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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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• How do I use depth testing and texture transparency together in my 2.5D world?

  - by nbolton

  Note: I've already found an answer (which I will post after this question) - I was just wondering if I was doing it right, or if there is a better way. I'm making a "2.5D" isometric game using OpenGL ES (JOGL). By "2.5D", I mean that the world is 3D, but it is rendered using 2D isometric tiles. The original problem I had to solve was that my textures had to be rendered in order (from back to front), so that the tiles overlapped properly to create the proper effect. After some reading, I quickly realised that this is the "old hat" 2D approach. This became difficult to do efficiently, since the 3D world can be modified by the player (so stuff can appear anywhere in 3D space) - so it seemed logical that I take advantage of the depth buffer. This meant that I didn't have to worry about rendering stuff in the correct order. However, I faced a problem. If you use GL_DEPTH_TEST and GL_BLEND together, it creates an effect where objects are blended with the background before they are "sorted" by z order (meaning that you get a weird kind of overlap where the transparency should be). Here's some pseudo code that should illustrate the problem (incidentally, I'm using libgdx for Android). create() { // ... // some other code here // ... Gdx.gl.glEnable(GL10.GL_DEPTH_TEST); Gdx.gl.glEnable(GL10.GL_BLEND); } render() { Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); Gdx.gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA); // ... // bind texture and create vertices // ... } So the question is: How do I solve the transparency overlap problem?

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• Strange rendering in XNA/Monogame

  - by Gerhman

  I am trying to render G-Code generated for a 3d-printer as the printed product by reading the file as line segments and the drawing cylinders with the diameter of the filament around the segment. I think I have managed to do this part right because the vertex I am sending to the graphics device appear to have been processed correctly. My problem I think lies somewhere in the rendering. What basically happens is that when I start rotating my model in the X or Y axis then it renders perfectly for half of the rotation but then for the other half it has this weird effect where you start seeing through the outer filament into some of the shapes inside. This effect is the strongest with X rotations though. Here is a picture of the part of the rotation that looks correct: And here is one that looks horrible: I am still quite new to XNA and/Monogame and 3d programming as a whole. I have no idea what could possibly be causing this and even less of an idea of what this type of behavior is called. I am guessing this has something to do with rendering so have added the code for that part: protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.Black); basicEffect.World = world; basicEffect.View = view; basicEffect.Projection = projection; basicEffect.VertexColorEnabled = true; basicEffect.EnableDefaultLighting(); GraphicsDevice.SetVertexBuffer(vertexBuffer); RasterizerState rasterizerState = new RasterizerState(); rasterizerState.CullMode = CullMode.CullClockwiseFace; rasterizerState.ScissorTestEnable = true; GraphicsDevice.RasterizerState = rasterizerState; foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes) { pass.Apply(); GraphicsDevice.DrawPrimitives(PrimitiveType.TriangleList, 0, vertexBuffer.VertexCount); } base.Draw(gameTime); } I don't know if it could be because I am shading something that does not really have a texture. I am using this custom vertex declaration I found on some tutorial that allows me to store a vertex with a position, color and normal: public struct VertexPositionColorNormal { public Vector3 Position; public Color Color; public Vector3 Normal; public readonly static VertexDeclaration VertexDeclaration = new VertexDeclaration ( new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0), new VertexElement(sizeof(float) * 3, VertexElementFormat.Color, VertexElementUsage.Color, 0), new VertexElement(sizeof(float) * 3 + 4, VertexElementFormat.Vector3, VertexElementUsage.Normal, 0) ); } If any of you have ever seen this type of thing please help. Also, if you think that the problem might lay somewhere else in my code then please just request what part you would like to see in the comments section.

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• How display path ball will bounce?

  - by boolean

  I'm trying to figure out a way to show the path a ball will travel, so that the player can line up a shot before they fire the ball. I can't think of a way to calculate this path in advance and show it to the player, especially if it involves collision detection. At first I thought I would run the game at a super high speed for one update, plot the path with some dotted lines where the ball bounced, and then in the next frame hide the 'tracer' ball. This seems to have two issues - Calculating collision detection without actually updating the frames and collision detection getting less reliable at high speeds. If they were straight lines I think I could figure this out in a while loop, but trying to take into account the speed of the ball, the curve of the path, the reflecting from other objects..it all seems a bit much. I'm not looking for any code and this isn't a platform specific question, more just help trying to figure out conceptually how this would work. Can this be done? Are there techniques to achieve this?

