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• Using unordered_multimap as entity and component storage

  - by natebot13

  The Setup I've made a few games (more like animations) using the Object Oriented method with base classes for objects that extend them, and objects that extend those, and found I couldn't wrap my head around expanding that system to larger game ideas. So I did some research and discovered the Entity-Component system of designing games. I really like the idea, and thoroughly understood the usefulness of it after reading Byte54's perfect answer here: Role of systems in entity systems architecture. With that said, I have decided to create my current game idea using the described Entity-Component system. Having basic knowledge of C++, and SFML, I would like to implement the backbone of this entity component system using an unordered_multimap without classes for the entities themselves. Here's the idea: An unordered_mulitmap stores entity IDs as the lookup term, while the value is an inherited Component object. Examlpe: ____________________________ |ID |Component | ---------------------------- |0 |Movable | |0 |Accelable | |0 |Renderable | |1 |Movable | |1 |Renderable | |2 |Renderable | ---------------------------- So, according to this map of objects, the entity with ID 0 has three components: Movable, Accelable, and Renderable. These component objects store the entity specific data, such as the location, the acceleration, and render flags. The entity is simply and ID, with the components attached to that ID describing its attributes. Problem I want to store the component objects within the map, allowing the map have full ownership of the components. The problem I'm having, is I don't quite understand enough about pointers, shared pointers, and references in order to get that set up. How can I go about initializing these components, with their various member variables, within the unordered_multimap? Can the base component class take on the member variables of its child classes, when defining the map as unordered_multimap<int, component>? Requirements I need a system to be able to grab an entity, with all of its' attached components, and access members from the components in order to do the necessary calculations and reassignments for position, velocity, etc. Need a clarification? Post a comment with your concerns and I will gladly edit or comment back! Thanks in advance! natebot13

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• How to create Executable Jar

  - by Siddharth

  When I try to create a jar file i found the following error, so please someone help me to out of this. Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: Couldn't load file: img/black_ring.png at com.badlogic.gdx.graphics.Pixmap.(Pixmap.java:137) at com.badlogic.gdx.graphics.glutils.FileTextureData.prepare(FileTextureData.java:55) at com.badlogic.gdx.graphics.Texture.load(Texture.java:175) at com.badlogic.gdx.graphics.Texture.create(Texture.java:159) at com.badlogic.gdx.graphics.Texture.(Texture.java:133) at com.badlogic.gdx.graphics.Texture.(Texture.java:122) at com.badlogic.runningball.UserBall.(UserBall.java:19) at com.badlogic.runningball.GameScreen.(GameScreen.java:25) at com.badlogic.runningball.RunningBall.create(RunningBall.java:12) at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:126) at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:113) Caused by: com.badlogic.gdx.utils.GdxRuntimeException: File not found: img/black_ring.png (Internal) at com.badlogic.gdx.files.FileHandle.read(FileHandle.java:108) at com.badlogic.gdx.files.FileHandle.length(FileHandle.java:364) at com.badlogic.gdx.files.FileHandle.readBytes(FileHandle.java:156) at com.badlogic.gdx.graphics.Pixmap.(Pixmap.java:134) ... 10 more

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• Platformer Starter Kit - Collision Issues

  - by Cyral

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

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• How do I generate terrain like that of Scorched Earth?

  - by alex

  Hi, I'm a web developer and I am keen to start writing my own games. For familiarity, I've chosen JavaScript and canvas element for now. I want to generate some terrain like that in Scorched Earth. My first attempt made me realise I couldn't just randomise the y value; there had to be some sanity in the peaks and troughs. I have Googled around a bit, but either I can't find something simple enough for me or I am using the wrong keywords. Can you please show me what sort of algorithm I would use to generate something in the example, keeping in mind that I am completely new to games programming (since making Breakout in 2003 with Visual Basic anyway)?

