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Scaling along an arbitrary axis (Dealing with non-uniform scale)

- by Jon

I'm trying to build my own little engine to get more familiar with the concepts of 3D programming. I have a transform class that on each frame it creates a Scaling Matrix (S), a Rotation Matrix from a Quaternion (R) and concatenates them together (S*R). Once i have SR, I insert the translation values into the bottom of the three columns. So i end up with a transformation matrix that looks like: [SR SR SR 0] [SR SR SR 0] [SR SR SR 0] [tx ty tz 1] This works perfectly in all cases except when rotating an object that has a non-uniform scale. For example a unit cube with ScaleX = 4, ScaleY = 2, ScaleZ = 1 will give me a rectangular box that is 4 times as wide as the depth and twice as high as the depth. If i then translate this around, the box stays the same and looks normal. The problem happens whenever I try to rotate this scaled box. The shape itself becomes distorted and it appears as though the Scale factors are affecting the object on the World X,Y,Z axis rather than the local X,Y,Z axis of the object. I've done some pretty extensive research through a variety of textbooks (Eberly, Moller/Hoffman, Phar etc) and there isn't a ton there to go off of. Online, most of the answers say to avoid non-uniform scaling which I understand the desire to avoid it, but I'd still like to figure out how to support it. The only thing I can think off is that when constructing a Scale Matrix: [sx 0 0 0] [0 sy 0 0] [0 0 sz 0] [0 0 0 1] This is scaling along the World Axis instead of the object's local Direction, Up and Right vectors or it's local Z, Y, X axis. Does anyone have any tips or ideas on how to handle construction a transformation matrix that allows for non-uniform scaling and rotation? Thanks!

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Sorting objects before rendering

- by dreta

I'm trying to implement a scene graph and in all the articles i've come across there is talk about object sorting. So you'd sort your objects by "material" for example. Now untill i sat down and started implementing it, i kind of took this for granted, because it made sense. But now i'm wondering what does sorting actually change? In my engine, i have a manager for UBOs, i use those to store data that'll be shared between programs, at the moment that only involves time, camera and projection matrices and lights (i'm not worrying about managing which lights affect which objects ATM). Now for each model i have to change the model to world matrix uniform, no sorting is going to change that. So is the jump from changing this matrix to also setting a material for each object that bad? I vaguely remember reading somewhere that each time you change something in the pipeline, it has to get flushed and that can cause performance issues. But for each drawing call i'm setting up a model to world matrix anyway, so what sense does it make to ever be concerned about this? BTW is there any information about whether changing a uniform and calling glBufferSubData is more (or less) expensive.

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About online game servers and how to handle data

- by TreantBG

So my question isn't about what technology to use or how to do this or that, but a more general question. I'm currently developing a action third person shooter. With elements of RPG - weapon,armor upgrades and items. Players will be able to create new games or join old ones. So my question is how to create the game server that players will play in. I have two ideas on my mind. The player who made the game is the server. All data passes trough him and he send this data to the server updating the database of the players with their XP points kills/deaths score and other. Or my host machine is the server, the player who made the game just will open new instance on my host and will be like client. And all players send their input data to the host, the host updates the game and send response back to client for any new changes like where is the enemy and other. And if i choose option 1 is there a chance the host to change the game content and manipulate the game results? (I think there is but i'm not sure) And if i choose option 2 isn't that raising the response time and potentially the game lag? or maybe there is another option?