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• Seek Steering Behavior with Target Direction for Group of Fighters

  - by SebastianStehle

  I am implementing steering algorithms with group management for spaceships (fighters). I select a leader and assign the target positions for the other spaceships based on the target position of the leader and an offset. This works well. But when my spaceships arrive they all have a different direction. I want them to keep to look in the same direction (target - start). I also want to combine this behavior with a minimum turning radius that is based on the speed. The only idea I have is to calculate a path for each spaceship with an point before the target position, so the ships have some time left to turn into the right position. But I dont know if this is a good idea. I guess there will be a lot of rare cases where this can cause a problem. So the question is, if anybody knows how to solve this problem and has some (simple code) or pseudocode for me or at least some good explanation.

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• A*, Tile costs and heuristic; How to approach

  - by Kevin Toet

  I'm doing exercises in tile games and AI to improve my programming. I've written a highly unoptimised pathfinder that does the trick and a simple tile class. The first problem i ran into was that the heuristic was rounded to int's which resulted in very straight paths. Resorting a Euclidian Heuristic seemed to fixed it as opposed to use the Manhattan approach. The 2nd problem I ran into was when i tried added tile costs. I was hoping to use the value's of the flags that i set on the tiles but the value's were too small to make the pathfinder consider them a huge obstacle so i increased their value's but that breaks the flags a certain way and no paths were found anymore. So my questions, before posting the code, are: What am I doing wrong that the Manhatten heuristic isnt working? What ways can I store the tile costs? I was hoping to (ab)use the enum flags for this The path finder isnt considering the chance that no path is available, how do i check this? Any code optimisations are welcome as I'd love to improve my coding. public static List<Tile> FindPath( Tile startTile, Tile endTile, Tile[,] map ) { return FindPath( startTile, endTile, map, TileFlags.WALKABLE ); } public static List<Tile> FindPath( Tile startTile, Tile endTile, Tile[,] map, TileFlags acceptedFlags ) { List<Tile> open = new List<Tile>(); List<Tile> closed = new List<Tile>(); open.Add( startTile ); Tile tileToCheck; do { tileToCheck = open[0]; closed.Add( tileToCheck ); open.Remove( tileToCheck ); for( int i = 0; i < tileToCheck.neighbors.Count; i++ ) { Tile tile = tileToCheck.neighbors[ i ]; //has the node been processed if( !closed.Contains( tile ) && ( tile.flags & acceptedFlags ) != 0 ) { //Not in the open list? if( !open.Contains( tile ) ) { //Set G int G = 10; G += tileToCheck.G; //Set Parent tile.parentX = tileToCheck.x; tile.parentY = tileToCheck.y; tile.G = G; //tile.H = Math.Abs(endTile.x - tile.x ) + Math.Abs( endTile.y - tile.y ) * 10; //TODO omg wtf and other incredible stories tile.H = Vector2.Distance( new Vector2( tile.x, tile.y ), new Vector2(endTile.x, endTile.y) ); tile.Cost = tile.G + tile.H + (int)tile.flags; //Calculate H; Manhattan style open.Add( tile ); } //Update the cost if it is else { int G = 10;//cost of going to non-diagonal tiles G += map[ tile.parentX, tile.parentY ].G; //If this path is shorter (G cost is lower) then change //the parent cell, G cost and F cost. if ( G < tile.G ) //if G cost is less, { tile.parentX = tileToCheck.x; //change the square's parent tile.parentY = tileToCheck.y; tile.G = G;//change the G cost tile.Cost = tile.G + tile.H + (int)tile.flags; // add terrain cost } } } } //Sort costs open = open.OrderBy( o => o.Cost).ToList(); } while( tileToCheck != endTile ); closed.Reverse(); List<Tile> validRoute = new List<Tile>(); Tile currentTile = closed[ 0 ]; validRoute.Add( currentTile ); do { //Look up the parent of the current cell. currentTile = map[ currentTile.parentX, currentTile.parentY ]; currentTile.renderer.material.color = Color.green; //Add tile to list validRoute.Add( currentTile ); } while ( currentTile != startTile ); validRoute.Reverse(); return validRoute; } And my Tile class: [Flags] public enum TileFlags: int { NONE = 0, DIRT = 1, STONE = 2, WATER = 4, BUILDING = 8, //handy WALKABLE = DIRT | STONE | NONE, endofenum } public class Tile : MonoBehaviour { //Tile Properties public int x, y; public TileFlags flags = TileFlags.DIRT; public Transform cachedTransform; //A* properties public int parentX, parentY; public int G; public float Cost; public float H; public List<Tile> neighbors = new List<Tile>(); void Awake() { cachedTransform = transform; } }