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• 3D BSP rendering for maps made in 2d platform style

  - by Dev Joy

  I wish to render a 3D map which is always seen from top, camera is in sky and always looking at earth. Sample of a floor layout: I don't think I need complex structures like BSP trees to render them. I mean I can divide the map in grids and render them like done in 2D platform games. I just want to know if this is a good idea and what may go wrong if I don't choose a BSP tree rendering here. Please also mention is any better known rendering techniques are available for such situations.

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• Is it possible to calculate or mathematically prove if a game is balanced / fair?

  - by Lurca

  This question is not focussed on video games but games in general. I went to a boardgame trade fair yesterday and asked myself if there is a way to calculate the fairness of a game. Sure, some of them require a good portion of luck, but it might be possible to calculate if some character is overpowered. Especially in role-playing games and trading card games. How, for example, can the creators of "Magic: The Gathering" make sure that there isn't the "one card that beats them all", given the impressive number of available cards?

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• Node.js Lockstep Multiplayer Architecture

  - by Wakaka

  Background I'm using the lockstep model for a multiplayer Node.js/Socket.IO game in a client-server architecture. User input (mouse or keypress) is parsed into commands like 'attack' and 'move' on the client, which are sent to the server and scheduled to be executed on a certain tick. This is in contrast to sending state data to clients, which I don't wish to use due to bandwidth issues. Each tick, the server will send the list of commands on that tick (possibly empty) to each client. The server and all clients will then process the commands and simulate that tick in exactly the same way. With Node.js this is actually quite simple due to possibility of code sharing between server and client. I'll just put the deterministic simulator in the /shared folder which can be run by both server and client. The server simulation is required so that there is an authoritative version of the simulation which clients cannot alter. Problem Now, the game has many entity classes, like Unit, Item, Tree etc. Entities are created in the simulator. However, for each class, it has some methods that are shared and some that are client-specific. For instance, the Unit class has addHp method which is shared. It also has methods like getSprite (gets the image of the entity), isVisible (checks if unit can be seen by the client), onDeathInClient (does a bunch of stuff when it dies only on the client like adding announcements) and isMyUnit (quick function to check if the client owns the unit). Up till now, I have been piling all the client functions into the shared Unit class, and adding a this.game.isServer() check when necessary. For instance, when the unit dies, it will call if (!this.game.isServer()) { this.onDeathInClient(); }. This approach has worked pretty fine so far, in terms of functionality. But as the codebase grew bigger, this style of coding seems a little strange. Firstly, the client code is clearly not shared, and yet is placed under the /shared folder. Secondly, client-specific variables for each entity are also instantiated on the server entity (like unit.sprite) and can run into problems when the server cannot instantiate the variable (it doesn't have Image class like on browsers). So my question is, is there a better way to organize the client code, or is this a common way of doing things for lockstep multiplayer games? I can think of a possible workaround, but it does have its own problems. Possible workaround (with problems) I could use Javascript mixins that are only added when in a browser. Thus, in the /shared/unit.js file in the /shared folder, I would have this code at the end: if (typeof exports !== 'undefined') module.exports = Unit; else mixin(Unit, LocalUnit); Then I would have /client/localunit.js store an object LocalUnit of client-side methods for Unit. Now, I already have a publish-subscribe system in place for events in the simulator. To remove the this.game.isServer() checks, I could publish entity-specific events whenever I want the client to do something. For instance, I would do this.publish('Death') in /shared/unit.js and do this.subscribe('Death', this.onDeathInClient) in /client/localunit.js. But this would make the simulator's event listeners list on the server and the client different. Now if I want to clear all subscribed events only from the shared simulator, I can't. Of course, it is possible to create two event subscription systems - one client-specific and one shared - but now the publish() method would have to do if (!this.game.isServer()) { this.publishOnClient(event); }. All in all, the workaround off the top of my head seems pretty complicated for something as simple as separating the client and shared code. Thus, I wonder if there is an established and simpler method for better code organization, hopefully specific to Node.js games.

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• Can't read .cso files but I can read their .hlsl versions?

