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• How to properly do weapon cool-down reload timer in multi-player laggy environment?

  - by John Murdoch

  I want to handle weapon cool-down timers in a fair and predictable way on both client on server. Situation: Multiple clients connected to server, which is doing hit detection / physics Clients have different latency for their connections to server ranging from 50ms to 500ms. They want to shoot weapons with fairly long reload/cool-down times (assume exactly 10 seconds) It is important that they get to shoot these weapons close to the cool-down time, as if some clients manage to shoot sooner than others (either because they are "early" or the others are "late") they gain a significant advantage. I need to show time remaining for reload on player's screen Clients can have clocks which are flat-out wrong (bad timezones, etc.) What I'm currently doing to deal with latency: Client collects server side state in a history, tagged with server timestamps Client assesses his time difference with server time: behindServerTimeNs = (behindServerTimeNs + (System.nanoTime() - receivedState.getServerTimeNs())) / 2 Client renders all state received from server 200 ms behind from his current time, adjusted by what he believes his time difference with server time is (whether due to wrong clocks, or lag). If he has server states on both sides of that calculated time, he (mostly LERP) interpolates between them, if not then he (LERP) extrapolates. No other client-side prediction of movement, e.g., to make his vehicle seem more responsive is done so far, but maybe will be added later So how do I properly add weapon reload timers? My first idea would be for the server to send each player the time when his reload will be done with each world state update, the client then adjusts it for the clock difference and thus can estimate when the reload will be finished in client-time (perhaps considering also for latency that the shoot message from client to server will take as well?), and if the user mashes the "shoot" button after (or perhaps even slightly before?) that time, send the shoot event. The server would get the shoot event and consider the time shot was made as the server time when it was received. It would then discard it if it is nowhere near reload time, execute it immediately if it is past reload time, and hold it for a few physics cycles until reload is done in case if it was received a bit early. It does all seem a bit convoluted, and I'm wondering whether it will work (e.g., whether it won't be the case that players with lower ping get better reload rates), and whether there are more elegant solutions to this problem.

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• Sprite transparency not effected libGDX

  - by Aon GoltzCrank

  I am making a game using libGDX and Tween Universal Engine. My problem is as follows: I have 2 screens so fars, a splash screen with the logo, and a second one which is the main menu. In the splash screen I use a SpriteBatch and a Sprite with the Texture of the image I want (which goes through some scaling.) Now I use the Tween engine, along with a created SpriteAccessor to control the alpha of the sprite. I fade the picture in, then fade it out, then change it to the next screen. In the next screen I have a single sprite, and a single, 3 slot, sprite array. In this screen I also use the tween engine, I fade the single sprite into the screen (it's the background image) then I try to, using the same method, (Tween.to) to change the alpah of the sprite array (each sprite by itself.), I first set it to 0 using Tween.set, then using the method I change it. This didn't work, after some tests I tried setting the alpha of a single sprite from the array to 0, and that didn't work. It's like the program is ignoring the alpha value, I even printed out the alpha value, it saying 0, but the sprite is visible. How can I fix this, or why might it be caused?

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• How do I draw video frames onto the screen permanently using XNA?

  - by izb

  I have an app that plays back a video and draws the video onto the screen at a moving position. When I run the app, the video moves around the screen as it plays. Here is my Draw method... protected override void Draw(GameTime gameTime) { Texture2D videoTexture = null; if (player.State != MediaState.Stopped) videoTexture = player.GetTexture(); if (videoTexture != null) { spriteBatch.Begin(); spriteBatch.Draw( videoTexture, new Rectangle(x++, 0, 400, 300), /* Where X is a class member */ Color.White); spriteBatch.End(); } base.Draw(gameTime); } The video moves horizontally acros the screen. This is not exactly as I expected since I have no lines of code that clear the screen. My question is why does it not leave a trail behind? Also, how would I make it leave a trail behind?

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• Google Cloud Messaging (GCM) for turn-based mobile multiplayer server?