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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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• Are there any alternative JS ports of Box2D?

  - by Petteri Hietavirta

  I have been thinking about creating a top down 2D car game for HTML5. For my first game I wrote the physics and collisions my self but for this one I would like to use some ready made library. I found out Box2D and its JS port. http://box2d-js.sourceforge.net It seems to be quite old port, made in 2008. Is it lacking many features of current Box2D or does it have major issues with it? And are there any alternatives for it?

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• Multiple volumetric lights

  - by notabene

  I recently read this GPU GEMS 3 article Volumetric Light Scattering as a Post-Process. I like the idea to add volumetric light property to realtime render i'm working on. Question is will it work for multiple lights? Our renderer uses one render pass per light and uses additive blending to sum incoming light. I'm mostly convinced that it have to work nice. Do you agree? Maybe there can be problem where light rays crosses each other.

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• How to handle shoot instructions, in a multiplayer TD

  - by Martin Elvar Jensen

  I'm currently working on a Multiplayer Tower Defense game, using ImpactJS & Node. I seek some clarification about how to handle projectiles from towers, let me explain. So the server is running the master game, and the clients just follow the instruction from the server. Lets say there is about 20 towers on the stage, all needs instructions for which creeps to shoot at. Now lets say each towers fires twice in a second, that's 40 shots each second, (worst case scenario) which is 40 request per second to each client, would't this casue alot of stress to the server, saying that we have 50 games running the same time. So what i am really asking, is this method inefficient, and is there a smarter way to handle all these instructions. Thank you.

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• Unable to access A class variables in B Class - Unity-Monodevelop

  - by Syed

  I have made a class including variables in Monodevelop which is: public class GridInfo : MonoBehaviour { public float initPosX; public float initPosY; public bool inUse; public int f; public int g; public int h; public GridInfo parent; public int y,x; } Now I am using its class variable in another class, Map.cs which is: public class Map : MonoBehaviour { public static GridInfo[,] Tile = new GridInfo[17, 23]; void Start() { Tile[0,0].initPosX = initPosX; //Line 49 } } Iam not getting any error on runtime, but when I play in unity it is giving me error NullReferenceException: Object reference not set to an instance of an object Map.Start () (at Assets/Scripts/Map.cs:49) I am not inserting this script in any gameobject, as Map.cs will make a GridInfo type array, I have also tried using variables using GetComponent, where is the problem ?

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• Can anyone explain step-by-step how the as3isolib depth-sorts isometric objects?

  - by Rob Evans

  The library manages to depth-sort correctly, even when using items of non-1x1 sizes. I took a look through the code but it's a big project to go through line by line! There are some questions about the process such as: How are the x, y, z values of each object defined? Are they the center points of the objects or something else? I noticed that the IBounds defines the bounds of the object. If you were to visualise a cuboid of 40, 40, 90 in size, where would each of the IBounds metrics be? I would like to know how as3isolib achieves this although I would also be happy with a generalised pseudo-code version. At present I have a system that works 90% of the time but in cases of objects that are along the same horizontal line, the depth is calculated as the same value. The depth calculation currently works like this: x = object horizontal center point y = object vertical center point originX and Y = the origin point relative to the object so if you want the origin to be the center, the value would be originX = 0.5, originY = 0.5. If you wanted the origin to be vertical center, horizontal far right of the object it would be originX = 1.0, originY = 0.5. The origin adjusts the position that the object is transformed from. AABB_width = The bounding box width. AABB_height = The bounding box height. depth = x + (AABB_width * originX) + y + (AABB_height * originY) - z; This generates the same depth for all objects along the same horizontal x.