  - by Jader J Rivera

  Well I've been trying to read a .cso file to use as a shader for a DirectX program I'm currently making. Problem is no matter how I implemented a way to read the file it never worked. And after fidgeting around I discover that it's only the .cso files I can't read. I can read anything else (which means it works) even their .hlsl files. Which is strange because the .hlsl (high level shader language) files are supposed to turn into .cso (compiled shader object) files. What I'm currently doing is: vector<byte> Read(string File){ vector<byte> Text; fstream file(File, ios::in | ios::ate | ios::binary); if(file.is_open()){ Text.resize(file.tellg()); file.seekg(0 , ios::beg); file.read(reinterpret_cast<char*>(&Text[0]), Text.size()); file.close(); } return Text; }; If I then implement it. Read("VertexShader.hlsl"); //Works Read("VertexShader.cso"); //Doesn't Works?!?! And I need the .cso version of the shader to draw my sexy triangles. Without it my life and application will never continue and I have no idea what could be wrong. (I've also asked this at stack overflow but still no answers.)

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• Moving camera, or camera with discrete "screens"?

  - by Jacob Millward

  I'm making a game with a friend, but having trouble deciding on a camera style. The basic idea for the game, is having a randomly generated 2-dimensional world, with settlements in it. These settlements would have access to different resources, and it would be the job of the player to create bridges and ladders and links between these villages so they can trade. The player would advance personally by getting better gear, fighting monsters and looking for materials in the world, in order to craft and trade them at the settlements. My friend wants to use an old-style camera, where the world is split into a discrete number of screens that the player moves between. Similar to early Zelda dungeons, or Knytt Stories. This is opposite to me, as I want a standard camera that follows the player around as I feel the split-screen style camera limits the game. Can anyone argue the case either way? We've hit a massive roadblock here and can't seem to get past it.

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• 2D metaball liquid effect - how to feed output of one rendering pass as input to another shader

