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• How to keep balance / Unlock items / achievement rules

  - by Mark Knol

  I'm working on an engine for a game, too learn javascript and just because its fun. I'm a flashdeveloper, I know how to build websites. Now making games is a different challenge, javascript is a challenge, but I'd love to learn how to structure code and what patterns are common. I dont mind if the game ever finish, I'm mostly interested in the programming part of it. I dont have a particular endresult in mind, so I'll see where it takes me. I currently have a system where you can buy items. The items cost a specified amount of gold, silver, diamonds etc. When you have selected and bought the item, it takes time before getting rewarded. When time is over, you are getting rewarded with other properties (gold, energy, diamonds). For example, you can buy an apple for 50gold, It takes a minute, you get rewarded with 75energy. Or if you take a run, it cost 50energy, it takes 5minutes, reward is 25gold and 25silver. These definitions is what i call actions. Currently I already have a system where this already works and I can define as much actions with as much properties as I want. The definitions I have kinda looks like this: {id:101, category:544, onInit:{gold:-75}, onComplete:{energy:75}, time:2000, name:"Apple", locked: false} {id:102, category:544, onInit:{gold:-135}, onComplete:{energy:145}, time:2000, name:"Banana", locked: false} {id:106, category:302, onInit:{energy:-50, power: -25}, onComplete:{gold:100, diamonds:2}, time:10000, name:"Run", locked: false} {id:107, category:302, onInit:{energy:-70, silver: -55}, onComplete:{gold:100}, time:10000, name:"Dance", locked: false} {id:108, category:302, onInit:{energy:-230, power: -355}, onComplete:{gold:70, silver:70}, time:10000, name:"Fitness", locked: false} Now, I would love to add a system where I can lock/unlock the actions using achievement rules. Lets say, if you buy 10 apples, you unlock a new action, like bananas which cost more, and reward more. In the future I maybe want to restrict achievements and actions to levels. I am kinda stuck how to structure this. I have 2 questions: Which patterns are used to define achievements? How/where are they defined? Should it be part of the action, or should it be a separate controller? Is it a good idea to register all completed actions to it? I think I want multiple types of achievement rules, Id love to hear some ideas how to develop it. How do you create/find a good balance, so the user does not get stuck or can cheat by repeat a pattern of actions to get too much rewards. I know there is not a simple answer and i'm lacking of a good game-concept, but I wonder if anyone created such a game and how you dealed and played with it.

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• Translate extrinsic rotations to intrinsic rotations ( Euler angles )

  - by MineMan287

  The problem I have is very frustrating: I am using the Jitter Physics library which gives Quaternion rotations, you can extract the extrinsic rotations but I need intrinsic rotations to rotate in OpenTK (There are other reasons as well so I don't want to make OpenTK use a Matrix) GL.Rotate(xr, 1, 0, 0) GL.Rotate(yr, 0, 1, 0) GL.Rotate(zr, 0, 0, 1) EDIT : Response to the first answer Like This? GL.Rotate(zr, 0, 0, 1) GL.Rotate(yr, 0, 1, 0) GL.Rotate(xr, 1, 0, 0) Or This? GL.Rotate(xr, 1, 0, 0) GL.Rotate(yr, 0, 1, 0) GL.Rotate(zr, 0, 0, 1) GL.Rotate(zr, 0, 0, 1) GL.Rotate(yr, 0, 1, 0) GL.Rotate(xr, 1, 0, 0) GL.Rotate(xr, 1, 0, 0) GL.Rotate(yr, 0, 1, 0) GL.Rotate(zr, 0, 0, 1) I'm confused, please give an example

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• How AlphaBlend Blendstate works in XNA 4 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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• How to highlight non-rectangular hotspots?

  - by HuseyinUslu

  So my question is highly related to Creating non-rectangular hotspots and detecting clicks. Yet again, I've irregular hot-spots (think the game Risk). So basically, we can detect clicks on these hot-spots easily using color key mapping as discussed in above question which I don't have any problems implementing (which is also covered here in details). The problem is about highlighting these irreguar hotspots. So let me explain the question a bit more - the above color key mapping guide uses this as a world map: Then the author color-maps the imaginary countries: Now we can now detect the country the pointer is over. In the same article author mentions outlining countries on mouse-over. Though to get the effect, he creates unique border assets for each country - like: For the game I'm working on I'm using the same color-key mapping idea to detect hot-spots, but I didn't like the way of highlighting hot-spots. Coloring all the hot-spots is already a time-consuming job for me - as I have 25+ hot-spots for each map. Further, the need to have 25 unique border/highlight asset per hot-spot doesn't sound right. Anyone have a better idea/suggestion on highlighting these hot-spots?

