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• How do I get my polygons to be lighted by either side?

  - by Molmasepic

  Okay, I am using Ogre3D and Gorilla(2D library for ogre3D) and I am making Gorilla::Screenrenderables in the open scene. The problem that I am having is that when I make a light and have my SR(screenrenderable) near it, it does not light up unless the face of the SR is facing the light... I am wondering if there is a way to maybe set the material or code(which would be harder) so the SR is lit up whether the vertices of the polygon are facing the light or not. I feel it is possible but the main obstacle is how I would go about doing this.

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• Calculating up-vector to avoid gimbal lock using euler angles

  - by jessejuicer

  I wish to orbit a camera around a sphere, yet the problem is that when the camera rotates so that it is at the north pole (and pointing down) or the south pole (and pointing up) of the sphere the camera doesn't handle itself very well. It spins rapidly until arriving 180 degrees in the opposite direction. I believe this is known as gimbal lock. I understand you can avoid this problem using quaternions. But I also read in another forum that it's possible to avoid this easily using euler angles as well. Which I would prefer to do. It was said that all you need to do is "calculate a proper up-vector every frame, and that avoids the problem entirely." Well, I tried aligning the up-vector with the vertical axis of the camera whenever the camera changed orientation, but this didn't seem to work. Meaning that the up-vector followed exactly the orientation of the camera's y-axis (or it's up vector), instead of using a constant up-vector aligned to the up-vector of the world (0, 1, 0). How exactly do I go about calculating a proper up-vector as my camera orientation changes to avoid the gimbal lock problem mentioned above?

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• How can I select an audio output device in directshow

  - by Vibhore Tanwer

  I was wondering how I can select the output device for audio in directshow. I am able to get available audio output devices in directshow. But how can I make one of these to be audio output device. Its always going for the default audio device. I want to be able to output audio on my choice of device. I have been struggling through google but couldn't find anything useful. All I could get was this link but it doesn't really solve my problem. Any help will be really helpful for me.

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• Attaching two objects and changing their world matrices accordingly

  - by A-Type

  I'm having a hard time wrapping my head around the transformations required to bind two objects together in either a two-way or one-way relationship. I will need to implement both types. For the first case, I want to be able to 'couple' two ships together in space. The ships have different mass, of course. Forces applied to either ship will use combined mass and moment of inertia to calculate and move both ships. The trick is, being sure that the point at which they are coupled remains the same, and they don't move at all relative to each other. The second case is similar: I want a ship to be able to enter the atmosphere of a planet and move relative to the planet. The planet will be orbiting the sun, which is fixed at 0,0,0. Essentially, when the ship is sitting still outside of the atmosphere, the planet will move past it on its course-- but when the ship is sitting still inside the atmosphere, it moves and rotates with the planet, so that it is always relative to the horizon. Essentially, the vertices which make up the ship are now transformed just like the ones that make up the planet, except that the ship can move itself around relative to the planet. I get the feeling I can implement both of these with the same code. Essentially, I am thinking of giving each object (which I call Fixtures) a list of "slave" Fixtures onto which that Fixture's world matrix is imposed. So, this would be the planet imposing its world on any contained ships. In the case of coupling, I would simply make each ship a slave of the other, somehow. Obviously I can't just multiply the ship's world matrix by the planet's, or each ship by the others. What I'd like some help with is what calculations to make in order to get a nice, seamless relative world to the other object. I was thinking maybe I could just multiply the world of the slave by the inverse of the master, but then when you couple two ships you would lose all that world data. So, perhaps I need an intermediate "world" which is the absolute world, but use a secondary "final world" to actually transform the objects?