  - by Guye Incognito

  I'm attempting to make a shader for unity3d web project. I want to implement something like in the great answer by DMGregory in this question. in order to achieve a final look something like this.. Its metaballs with specular and shading. The steps to make this shader are. 1. Convert the feathered blobs into a heightmap. 2. Generate a normalmap from the heightmap 3. Feed the normal map and height map into a standard unity shader, for instance transparent parallax specular. I pretty much have all the pieces I need assembled but I am new to shaders and need help putting them together I can generate a heightmap from the blobs using some fragment shader code I wrote (I'm just using the red channel here cus i dont know if you can access the brightness) half4 frag (v2f i) : COLOR{ half4 texcol,finalColor; texcol = tex2D (_MainTex, i.uv); finalColor=_MyColor; if(texcol.r<_botmcut) { finalColor.r= 0; } else if((texcol.r>_topcut)) { finalColor.r= 0; } else { float r = _topcut-_botmcut; float xpos = _topcut - texcol.r; finalColor.r= (_botmcut + sqrt((xpos*xpos)-(r*r)))/_constant; } return finalColor; } turns these blobs.. into this heightmap Also I've found some CG code that generates a normal map from a height map. The bit of code that makes the normal map from finite differences is here void surf (Input IN, inout SurfaceOutput o) { o.Albedo = fixed3(0.5); float3 normal = UnpackNormal(tex2D(_BumpMap, IN.uv_MainTex)); float me = tex2D(_HeightMap,IN.uv_MainTex).x; float n = tex2D(_HeightMap,float2(IN.uv_MainTex.x,IN.uv_MainTex.y+1.0/_HeightmapDimY)).x; float s = tex2D(_HeightMap,float2(IN.uv_MainTex.x,IN.uv_MainTex.y-1.0/_HeightmapDimY)).x; float e = tex2D(_HeightMap,float2(IN.uv_MainTex.x-1.0/_HeightmapDimX,IN.uv_MainTex.y)).x; float w = tex2D(_HeightMap,float2(IN.uv_MainTex.x+1.0/_HeightmapDimX,IN.uv_MainTex.y)).x; float3 norm = normal; float3 temp = norm; //a temporary vector that is not parallel to norm if(norm.x==1) temp.y+=0.5; else temp.x+=0.5; //form a basis with norm being one of the axes: float3 perp1 = normalize(cross(norm,temp)); float3 perp2 = normalize(cross(norm,perp1)); //use the basis to move the normal in its own space by the offset float3 normalOffset = -_HeightmapStrength * ( ( (n-me) - (s-me) ) * perp1 + ( ( e - me ) - ( w - me ) ) * perp2 ); norm += normalOffset; norm = normalize(norm); o.Normal = norm; } Also here is the built-in transparent parallax specular shader for unity. Shader "Transparent/Parallax Specular" { Properties { _Color ("Main Color", Color) = (1,1,1,1) _SpecColor ("Specular Color", Color) = (0.5, 0.5, 0.5, 0) _Shininess ("Shininess", Range (0.01, 1)) = 0.078125 _Parallax ("Height", Range (0.005, 0.08)) = 0.02 _MainTex ("Base (RGB) TransGloss (A)", 2D) = "white" {} _BumpMap ("Normalmap", 2D) = "bump" {} _ParallaxMap ("Heightmap (A)", 2D) = "black" {} } SubShader { Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"} LOD 600 CGPROGRAM #pragma surface surf BlinnPhong alpha #pragma exclude_renderers flash sampler2D _MainTex; sampler2D _BumpMap; sampler2D _ParallaxMap; fixed4 _Color; half _Shininess; float _Parallax; struct Input { float2 uv_MainTex; float2 uv_BumpMap; float3 viewDir; }; void surf (Input IN, inout SurfaceOutput o) { half h = tex2D (_ParallaxMap, IN.uv_BumpMap).w; float2 offset = ParallaxOffset (h, _Parallax, IN.viewDir); IN.uv_MainTex += offset; IN.uv_BumpMap += offset; fixed4 tex = tex2D(_MainTex, IN.uv_MainTex); o.Albedo = tex.rgb * _Color.rgb; o.Gloss = tex.a; o.Alpha = tex.a * _Color.a; o.Specular = _Shininess; o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_BumpMap)); } ENDCG } FallBack "Transparent/Bumped Specular" }

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• map data structure in pacman

  - by Sam Fisher

  i am trying to make a pacman game in c# using GDI+, i have done some basic work and i have previously replicated games like copter-it and minesweeper. but i am confused about how do i implement the map in pacman, i mean which datastructure to use, so i can use it for moving AI controlled objects and check collisions with walls. i thought of a 2d array of ints but that didnt make sense to me. looking for some help. thanks.

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• Full screen blackout using allegro in codeblocks

  - by Armando Ortiz

  I'm very interested in game programming and I'm taking my first steps alone. So I installed allegro. Although Dev-C++ didn't work, Code::Blocks compiled successfully. I started out with this basic program: #include <allegro.h> int main(){ allegro_init(); install_keyboard(); set_gfx_mode( GFX_AUTODETECT, 640, 480, 0, 0); readkey(); return 0; } END_OF_MAIN(); The problem comes in when I try to run it. It opens the little window as always, but rapidly blacks out my whole screen. I press any key and it takes me back to the little window telling me that it finished, which means the program worked. But I try any other program with allegro, like: #include <allegro.h> int x = 10; int y = 10; int main(){ allegro_init(); install_keyboard(); set_gfx_mode( GFX_AUTODETECT, 640, 480, 0, 0); while ( !key[KEY_ESC] ){ clear_keybuf(); acquire_screen(); textout_ex( screen, font, " ", x, y, makecol( 0, 0, 0), makecol( 0, 0, 0) ); if (key[KEY_UP]) --y; else if (key[KEY_DOWN]) ++y; else if (key[KEY_RIGHT]) ++x; else if (key[KEY_LEFT]) --x; textout_ex( screen, font, "@", x, y, makecol( 255, 0, 0), makecol( 0, 0, 0) ); release_screen(); rest(50); } return 0; } END_OF_MAIN(); And the same thing happens over and over again! Is there something I'm doing wrong?