  - by Chris

  I'm designing a multiplayer turn-based game for Android (over 3g). I'm thinking the clients will send data to a central server over a socket or http, and receive data via GCM push messaging. I'd like to know if anyone has practical experience with GCM for pushing 'real-time' turn data to game clients. What kind of performance and limitations does it have? I'm also considering using a RESTful approach with GAE or Amazon EC2. Any advice about these approaches is appreciated.

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• Beginner question about vertex arrays in OpenGL

  - by MrDatabase

  Is there a special order in which vertices are entered into a vertex array? Currently I'm drawing single textures like this: glBindTexture(GL_TEXTURE_2D, texName); glVertexPointer(2, GL_FLOAT, 0, vertices); glTexCoordPointer(2, GL_FLOAT, 0, coordinates); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); where vertices has four "xy pairs". This is working fine. As a test I doubled the sizes of the vertices and coordinates arrays and changed the last line above to: glDrawArrays(GL_TRIANGLE_STRIP, 0, 8); since vertices now contains eight "xy pairs". I do see two textures (the second is intentionally offset from the first). However the textures are now distorted. I've tried passing GL_TRIANGLES to glDrawArrays instead of GL_TRIANGLE_STRIP but this doesn't work either. I'm so new to OpenGL that I thought it's best to just ask here :-) Cheers!

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• How to code Time Stop or Bullet Time in a game?

  - by David Miler

  I am developing a single-player RPG platformer in XNA 4.0. I would like to add an ability that would make the time "stop" or slow down, and have only the player character move at the original speed(similar to the Time Stop spell from the Baldur's Gate series). I am not looking for an exact implementation, rather some general ideas and design-patterns. EDIT: Thanks all for the great input. I have come up with the following solution public void Update(GameTime gameTime) { GameTime newGameTime = new GameTime(gameTime.TotalGameTime, new TimeSpan(gameTime.ElapsedGameTime.Ticks / DESIRED_TIME_MODIFIER)); gameTime = newGameTime; or something along these lines. This way I can set a different time for the player component and different for the rest. It certainly is not universal enough to work for a game where warping time like this would be a central element, but I hope it should work for this case. I kinda dislike the fact that it litters the main Update loop, but it certainly is the easiest way to implement it. I guess that is essentialy the same as tesselode suggested, so I'm going to give him the green tick :)

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• how to transform child elements position into a world position

  - by MrGreg

  So Im making a 2d space game and I have a bunch of spaceships that have turrets. Objects have a position and orientation, the ships being in world coordinates while the turrets are children and coordinates are relative to their parents. How do I efficiently calculate the position of a turret in world coordinates (i.e. when it fires and I need to know where to place a bullet in the world)? Calculating the turrets orientation is trivial - I just add the turrets relative angle to its parents. For position though, I guess I could do a bunch of trigonometry but this MUST be a common problem with a good/fast general solution? Should I be relearning how to do matrix math again? :) btw - Im creating the game in javascript+canvas but its the math/algorithm im interested in here Cheers, Greg

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• 2D camera perspective projection from 3D coordinates -- HOW?

  - by Jack

  I am developing a camera for a 2D game with a top-down view that has depth. It's almost a 3D camera. Basically, every object has a Z even though it is in 2D, and similarly to parallax layers their position, scale and rotation speed vary based on their Z. I guess this would be a perspective projection. But I am having trouble converting the objects' 3D coordinates into the 2D space of the screen so that everything has correct perspective and scale. I never learned matrices though I did dig the topic a bit today. I tried without using matrices thanks to this article but every attempt gave awkward results. I'm using ActionScript 3 and Flash 11+ (Starling), where the screen coordinates work like this: Left-handed coordinates system illustration I can explain further what I did if you want to help me sort out what's wrong, or you can directly tell me how you would do it properly. In case you prefer the former, read on. These are images showing the formulas I used: upload.wikimedia.org/math/1/c/8/1c89722619b756d05adb4ea38ee6f62b.png upload.wikimedia.org/math/d/4/0/d4069770c68cb8f1aa4b5cfc57e81bc3.png (Sorry new users can't post images, but both are from the wikipedia article linked above, section "Perspective projection". That's where you'll find what all variables mean, too) The long formula is greatly simplified because I believe a normal top-down 2D camera has no X/Y/Z rotation values (correct ?). Then it becomes d = a - c. Still, I can't get it to work. Maybe you could explain what numbers I should put in a(xyz), c(xyz), theta(xyz), and particularly, e(xyz) ? I don't quite get how e is different than c in my case. c.z is also an issue to me. If the Z of the camera's target object is 0, should the camera's Z be something like -600 ? ( = focal length of 600) Whatever I do, it's wrong. I only got it to work when I used arbitrary calculations that "looked" right, like most cameras with parallax layers seem to do, but that's fake! ;) If I want objects to travel between Z layers I might as well do it right. :) Thanks a lot for your help!