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Best peer-to-peer game architecture

- by Dejw

Consider a setup where game clients: have quite small computing resources (mobile devices, smartphones) are all connected to a common router (LAN, hotspot etc) The users want to play a multiplayer game, without an external server. One solution is to host an authoritative server on one phone, which in this case would be also a client. Considering point 1 this solution is not acceptable, since the phone's computing resources are not sufficient. So, I want to design a peer-to-peer architecture that will distribute the game's simulation load among the clients. Because of point 2 the system needn't be complex with regards to optimization; the latency will be very low. Each client can be an authoritative source of data about himself and his immediate environment (for example bullets.) What would be the best approach to designing such an architecture? Are there any known examples of such a LAN-level peer-to-peer protocol? Notes: Some of the problems are addressed here, but the concepts listed there are too high-level for me. Security I know that not having one authoritative server is a security issue, but it is not relevant in this case as I'm willing to trust the clients. Edit: I forgot to mention: it will be a rather fast-paced game (a shooter). Also, I have already read about networking architectures at Gaffer on Games.

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How to implement explosion in OpenGL with a particle effect?

- by Chan

I'm relatively new to OpenGL and I'm clueless how to implement explosion. So could anyone give me some ideas how to start? Suppose the explosion occurs at location $(x, y, z)$, then I'm thinking of randomly generate a collection of vectors with $(x, y, z)$ as origin, then draw some particle (glutSolidCube) which move along this vector for some period of time, says after 1000 updates, it disappear. Is this approach feasible? A minimal example would be greatly appreciated.

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Using SVN post-commit hook to update only files that have been commited

- by fondie

I am using an SVN repository for my web development work. I have a development site set up which holds a checkout of the repository. I have set up an SVN post-commit hook so that whenever a commit is made to the repository the development site is updated: cd /home/www/dev_ssl /usr/bin/svn up This works fine but due to the size of the repository the updates take a long time (approx. 3 minutes) which is rather frustrating when making regular commits. What I'd like is to change the post-commit hook to only update those files/directories that have been committed but I don't know how to go about doing this. Updating the "lowest common directory" would probably be the best solution, e.g. If committing the follow files: /branches/feature_x/images/logo.jpg /branches/feature_x/css/screen.css It would update the directory: /branches/feature_x/ Can anyone help me create a solution that achieves this please? Thanks! Update: The repository and development site are located on the same server so network issues shouldn't be involved. CPU usage is very low, and I/O should be ok (it's running on hi-spec dedicated server) The development site is approx. 7.5GB in size and contains approx. 600,000 items, this is mainly due to having multiple branches/tags

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Slerping rotation mirrors

- by Esa

I rotate my game character to watch at the target using the following code: transform.rotation = Quaternion.Slerp(startQuaternion, lookQuaternion, turningNormalizer*turningSpeed/10f) startQuaternion is the character's current rotation when a new target is given. lookQuaternion is the direction the character should look at and it's set like this: destinationVector = currentWaypoint.transform.position - transform.position; lookQuaternion = Quaternion.LookRotation(destinationVector, Vector3.up); turningNormalizer is just Time.deltaTime incremented and turningSpeed is a static value given in the editor. The problem is that while the character turns as it should most of the time, it has problems when it has to do close to 180 degrees. Then it at times jitters and mirrors the rotation: In this poorly drawn image the character(on the right) starts to turn towards the circle on the left. Instead of just turning either through left or right it starts this "mirror dance": It starts to rotate towards the new facing Then it suddenly snaps to the same angle but on other side and keeps rotating It does this "mirroring" so long until it looks at the target. Is this a thing with quaternions, slerping/lerping or something else?

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How do client-server cooperation based games like Diablo 3 work?

- by edgar

Diablo 3 cooperates with Blizzard servers even during single player games. In fact, Blizzard has had problems with the games "melting their servers." I would like to ask: How do the client and the server communicate? What details does the client leave to the server, and vice versa? What details are redundant - both the client and the server know - and how often do they disagree? The previous paragraph contains the important questions, but I have a few more that I must explain my motivation towards. I am interested in the programming of botting. Ethical botting - I don't plan on actually abusing the automation to run 24/7. I just find it to be a great programming challenge to glean information from a game, and then make decisions from that information. I am stuck in the starting gate. The unofficial questions from this post would be: How can I make a bot (language, tools, libraries)? Can I get information through the communication between client and server, rather than the brute force pixel detection easily used in more static games? There probably is a trust issue, and to that all I can say is that I promise not to abuse the answers. But please feel free to answer any of the questions you feel comfortable with. Thank you!