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• Fitting a rectangle into screen with XNA

  - by alecnash

  I am drawing a rectangle with primitives in XNA. The width is: width = GraphicsDevice.Viewport.Width and the height is height = GraphicsDevice.Viewport.Height I am trying to fit this rectangle in the screen (using different screens and devices) but I am not sure where to put the camera on the Z-axis. Sometimes the camera is too close and sometimes to far. This is what I am using to get the camera distance: //Height of piramid float alpha = 0; float beta = 0; float gamma = 0; alpha = (float)Math.Sqrt((width / 2 * width/2) + (height / 2 * height / 2)); beta = height / ((float)Math.Cos(MathHelper.ToRadians(67.5f)) * 2); gamma = (float)Math.Sqrt(beta*beta - alpha*alpha); position = new Vector3(0, 0, gamma); Any idea where to put the camera on the Z-axis?

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• Pathfinding in multi goal, multi agent environment

  - by Rohan Agrawal

  I have an environment in which I have multiple agents (a), multiple goals (g) and obstacles (o). . . . a o . . . . . . . o . g . . a . . . . . . . . . . o . . . . o o o o . g . . o . . . . . . . o . . . . o . . . . o o o o a What would an appropriate algorithm for pathfinding in this environment? The only thing I can think of right now, is to Run a separate version of A* for each goal separately, but i don't think that's very efficient.

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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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• As an indie game dev, what processes are the best for soliciting feedback on my design/spec/idea? [closed]

  - by Jess Telford

  Background I have worked in a professional environment where the process usually goes like the following: Brain storm idea Solidify the game mechanics / design Iterate on design/idea to create a more solid experience Spec out the details of the design/idea Build it Step 3. is generally done with the stakeholders of the game (developers, designers, investors, publishers, etc) to reach an 'agreement' which meets the goals of all involved. Due to this process involving a series of often opposing and unique view points, creative solutions can surface through discussion / iteration. This is backed up by a process for collating the changes / new ideas, as well as structured time for discussion. As a (now) indie developer, I have to play the role of all the stakeholders (developers, designers, investors, publishers, etc), and often find myself too close to the idea / design to do more than minor changes, which I feel to be local maxima when it comes to the best result (I'm looking for the global maxima, of course). I have read that ideas / game designs / unique mechanics are merely multipliers of execution, and that keeping them secret is just silly. In sharing the idea with others outside the realm of my own thinking, I hope to replicate the influence other stakeholders have. I am struggling with the collation of changes / new ideas, and any kind of structured method of receiving feedback. My question: As an indie game developer, how and where can I share my ideas/designs to receive meaningful / constructive feedback? How can I successfully collate the feedback into a new iteration of the design? Are there any specialized websites, etc?

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• Character creation using spritesheets

  - by Patrick Developer

  I am currently creating a 2D fighting game and have implemented a system where upon starting a new game, the player is presented with the option to create a custom character. I have a set of string arrays set with values that correspond to hair, headgear, chest, lower body and shoes. When done selecting a variety of items from the lists, a code is generated based off the index of each item (i.e 01123), which is then used to assign the correct Spritesheet to the player character. This has already presented a lot of work as I have had to create quite a few spreadsheets based of possible combinations, but I am now looking at a massive amount of work to implement each variation. I have started to look into setting layers for each item to reduce workload, but I am also looking at having different stances for the character - Depending on the currently equipped weapon - so this may present a lot of work either way. My question is, do I have any alternatives or am I stuck creating masses of Spritesheets to cover all combinations? As a side note, how much impact will assigning layered items have on overall performance?