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• Which Graphics/Geometry abstraction to choose?

  - by Robz

  I've been thinking about the design for a browser app on the HTML5 canvas that simulates a 2D robot zooming around, sensing the world around it. I decided to do this from scratch just for fun. I need shapes, like polygons, circles, and lines in order to model the robot and the world it lives in. These shapes need to be drawn with different appearance attributes, like border/fill style/width/color. I also need to have geometry functions to detect intersections and containment for the robot's sensors and so that the robot doesn't go inside stuff. One idea for functions is to have two totally separate libraries, one to implement graphics (like drawShape(context, shape)) and one for geometry operations (like shapeIntersectsShape(shape1, shape2)). Or, in a more object-oriented approach, the shape objects themselves could implement methods to do their own graphics (shape.draw(context)) and geometry operations (shape1.intersects(shape2)). Then there is the data itself: whether the data to draw a shape and the data to do geometric operations on that shape should be encapsulated within the same object, or be separate structures (where one would contain the other, or both be contained inside another structure). How do existing applications that do graphics/geometry stuff deal with this? Is there one model that is best, or is each good for certain applications? Should the fact that I'm using Javascript instead of a more classical language change how I approach the design?

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• Where to start learning OpenGL with C++?

  - by NERDcustard

  I'm 16 years old and my name is Norbert. I have learnt C++ and made some cool text based games and such but I would love to start graphic's programming. I'm a decent artiest (I will have some of my work bellow) I know the base of C++ but I really would like to get into OpenGL. I need someone to show me some good tutorials for OpenGl with C++ so I can really get into game dev. My goal is to be able to program a simple 2d game by the end of the year and I have lots of time to do so. I'm en-rolled in a game dev next year and really need some help with starting off. http://imgur.com/QZjKX http://imgur.com/3CZy7

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• Best way to load rigid bodies from file

  - by Mel

  I'm trying to switch to bullet for physics simulation. Lemme just say first that I am so pleased with bullet's accuracy and performance. After messing around it for a bit, I'm now trying to load rigid bodies from files. Most of my models are in blender and with some searching, I was able to export them in .bullet format. However, loading the files into bullet doesn't look like an easy task. I've come across this page that points me to a sample application that loads bullet files. But then it goes and says that this loader is just a starting point. Is there any open source library out there that will allow me to load rigid bodies from a file? I don't really wanna spend that much time trying to create my own loader.

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• How to emulate Mode 13h in a modern 3D renderer?

  - by David Gouveia

  I was indulging in nostalgia and remembered the first game I created, which used Mode 13h. This mode was really simple to work with, since it was essentially just an array of bytes with an element for each pixel on the screen (using an indexed color scheme). So I thought it might be fun to create something nowadays under these restrictions, but on modern hardware. The API could be as simple as: public class Mode13h { public byte[] VideoMemory = new byte[320 * 200]; public Color[] Palette = new Color[256]; } Now I'm wondering what would be the best way to get this data on the screen, using something like XNA / DirectX / OpenGL. The only solution I could think of was to create a texture with the same size as the VideoMemory array, write the contents of VideoMemory to it every frame, then render that texture in a full screen quad with the correct aspect ratio and using point texture filtering for that retro look. Is there a better way?

