With lots of great help, I have already coded the EventListeners, etc. necessary for the 'SkullDemons' to move. Unfortunately, I am having trouble getting them to move along the terrain. In fact, they do not touch the terrain at all; they move along the top of the boundary of the 'floor' MovieClip! I had a simple text diagram showing what I mean, but unfortunately Stackoverflow does not format it correctly. I hope my problem is clear from my description. Strangely enough, my code for the Player's movement and the 'SkullDemon's' movement is almost exactly the same, yet the 'SkullDemons' do not move like the Player does. Here is my code for the SkullDemon movement: // Move all of the Skull Demons using this method protected function moveSkullDemons():void { // Go through the whole 'skullDemonContainer' for (var skullDi:int = 0; skullDi < skullDemonContainer.numChildren; skullDi++) { // Set the SkullDemon 'instance' variable to equal the current SkullDemon skullDIns = SkullDemon(skullDemonContainer.getChildAt(skullDi)); // For now, just move the Skull Demons left at 5 units per second skullDIns.x -= 5; // If the Skull Demon has not hit the 'floor,' increase his falling //speed if (! floor.hitTestPoint(skullDIns.x, skullDIns.y, true)) { // Increase the Skull Demon's 'y' position by his 'y' velocity skullDIns.y += skullDIns.sdYVel; // The Skull Demon is not on the ground when he's not touching it skullDIns.sdOnGround = false; } // Increase the 'sdYVel' variable so that the Skull Demon will fall // progressively faster down the screen. This code technically // runs "all the time" but in reality it only affects the Skull Demon // when he's off the ground. if (! skullDIns.sdOnGround) { skullDIns.sdYVel += skullDIns.sdGravity; // Give the Skull Demon a terminal velocity of 15 px/frame if (skullDIns.sdYVel > 15) { skullDIns.sdYVel = 15; } } // What happens when the Skull Demon lands on the ground after a fall? // The Skull Demon is only on the ground ('onGround == true') when // the ground is touching the Skull Demon MovieClip's origin point, // which is at the Skull Demon's bottom centre for (var i:int = 0; i < 10; i++) { // The Skull Demon is only on the ground ('onGround == true') when // the ground is touching the Skull Demon MovieClip's origin point, // which is at the Skull Demon's bottom centre if (floor.hitTestPoint(skullDIns.x, skullDIns.y, true)) { skullDIns.y = skullDIns.y; // Set the Skull Demon's y-axis speed to 0 skullDIns.sdYVel = 0; // The Skull Demon is on the ground again skullDIns.sdOnGround = true; } } } } // End of 'moveSkullDemons()' function It is almost like the 'SkullDemons' are interacting with the 'floor' MovieClip using the hitTestObject() function, and not the hitTestPoint() function which is what I want, and which works for the Player character. I am confused about this problem and would appreciate any help you could give me. Thanks!

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• How is this lighting effect done?

  - by Mike

  This is the most beautiful 2d lighting I have ever seen. Does anyone know how he went about doing it? http://www.youtube.com/watch?v=BIQRhOFkvQY http://www.youtube.com/watch?v=tnTYXPuecMs http://www.youtube.com/watch?v=rhC_jVM8IYU http://www.youtube.com/watch?v=_Aw5BdjWqqU Or download it here: http://grantkot.com/PollutedPlanet/publish.htm edit: I am not asking how the particles are simulated; I don't care about the physics.

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• Marketing: Angry Birds - How it's done

  - by John

  Why do some apps, like Angry Birds, dominate the market while other cool/fun/addicting apps are never heard of? I'm trying to figure out the best marketing strategy, or best way to sell an app to mass market. Does anybody have any ideas or things they noticed about the marketing of major blockbuster apps, like Angry Birds, why they get so popular and stay at the top of charts. Thanks for any ideas, comments ...