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Show path of a body of where it should go after linear impulse is applied

- by Farooq Arshed

I am making a game with Andengine and Box2D. I have a dynamic body and I apply linear impulse on the body to move it around when the user have touched the screen. Now I want to show the path where the body will go when the user have touched. If you have played Angry Birds or Basket Ball Shoot or any other which have projectile motion with a path shown you will get my point. I want to show the white dots which are shown in those games.

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Behaviour tree code example?

- by jokoon

http://altdevblogaday.org/2011/02/24/introduction-to-behavior-trees/ Obviously the most interesting article I found on this website. What do you think about it ? It lacks some code example, don't you know any ? I also read that state machines are not very flexible compared to behaviour trees... On top of that I'm not sure if there is a true link between state machines and the state pattern... is there ?

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How do I prevent my platformer's character from clipping on wall tiles?

- by Jonathan Hobbs

Currently, I have a platformer with tiles for terrain (graphics borrowed from Cave Story). The game is written from scratch using XNA, so I'm not using an existing engine or physics engine. The tile collisions are described pretty much exactly as described in this answer (with simple SAT for rectangles and circles), and everything works fine. Except when the player runs into a wall whilst falling/jumping. In that case, they'll catch on a tile and begin thinking they've hit a floor or ceiling that isn't actually there. The player is moving right and falling downwards. So after movement, collisions are checked - and first, it turns out the player character is colliding with the tile 3rd from the floor, and pushed upwards. Second, he's found to be colliding with the tile beside him, and pushed sideways - the end result being the player character thinks he's on the ground and isn't falling, and 'catches' on the tile for as long as he's running into it. I could solve this by defining the tiles from top to bottom instead, which makes him fall smoothly, but then the inverse case happens and he'll hit a ceiling that isn't there when jumping upwards against the wall. How should I approach resolving this, so that the player character can just fall along the wall as it should?

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How do I set an event off when player is on certain tile?

- by Tom Burman

Here is the code I use to create and print my map to the canvas: var board = []; function loadMap(map) { if (map == 1) { return [ [2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,3,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,3,3,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,3,0,0,2], [2,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,3,3,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,3,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,3,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,3,0,3,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,3,3,3,3,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,2], 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[2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,3,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,3,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,3,3,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,3,3,3,3,3,3,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,3,3,3,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2], [2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2] ]; } } board = loadMap(1); enterfor (y = 0; y <= viewHeight; y++) { for (x = 0; x <= viewWidth; x++) { var theX = x * 32; var theY = y * 32; context.drawImage(mapTiles[board[y+viewY][x+viewX]], theX, theY, 32, 32); } } And here is the code I use for player movement: canvas.addEventListener('keydown', function(e) { console.log(e); var key = null; switch (e.which) { case 37: // Left if (playerX > 0) playerX--; break; case 38: // Up if (playerY > 0) playerY--; break; case 39: // Right if (playerX < worldWidth) playerX++; break; case 40: // Down if (playerY < worldHeight) playerY++; break; } viewX = playerX - Math.floor(0.5 * viewWidth); if (viewX < 0) viewX = 0; if (viewX+viewWidth > worldWidth) viewX = worldWidth - viewWidth; viewY = playerY - Math.floor(0.5 * viewHeight); if (viewY < 0) viewY = 0; if (viewY+viewHeight > worldHeight) viewY = worldHeight - viewHeight; }, false); What I am looking for is a method for when the player lands on tile 3 he loses health. I have tried to use this in the player movement but it doesnt seem to work e.g the left movement: case 37: // Left if (playerX > 0) playerX--; if(board[x2 - 1] == 3) { health--; playerX--; }