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• Implementing Circle Physics in Java

  - by Shijima

  I am working on a simple physics based game where 2 balls bounce off each other. I am following a tutorial, 2-Dimensional Elastic Collisions Without Trigonometry, for the collision reactions. I am using Vector2 from the LIBGDX library to handle vectors. I am a bit confused on how to implement step 6 in Java from the tutorial. Below is my current code, please note that the code strictly follows the tutorial and there are redundant pieces of code which I plan to refactor later. Note: refrences to this refer to ball 1, and ball refers to ball 2. /* * Step 1 * * Find the Normal, Unit Normal and Unit Tangential vectors */ Vector2 n = new Vector2(this.position[0] - ball.position[0], this.position[1] - ball.position[1]); Vector2 un = n.normalize(); Vector2 ut = new Vector2(-un.y, un.x); /* * Step 2 * * Create the initial (before collision) velocity vectors */ Vector2 v1 = this.velocity; Vector2 v2 = ball.velocity; /* * Step 3 * * Resolve the velocity vectors into normal and tangential components */ float v1n = un.dot(v1); float v1t = ut.dot(v1); float v2n = un.dot(v2); float v2t = ut.dot(v2); /* * Step 4 * * Find the new tangential Velocities after collision */ float v1tPrime = v1t; float v2tPrime = v2t; /* * Step 5 * * Find the new normal velocities */ float v1nPrime = v1n * (this.mass - ball.mass) + (2 * ball.mass * v2n) / (this.mass + ball.mass); float v2nPrime = v2n * (ball.mass - this.mass) + (2 * this.mass * v1n) / (this.mass + ball.mass); /* * Step 6 * * Convert the scalar normal and tangential velocities into vectors??? */

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• Unable to use Maya animation with scripts when imported to Unity

  - by keshk

  I am testing to import Maya animation over to Unity. I set up a simple cylinder with 2 bones and an IK handle. Made a simple animation where the cylinder bends and goes back to straight position over 24 frames. Following that, I selected everything and baked, all bones,ik,(animation by selecting all at the graph editor) and even the cylinder. I saved the scene and then select all and export as FBX with animation and bake checked. In unity imported it and at the preview able to see the animation. When I load the model into scene and play (after assigning the controller), able to see animation too. But now when I try to script it and control the animation, nothing happens. Even to test, I tried the following under the Update method. if(animation.isPlaying) Debug.Log("Animation Works"); else Debug.Log("Animation not working"); The bool doesn't even return true nor false. My animation is called "bend", thus just for try I did the following and nothing happens. animation.Play("bend"); Can please advice based on my steps, am I missing something. Do I need to add the controller or is that an unnecessary step? Did I screw up on the Maya part or the Unity part. Thanks for help.

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• OpenGl / C++ and some strange light problem on half board