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• How to capture the screen in DirectX 9 to a raw bitmap in memory without using D3DXSaveSurfaceToFile

  - by cloudraven

  I know that in OpenGL I can do something like this glReadBuffer( GL_FRONT ); glReadPixels( 0, 0, _width, _height, GL_RGB, GL_UNSIGNED_BYTE, _buffer ); And its pretty fast, I get the raw bitmap in _buffer. When I try to do this in DirectX. Assuming that I have a D3DDevice object I can do something like this if (SUCCEEDED(D3DDevice->GetBackBuffer(0, 0, D3DBACKBUFFER_TYPE_MONO, &pBackbuffer))) { HResult hr = D3DXSaveSurfaceToFileA(filename, D3DXIFF_BMP, pBackbuffer, NULL, NULL); But D3DXSaveSurfaceToFile is pretty slow, and I don't need to write the capture to disk anyway, so I was wondering if there was a faster way to do this

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• Subdividing a polygon into boxes of varying size

  - by Michael Trouw

  I would like to be pointed to information / resources for creating algorithms like the one illustrated on this blog, which is a subdivision of a polygon (in my case a voronoi cell) into several boxes of varying size: http://procworld.blogspot.nl/2011/07/city-lots.html In the comments a paper by among others the author of the blog can be found, however the only formula listed is about candidate location suitability: http://www.groenewegen.de/delft/thesis-final/ProceduralCityLayoutGeneration-Preprint.pdf Any language will do, but if examples can be given Javascript is preferred (as it is the language i am currently working with) A similar question is this one: What is an efficient packing algorithm for packing rectangles into a polygon?

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• How Do I Do Alpha Transparency Properly In XNA 4.0?

  - by Soshimo

  Okay, I've read several articles, tutorials, and questions regarding this. Most point to the same technique which doesn't solve my problem. I need the ability to create semi-transparent sprites (texture2D's really) and have them overlay another sprite. I can achieve that somewhat with the code samples I've found but I'm not satisfied with the results and I know there is a way to do this. In mobile programming (BREW) we did it old school and actually checked each pixel for transparency before rendering. In this case it seems to render the sprite below it blended with the alpha above it. This may be an artifact of how I'm rendering the texture but, as I said before, all examples point to this one technique. Before I go any further I'll go ahead and paste my example code. public void Draw(SpriteBatch batch, Camera camera, float alpha) { int tileMapWidth = Width; int tileMapHeight = Height; batch.Begin(SpriteSortMode.Texture, BlendState.AlphaBlend, SamplerState.PointWrap, DepthStencilState.Default, RasterizerState.CullNone, null, camera.TransformMatrix); for (int x = 0; x < tileMapWidth; x++) { for (int y = 0; y < tileMapHeight; y++) { int tileIndex = _map[y, x]; if (tileIndex != -1) { Texture2D texture = _tileTextures[tileIndex]; batch.Draw( texture, new Rectangle( (x * Engine.TileWidth), (y * Engine.TileHeight), Engine.TileWidth, Engine.TileHeight), new Color(new Vector4(1f, 1f, 1f, alpha ))); } } } batch.End(); } As you can see, in this code I'm using the overloaded SpriteBatch.Begin method which takes, among other things, a blend state. I'm almost positive that's my problem. I don't want to BLEND the sprites, I want them to be transparent when alpha is 0. In this example I can set alpha to 0 but it still renders both tiles, with the lower z ordered sprite showing through, discolored because of the blending. This is not a desired effect, I want the higher z-ordered sprite to fade out and not effect the color beneath it in such a manner. I might be way off here as I'm fairly new to XNA development so feel free to steer me in the correct direction in the event I'm going down the wrong rabbit hole. TIA

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• XNA hlsl tex2D() only reads 3 channels from normal maps and specular maps

  - by cubrman

  Our engine uses deferred rendering and at the main draw phase gathers plenty of data from the objects it draws. In order to save on tex2D calls, we packed our objects' specular maps with all sorts of data, so three out of four channels are already taken. To make it clear: I am talking about the assets that come with the models and are stored in their material's Specular Level channel, not about the RenderTarget. So now I need another information to be stored in the alpha channel, but I cannot make the shader to read it properly! Nomatter what I write into alpha it ends up being 1 (255)! I tried: saving the textures in PNG/TGA formats. turning off pre-computed alpha in model's properties. Out of every texture available to me (we use Diffuse map, Normal Map and Specular Map) I was only able to read alpha successfully from the Diffuse Map! Here is how I add specular and normal maps to my model's material in the content processor: if (geometry.Material.Textures.ContainsKey(normalMapKey)) { ExternalReference<TextureContent> texRef = geometry.Material.Textures[normalMapKey]; geometry.Material.Textures.Remove("NormalMap"); geometry.Material.Textures.Add("NormalMap", texRef); } ... foreach (KeyValuePair<String, ExternalReference<TextureContent>> texture in material.Textures) { if ((texture.Key == "Texture") || (texture.Key == "NormalMap") || (texture.Key == "SpecularMap")) mat.Textures.Add(texture.Key, texture.Value); } In the shader I obviously use: float4 data = tex2D(specularMapSampler, TexCoords); so data.a is always 1 in my case, could you suggest a reason?