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• Preferred way to render text in OpenGL

  - by dukeofgaming

  Hi, I'm about tu pick up computer graphics once again for an university project. For a previous project I used a library called ftgl that didn't leave me quite satisfied as it felt kind of heavy (I tried all rendering techniques, text rendering didn't scale very well). My question is, is there a good and efficient library for this?, if not, what would be the way to implement fast but nice looking text?. Some intended uses are: Floating object/character labels Dialogues Menus HUD Regards and thanks in advance. EDIT: Preferrably that it can load fonts

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• XNA 4.0 SpriteFont not displaying all Characters

  - by Iain Brown

  Am looking for a little help and trying to use SpriteFont in my XNA 4.0 game but the problem is am displaying to string "This is a test" but all that's displayed on the screen is "This is st" so the "a te" are missing from the screen. The space is there for the characters but the letters are not. The code am using is: spriteBatch.Begin(SpriteSortMode.BackToFront, BlendState.AlphaBlend); spriteBatch.DrawString(font,"this is a test",new Vector2(692,372),Color.White); spriteBatch.Draw(texture,new Rectangle(0,0,100,100),Color.White); spriteBatch.End(); Any help with this would be great!

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• Flickering when accessing texture by offset

  - by TravisG

  I have this simple compute shader that basically just takes the input from one image and writes it to another. Both images are 128/128/128 in size and glDispatchCompute is called with (128/8,128/8,128/8). The source images are cleared to 0 before this compute shader is executed, so no undefined values should be floating around in there. (I have the appropriate memory barrier on the C++ side set before the 3D texture is accessed). This version works fine: #version 430 layout (location = 0, rgba16f) uniform image3D ping; layout (location = 1, rgba16f) uniform image3D pong; layout (local_size_x = 8, local_size_y = 8, local_size_z = 8) in; void main() { ivec3 sampleCoord = gl_GlobalInvocationID.xyz; imageStore(pong, imageLoad(ping,sampleCoord)); } Reading values from pong shows that it's just a copy, as intended. However, when I load data from ping with an offset: #version 430 layout (location = 0, rgba16f) uniform image3D ping; layout (location = 1, rgba16f) uniform image3D pong; layout (local_size_x = 8, local_size_y = 8, local_size_z = 8) in; void main() { ivec3 sampleCoord = gl_GlobalInvocationID.xyz; imageStore(pong, imageLoad(ping,sampleCoord+ivec3(1,0,0))); } The data that is written to pong seems to depend on the order of execution of the threads within the work groups, which makes no sense to me. When reading from the pong texture, visible flickering occurs in some spots on the texture. What am I doing wrong here?

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• Light shaped like a line

  - by Michael

  I am trying to figure out how line-shaped lights fit into the standard point light/spotlight/directional light scheme. The way I see it, there are two options: Seed the line with regular point lights and just deal with the artifacts. Easy, but seems wasteful. Make the line some kind of emissive material and apply a bloom effect. Sounds like it could work, but I can't test it in my engine yet. Is there a standard way to do this? Or for non-point lights in general?

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• Entity Component System for HUD and GUI

  - by Jason L.

  This is a very rough sketch of how I currently have things designed. It should, at least, give an idea of how my ECS is currently designed. If you notice in that diagram, I have basically split the HUD out of the ECS. They have their own set of things (HudLayer, HudComponent, etc) and are handled differently. This is where I'm struggling, though. There are many different instances in which the HUD will need to know about entities. Not just data changing (I have an event dispatcher for that), but the actual entity and all it encompasses. There are also situations where entities will need to be able to query the HUD for data. Let's take a couple examples: First, my equipment screen. On here I can change the equipment on a character (Entity). In order for this to happen, I need to know about the entity. At least I think I do? How can I handle this? The second scenario involves my Systems needing to query a HudComponent for data. A specific example would be my battle system. Each "team" is given a 3x3 grid they can move around in. See here: Skills target these cells, and not the player, so I would need a way for my systems to determine which cells are occupied and which are not. Basically I need a way for two way communication between Systems and my HUD. I know it's recommended (by some people, anyways) to take your HUD out of the ECS. Is that appropriate in my case?