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• Starting point for a simple game written in action script [closed]

  - by Hossein

  Possible Duplicate: AS3/Flash Game Dev: Looking for good & current step by step. Hi, I want to develop a simple game like: http://www.albinoblacksheep.com/games/falldown2 And then making it a bit more fancy. But I don't know where to start. I have already started AS3 so I know about the syntax and stuff, but I am kinda lost. Does anyone knows of a nice starting point or a tutorial that can help me with this? Thanks

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• Breakout clone, how to handle/design for collision detection/physics between objects?

  - by Zolomon

  I'm working on a breakout clone, and I wish to create some realistic physics effects for collision - angles on the paddle should allow the ball to bounce, as well as doing curve balls etc. I could use per-pixel based collision detection, but then I thought it might be easier with line/circle intersection testing. So, then I naturally consider making a polygon class for the line-based objects and use the built-in circle class for the circular objects. That sounds like an OK approach, right? And then just check for collision using the specified algorithm based on the objects that might be within each other's range?

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• Can I run into legal issues with random names?

  - by Nathan Sabruka

  I'm currently building a game whose NPC's are going to be assigned a random gender and a random name for the right gender. To do this I will be using a "database" of names (actually a text file with tuples). There would also be a list of last names, which will be added to the first name also randomly. My question is the following. Suppose one such random name is "George Bush", and this person has been randomly assigned the job of president. As you can see, this could easily be seen as having been "copied" from a real-life person. The main issue is this. Names will be randomly-generated, yes, but the seed for random-number generation will be constant. In other words, the name of an NPC would be randomly-generated, i.e. I wouldn't choose it, but it would be the same for every player. Could this get me in trouble? We cannot verify all possible names, since the generated number of NPC's could be potentially limitless (new NPC's are being created whenever needed).

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• Examples of good Javascript/HTML5 based games

  - by Zuch

  Now that Flash is largely being replaced with HTML5 elements (video, audio, canvas, etc.) are there any good examples of web-based games built on completely open standards (meaning Javascript, HTML and CSS)? I see a lot of examples of pure HTML5 implementations of what was once only in Flash (like stuff here: http://www.html5rocks.com/) but not many games, a domain which still seem dominated by Flash. I'm curious what's possible and what the limitations are.

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• XNA Skinned Animated Mesh Rendering Exported from Maya

  - by Devin Garner

  I am working on translating an old RTS game engine I wrote from DirectX9 to XNA. My old models didn't have animation & are an old format, so I'm trying with an FBX file. I temporarily "borrowed" a model from League of Legends just to test if my rendering is working correctly. I imported the mesh/bones/skin/animation into Maya 2012 using an "unnamed" 3rd-party import tool. (obviously I'll have to get legit models later, but I just want to test if my programming is correct). Everything looks correct in maya and it renders the animations flawlessly. I exported everything into a single FBX file (with only a single animation). I then tried to load this model using the example at the following site: http://create.msdn.com/en-US/education/catalog/sample/skinned_model With my exported FBX, the animation looks correct for most of the frames, however at random times it screws up for a split second. Basically, the body/arms/head will look right, but the leg/foot will shoot out to a random point in space for a second & then go back to the normal position. The original FBX from the sample looks correct in my program. It seems odd that my model was imported into maya wrong, since it displays fine in Maya. So, I'm thinking either I'm exporting it wrong, or the sample code is bad & the model from the sample caters to the samples bad code. I'm new to 3D programming & maya, so chances are I'm doing something wrong in the export. I'm using mostly the defaults, but I've tried all 3 interpolation modes (quaternion, euler, resample). Thanks

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• Marketing: Angry Birds - How it's done

  - by John

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

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• Collision detection with heightmap based terrain

  - by Truman's world

  I am developing a 2D tank game. The terrain is generated by Midpoint Displacement Algorithm, so the terrain is represented by an array: index ---> height of terrain [0] ---> 5 [1] ---> 8 [2] ---> 4 [3] ---> 6 [4] ---> 8 [5] ---> 9 ... ... The rendered mountain looks like this: * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 0 1 2 3 4 5 ... I want tanks to be able to move smoothly on the terrain (I mean tanks can rotate according to the height when they move), but the surface of the terrain is not flat, it is polygonal. Can anyone give me some help with collision detection in this situation? Thanks in advance.