  - by mlodziaszka

  I have some problem with lights in my opengl "game". I have board with is square (-50,50), (50, 50), (50, -50), (-50,-50) x and z since y doesn't matter at all. I tried to make something like flashlight its moving and rotating with camera (me), but when i try to rotate more then 90 degree to left or right it just give diffrend light: http://imageshack.us/photo/my-images/688/lightij.jpg/ (left is spotlight, right point light) There is also a point light in the middle, but its working strange(not like a pointlight) it shines only on half of the board from (-50,50), (50, 50), (50, 0), (-50,-0) x and y: Link to my repo where u can find game exe in download and full code in source: https://bitbucket.org/mlodziaszka/my_game All more fragments of light: float gl_amb[] = { 0.2f, 0.2f, 0.2f, 1.0f }; glLightModelfv(GL_LIGHT_MODEL_AMBIENT, gl_amb); glEnable(GL_LIGHTING); // Wlaczenie oswietlenia glShadeModel(GL_SMOOTH); // Wybor techniki cieniowania glEnable(GL_LIGHT0); // Wlaczenie 0-go zrodla swiatla glEnable(GL_LIGHT1); Cubes parametri: float m1_amb[] = { 1.0f, 0.0f, 0.0f, 1.0f }; float m1_dif[] = { 1.0f, 0.0f, 0.0f, 1.0f }; float m1_spe[] = { 1.0f, 0.0f, 0.0f, 1.0f }; glMaterialfv(GL_FRONT, GL_AMBIENT, m1_amb); glMaterialfv(GL_FRONT, GL_DIFFUSE, m1_dif); glMaterialfv(GL_FRONT, GL_SPECULAR, m1_spe); glMaterialf(GL_FRONT, GL_SHININESS, 50.0f); Texture parametri: float m1_amb[] = { 1.0f, 1.0f, 1.0f, 1.0f }; float m1_dif[] = { 1.0f, 1.0f, 1.0f, 1.0f }; float m1_spe[] = { 1.0f, 1.0f, 1.0f, 1.0f }; glMaterialfv(GL_FRONT, GL_AMBIENT, m1_amb); glMaterialfv(GL_FRONT, GL_DIFFUSE, m1_dif); glMaterialfv(GL_FRONT, GL_SPECULAR, m1_spe); glMaterialf(GL_FRONT, GL_SHININESS, 0.0f); glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE ); Light0: //with some magic sn't working anyway float l0_amb[] = { 0.2f, 0.2f, 0.2f, 1.0f }; float l0_dif[] = { 1.0f, 1.0f, 1.0f, 1.0f }; float l0_spe[] = { 1.0f, 1.0f, 1.0f, 1.0f }; float l0_pos[] = { g_Camera.m_vPosition.x, g_Camera.m_vPosition.y, g_Camera.m_vPosition.z, 1.0f }; float temp = 0.0f, temp2 = 0.0f, temp3 = 0.0f; if(g_Camera.m_vView.z < g_Camera.m_vPosition.z) { temp = g_Camera.m_vView.x - g_Camera.m_vPosition.x; temp2 = g_Camera.m_vView.z - g_Camera.m_vPosition.z; } else { temp = g_Camera.m_vView.x - g_Camera.m_vPosition.x; temp2 = g_Camera.m_vView.z - g_Camera.m_vPosition.z; } float l0_pos1[] = {temp, 0.0f, temp2}; //float l0_pos1[] = {-1.0f, 0.0f, -1.0f}; glLightfv(GL_LIGHT0, GL_AMBIENT, l0_amb); glLightfv(GL_LIGHT0, GL_DIFFUSE, l0_dif); glLightfv(GL_LIGHT0, GL_SPECULAR, l0_spe); glLightfv(GL_LIGHT0, GL_POSITION, l0_pos); glLightf (GL_LIGHT0, GL_SPOT_CUTOFF, 15.0f); glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, l0_pos1); Light1: float l1_amb[] = { 0.2f, 0.2f, 0.2f, 1.0f }; float l1_dif[] = { 1.0f, 1.0f, 1.0f, 1.0f }; float l1_spe[] = { 1.0f, 1.0f, 1.0f, 1.0f }; float l1_pos[] = { 0.0f, 0.0f, 0.0f, 1.0f }; glLightfv(GL_LIGHT1, GL_AMBIENT, l1_amb); glLightfv(GL_LIGHT1, GL_DIFFUSE, l1_dif); glLightfv(GL_LIGHT1, GL_SPECULAR, l1_spe); glLightfv(GL_LIGHT1, GL_POSITION, l1_pos); I know that way I made this very old, but for now i want to keep this like that. I wouldbe realy gratefull if someone can tell me what is wrong with my lights xD full code: link up ^^

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• Question about JPanel "transition" for Java Swing

  - by user16778

  I want to make like a sort of main menu (in GUI). When the user clicks the start button, the screen transition into another "screen" (JPanel). This image will make it easier to understand. http://i.imgur.com/Cfdry.png Currently, I have a MainMenu extends JPanel and that gets added into a driver class with a JFrame. I can't figure how to switch to another class like Game extends JPanel. So when the user clicks the start button in MainMenu, I want it to somehow hide itself and the Game to show itself. Thanks.

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• xbox thumbstick used to rotate sprite, basic formula makes it "stick" or feel "sticky" at 90 degree intervals! how do get smooth rotation?