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• Novice prototyping a massive multiplayer webpage based gaming system

  - by Sean Hendlin

  I'm trying to build a website based game in which various pages of the site act as different areas of the game. I am wondering what you would recommended as a design structure. Which languages would be best if building what will hopefully becomes a massive system able to scale to massive amounts of users. I am wondering if and how various elements from differing languages could be meshed to interact with each other. For example could I use html5, javascript, and PHP? What about asp.net how might that factor in? I'm a newbie programmer but I've been working on this idea for years and I want to build it to reality. Your comments and suggestions are appreciated. P.S.: The game is not all graphics and animation (though flash like appearance and some animation would be nice). What I am thinking of is essentially a heavily gamified system of forms. And LOTS of data in many different categories cross referencing each-other. I'm not sure how to go about structuring the collection of data. Also while I know javascript can be used to process some functions, I'm wondering what sort of base system I would need to handle the server side processing of what I am expecting to be some pretty significant algorithm processing. That is to say I expect to have many many many functions and I'm not sure how to mange this using javascript. I feel like they would be forgotten, mixed up, disorganizes as they essentially only exist where they are coded. I guess I need to learn something of libraries? OK, Thank you! Is enough from me for now.

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• 1136: Incorrect number of arguments. Expected 0 AS3 Flash CS5.5 [on hold]

  - by Erick

  how do I solve this error? I've been trying to get the answer online but have not been successful. I'm trying to learn As3 for flash so I decided to try making a preloader for a game. Preloader.as package com.game.moran { import flash.display.LoaderInfo; import flash.display.MovieClip; import flash.events.*; public class ThePreloader extends MovieClip { private var fullWidth:Number; public var ldrInfo:LoaderInfo; public function ThePreloader (fullWidth:Number = 0, ldrInfo:LoaderInfo = null) { this.fullWidth = fullWidth; this.ldrInfo = ldrInfo; addEventListener(Event.ENTER_FRAME, checkLoad); } private function checkLoad (e:Event) : void { if (ldrInfo.bytesLoaded == ldrInfo.bytesTotal && ldrInfo.bytesTotal !=0) { dispatchEvent (new Event ("loadComplete")); phaseOut(); } updateLoader (ldfInfo.bytesLoaded / ldrInfo.bytesTotal); } private function updateLoader(num:Number) : void { mcPreloaderBar.Width = num * fullWidth; } private function phaseOut() : void { removeEventListener (Event.ENTER_FRAME, checkLoad); phaseComplete(); } private function phaseComplete() : void { dispatchEvent (new Event ("preloaderFinished")); } } } Engine.as package com.game.moran { import flash.display.MovieClip; import flash.display.Sprite; import flash.events.Event; public class Engine extends MovieClip { private var preloader:ThePreloader; public function Engine() { preloader = new ThePreloader(732, this.loaderInfo); stage.addChild(preloader); preloader.addEventListener("loadComplete", loadAssets); preloader.addEventListener("preloaderFinished", showSponsors); } private function loadAssets (e:Event) : void { this.play(); } private function showSponsors(e:Event) : void { stage.removeChild(preloader); trace("show sponsors") } } } The line being flagged as an error is line 13 in Engine.as.

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• Queries regarding Geometry Shaders