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Displaying and updating score in Android (OpenGL ES 2)

- by user16547

I'm using a FrameLayout where I have a GLSurfaceView at the bottom and a few Views on top of it. One of those Views is a TextView that displays the current score. Here's how I'm updating the score TextView based on what happens in my game loop: whenever an event happens that increases the score, I call activity.runOnUiThread(updater), where activity is the activity that has the above FrameLayout (my main game activity) and updater is just a Runnable that increments the score. From my understanding, using runOnUiThread() from the OpenGL thread is standard practice - otherwise you'll get an exception, I can't remember its name. The problem is that there's a very noticeable lag between the event and the score update. For example the character gets a coin, but the coin count is not updated quickly. I tried summing all the score events from my game loop and calling runOnUiThread() only once per loop, but it doesn't seem to make much of a difference - the lag is still noticeable. How can I improve my design to avoid this lag?

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Physic engine for snooker/billard game

- by Marc Gillé

I think most billard/snooker games have a lot of problems with their physic engines. They are far away from realistic and you can't really enjoy the game (especially when snooker is your hobby :) ) So I want to try to make an own physic engine (and own snooker game). I think the physic engine is the most important part of such a game. So my question is: Do anybody know an open physic enginge I can start with? Is there any literature about such physic problems?

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Android: Layouts and views or a single full screen custom view?

- by futlib

I'm developing an Android game, and I'm making it so that it can run on low end devices without GPU, so I'm using the 2D API. I have so far tried to use Android's mechanisms such as layouts and activities where possible, but I'm beginning to wonder if it's not easier to just create a single custom view (or one per activity) and do all the work there. Here's an example of how I currently do things: I'm using a layout to display the game's background as an image view and the square game area, which is a custom view, centered in the middle. What would you say? Should I continue to use layouts where possible or is it more common/reasonable to just use a large custom view? I'm thinking that this would probably also make it easier to port my code to other platforms.

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Calculate the intersection depth between a rectangle and a right triangle

- by Celarix

all. I'm working on a 2D platformer built in C#/XNA, and I'm having a lot of problems calculating the intersection depth between a standard rectangle (used for sprites) and a right triangle (used for sloping tiles). Ideally, the rectangle will collide with the solid edges of the triangle, and its bottom-center point will collide with the sloped edge. I've been fighting with this for a couple of days now, and I can't make sense of it. So far, the method detects intersections (somewhat), but it reports wildly wrong depths. How does one properly calculate the depth? Is there something I'm missing? Thanks!

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Best way to blend colors in tile lighting? (XNA)

- by Lemoncreme

I have made a color, decent, recursive, fast tile lighting system in my game. It does everything I need except one thing: different colors are not blended at all: Here is my color blend code: return (new Color( (byte)MathHelper.Clamp(color.R / factor, 0, 255), (byte)MathHelper.Clamp(color.G / factor, 0, 255), (byte)MathHelper.Clamp(color.B / factor, 0, 255))); As you can see it does not take the already in place color into account. color is the color of the previous light, which is weakened by the above code by factor. If I wanted to blend using the color already in place, I would use the variable blend. Here is an example of a blend that I tried that failed, using blend: return (new Color( (byte)MathHelper.Clamp(((color.R + blend.R) / 2) / factor, 0, 255), (byte)MathHelper.Clamp(((color.G + blend.G) / 2) / factor, 0, 255), (byte)MathHelper.Clamp(((color.B + blend.B) / 2) / factor, 0, 255))); This color blend produces inaccurate and strange results. I need a blend that is accurate, like the first example, that blends the two colors together. What is the best way to do this?