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• Scanline filling of polygons that share edges and vertices

  - by Belgin

  In this picture (a perspective projection of an icosahedron), the scanline (red) intersects that vertex at the top. In an icosahedron each edge belongs to two triangles. From edge a, only one triangle is visible, the other one is in the back. Same for edge d. Also, in order to determine what color the current pixel should be, each polygon has a flag which can either be 'in' or 'out', depending upon where on the scanline we currently are. Flags are flipped according to the intersection of the scanline with the edges. Now, as we go from a to d (because all edges are intersected with the scanline at that vertex), this happens: the triangle behind triangle 1 and triangle 1 itself are set 'in', then 2 is set in and 1 is 'out', then 3 is set 'in', 2 is 'out' and finally 3 is 'out' and the one behind it is set 'in', which is not the desired behavior because we only need the triangles which are facing us to be set 'in', the rest should be 'out'. How do process the edges in the Active Edge List (a list of edges that are currently intersected by the scanline) so the right polys are set 'in'? Also, I should mention that the edges are unique, which means there exists an array of edges in the data structure of the icosahedron which are pointed to by edge pointers in each of the triangles.

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• Too sell or give for free

  - by QAH

  Hello everyone! I am currently making a game that I was originally planning to sell. It is a simple 2D arcade style game for the PC. I've seen many indie games become popular and generate revenue from advertisements, but the game itself remains free. I need some advice on whether or not I should sell my game, release it for free with advertisements, or ask for donations and keep the game free. I feel that my game is fun, but of course the graphics aren't tip top because I am a programmer, not an artist. I just take screenshots of 3D models I get from Turbosquid and crop around it to make a sprite. Also, and I could be very wrong about this, it seems that there are more legal issues surrounding selling a game than making it free and generating revenue from advertisement, or asking for donations. If I am wrong, someone please correct me. Also, I am very interested in generating some revenue for my work, but that isn't at the very top of my list. I am in my last year of high school, soon to be going to college, and I am going to major in computer science/software engineering. So I am trying to gain some preliminary experience at home by coding stuff every day. One way of getting this experience is by making this game. So what do you think? What route should I take? What has worked well with other indie games? Thanks in advance.

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• How do game engines implement certain features?

  - by Milo

  I have always wondered how modern game engines do things such as realistic water, ambient occluded lighting, eye adaptation, global illumination, etc. I'm not so much interested in the implementation details, but more on what part of the graphics API such as D3D or OpenGL allow adding such functionality. The only thing I can think of is shaders, but I do not think just shaders can do all that. So really what I'm asking is, what functions or capabilities of graphics APIs enable developers to implement these types of features into their engines? Thanks

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• How to draw a global day night curve

  - by Lumis

  I see many applications which have world-clock map, and I would like to make my own to enhance some of my mobile apps. I wonder if anybody has any knowledge where to start, how to draw a curved shadow representing the dawn and the sunset on the globe. See the example: http://aa.usno.navy.mil/imagery/earth/map?year=2012&month=6&day=19&hour=14&minute=47 I think that this curve goes up and down and creates an artic day/night etc Perhaps there is some acceptable approximation formula without a need to load data for each our and each global parallel and meridian...

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• matrix 4x4 position data

  - by freefallr

  I understand that a 4x4 matrix holds rotation and position data. The rotation data is held in the 3x3 sub-matrix at the top left of the matrix. The position data is held in the last column of the matrix. e.g. glm::vec3 vParentPos( mParent[3][0], mParent[3][1], mParent[3][2] ); My question is - am I accessing the parent matrix correctly in the example above? I know that opengl uses a different matrix ordering that directx, (row order instead of column order or something), so, should the mParent be accessed as follows instead? glm::vec3 vParentPos( mParent[0][3], mParent[1][3], mParent[2][3] ); thanks!