  - by maverick9888

  I am dealing with geometry shaders using GL_ARB_geometry_shader4 extension. My code goes like : GLfloat vertices[] = { 0.5,0.25,1.0, 0.5,0.75,1.0, -0.5,0.75,1.0, -0.5,0.25,1.0, 0.6,0.35,1.0, 0.6,0.85,1.0, -0.6,0.85,1.0, -0.6,0.35,1.0 }; glProgramParameteriEXT(psId, GL_GEOMETRY_INPUT_TYPE_EXT, GL_TRIANGLES); glProgramParameteriEXT(psId, GL_GEOMETRY_OUTPUT_TYPE_EXT, GL_TRIANGLE_STRIP); glLinkProgram(psId); glBindAttribLocation(psId,0,"Position"); glEnableVertexAttribArray (0); glVertexAttribPointer(0, 3, GL_FLOAT, 0, 0, vertices); glDrawArrays(GL_TRIANGLE_STRIP,0,4); My vertex shader is : #version 150 in vec3 Position; void main() { gl_Position = vec4(Position,1.0); } Geometry shader is : #version 150 #extension GL_EXT_geometry_shader4 : enable in vec4 pos[3]; void main() { int i; vec4 vertex; gl_Position = pos[0]; EmitVertex(); gl_Position = pos[1]; EmitVertex(); gl_Position = pos[2]; EmitVertex(); gl_Position = pos[0] + vec4(0.3,0.0,0.0,0.0); EmitVertex(); EndPrimitive(); } Nothing is rendered with this code. What exactly should be the mode in glDrawArrays() ? How does the GL_GEOMETRY_OUTPUT_TYPE_EXT parameter will affect glDrawArrays() ? What I expect is 3 vertices will be passed on to Geometry Shader and using those we construct a primitive of size 4 (assuming GL_TRIANGLE_STRIP requires 4 vertices). Can somebody please throw some light on this ?

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• Libgdx ParallaxScrolling and TiledMaps

  - by kirchhoff

  I implemented ParallaxScrolling for my SideScroller project, everything is working but the tiled map (the most important part!). I've been trying out everything but it doesn't work (see the code below). I'm using ParallaxCamera from GdxTests, it's working perfectly for the background layers. I can't explain myself properly in english, so I recorded 2 videos: Before parallaxScrolling After parallaxScrolling As you can see, now the platforms appear in the middle of the Y-axis. I've got a Map class with 2 tiled maps, so I need two renderers too: private TiledMapRenderer renderer1; private TiledMapRenderer renderer2; public void update(GameCamera camera) { renderer1.setView(camera.calculateParallaxMatrix(1f, 0f), camera.position.x - camera.viewportWidth / 2, **camera.position.y - camera.viewportHeight/2**, camera.viewportWidth, camera.viewportHeight); renderer2.setView(camera.calculateParallaxMatrix(1f, 0f), camera.position.x - camera.viewportWidth / 2, **camera.position.y - camera.viewportHeight/2**, camera.viewportWidth, camera.viewportHeight); } In bold, the code I think I should change. I've tried changing parameters, even adding hardcoded values, etc, but one of two: 1. Nothing happens. 2. Platforms disappear. Here is some aditional code. The render method: world.update(delta); parallaxBackground.update(camera); clear(0.5f, 0.7f, 1.0f, 1); batch.setProjectionMatrix(camera.calculateParallaxMatrix(0, 0)); batch.disableBlending(); batch.begin(); batch.draw(background, -(int)background.getRegionWidth()/2, -(int)background.getRegionHeight()/2); batch.end(); batch.enableBlending(); parallaxBackground.draw(batch, camera); renderer.render(batch);

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• How can I cull non-visible isometric tiles?

  - by james

  I have a problem which I am struggling to solve. I have a large map of around 100x100 tiles which form an isometric map. The user is able to move the map around by dragging the mouse. I am trying to optimize my game only to draw the visible tiles. So far my code is like this. It appears to be ok in the x direction, but as soon as one tile goes completely above the top of the screen, the entire column disappears. I am not sure how to detect that all of the tiles in a particular column are outside the visible region. double maxTilesX = widthOfScreen/ halfTileWidth + 4; double maxTilesY = heightOfScreen/ halfTileHeight + 4; int rowStart = Math.max(0,( -xOffset / halfTileWidth)) ; int colStart = Math.max(0,( -yOffset / halfTileHeight)); rowEnd = (int) Math.min(mapSize, rowStart + maxTilesX); colEnd = (int) Math.min(mapSize, colStart + maxTilesY); EDIT - I think I have solved my problem, but perhaps not in a very efficient way. I have taken the center of the screen coordinates, determined which tile this corresponds to by converting the coordinates into cartesian format. I then update the entire box around the screen.