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why are my players drawn to the side of my viewport

- by Jetbuster

Following this admittedly brilliant and clean 2d camera class I have a camera on each player, and it works for multiplayer and i've divided the screen into two sections for split screen by giving each camera a viewport. However in the game it looks like this I'm not sure if thats their position relative to the screen or what The relevant gameScreen code, the makePlayers is setup so it could theoretically work for up to 4 players private void makePlayers() { int rowCount = 1; if (NumberOfPlayers > 2) rowCount = 2; players = new Player[NumberOfPlayers]; for (int i = 0; i < players.Length; i++) { int xSize = GameRef.Window.ClientBounds.Width / 2; int ySize = GameRef.Window.ClientBounds.Height / rowCount; int col = i % rowCount; int row = i / rowCount; int xPoint = 0 + xSize * row; int yPoint = 0 + ySize * col; Viewport viewport = new Viewport(xPoint, yPoint, xSize, ySize); Vector2 playerPosition = new Vector2(viewport.TitleSafeArea.X + viewport.TitleSafeArea.Width / 2, viewport.TitleSafeArea.Y + viewport.TitleSafeArea.Height / 2); players[i] = new Player(playerPosition, playerSprites[i], GameRef, viewport); } //players[1].Keyboard = true; } public override void Draw(GameTime gameTime) { base.Draw(gameTime); foreach (Player player in players) { GraphicsDevice.Viewport = player.PlayerCamera.ViewPort; GameRef.spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.PointClamp, null, null, null, player.PlayerCamera.Transform); map.Draw(GameRef.spriteBatch); // Draw the Player player.Draw(GameRef.spriteBatch); // Draw UI screen elements GraphicsDevice.Viewport = Viewport; ControlManager.Draw(GameRef.spriteBatch); GameRef.spriteBatch.End(); } } the player's initialize and draw methods are like so internal void Initialize() { this.score = 0; this.angle = (float)(Math.PI * 0 / 180);//Start sprite at it's default rotation int width = utils.scaleInt(picture.Width, imageScale); int height = utils.scaleInt(picture.Height, imageScale); this.hitBox = new HitBox(new Vector2(centerPos.X - width / 2, centerPos.Y - height / 2), width, height, Color.Black, game.Window.ClientBounds); playerCamera.Initialize(); } #region Methods public void Draw(SpriteBatch spriteBatch) { //Console.WriteLine("Hitbox: X({0}),Y({1})", hitBox.Points[0].X, hitBox.Points[0].Y); //Console.WriteLine("Image: X({0}),Y({1})", centerPos.X, centerPos.Y); Vector2 orgin = new Vector2(picture.Width / 2, picture.Height / 2); hitBox.Draw(spriteBatch); utils.DrawCrosshair(spriteBatch, Position, game.Window.ClientBounds, Color.Red); spriteBatch.Draw(picture, Position, null, Color.White, angle, orgin, imageScale, SpriteEffects.None, 0.1f); } as I said I think I'm gonna need to do something with the render position but I'm to entirely sure what or how it would be elegant to say the least

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Suggestions to start a cross-platform project

- by Gabriele

I have a big project in my head, it should be cross-platform (Win, Max and Linux), online (Client - Server) and with 3D graphics. I would like some suggestions to start with the right things. Currently I'm a PHP/MySQL coder, I used to code in C and Pascal on DOS ages (Borland Times ;)), my C knowlegde need a refresh but it's ok. I guess C++ it's the right language. What platform and what i should use to code? I can choose from all three platforms. My idea was to use Visual Studio 2010 C++, but i'm not sure if it support Native code. What kind of libraries should i use? I guessed OpenSSL for the login, OpenGL for graphics part. For the Audio or the GUI? Any other suggestions are well accepted. I know it's a "BIG DEAL" but I have no rush and it'll be a free-time project, only for my pleasure. Thank you in advance.