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• How do I calculate opposite of a vector, add some slack

  - by Jason94

  How can i calulate a valid range (RED) for my object's (BLACK) traveling direction (GREEN). The green is a Vector2 where x and y range is -1 to 1. What I'm trying to do here is to create rocket fuel burn effekt. So what i got is rocket speed (float) rocket direction (Vector2 x = [-1, 1], y = [-1, 1]) I may think that rocket speed does not matter as fuel burn effect (particle) is created on position with its own speed.

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• Checking is sides of cubes are solid

  - by Christian Frantz

  In relation to this question: http://gamedev.stackexchange.com/a/28524/31664 And a question I asked earlier: Creating a DrawableGameComponent And also because my internet is too slow to get on chat. I'm wondering how to check if the sides of a cube are solid. I've created 12 methods, each one creating indices and vertices for sides of a cube. Now when I use these methods, the cube creates how it should. All 6 sides show up and its like I didnt change a thing. How can use if statements to check if the side of a cube is solid? The pseudocode from the question above shows this: if(!isSolidAt(x+1,y,z)) verticesToDraw += AddXPlusFace(x,y,z) But in my case is would be: if(!sideIsSolid) SetUpFrontFaceIndices(); My method simply takes these index and vertex values and adds them to a list indicesToDraw and verticesToDraw, as shown in the answer above

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• Trying to detect collision between two polygons using Separating Axis Theorem

  - by Holly

  The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(vertices[0]); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(vertices[i]); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if( other.x <= y || other.y >= x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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• How do I draw a point sprite using OpenGL ES on Android?

  - by nbolton

  Edit: I'm using the GL enum, which is incorrect since it's not part of OpenGL ES (see my answer). I should have used GL10, GL11 or GL20 instead. Here's a few snippets of what I have so far... void create() { renderer = new ImmediateModeRenderer(); tiles = Gdx.graphics.newTexture( Gdx.files.getFileHandle("res/tiles2.png", FileType.Internal), TextureFilter.MipMap, TextureFilter.Linear, TextureWrap.ClampToEdge, TextureWrap.ClampToEdge); } void render() { Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); Gdx.gl.glClearColor(0.6f, 0.7f, 0.9f, 1); } void renderSprite() { int handle = tiles.getTextureObjectHandle(); Gdx.gl.glBindTexture(GL.GL_TEXTURE_2D, handle); Gdx.gl.glEnable(GL.GL_POINT_SPRITE); Gdx.gl11.glTexEnvi(GL.GL_POINT_SPRITE, GL.GL_COORD_REPLACE, GL.GL_TRUE); renderer.begin(GL.GL_POINTS); renderer.vertex(pos.x, pos.y, pos.z); renderer.end(); } create() is called once when the program starts, and renderSprites() is called for each sprite (so, pos is unique to each sprite) where the sprites are arranged in a sort-of 3D cube. Unfortunately though, this just renders a few white dots... I suppose that the texture isn't being bound which is why I'm getting white dots. Also, when I draw my sprites on anything other than 0 z-axis, they do not appear -- I read that I need to crease my zfar and znear, but I have no idea how to do this using libgdx (perhaps it's because I'm using ortho projection? What do I use instead?). I know that the texture is usable, since I was able to render it using a SpriteBatch, but I guess I'm not using it properly with OpenGL.

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• Appropriate level of granularity for component-based architecture

  - by Jon Purdy

  I'm working on a game with a component-based architecture. An Entity owns a set of Component instances, each of which has a set of Slot instances with which to store, send, and receive values. Factory functions such as Player produce entities with the required components and slot connections. I'm trying to determine the best level of granularity for components. For example, right now Position, Velocity, and Acceleration are all separate components, connected in series. Velocity and Acceleration could easily be rewritten into a uniform Delta component, or Position, Velocity, and Acceleration could be combined alongside such components as Friction and Gravity into a monolithic Physics component. Should a component have the smallest responsibility possible (at the cost of lots of interconnectivity) or should related components be combined into monolithic ones (at the cost of flexibility)? I'm leaning toward the former, but I could use a second opinion.