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• write to depth buffer while using multiple render targets

  - by DocSeuss

  Presently my engine is set up to use deferred shading. My pixel shader output struct is as follows: struct GBuffer { float4 Depth : DEPTH0; //depth render target float4 Normal : COLOR0; //normal render target float4 Diffuse : COLOR1; //diffuse render target float4 Specular : COLOR2; //specular render target }; This works fine for flat surfaces, but I'm trying to implement relief mapping which requires me to manually write to the depth buffer to get correct silhouettes. MSDN suggests doing what I'm already doing to output to my depth render target - however, this has no impact on z culling. I think it might be because XNA uses a different depth buffer for every RenderTarget2D. How can I address these depth buffers from the pixel shader?

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• How to implement an intelligent enemy in a shoot-em-up?

  - by bummzack

  Imagine a very simple shoot-em-up, something we all know: You're the player (green). Your movement is restricted to the X axis. Our enemy (or enemies) is at the top of the screen, his movement is also restricted to the X axis. The player fires bullets (yellow) at the enemy. I'd like to implement an A.I. for the enemy that should be really good at avoiding the players bullets. My first idea was to divide the screen into discrete sections and assign weights to them: There are two weights: The "bullet-weight" (grey) is the danger imposed by a bullet. The closer the bullet is to the enemy, the higher the "bullet-weight" (0..1, where 1 is highest danger). Lanes without a bullet have a weight of 0. The second weight is the "distance-weight" (lime-green). For every lane I add 0.2 movement cost (this value is kinda arbitrary now and could be tweaked). Then I simply add the weights (white) and go to the lane with the lowest weight (red). But this approach has an obvious flaw, because it can easily miss local minima as the optimal place to go would be simply between two incoming bullets (as denoted with the white arrow). So here's what I'm looking for: Should find a way through bullet-storm, even when there's no place that doesn't impose a threat of a bullet. Enemy can reliably dodge bullets by picking an optimal (or almost optimal) solution. Algorithm should be able to factor in bullet movement speed (as they might move with different velocities). Ways to tweak the algorithm so that different levels of difficulty can be applied (dumb to super-intelligent enemies). Algorithm should allow different goals, as the enemy doesn't only want to evade bullets, he should also be able to shoot the player. That means that positions where the enemy can fire at the player should be preferred when dodging bullets. So how would you tackle this? Contrary to other games of this genre, I'd like to have only a few, but very "skilled" enemies instead of masses of dumb enemies.

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• openGL Camera setup for Zoom in/out centered at point under cursor

  - by user3228921

  I am trying to implement a zoom in/out navigation mode in a openGL 3dViewer. I was able to implement zoom functionality centered at screen center just by moving eye towards the center in perspective mode. Now i am trying to do the zoom centered at arbitrary position under the cursor. I am unable to figure out how should i move my camera forward and backward such that point under cursor remains at the same screen coordinates after zoom in/out. Any help would be appreciated. Below are the images which show the desired effect. Just to mention, I am working in a perspective mode with eye target and up vectors to control camera. Same effect i found in google sketchup and 'zoom to mouse position' setting in blender.