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My rhythm game runs choppy even with high frame rate

- by felipedrl

I'm coding a rhythm game and the game runs smoothly with uncapped fps. But when I try to cap it around 60 the game updates in little chunks, like hiccups, as if it was skipping frames or at a very low frame rate. The reason I need to cap frame rate is because in some computers I tested, the fps varies a lot (from ~80 - ~250 fps) and those drops are noticeable and degrade response time. Since this is a rhythm game this is very important. This issue is driving me crazy. I've spent a few weeks already on it and still can't figure out the problem. I hope someone more experienced than me could shed some light on it. I'll try to put here all the hints I've tried along with two pseudo codes for game loops I tried, so I apologize if this post gets too lengthy. 1st GameLoop: const uint UPDATE_SKIP = 1000 / 60; uint nextGameTick = SDL_GetTicks(); while(isNotDone) { // only false when a QUIT event is generated! if (processEvents()) { if (SDL_GetTicks() > nextGameTick) { update(UPDATE_SKIP); render(); nextGameTick += UPDATE_SKIP; } } } 2nd Game Loop: const uint UPDATE_SKIP = 1000 / 60; while (isNotDone) { LARGE_INTEGER startTime; QueryPerformanceCounter(&startTime); // process events will return false in case of a QUIT event processed if (processEvents()) { update(frameTime); render(); } LARGE_INTEGER endTime; do { QueryPerformanceCounter(&endTime); frameTime = static_cast<uint>((endTime.QuadPart - startTime.QuadPart) * 1000.0 / frequency.QuadPart); } while (frameTime < UPDATE_SKIP); } [1] At first I thought it was a timer resolution problem. I was using SDL_GetTicks, but even when I switched to QueryPerformanceCounter, supposedly less granular, I saw no difference. [2] Then I thought it could be due to a rounding error in my position computation and since game updates are smaller in high FPS that would be less noticeable. Indeed there is an small error, but from my tests I realized that it is not enough to produce the position jumps I'm getting. Also, another intriguing factor is that if I enable vsync I'll get smooth updates @60fps regardless frame cap code. So why not rely on vsync? Because some computers can force a disable on gfx card config. [3] I started printing the maximum and minimum frame time measured in 1sec span, in the hope that every a few frames one would take a long time but still not enough to drop my fps computation. It turns out that, with frame cap code I always get frame times in the range of [16, 18]ms, and still, the game "does not moves like jagger". [4] My process' priority is set to HIGH (Windows doesn't allow me to set REALTIME for some reason). As far as I know there is only one thread running along with the game (a sound callback, which I really don't have access to it). I'm using AudiereLib. I then disabled Audiere by removing it from the project and still got the issue. Maybe there are some others threads running and one of them is taking too long to come back right in between when I measured frame times, I don't know. Is there a way to know which threads are attached to my process? [5] There are some dynamic data being created during game run. But It is a little bit hard to remove it to test. Maybe I'll have to try harder this one. Well, as I told you I really don't know what to try next. Anything, I mean, anything would be of great help. What bugs me more is why at 60fps & vsync enabled I get an smooth update and at 60fps & no vsync I don't. Is there a way to implement software vsync? I mean, query display sync info? Thanks in advance. I appreciate the ones that got this far and yet again I apologize for the long post. Best Regards from a fellow coder.

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Drawing texture does not work anymore with a small amount of triangles