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• Pathfinding results in false path costs that are too high

  - by user2144536

  I'm trying to implement pathfinding in a game I'm programming using this method. I'm implementing it with recursion but some of the values after the immediate circle of tiles around the player are way off. For some reason I cannot find the problem with it. This is a screen cap of the problem: The pathfinding values are displayed in the center of every tile. Clipped blocks are displayed with the value of 'c' because the values were too high and were covering up the next value. The red circle is the first value that is incorrect. The code below is the recursive method. //tileX is the coordinates of the current tile, val is the current pathfinding value, used[][] is a boolean //array to keep track of which tiles' values have already been assigned public void pathFind(int tileX, int tileY, int val, boolean[][] used) { //increment pathfinding value int curVal = val + 1; //set current tile to true if it hasn't been already used[tileX][tileY] = true; //booleans to know which tiles the recursive call needs to be used on boolean topLeftUsed = false, topUsed = false, topRightUsed = false, leftUsed = false, rightUsed = false, botomLeftUsed = false, botomUsed = false, botomRightUsed = false; //set value of top left tile if necessary if(tileX - 1 >= 0 && tileY - 1 >= 0) { //isClipped(int x, int y) returns true if the coordinates givin are in a tile that can't be walked through (IE walls) //occupied[][] is an array that keeps track of which tiles have an enemy in them // //if the tile is not clipped and not occupied set the pathfinding value if(isClipped((tileX - 1) * 50 + 25, (tileY - 1) * 50 + 25) == false && occupied[tileX - 1][tileY - 1] == false && !(used[tileX - 1][tileY - 1])) { pathFindingValues[tileX - 1][tileY - 1] = curVal; topLeftUsed = true; used[tileX - 1][tileY - 1] = true; } //if it is occupied set it to an arbitrary high number so enemies find alternate routes if the best is clogged if(occupied[tileX - 1][tileY - 1] == true) pathFindingValues[tileX - 1][tileY - 1] = 1000000000; //if it is clipped set it to an arbitrary higher number so enemies don't travel through walls if(isClipped((tileX - 1) * 50 + 25, (tileY - 1) * 50 + 25) == true) pathFindingValues[tileX - 1][tileY - 1] = 2000000000; } //top middle if(tileY - 1 >= 0 ) { if(isClipped(tileX * 50 + 25, (tileY - 1) * 50 + 25) == false && occupied[tileX][tileY - 1] == false && !(used[tileX][tileY - 1])) { pathFindingValues[tileX][tileY - 1] = curVal; topUsed = true; used[tileX][tileY - 1] = true; } if(occupied[tileX][tileY - 1] == true) pathFindingValues[tileX][tileY - 1] = 1000000000; if(isClipped(tileX * 50 + 25, (tileY - 1) * 50 + 25) == true) pathFindingValues[tileX][tileY - 1] = 2000000000; } //top right if(tileX + 1 <= used.length && tileY - 1 >= 0) { if(isClipped((tileX + 1) * 50 + 25, (tileY - 1) * 50 + 25) == false && occupied[tileX + 1][tileY - 1] == false && !(used[tileX + 1][tileY - 1])) { pathFindingValues[tileX + 1][tileY - 1] = curVal; topRightUsed = true; used[tileX + 1][tileY - 1] = true; } if(occupied[tileX + 1][tileY - 1] == true) pathFindingValues[tileX + 1][tileY - 1] = 1000000000; if(isClipped((tileX + 1) * 50 + 25, (tileY - 1) * 50 + 25) == true) pathFindingValues[tileX + 1][tileY - 1] = 2000000000; } //left if(tileX - 1 >= 0) { if(isClipped((tileX - 1) * 50 + 25, (tileY) * 50 + 25) == false && occupied[tileX - 1][tileY] == false && !