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• Outline Shader Effect for Orthogonal Geometry in XNA

  - by Griffin

  I just recently started learning the art of shading, but I can't give an outline width to 2D, concave geometry when restrained to a single vertex/pixel shader technique (thanks to XNA). the shape I need to give an outline to has smooth, per-vertex coloring, as well as opacity. The outline, which has smooth, per-vertex coloring, variable width, and opacity cannot interfere with the original shape's colors. A pixel depth border detection algorithm won't work because pixel depth isn't a 3.0 semantic. expanding geometry / redrawing won't work because it interferes with the original shape's colors. I'm wondering if I can do something with the stencil/depth buffer outside of the shader functions since I have access to that through the graphics device. But I don't believe I'm able to manipulate actual values. How might I do this?

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• Strange behavior of RigidBody with gravity and impulse applied

  - by Heisenbug

  I'm doing some experiments trying to figure out how physics works in Unity. I created a cube mesh with a BoxCollider and a RigidBody. The cuve is laying on a mesh plane with a BoxCollider. I'm trying to update the object position applying a force on its RigidBody. Inside script FixedUpdate function I'm doing the following: public void FixedUpdate() { if (leftButtonPressed()) this.rigidbody.AddForce( this.transform.forward * this.forceStrength, ForceMode.Impulse); } Despite the object is aligned with the world axis and the force is applied along Z axis, it performs a quite big rotation movement around its y axis. Since I didn't modify the center of mass and the BoxCollider position and dimension, all values should be fine. Removing gravity and letting the object flying without touching the plane, the problem doesn't show. So I suppose it's related to the friction between objects, but I can't understand exactly which is the problem. Why this? What's my mistake? How can I fix this, or what's the right way to do such a moving an object on a plane through a force impulse?

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• OpenGL ES 2. How do I Create a Basic Fading Streak Effect?

  - by dugla

  For the iPad app I am writing using OpenGL ES 2 I have a single quad - shaded using GLSL - that is dragged around the screen. Very basic. This works fine. But is rather boring. I want to increase the coolness a bit in the following way: when the user drags the quad it leaves a streak behind that fades over time. Continuous dragging would be a bit like a streaking comet across the night sky. What is the simplest way to implement this? Thanks.

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• GLSL Normals not transforming propertly

  - by instancedName

  I've been stuck on this problem for two days. I've read many articles about transforming normals, but I'm just totaly stuck. I understand choping off W component for "turning off" translation, and doing inverse/traspose transformation for non-uniform scaling problem, but my bug seems to be from a different source. So, I've imported a simple ball into OpenGL. Only transformation that I'm applying is rotation over time. But when my ball rotates, the illuminated part of the ball moves around just as it would if direction light direction was changing. I just can't figure out what is the problem. Can anyone help me with this? Here's the GLSL code: Vertex Shader: #version 440 core uniform mat4 World, View, Projection; layout(location = 0) in vec3 VertexPosition; layout(location = 1) in vec3 VertexColor; layout(location = 2) in vec3 VertexNormal; out vec4 Color; out vec3 Normal; void main() { Color = vec4(VertexColor, 1.0); vec4 n = World * vec4(VertexNormal, 0.0f); Normal = n.xyz; gl_Position = Projection * View * World * vec4(VertexPosition, 1.0); } Fragment Shader: #version 440 core uniform vec3 LightDirection = vec3(0.0, 0.0, -1.0); uniform vec3 LightColor = vec3(1f); in vec4 Color; in vec3 Normal; out vec4 FragColor; void main() { diffuse = max(0.0, dot(normalize(-LightDirection), normalize(Normal))); vec4 scatteredLight = vec4(LightColor * diffuse, 1.0f); FragColor = min(Color * scatteredLight, vec4(1.0)); }

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• Realtime rendering using a ray tracing engine

  - by Keyhan Asghari

  I want to render an object that has a mesh with one million hexagonal elements(100 * 100 * 100). Lights, shadows and textures is not important and each element has a solid color. and finally, the actions I want to have, is simply rotating the object, zooming and panning. I am wondering what ray tracing engine is better for my conditions. or, do I have to take another approach? any help will be appreciated.