- by Paul

When i draw lines, the vertices are well connected. But when i draw the texture inside the triangles, it only works with i<4 in the for loop, otherwise with i<5 for example, there is a EXC_BAD_ACCESS message, at @synthesize textureImage = _textureImage. I don't understand why. (The generatePolygons method seems to work fine as i tried to draw lines with many vertices as in the second image below. And textureImage remains the same for i<4 or i<5 : it's a 512px square image). Here are the images : What i want to achieve is to put the red points and connect them to the y-axis (the green points) and color the area (the green triangles) : If i only draw lines, it works fine : Then with a texture color, it works for i<4 in the loop (the red points in my first image, plus the fifth one to connect the last y) : But then, if i set i<5, the debug tool says EXC_BAD_ACCESS at the synthesize of _textureImage. Here is my code : I set a texture color in HelloWordLayer.mm with : CCSprite *textureImage = [self spriteWithColor:color3 textureSize:512]; _terrain.textureImage = textureImage; Then in the class Terrain, i create the vertices and put the texture in the draw method : @implementation Terrain @synthesize textureImage = _textureImage; //EXC_BAD_ACCESS for i<5 - (void)generatePath2{ CGSize winSize = [CCDirector sharedDirector].winSize; float x = 40; float y = 0; for(int i = 0; i < kMaxKeyPoints+1; ++i) { _hillKeyPoints[i] = CGPointMake(x, y); x = 150 + (random() % (int) 30); y += 30; } } -(void)generatePolygons{ _nPolyVertices = 0; float x1 = 0; float y1 = 0; int keyPoints = 0; for (int i=0; i<4; i++){ /* HERE : 4 = OK / 5 = crash */ //V0: at (0,0) _polyVertices[_nPolyVertices] = CGPointMake(x1, y1); _polyTexCoords[_nPolyVertices++] = CGPointMake(x1, y1); //V1: to the first "point" _polyVertices[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices++] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); keyPoints++; //from point at index 0 to 1 //V2, same y as point n°2: _polyVertices[_nPolyVertices] = CGPointMake(0, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices++] = CGPointMake(0, _hillKeyPoints[keyPoints].y); //V1 again _polyVertices[_nPolyVertices] = _polyVertices[_nPolyVertices-2]; _polyTexCoords[_nPolyVertices++] = _polyVertices[_nPolyVertices-2]; //V2 again _polyVertices[_nPolyVertices] = _polyVertices[_nPolyVertices-2]; _polyTexCoords[_nPolyVertices++] = _polyVertices[_nPolyVertices-2]; //V3 = same x,y as point at index 1 _polyVertices[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); y1 = _polyVertices[_nPolyVertices].y; _nPolyVertices++; } } - (id)init { if ((self = [super init])) { [self generatePath2]; [self generatePolygons]; } return self; } - (void) draw { //glDisable(GL_TEXTURE_2D); glDisableClientState(GL_COLOR_ARRAY); glDisableClientState(GL_TEXTURE_COORD_ARRAY); glBindTexture(GL_TEXTURE_2D, _textureImage.texture.name); glColor4f(1, 1, 1, 1); glVertexPointer(2, GL_FLOAT, 0, _polyVertices); glTexCoordPointer(2, GL_FLOAT, 0, _polyTexCoords); glDrawArrays(GL_TRIANGLE_STRIP, 0, (GLsizei)_nPolyVertices); glColor4f(1, 1, 1, 1); for(int i = 1; i < 40; ++i) { ccDrawLine(_polyVertices[i-1], _polyVertices[i]); } // restore default GL states glEnable(GL_TEXTURE_2D); glEnableClientState(GL_COLOR_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); } Do you see anything wrong in this code? Thanks for your help

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What data should be cached in a multiplayer server, relative to AI and players?

- by DevilWithin

In a virtual place, fully network driven, with an arbitrary number of players and an arbitrary number of enemies, what data should be cached in the server memory, in order to optimize smooth AI simulation? Trying to explain, lets say player A sees player B to E, and enemy A to G. Each of those players, see player A, but not necessarily each other. Same applies to enemies. Think of this question from a topdown perspective please. In many cases, for example, when a player shoots his gun, the server handles the sound as a radial "signal" that every other entity within reach "hear" and react upon. Doing these searches all the time for a whole area, containing possibly a lot of unrelated players and enemies, seems to be an issue, when the budget for each AI agent is so small. Should every entity cache whatever enters and exits from its radius of awareness? Is there a great way to trace the entities close by without flooding the memory with such caches? What about other AI related problems that may arise, after assuming the previous one works well? We're talking about environments with possibly hundreds of enemies, a swarm.