(used[tileX - 1][tileY])) { pathFindingValues[tileX - 1][tileY] = curVal; leftUsed = true; used[tileX - 1][tileY] = true; } if(occupied[tileX - 1][tileY] == true) pathFindingValues[tileX - 1][tileY] = 1000000000; if(isClipped((tileX - 1) * 50 + 25, (tileY) * 50 + 25) == true) pathFindingValues[tileX - 1][tileY] = 2000000000; } //right if(tileX + 1 <= used.length) { if(isClipped((tileX + 1) * 50 + 25, (tileY) * 50 + 25) == false && occupied[tileX + 1][tileY] == false && !(used[tileX + 1][tileY])) { pathFindingValues[tileX + 1][tileY] = curVal; rightUsed = true; used[tileX + 1][tileY] = true; } if(occupied[tileX + 1][tileY] == true) pathFindingValues[tileX + 1][tileY] = 1000000000; if(isClipped((tileX + 1) * 50 + 25, (tileY) * 50 + 25) == true) pathFindingValues[tileX + 1][tileY] = 2000000000; } //botom left if(tileX - 1 >= 0 && tileY + 1 <= used[0].length) { if(isClipped((tileX - 1) * 50 + 25, (tileY + 1) * 50 + 25) == false && occupied[tileX - 1][tileY + 1] == false && !(used[tileX - 1][tileY + 1])) { pathFindingValues[tileX - 1][tileY + 1] = curVal; botomLeftUsed = true; used[tileX - 1][tileY + 1] = true; } if(occupied[tileX - 1][tileY + 1] == true) pathFindingValues[tileX - 1][tileY + 1] = 1000000000; if(isClipped((tileX - 1) * 50 + 25, (tileY + 1) * 50 + 25) == true) pathFindingValues[tileX - 1][tileY + 1] = 2000000000; } //botom middle if(tileY + 1 <= used[0].length) { if(isClipped((tileX) * 50 + 25, (tileY + 1) * 50 + 25) == false && occupied[tileX][tileY + 1] == false && !(used[tileX][tileY + 1])) { pathFindingValues[tileX][tileY + 1] = curVal; botomUsed = true; used[tileX][tileY + 1] = true; } if(occupied[tileX][tileY + 1] == true) pathFindingValues[tileX][tileY + 1] = 1000000000; if(isClipped((tileX) * 50 + 25, (tileY + 1) * 50 + 25) == true) pathFindingValues[tileX][tileY + 1] = 2000000000; } //botom right if(tileX + 1 <= used.length && tileY + 1 <= used[0].length) { if(isClipped((tileX + 1) * 50 + 25, (tileY + 1) * 50 + 25) == false && occupied[tileX + 1][tileY + 1] == false && !(used[tileX + 1][tileY + 1])) { pathFindingValues[tileX + 1][tileY + 1] = curVal; botomRightUsed = true; used[tileX + 1][tileY + 1] = true; } if(occupied[tileX + 1][tileY + 1] == true) pathFindingValues[tileX + 1][tileY + 1] = 1000000000; if(isClipped((tileX + 1) * 50 + 25, (tileY + 1) * 50 + 25) == true) pathFindingValues[tileX + 1][tileY + 1] = 2000000000; } //call the method on the tiles that need it if(tileX - 1 >= 0 && tileY - 1 >= 0 && topLeftUsed) pathFind(tileX - 1, tileY - 1, curVal, used); if(tileY - 1 >= 0 && topUsed) pathFind(tileX , tileY - 1, curVal, used); if(tileX + 1 <= used.length && tileY - 1 >= 0 && topRightUsed) pathFind(tileX + 1, tileY - 1, curVal, used); if(tileX - 1 >= 0 && leftUsed) pathFind(tileX - 1, tileY, curVal, used); if(tileX + 1 <= used.length && rightUsed) pathFind(tileX + 1, tileY, curVal, used); if(tileX - 1 >= 0 && tileY + 1 <= used[0].length && botomLeftUsed) pathFind(tileX - 1, tileY + 1, curVal, used); if(tileY + 1 <= used[0].length && botomUsed) pathFind(tileX, tileY + 1, curVal, used); if(tileX + 1 <= used.length && tileY + 1 <= used[0].length && botomRightUsed) pathFind(tileX + 1, tileY + 1, curVal, used); }

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