  - by Hugh

  Context: C#, XNA game I am using a very basic formula to calculate what angle my sprite (spaceship for example) should be facing based on the xbox controller thumbstick ie. you use the thumbstick to rotate the ship! in my main update method: shuttleAngle = (float) Math.Atan2(newGamePadState.ThumbSticks.Right.X, newGamePadState.ThumbSticks.Right.Y); in my main draw method: spriteBatch.Draw(shuttle, shuttleCoords, sourceRectangle, Color.White, shuttleAngle, origin, 1.0f, SpriteEffects.None, 1); as you can see its quite simple, i take the current radians from the thumbstick and store it in a float "shuttleAngle" and then use this as the rotation angle (in radians) arguement for drawing the shuttle. For some reason when i rotate the sprint it feels sticky at 0, 90, 180 and 270 degrees angles, it wants to settle at those angles. its not giving me a smooth and natural rotation like i would feel in a game that uses a similar mechanic. PS: my xbox controller is fine!

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• How do I create a camera?

  - by Morphex

  I am trying to create a generic camera class for a game engine, which works for different types of cameras (Orbital, GDoF, FPS), but I have no idea how to go about it. I have read about quaternions and matrices, but I do not understand how to implement it. Particularly, it seems you need "Up", "Forward" and "Right" vectors, a Quaternion for rotations, and View and Projection matrices. For example, an FPS camera only rotates around the World Y and the Right Axis of the camera; the 6DoF rotates always around its own axis, and the orbital is just translating for a set distance and making it look always at a fixed target point. The concepts are there; implementing this is not trivial for me. SharpDX seems to have has already Matrices and Quaternions implemented, but I don't know how to use them to create a camera. Can anyone point me on what am I missing, what I got wrong? I would really enjoy if you could give a tutorial, some piece of code, or just plain explanation of the concepts.

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• Creating smooth lighting transitions using tiles in HTML5/JavaScript game

  - by user12098

  I am trying to implement a lighting effect in an HTML5/JavaScript game using tile replacement. What I have now is kind of working, but the transitions do not look smooth/natural enough as the light source moves around. Here's where I am now: Right now I have a background map that has a light/shadow spectrum PNG tilesheet applied to it - going from darkest tile to completely transparent. By default the darkest tile is drawn across the entire level on launch, covering all other layers etc. I am using my predetermined tile sizes (40 x 40px) to calculate the position of each tile and store its x and y coordinates in an array. I am then spawning a transparent 40 x 40px "grid block" entity at each position in the array The engine I'm using (ImpactJS) then allows me to calculate the distance from my light source entity to every instance of this grid block entity. I can then replace the tile underneath each of those grid block tiles with a tile of the appropriate transparency. Currently I'm doing the calculation like this in each instance of the grid block entity that is spawned on the map: var dist = this.distanceTo( ig.game.player ); var percentage = 100 * dist / 960; if (percentage < 2) { // Spawns tile 64 of the shadow spectrum tilesheet at the specified position ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 64 ); } else if (percentage < 4) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 63 ); } else if (percentage < 6) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 62 ); } // etc... (sorry about the weird spacing, I still haven't gotten the hang of pasting code in here properly) The problem is that like I said, this type of calculation does not make the light source look very natural. Tile switching looks too sharp whereas ideally they would fade in and out smoothly using the spectrum tilesheet (I copied the tilesheet from another game that manages to do this, so I know it's not a problem with the tile shades. I'm just not sure how the other game is doing it). I'm thinking that perhaps my method of using percentages to switch out tiles could be replaced with a better/more dynamic proximity forumla of some sort that would allow for smoother transitions? Might anyone have any ideas for what I can do to improve the visuals here, or a better way of calculating proximity with the information I'm collecting about each tile? (PS: I'm reposting this from Stack Overflow at someone's suggestion, sorry about the duplicate!)

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• Elliptical orbit modeling

  - by Nathon

  I'm playing with orbits in a simple 2-d game where a ship flies around in space and is attracted to massive things. The ship's velocity is stored in a vector and acceleration is applied to it every frame as appropriate given Newton's law of universal gravitation. The point masses don't move (there's only 1 right now) so I would expect an elliptical orbit. Instead, I see this: I've tried with nearly circular orbits, and I've tried making the masses vastly different (a factor of a million) but I always get this rotated orbit. Here's some (D) code, for context: void accelerate(Vector delta) { velocity = velocity + delta; // Velocity is a member of the ship class. } // This function is called every frame with the fixed mass. It's a // method of the ship's. void fall(Well well) { // f=(m1 * m2)/(r**2) // a=f/m // Ship mass is 1, so a = f. float mass = 1; Vector delta = well.position - loc; float rSquared = delta.magSquared; float force = well.mass/rSquared; accelerate(delta * force * mass); }