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• Convience of mySQL over xml

  - by Bonechilla

  Currently I use XML to store specific information to correctly load a few things such as a list of specfied characters, scenes and music, Once more I use JAXB in combination with standard compression/decompression(ZIP) functionality to store a list of extrenous data. This data is called to add functionality to the character, somewhat like Skills in an RPG. Each skill is seperated into its own XML file with a grandlist which contains the names of each file with their extensions omitted and zipped in folder that gets encrypted. At first using xml was working fine however as the skill list grow i worry about its stability. I was wondering if I should begin storing the data in mySQL. Originally I planned to simply convert everything to JSON over xml but i think possibly mySQL would be a better move. Can anyone inform me of the key difference and pros and cons of each I guess i'm looking for the best way to store the data more conviently and would be easier to operate on. The data is mostly primatives and strings and the only arraylist of values i have i can just concat into a single field and parse later

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• OpenGLES GLSL Shader attributes always bound to 0

  - by codemonkey

  So I have a very simple vertex shader as follows #version 120 attribute vec3 position; attribute vec3 inColor; uniform mat4 mvp; varying vec3 fragColor; void main(void){ fragColor = inColor; gl_Position = mvp * vec4(position, 1.0); } Which I load, as well as the fragment shader: #version 120 varying vec3 fragColor; void main(void) { gl_FragColor = vec4(fragColor,1.0); } Which I then load, compile, and link to my shader program. I check for link status using glGetProgramiv(shaderProgram, GL_LINK_STATUS, &shaderSuccess); which returns GL_TRUE so I think its ok. However, when I query the active attributes and uniforms using #ifdef DEBUG int totalAttributes = -1; glGetProgramiv(shaderProgram, GL_ACTIVE_ATTRIBUTES, &totalAttributes); for(int i=0; i<totalAttributes; ++i) { int name_len=-1, num=-1; GLenum type = GL_ZERO; char name[100]; glGetActiveAttrib(shaderProgram, GLuint(i), sizeof(name)-1, &name_len, &num, &type, name ); name[name_len] = 0; GLuint location = glGetAttribLocation(shaderProgram, name); fprintf(stderr, "Attribute %s is bound at %d\n", name, location); } int totalUniforms = -1; glGetProgramiv(shaderProgram, GL_ACTIVE_UNIFORMS, &totalUniforms); for(int i=0; i<totalUniforms; ++i) { int name_len=-1, num=-1; GLenum type = GL_ZERO; char name[100]; glGetActiveUniform(shaderProgram, GLuint(i), sizeof(name)-1, &name_len, &num, &type, name ); name[name_len] = 0; GLuint location = glGetUniformLocation(shaderProgram, name); fprintf(stderr, "Uniform %s is bound at %d\n", name, location); } #endif I get: Attribute inColor is bound at 0 Attribute position is bound at 1 Uniform mvp is bound at 0 Which leads to failure when trying to use the shader to render the objects. I have tried switching the order of declaration of position & inColor, but still, only position is bound with the other two giving 0 Can someone please explain why this is happening? Thanks

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• Most efficient way to implement delta time