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• Creating a 2D Line Branch

  - by Danran

  I'm looking into creating a 2D line branch, something for a "lightning effect". I did ask this question before on creating a "lightning effect" (mainly though referring to the process of the glow & after effects the lightning has & to whether it was a good method to use or not); Methods of Creating a "Lightning" effect in 2D However i never did get around to getting it working. So i've been trying today to get a seconded attempt going but i'm getting now-were :/. So to be clear on what i'm trying to-do, in this article posted; http://drilian.com/2009/02/25/lightning-bolts/ I'm trying to create the line segments seen in the images on the site. I'm confused mainly by this line in the pseudo code; // Offset the midpoint by a random amount along the normal. midPoint += Perpendicular(Normalize(endPoint-startPoint))*RandomFloat(-offsetAmount,offsetAmount); If someone could explain this to me it would be really grateful :).

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• Why the clip space in OpenGL has 4 dimensions?

  - by user827992

  I will use this as a generic reference, but the more i browser online docs and books, the less i understand about this. const float vertexPositions[] = { 0.75f, 0.75f, 0.0f, 1.0f, 0.75f, -0.75f, 0.0f, 1.0f, -0.75f, -0.75f, 0.0f, 1.0f, }; in this online book there is an example about how to draw the first and classic hello world for OpenGL about making a triangle. The vertex structure for the triangle is declared as stated in the code above. The book, as all the other sources about this, stress the point that the Clip Space is a 4D structure that is used to basically decide what will be rasterized and rendered to the screen. Here I have my questions: i can't imagine something in 4D, i don't think that a human can do that, what is a 4D for this Clip space ? the most human-readable doc that i have read speaks about a camera, which is just an abstraction over the clipping concept, and i get that, the problem is, why not using the concept of a camera in the first place which is a more familiar 3D structure? The only problem with the concept of a camera is that you need to define the prospective in other way and so you basically have to add another statement about what kind of camera you wish to have. How i'm supposed to read this 0.75f, 0.75f, 0.0f, 1.0f ? All i get is that they are all float values and i get the meaning of the first 3 values, what does it mean the last one?

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• Does anybody know of any resources to achieve this particular "2.5D" isometric engine effect?

  - by Craig Whitley

  I understand this is a little vague, but I was hoping somebody might be able to describe a high-level workflow or link to a resource to be able to achieve a specific isometric "2.5D" tile engine effect. I fell in love with http://www.youtube.com/watch?v=-Q6ISVaM5Ww this engine. Especially with the lighting and the shaders! He has a brief description of how he achieved what he did, but I could really use a brief flow of where you would start, what you would read up on and learn and the logical order to implement these things. A few specific questions: 1) Is there a heightmap on the ground texture that lets the light reflect brighter on certain parts of it? 2) "..using a special material which calculates the world-space normal vectors of every pixel.." - is this some "magic" special material he has created himself, or can you hazard a guess at what he means? 3) with relation to the above quote - what does he mean by 'world-space normal vectors of every pixel'? 4) I'm guessing I'm being a little bit optimistic when I ask if there's any 'all-in-one' tutorial out there? :)

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• Debugging Minimum Translation Vector

  - by SyntheCypher

  I implemented the minimum translation vector from codezealot's tutorial on SAT (Separating Axis Theorem) but I'm having an issue I can't quite figure out. Here's the example I have: As you can see in top and bottom left images regardless of the side the of the green car which red car is penetrating the MTV for the red car still remains as a negative number also here is the same example when the front of the red car is facing the opposite direction the number will always be positive. When the red car is past the half way through the green car it should switch polarity. I thought I'd compensated for this in my code, but apparently not either that or it's a bug I can find. Here is my function for finding and returning the MTV, any help would be much appreciated: Code

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• How do I find which isometric tiles are inside the cameras current view?