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• Character movement on a 2D tile map

  - by Chris Morris

  I'm working at making a HTML5 game. Top down, closest thing I can equate it to is the gameboy zeldas, but open world and no rooms. What I have so far is a procedurally generated map in a multi dimensional array. And a starting position on the map. Along with this I have an array of movable and non movable tile ID's. I also have a class for my player and have him being rendered out in the center of the starting tile. My problem however is getting the movement sorted out for the player. I want to be able to have the character free move around the map (pixel by pixel essentially) ontop of this 2D generated world. Ideally this would allow the user to move around the walk able area of the canvas. this is simple enough for me to do, but I am having problems now moving the world. If the user is 20% from the edge of the screen i want the world to start panning in the direction the player is heading. But I'm rather lacking in ideas of how to do this. I've looked around for some tutorials, but am coming up blank on ideas of how to generate the playable area (zoomed in) and to then move this generated area under the player when they reach near the end of the screen. My current idea was to generate a certain amount of tiles full size to fill the screen and place the player i the middle. Then when the user approaches the edge of the screen start generating the tiles offset by the distance moved and the direction. I can kind of see this working but I really have no idea if this is the best or easiest to code of methods for generating the world. sorry for the lack of code but I'm still just in the theory stages of working this all out.

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• Component-based design: handling objects interaction

  - by Milo

  I'm not sure how exactly objects do things to other objects in a component based design. Say I have an Obj class. I do: Obj obj; obj.add(new Position()); obj.add(new Physics()); How could I then have another object not only move the ball but have those physics applied. I'm not looking for implementation details but rather abstractly how objects communicate. In an entity based design, you might just have: obj1.emitForceOn(obj2,5.0,0.0,0.0); Any article or explanation to get a better grasp on a component driven design and how to do basic things would be really helpful.

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• Deformation of Sphere using Transformations

  - by Mert Toka

  I have a graphic related question. I need to have a transformation matrix that I have no idea about what it is. The problem is to create right image from the right sphere. I created those images in Maya, but I need some matrices for the graphics course. Here is the image: Our professor told us to use some sine and cosine in our transformations, but I have no idea what he meant. I thought of intersecting a plane from the grid(that is xz plane) and sphere, and then scaling down the resulting circle. Would that work? I also checked this paper, however it looks like a bit advanced for me. Another thing is I guess that paper is not about the same type of information I was looking for. It would be great if you could help me.

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• Dynamic audio score/music

  - by Joel Martinez

  I'm interested in developing a game who's background music changes with the mood and scenario of the game's action. Of course many existing games do this (halo for example), but I was interested in any resources/papers/articles talking about the techniques to develop a system like this. I have some ideas, and I understand that this will be equally challenging to implement at the code level as it will be to come up or acquire music that fits this model. Any links or, answers with ideas in them would he appreciated. Edit: this is the kind of info I'm looking for :) http://halo.bungie.org/misc/gdc.2002.music/

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• Circular motion on low powered hardware

  - by Akroy

  I was thinking about platforms and enemies moving in circles in old 2D games, and I was wondering how that was done. I understand parametric equations, and it's trivial to use sin and cos to do it, but could an NES or SNES make real time trig calls? I admit heavy ignorance, but I thought those were expensive operations. Is there some clever way to calculate that motion more cheaply? I've been working on deriving an algorithm from trig sum identities that would only use precalculated trig, but that seems convoluted.

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• Using copyrighted sprites

  - by Zertalx

  I was thinking about making a pacman clone, I know there is a similar question here Using Copyrighted Images , but I know i can't use the original art from the game because it belongs to Namco, so if I design a character that has the shape of the slice circle it will look exactly like pacman, maybe if I use green instead of yellow? Also if the game plays like the original pacman, it is wrong? I just want to make the game as a personal project and and publish it in my site without getting in trouble

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• Customize Colors for Sprites in Web Game

  - by NateDSaint

  So I'm working on an html5/javascript/css3-based game. Without going into too much detail, I'm thinking of having the characters be simple 8 or 16-bit style sprites, but I'd like to allow the user to customize the colors of their character. Here are some examples of what I'm talking about : http://jsfiddle.net/simurai/CGmCe/light/ http://www.splashnology.com/article/sprite-animation-in-css3/1485/ So the problem I'm having is two-fold: 1) Should I use something other than a sprite map for my characters, like actually draw them as shapes and animate them in a canvas element? That way I can fill the sprite with colors of the user's choosing? My fear there is that this would be inefficient as far as resources and also waste a lot of time hand-drawing everything, but could allow other customization (like height/width etc). 2) Are there potentially some web apis that would allow you to alter colors inside of a sprite? I suppose I could do it on the back-end with GD, but I'm trying to make it entirely in-browser (including local storage). It's not a definitive one-answer only question, but I'm hoping someone can suggest something they've seen that approaches the same problem from another angle or gives us a way to customize the sprites or manipulate them in some manner. Or avoid them altogether, and use a different method.