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Quaternion LookAt for camera

- by Homar

I am using the following code to rotate entities to look at points. glm::vec3 forwardVector = glm::normalize(point - position); float dot = glm::dot(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector); float rotationAngle = (float)acos(dot); glm::vec3 rotationAxis = glm::normalize(glm::cross(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector)); rotation = glm::normalize(glm::quat(rotationAxis * rotationAngle)); This works fine for my usual entities. However, when I use this on my Camera entity, I get a black screen. If I flip the subtraction in the first line, so that I take the forward vector to be the direction from the point to my camera's position, then my camera works but naturally my entities rotate to look in the opposite direction of the point. I compute the transformation matrix for the camera and then take the inverse to be the View Matrix, which I pass to my OpenGL shaders: glm::mat4 viewMatrix = glm::inverse( cameraTransform->GetTransformationMatrix() ); The orthographic projection matrix is created using glm::ortho. What's going wrong?

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Delaying a Foreach loop half a second

- by Sigh-AniDe

I have created a game that has a ghost that mimics the movement of the player after 10 seconds. The movements are stored in a list and i use a foreach loop to go through the commands. The ghost mimics the movements but it does the movements way too fast, in split second from spawn time it catches up to my current movement. How do i slow down the foreach so that it only does a command every half a second? I don't know how else to do it. Please help this is what i tried : The foreach runs inside the update method DateTime dt = DateTime.Now; foreach ( string commandDirection in ghostMovements ) { int mapX = ( int )( ghostPostition.X / scalingFactor ); int mapY = ( int )( ghostPostition.Y / scalingFactor ); // If the dt is the same as current time if ( dt == DateTime.Now ) { if ( commandDirection == "left" ) { switch ( ghostDirection ) { case ghostFacingUp: angle = 1.6f; ghostDirection = ghostFacingRight; Program.form.direction = ""; dt.AddMilliseconds( 500 );// add half a second to dt break; case ghostFacingRight: angle = 3.15f; ghostDirection = ghostFacingDown; Program.form.direction = ""; dt.AddMilliseconds( 500 ); break; case ghostFacingDown: angle = -1.6f; ghostDirection = ghostFacingLeft; Program.form.direction = ""; dt.AddMilliseconds( 500 ); break; case ghostFacingLeft: angle = 0.0f; ghostDirection = ghostFacingUp; Program.form.direction = ""; dt.AddMilliseconds( 500 ); break; } } } }

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How to procedurally (create) grow an artistic (2D) tree in real-time (L-System?).

- by lalan

Recently I programmed an L-system module, It got me interested further. I am a Plants vs Zombies junkie as well, really liked the concept of Tree of Wisdom. Would love to create similar procedural art just for fun and learn more. Question: How should I approach the process of creating an artistic tree (2d perhaps with fixed camera/perspective) dynamically? Ideally I would like to start with a plant (only a stem with a leaf) and grow it dynamically using some influence (input/user action) over its structure. These influences may result in different type of branching, curves in branches, its spread, location of fruits, color of flowers, etc. Want it to be really full of life/spirit. :) Plants vs Zombies: Tree of wisdom It would be great to dynamically grow a similar tree, but with lot more variation and animations happening. My Background: Student / Programmer, have used few game engines (Ogre3d, cocos2d, unity). Haven't really programmed directly using openGL, trying to fix that :). I am ready to spend considerable time, Please let me know about the APIs? and how would an expert like you would take on this problem? Why 2D? I think it's easier to solve the problem only considering 2 dimensions. Artistic inspirations: Only the tree, with fruits and leaves, without the shrubs at the bottom The large tree (visible branches, green leaves, flowers, fruits, etc) on the left, behind monkey. PixelJunk's Eden (Art style inspiration). Procedurally Generated Apple Tree using Fractals Please let me know if it was easy for you to understand the question, I may elaborate further. I hope a discussion of various approach would be helpful for everyone. You guys are awesome.

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