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• Omni-directional light shadow mapping with cubemaps in WebGL

  - by Winged

  First of all I must say, that I have read a lot of posts describing an usage of cubemaps, but I'm still confused about how to use them. My goal is to achieve a simple omni-directional (point) light type shading in my WebGL application. I know that there is a lot more techniques (like using Two-Hemispheres or Camera Space Shadow Mapping) which are way more efficient, but for an educational purpose cubemaps are my primary goal. Till now, I have adapted a simple shadow mapping which works with spotlights (with one exception: I don't know how to cut off the glitchy part beyond the reach of a single shadow map texture): glitchy shadow mapping<<< So for now, this is how I understand the usage of cubemaps in shadow mapping: Setup a framebuffer (in case of cubemaps - 6 framebuffers; 6 instead of 1 because every usage of framebufferTexture2D slows down an execution which is nicely described here <<<) and a texture cubemap. Also in WebGL depth components are not well supported, so I need to render it to RGBA first. this.texture = gl.createTexture(); gl.bindTexture(gl.TEXTURE_CUBE_MAP, this.texture); gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MIN_FILTER, gl.LINEAR); gl.texParameteri(gl.TEXTURE_CUBE_MAP, gl.TEXTURE_MAG_FILTER, gl.LINEAR); for (var face = 0; face < 6; face++) gl.texImage2D(gl.TEXTURE_CUBE_MAP_POSITIVE_X + face, 0, gl.RGBA, this.size, this.size, 0, gl.RGBA, gl.UNSIGNED_BYTE, null); gl.bindTexture(gl.TEXTURE_CUBE_MAP, null); this.framebuffer = []; for (face = 0; face < 6; face++) { this.framebuffer[face] = gl.createFramebuffer(); gl.bindFramebuffer(gl.FRAMEBUFFER, this.framebuffer[face]); gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_CUBE_MAP_POSITIVE_X + face, this.texture, 0); gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, this.depthbuffer); var e = gl.checkFramebufferStatus(gl.FRAMEBUFFER); // Check for errors if (e !== gl.FRAMEBUFFER_COMPLETE) throw "Cubemap framebuffer object is incomplete: " + e.toString(); } Setup the light and the camera (I'm not sure if should I store all of 6 view matrices and send them to shaders later, or is there a way to do it with just one view matrix). Render the scene 6 times from the light's position, each time in another direction (X, -X, Y, -Y, Z, -Z) for (var face = 0; face < 6; face++) { gl.bindFramebuffer(gl.FRAMEBUFFER, shadow.buffer.framebuffer[face]); gl.viewport(0, 0, shadow.buffer.size, shadow.buffer.size); gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT); camera.lookAt( light.position.add( cubeMapDirections[face] ) ); scene.draw(shadow.program); } In a second pass, calculate the projection a a current vertex using light's projection and view matrix. Now I don't know If should I calculate 6 of them, because of 6 faces of a cubemap. ScaleMatrix pushes the projected vertex into the 0.0 - 1.0 region. vDepthPosition = ScaleMatrix * uPMatrixFromLight * uVMatrixFromLight * vWorldVertex; In a fragment shader calculate the distance between the current vertex and the light position and check if it's deeper then the depth information read from earlier rendered shadow map. I know how to do it with a 2D Texture, but I have no idea how should I use cubemap texture here. I have read that texture lookups into cubemaps are performed by a normal vector instead of a UV coordinate. What vector should I use? Just a normalized vector pointing to the current vertex? For now, my code for this part looks like this (not working yet): float shadow = 1.0; vec3 depth = vDepthPosition.xyz / vDepthPosition.w; depth.z = length(vWorldVertex.xyz - uLightPosition) * linearDepthConstant; float shadowDepth = unpack(textureCube(uDepthMapSampler, vWorldVertex.xyz)); if (depth.z > shadowDepth) shadow = 0.5; Could you give me some hints or examples (preferably in WebGL code) how I should build it?