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• building a game for different resoulution phones

  - by Jason

  Hi, I am starting some tests for building a game on the android program. So far everything is working and seems nice. However I do not understand how to make sure my game looks correct on all phones as the all will have slightly different screen ratios (and even very different on some odd phones) What I am doing right now is making a view frustrum ( could also be ortho ) which I set to go from -ratio to +ratio ( as I have seen on many examples) however this causes my test shape to be stretched and sometimes cut off by the edge of the screen. I am tilting my phone to landscape to do my tests ( a bit extreame) but it should still render correctly if I have dome things right. Should I be scaling by some ratio before drawing or something? An example would be greatly apriciated PS I am doing a 2d game

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• Achieving certain rendering styles

  - by milesmeow

  I'm trying to assess the difficulty of creating a rendering style that is more like the game Okami and the Quake mods (as shown on this page...search for 'okami','quake npr'). Here's a better page describing the Quake rendering mod. Can a game engine such as Unity be used and programmed to achieve these kind of rendering styles? I'm doing research and am totally new to this so any insight into this would help tremendously.

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• Bouncing off a circular Boundary with multiple balls?

  - by Anarkie

  I am making a game like this : Yellow Smiley has to escape from red smileys, when yellow smiley hits the boundary game is over, when red smileys hit the boundary they should bounce back with the same angle they came, like shown below: Every 10 seconds a new red smiley comes in the big circle, when red smiley hits yellow, game is over, speed and starting angle of red smileys should be random. I control the yellow smiley with arrow keys. The biggest problem I have reflecting the red smileys from the boundary with the angle they came. I don't know how I can give a starting angle to a red smiley and bouncing it with the angle it came. I would be glad for any tips! My js source code : var canvas = document.getElementById("mycanvas"); var ctx = canvas.getContext("2d"); // Object containing some global Smiley properties. var SmileyApp = { radius: 15, xspeed: 0, yspeed: 0, xpos:200, // x-position of smiley ypos: 200 // y-position of smiley }; var SmileyRed = { radius: 15, xspeed: 0, yspeed: 0, xpos:350, // x-position of smiley ypos: 65 // y-position of smiley }; var SmileyReds = new Array(); for (var i=0; i<5; i++){ SmileyReds[i] = { radius: 15, xspeed: 0, yspeed: 0, xpos:350, // x-position of smiley ypos: 67 // y-position of smiley }; SmileyReds[i].xspeed = Math.floor((Math.random()*50)+1); SmileyReds[i].yspeed = Math.floor((Math.random()*50)+1); } function drawBigCircle() { var centerX = canvas.width / 2; var centerY = canvas.height / 2; var radiusBig = 300; ctx.beginPath(); ctx.arc(centerX, centerY, radiusBig, 0, 2 * Math.PI, false); // context.fillStyle = 'green'; // context.fill(); ctx.lineWidth = 5; // context.strokeStyle = '#003300'; // green ctx.stroke(); } function lineDistance( positionx, positiony ) { var xs = 0; var ys = 0; xs = positionx - 350; xs = xs * xs; ys = positiony - 350; ys = ys * ys; return Math.sqrt( xs + ys ); } function drawSmiley(x,y,r) { // outer border ctx.lineWidth = 3; ctx.beginPath(); ctx.arc(x,y,r, 0, 2*Math.PI); //red ctx.fillStyle="rgba(255,0,0, 0.5)"; ctx.fillStyle="rgba(255,255,0, 0.5)"; ctx.fill(); ctx.stroke(); // mouth