  - by Starkers

  Here's one way to implement delta time: /// init /// var duration = 5000, currentTime = Date.now(); // and create cube, scene, camera ect ////// function animate() { /// determine delta /// var now = Date.now(), deltat = now - currentTime, currentTime = now, scalar = deltat / duration, angle = (Math.PI * 2) * scalar; ////// /// animate /// cube.rotation.y += angle; ////// /// update /// requestAnimationFrame(render); ////// } Could someone confirm I know how it works? Here what I think is going on: Firstly, we set duration at 5000, which how long the loop will take to complete in an ideal world. With a computer that is slow/busy, let's say the animation loop takes twice as long as it should, so 10000: When this happens, the scalar is set to 2.0: scalar = deltat / duration scalar = 10000 / 5000 scalar = 2.0 We now times all animation by twice as much: angle = (Math.PI * 2) * scalar; angle = (Math.PI * 2) * 2.0; angle = (Math.PI * 4) // which is 2 rotations When we do this, the cube rotation will appear to 'jump', but this is good because the animation remains real-time. With a computer that is going too quickly, let's say the animation loop takes half as long as it should, so 2500: When this happens, the scalar is set to 0.5: scalar = deltat / duration scalar = 2500 / 5000 scalar = 0.5 We now times all animation by a half: angle = (Math.PI * 2) * scalar; angle = (Math.PI * 2) * 0.5; angle = (Math.PI * 1) // which is half a rotation When we do this, the cube won't jump at all, and the animation remains real time, and doesn't speed up. However, would I be right in thinking this doesn't alter how hard the computer is working? I mean it still goes through the loop as fast as it can, and it still has render the whole scene, just with different smaller angles! So this a bad way to implement delta time, right? Now let's pretend the computer is taking exactly as long as it should, so 5000: When this happens, the scalar is set to 1.0: angle = (Math.PI * 2) * scalar; angle = (Math.PI * 2) * 1; angle = (Math.PI * 2) // which is 1 rotation When we do this, everything is timsed by 1, so nothing is changed. We'd get the same result if we weren't using delta time at all! My questions are as follows Mostly importantly, have I got the right end of the stick here? How do we know to set the duration to 5000 ? Or can it be any number? I'm a bit vague about the "computer going too quickly". Is there a way loop less often rather than reduce the animation steps? Seems like a better idea. Using this method, do all of our animations need to be timesed by the scalar? Do we have to hunt down every last one and times it? Is this the best way to implement delta time? I think not, due to the fact the computer can go nuts and all we do is divide each animation step and because we need to hunt down every step and times it by the scalar. Not a very nice DSL, as it were. So what is the best way to implement delta time? Below is one way that I do not really get but may be a better way to implement delta time. Could someone explain please? // Globals INV_MAX_FPS = 1 / 60; frameDelta = 0; clock = new THREE.Clock(); // In the animation loop (the requestAnimationFrame callback)… frameDelta += clock.getDelta(); // API: "Get the seconds passed since the last call to this method." while (frameDelta >= INV_MAX_FPS) { update(INV_MAX_FPS); // calculate physics frameDelta -= INV_MAX_FPS; } How I think this works: Firstly we set INV_MAX_FPS to 0.01666666666 How we will use this number number does not jump out at me. We then intialize a frameDelta which stores how long the last loop took to run. Come the first loop frameDelta is not greater than INV_MAX_FPS so the loop is not run (0 = 0.01666666666). So nothing happens. Now I really don't know what would cause this to happen, but let's pretend that the loop we just went through took 2 seconds to complete: We set frameDelta to 2: frameDelta += clock.getDelta(); frameDelta += 2.00 Now we run an animation thanks to update(0.01666666666). Again what is relevance of 0.01666666666?? And then we take away 0.01666666666 from the frameDelta: frameDelta -= INV_MAX_FPS; frameDelta = frameDelta - INV_MAX_FPS; frameDelta = 2 - 0.01666666666 frameDelta = 1.98333333334 So let's go into the second loop. Let's say it took 2(? Why not 2? Or 12? I am a bit confused): frameDelta += clock.getDelta(); frameDelta = frameDelta + clock.getDelta(); frameDelta = 1.98333333334 + 2 frameDelta = 3.98333333334 This time we enter the while loop because 3.98333333334 = 0.01666666666 We run update We take away 0.01666666666 from frameDelta again: frameDelta -= INV_MAX_FPS; frameDelta = frameDelta - INV_MAX_FPS; frameDelta = 3.98333333334 - 0.01666666666 frameDelta = 3.96666666668 Now let's pretend the loop is super quick and runs in just 0.1 seconds and continues to do this. (Because the computer isn't busy any more). Basically, the update function will be run, and every loop we take away 0.01666666666 from the frameDelta untill the frameDelta is less than 0.01666666666. And then nothing happens until the computer runs slowly again? Could someone shed some light please? Does the update() update the scalar or something like that and we still have to times everything by the scalar like in the first example?

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