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• Generate texture for a heightmap

  - by James

  I've recently been trying to blend multiple textures based on the height at different points in a heightmap. However i've been getting poor results. I decided to backtrack and just attempt to recreate one single texture from an SDL_Surface (i'm using SDL) and just send that into opengl. I'll put my code for creating the texture and reading the colour values. It is a 24bit TGA i'm loading, and i've confirmed that the rest of my code works because i was able to send the surfaces pixels directly to my createTextureFromData function and it drew fine. struct RGBColour { RGBColour() : r(0), g(0), b(0) {} RGBColour(unsigned char red, unsigned char green, unsigned char blue) : r(red), g(green), b(blue) {} unsigned char r; unsigned char g; unsigned char b; }; // main loading code SDLSurfaceReader* reader = new SDLSurfaceReader(m_renderer); reader->readSurface("images/grass.tga"); // new texture unsigned char* newTexture = new unsigned char[reader->m_surface->w * reader->m_surface->h * 3 * reader->m_surface->w]; for (int y = 0; y < reader->m_surface->h; y++) { for (int x = 0; x < reader->m_surface->w; x += 3) { int index = (y * reader->m_surface->w) + x; RGBColour colour = reader->getColourAt(x, y); newTexture[index] = colour.r; newTexture[index + 1] = colour.g; newTexture[index + 2] = colour.b; } } unsigned int id = m_renderer->createTextureFromData(newTexture, reader->m_surface->w, reader->m_surface->h, RGB); // functions for reading pixels RGBColour SDLSurfaceReader::getColourAt(int x, int y) { Uint32 pixel; Uint8 red, green, blue; RGBColour rgb; pixel = getPixel(m_surface, x, y); SDL_LockSurface(m_surface); SDL_GetRGB(pixel, m_surface->format, &red, &green, &blue); SDL_UnlockSurface(m_surface); rgb.r = red; rgb.b = blue; rgb.g = green; return rgb; } // this function taken from SDL documentation // http://www.libsdl.org/cgi/docwiki.cgi/Introduction_to_SDL_Video#getpixel Uint32 SDLSurfaceReader::getPixel(SDL_Surface* surface, int x, int y) { int bpp = m_surface->format->BytesPerPixel; Uint8 *p = (Uint8*)m_surface->pixels + y * m_surface->pitch + x * bpp; switch (bpp) { case 1: return *p; case 2: return *(Uint16*)p; case 3: if (SDL_BYTEORDER == SDL_BIG_ENDIAN) return p[0] << 16 | p[1] << 8 | p[2]; else return p[0] | p[1] << 8 | p[2] << 16; case 4: return *(Uint32*)p; default: return 0; } } I've been stumped at this, and I need help badly! Thanks so much for any advice.

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• Is there a good way to get pixel-perfect collision detection in XNA?

  - by ashes999

  Is there a well-known way (or perhaps reusable bit of code) for pixel-perfect collision detection in XNA? I assume this would also use polygons (boxes/triangles/circles) for a first-pass, quick-test for collisions, and if that test indicated a collision, it would then search for a per-pixel collision. This can be complicated, because we have to account for scale, rotation, and transparency. WARNING: If you're using the sample code from the link from the answer below, be aware that the scaling of the matrix is commented out for good reason. You don't need to uncomment it out to get scaling to work.

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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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• What 2D game engines are there available for C++?

  - by dysoco

  I just realized there are not C++ 2D Game Engines that I know of. For example, something like Pygame in Python, or Slick2D in Java. We have the following: SDL - Too low level, not a Game Engine SFML - Handles more things than SDL and it's more modern, but still not a Game Engine. I like it, but I have found it a little bit buggy with the 2.0 version. Irrlitch - It's a Game Engine, but 3D focused. Ogre3D - Same as Irrlitch Allegro - This is a Game Engine, but it's C based, I'd like a modern C++ library. Monocle Engine - This looks like what I need... but sadly there is no Documentation, no community... nothing, all I have is the Github repo. So, do you know any ? I'd like to use C++, not C#, not Java: I'm just more comfortable with C++.

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