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• Capitalizing on JavaScript's prototypal inheritance

  - by keithjgrant

  JavaScript has a class-free object system in which objects inherit properties directly from other objects. This is really powerful, but it is unfamiliar to classically trained programmers. If you attempt to apply classical design patterns directly to JavaScript, you will be frustrated. But if you learn to work with JavaScript's prototypal nature, your efforts will be rewarded. ... It is Lisp in C's clothing. -Douglas Crockford What does this mean for a game developer working with canvas and HTML5? I've been looking over this question on useful design patterns in gaming, but prototypal inheritance is very different than classical inheritance, and there are surely differences in the best way to apply some of these common patterns. For example, classical inheritance allows us to create a moveableEntity class, and extend that with any classes that move in our game world (player, monster, bullet, etc.). Sure, you can strongarm JavaScript to work that way, but in doing so, you are kind of fighting against its nature. Is there a better approach to this sort of problem when we have prototypal inheritance at our fingertips?

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• What light attenuation function does UDK use?

  - by ananamas

  I'm a big fan of the light attenuation in UDK. Traditionally I've always used the constant-linear-quadratic falloff function to control how "soft" the falloff is, which gives three values to play with. In UDK you can get similar results, but you only need to tweak one value: FalloffExponent. I'm interested in what the actual mathematical function here is. The UDK lighting reference describes it as follows: FalloffExponent: This allows you to modify the falloff of a light. The default falloff is 2. The smaller the number, the sharper the falloff and the more the brightness is maintained until the radius is reached. Does anyone know what it's doing behind the scenes?

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• How AlphaBlend Blendstate works in XNA when accumulighting light into a RenderTarget?

  - by cubrman

  I am using a Deferred Rendering engine from Catalin Zima's tutorial: His lighting shader returns the color of the light in the rgb channels and the specular component in the alpha channel. Here is how light gets accumulated: Game.GraphicsDevice.SetRenderTarget(LightRT); Game.GraphicsDevice.Clear(Color.Transparent); Game.GraphicsDevice.BlendState = BlendState.AlphaBlend; // Continuously draw 3d spheres with lighting pixel shader. ... Game.GraphicsDevice.BlendState = BlendState.Opaque; MSDN states that AlphaBlend field of the BlendState class uses the next formula for alphablending: (source × Blend.SourceAlpha) + (destination × Blend.InvSourceAlpha), where "source" is the color of the pixel returned by the shader and "destination" is the color of the pixel in the rendertarget. My question is why do my colors are accumulated correctly in the Light rendertarget even when the new pixels' alphas equal zero? As a quick sanity check I ran the following code in the light's pixel shader: float specularLight = 0; float4 light4 = attenuation * lightIntensity * float4(diffuseLight.rgb,specularLight); if (light4.a == 0) light4 = 0; return light4; This prevents lighting from getting accumulated and, subsequently, drawn on the screen. But when I do the following: float specularLight = 0; float4 light4 = attenuation * lightIntensity * float4(diffuseLight.rgb,specularLight); return light4; The light is accumulated and drawn exactly where it needs to be. What am I missing? According to the formula above: (source x 0) + (destination x 1) should equal destination, so the "LightRT" rendertarget must not change when I draw light spheres into it! It feels like the GPU is using the Additive blend instead: (source × Blend.One) + (destination × Blend.One)

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• Z Order in 2D with orthographic projection and texture atlas

  - by Carbon Crystal

  I am working with a 2D game in OpenGL ES and have a question about z-order together with a texture atlas. I am using an orthographic projection because I want pixel-perfect rendering of 2D sprites, however from what I can determine the draw order is really the only thing that will determine which textures (sprites) appear above or below their neighbors. That is, the "z-index" is a function of the order in which the textures are drawn as opposed to the z coordinate on the vertex array being drawn. So.. I have a texture atlas to save binding multiple textures for each draw call but this immediately creates a problem if there is more than one atlas in play. If I need to draw textures from more than one atlas (typically the case if I have too many sprites to fit in a single atlas of a reasonable size), then I can't maintain a "draw order" across atlases unless I want to bind/unbind the atlas textures more than once.. which kinda defeats the purpose. Does anyone have any clues as to what the best approach is here? Currently I'm running under an assumption that I will have to declare different fixed "depths" (e.g foreground, background etc) in my 2D scene and assume that the z-order for sprites at a given depth is the same. Then I can have as many atlases as I need at each depth and simply draw the depths in order (along with their associated atlases) I'd love to hear what other people are doing.