  - by Steve

  I'm putting together an isometric engine and need to cull the tiles that aren't in the camera's current view. My tile coordinates go from left to right on the X and top to bottom on the Y with (0,0) being the top left corner. If I have access to say the top left, top right, bottom left and bottom right corner coordinates, is there a formula or something I could use to determine which tiles fall in range? This is a screenshot of the layout of the tiles for reference. If there isn't one, or there's a better way to determine which tiles are on screen and which to cull, I'm all ears and am grateful for any ideas. I've got a few other methods I may be able to try such as checking the position of the tile against a rectangle. I pretty much just need something quick. Thanks for giving this a read =)

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• Movement of body after applying weld joint

  - by ved

  I have two rectangular bodies. I've applied Weldjoint successfully on these bodies. I want to move that joined body by applying linear impulse. After weld joint, these two bodies becomes single body right? How do I apply force/impulse on the joined body? I am using Box2D with LibGDX. I've tried this: polygon1.applyLinearImpulse(new Vector2(-5, 0), polygon1.getWorldCenter(), true); I thought that if I move polygon1 then polygon2 will also move due to my weld joint but it is not working properly. Why don't they move together after being welded?

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• What is a good practice for 2D scene graph partitioning for culling?

  - by DevilWithin

  I need to know an efficient way to cull the scene graph objects, to render exclusively the ones in the view, and as fast as possible. I am thinking of doing it the following way, having in each object a local boundingbox which holds the object bounds, and a global boundingbox which holds the bounds of the object and all children. When a camera is moved, the render list is updated by traversing the global boundingboxes. When only the object is being moved, it tries to enlarge or shrink the ancestors global boundingboxes, and in the end updating or not the renderlist. What do you think of this approach? Do you think it will provide a fast and efficient culling? Also, because the render list is a contiguous list, it could accelerate the rendering, right? Any further tips for a 2D scene graphs are highly appreciated!

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• Continuous Collision Detection Techniques

  - by Griffin

  I know there are quite a few continuous collision detection algorithms out there , but I can't find a list or summary of different 2D techniques; only tutorials on specific algorithms. What techniques are out there for calculating when different 2D bodies will collide and what are the advantages / disadvantages of each? I say techniques and not algorithms because I have not yet decided on how I will store different polygons which might be concave or even have holes. I plan to make a decision on this based on what the algorithm requires (for instance if an algorithm breaks down a polygon into triangles or convex shapes I will simply store the polygon data in this form).

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• Why does my code dividing a 2D array into chunks fail?

  - by Borog

  I have a 2D-Array representing my world. I want to divide this huge thing into smaller chunks to make collision detection easier. I have a Chunk class that consists only of another 2D Array with a specific width and height and I want to iterate through the world, create new Chunks and add them to a list (or maybe a Map with Coordinates as the key; we'll see about that). world = new World(8192, 1024); Integer[][] chunkArray; for(int a = 0; a < map.getHeight() / Chunk.chunkHeight; a++) { for(int b = 0; b < map.getWidth() / Chunk.chunkWidth; b++) { Chunk chunk = new Chunk(); chunkArray = new Integer[Chunk.chunkWidth][Chunk.chunkHeight]; for(int x = Chunk.chunkHeight*a; x < Chunk.chunkHeight*(a+1); x++) { for(int y = Chunk.chunkWidth*b; y < Chunk.chunkWidth*(b+1); y++) { // Yes, the tileMap actually is [height][width] I'll have // to fix that somewhere down the line -.- chunkArray[y][x] = map.getTileMap()[x*a][y*b]; // TODO:Attach to chunk } } chunkList.add(chunk); } } System.out.println(chunkList.size()); The two outer loops get a new chunk in a specific row and column. I do that by dividing the overall size of the map by the chunkSize. The inner loops then fill a new chunkArray and attach it to the chunk. But somehow my maths is broken here. Let's assume the chunkHeight = chunkWidth = 64. For the first Array I want to start at [0][0] and go until [63][63]. For the next I want to start at [64][64] and go until [127][127] and so on. But I get an out of bounds exception and can't figure out why. Any help appreciated! Actually I think I know where the problem lies: chunkArray[y][x] can't work, because y goes from 0-63 just in the first iteration. Afterwards it goes from 64-127, so sure it is out of bounds. Still no nice solution though :/ EDIT: if(y < Chunk.chunkWidth && x < Chunk.chunkHeight) chunkArray[y][x] = map.getTileMap()[y][x]; This works for the first iteration... now I need to get the commonly accepted formula.

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