ctx.beginPath(); ctx.moveTo(x+0.7*r, y); ctx.arc(x,y,0.7*r, 0, Math.PI, false); // eyes var reye = r/10; var f = 0.4; ctx.moveTo(x+f*r, y-f*r); ctx.arc(x+f*r-reye, y-f*r, reye, 0, 2*Math.PI); ctx.moveTo(x-f*r, y-f*r); ctx.arc(x-f*r+reye, y-f*r, reye, -Math.PI, Math.PI); // nose ctx.moveTo(x,y); ctx.lineTo(x, y-r/2); ctx.lineWidth = 1; ctx.stroke(); } function drawSmileyRed(x,y,r) { // outer border ctx.lineWidth = 3; ctx.beginPath(); ctx.arc(x,y,r, 0, 2*Math.PI); //red ctx.fillStyle="rgba(255,0,0, 0.5)"; //yellow ctx.fillStyle="rgba(255,255,0, 0.5)"; ctx.fill(); ctx.stroke(); // mouth ctx.beginPath(); ctx.moveTo(x+0.4*r, y+10); ctx.arc(x,y+10,0.4*r, 0, Math.PI, true); // eyes var reye = r/10; var f = 0.4; ctx.moveTo(x+f*r, y-f*r); ctx.arc(x+f*r-reye, y-f*r, reye, 0, 2*Math.PI); ctx.moveTo(x-f*r, y-f*r); ctx.arc(x-f*r+reye, y-f*r, reye, -Math.PI, Math.PI); // nose ctx.moveTo(x,y); ctx.lineTo(x, y-r/2); ctx.lineWidth = 1; ctx.stroke(); } // --- Animation of smiley moving with constant speed and bounce back at edges of canvas --- var tprev = 0; // this is used to calculate the time step between two successive calls of run function run(t) { requestAnimationFrame(run); if (t === undefined) { t=0; } var h = t - tprev; // time step tprev = t; SmileyApp.xpos += SmileyApp.xspeed * h/1000; // update position according to constant speed SmileyApp.ypos += SmileyApp.yspeed * h/1000; // update position according to constant speed for (var i=0; i<SmileyReds.length; i++){ SmileyReds[i].xpos += SmileyReds[i].xspeed * h/1000; // update position according to constant speed SmileyReds[i].ypos += SmileyReds[i].yspeed * h/1000; // update position according to constant speed } // change speed direction if smiley hits canvas edges if (lineDistance(SmileyApp.xpos, SmileyApp.ypos) + SmileyApp.radius > 300) { alert("Game Over"); } // redraw smiley at new position ctx.clearRect(0,0,canvas.height, canvas.width); drawBigCircle(); drawSmiley(SmileyApp.xpos, SmileyApp.ypos, SmileyApp.radius); for (var i=0; i<SmileyReds.length; i++){ drawSmileyRed(SmileyReds[i].xpos, SmileyReds[i].ypos, SmileyReds[i].radius); } } // uncomment these two lines to get every going // SmileyApp.speed = 100; run(); // --- Control smiley motion with left/right arrow keys function arrowkeyCB(event) { event.preventDefault(); if (event.keyCode === 37) { // left arrow SmileyApp.xspeed = -100; SmileyApp.yspeed = 0; } else if (event.keyCode === 39) { // right arrow SmileyApp.xspeed = 100; SmileyApp.yspeed = 0; } else if (event.keyCode === 38) { // up arrow SmileyApp.yspeed = -100; SmileyApp.xspeed = 0; } else if (event.keyCode === 40) { // right arrow SmileyApp.yspeed = 100; SmileyApp.xspeed = 0; } } document.addEventListener('keydown', arrowkeyCB, true); JSFiddle : http://jsfiddle.net/gj4Q7/

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• View matrix question (rotate by 180 degrees)

  - by King Snail

  I am using a third party rendering API on top of OpenGL code and I cannot get my matrices correct. The API states this: We're right handed by default, and we treat y as up by convention. Since IwGx's coordinate system has (0,0) as the top left, you typically need a 180 degree rotation around Z in your view matrix. I think the viewer does this by default. In my OpenGL app I have access to the view and projection matrices separately. How can I convert them to fit the criteria used by my third party rendering API? I don't understand what they mean to rotate 180 degrees around Z, is that in the view matrix itself or something in the camera before making the view matrix. Any code would be helpful, thanks.

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