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• x axis detection issues platformer starter kit

  - by dbomb101

  I've come across a problem with the collision detection code in the platformer starter kit for xna.It will send up the impassible flag on the x axis despite being nowhere near a wall in either direction on the x axis, could someone could tell me why this happens ? Here is the collision method. /// <summary> /// Detects and resolves all collisions between the player and his neighboring /// tiles. When a collision is detected, the player is pushed away along one /// axis to prevent overlapping. There is some special logic for the Y axis to /// handle platforms which behave differently depending on direction of movement. /// </summary> private void HandleCollisions() { // Get the player's bounding rectangle and find neighboring tiles. Rectangle bounds = BoundingRectangle; int leftTile = (int)Math.Floor((float)bounds.Left / Tile.Width); int rightTile = (int)Math.Ceiling(((float)bounds.Right / Tile.Width)) - 1; int topTile = (int)Math.Floor((float)bounds.Top / Tile.Height); int bottomTile = (int)Math.Ceiling(((float)bounds.Bottom / Tile.Height)) - 1; // Reset flag to search for ground collision. isOnGround = false; // For each potentially colliding tile, for (int y = topTile; y <= bottomTile; ++y) { for (int x = leftTile; x <= rightTile; ++x) { // If this tile is collidable, TileCollision collision = Level.GetCollision(x, y); if (collision != TileCollision.Passable) { // Determine collision depth (with direction) and magnitude. Rectangle tileBounds = Level.GetBounds(x, y); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if (depth != Vector2.Zero) { float absDepthX = Math.Abs(depth.X); float absDepthY = Math.Abs(depth.Y); // Resolve the collision along the shallow axis. if (absDepthY < absDepthX || collision == TileCollision.Platform) { // If we crossed the top of a tile, we are on the ground. if (previousBottom <= tileBounds.Top) isOnGround = true; // Ignore platforms, unless we are on the ground. if (collision == TileCollision.Impassable || IsOnGround) { // Resolve the collision along the Y axis. Position = new Vector2(Position.X, Position.Y + depth.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } //This is the section which deals with collision on the x-axis else if (collision == TileCollision.Impassable) // Ignore platforms. { // Resolve the collision along the X axis. Position = new Vector2(Position.X + depth.X, Position.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } } } } // Save the new bounds bottom. previousBottom = bounds.Bottom; }

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• Illumination and Shading for computer graphics class

  - by Sam I Am

  I am preparing for my test tomorrow and this is one of the practice questions. I solved it partially but I am confused with the rest. Here is the problem: Consider a gray world with no ambient and specular lighting ( only diffuse lighting). The screen coordinates of a triangle P1,P2,P3, are P1=(100,100), P2= (300,150), P3 = (200, 200). The gray values at P!,P2,P3 are 1/2, 3/4, and 1/4 respectively. The light is at infinity and its direction and gray color are (1,1,1) and 1.0 respectively. The coefficients of diffused reflection is 1/2. The normals of P1,P2,P3 are N1= (0,0,1), N2 = (1,0,0), and N3 = (0,1,0) respectively. Consider the coordinates of three points P1,P2,P3 to be 0. Do not normalize the normals. I have computed that the illumination at the 3 vertices P1,P2,P3 is (1/4,3/8,1/8). Also I computed that interpolation coefficients of a point P inside the triangle whose coordinates are (220, 160) are given by (1/5,2/5,2/5). Now I have 4 more questions regarding this problem. 1) The illumination at P using Gouraud Shading is: i) 1/2 The answer is 1/2, but I have no idea how to compute it.. 2) The interpolated normal at P is given by i) (2/5, 2/5,1/5) ii) (1/2, 1/4, 1/4) iii) (3/5, 1/5, 1/5) 3) The interpolated color at P is given by: i) 1/2 Again, I know the correct answer but no idea how to solve it 4) The illumination at P using Phong Shading is i) 1/4 ii) 9/40 iii) 1/2

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