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• Sorting for 2D Drawing

  - by Nexian

  okie, looked through quite a few similar questions but still feel the need to ask mine specifically (I know, crazy). Anyhoo: I am drawing a game in 2D (isometric) My objects have their own arrays. (i.e. Tiles[], Objects[], Particles[], etc) I want to have a draw[] array to hold anything that will be drawn. Because it is 2D, I assume I must prioritise depth over any other sorting or things will look weird. My game is turn based so Tiles and Objects won't be changing position every frame. However, Particles probably will. So I am thinking I can populate the draw[] array (probably a vector?) with what is on-screen and have it add/remove object, tile & particle references when I pan the screen or when a tile or object is specifically moved. No idea how often I'm going to have to update for particles right now. I want to do this because my game may have many thousands of objects and I want to iterate through as few as possible when drawing. I plan to give each element a depth value to sort by. So, my questions: Does the above method sound like a good way to deal with the actual drawing? What is the most efficient way to sort a vector? Most of the time it wont require efficiency. But for panning the screen it will. And I imagine if I have many particles on screen moving across multiple tiles, it may happen quite often. For reference, my screen will be drawing about 2,800 objects at any one time. When panning, it will be adding/removing about ~200 elements every second, and each new element will need adding in the correct location based on depth.

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• What is the recommended library for using Lua from C++?

  - by DevilWithin

  I am currently planning how to integrate Lua scripting in my 2D Game Engine, and i would like to go straight to the most adequate solution for having C++ classes and objects exposed. I've read this (if it helps you help): http://lua-users.org/wiki/BindingCodeToLua If you have a better scripting language to recomend, go for it ;D All help is welcome, i need to pickup the best solution to start implementing Thanks

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• Where i must put .xnb files in mono game project using VS2010?

  - by user23899

  Hello there my problem was describe below In the "The Content Pipeline" paragraph http://blogs.msdn.com/b/bobfamiliar/archive/2012/08/07/windows-8-xna-and-monogame-part-3-code-migration-and-windows-8-feature-support.aspx#comments Author describe how fix it using VS2012 put xnb files to \AppX\Content folder but i use VS2010 and mono game templates for it and there is no folders like this so where i must put this asstes to run game correctly

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• Rending 2D Tile World (With Player In The Middle)

  - by Mick

  What I have at the moment is a series of data structures I'm using, and I would like to render the world onto the screen (just the visible parts). I've actually already done this several times (lots of rewrites), but it's a bit buggy (rounding seems to make the screen jump ever so slightly every x tiles the player walks past). Basically I've been confusing myself heavily on what I feel should be a pretty simple problem... so here I am asking for some help! OK! So I have a 50x50 array holding the tiles of the world. I have the player position as 2 floats, x ([0, 49]) and y ([0, 49]) in that array. I have the application size exactly in pixels (x and y). I have an arbitrary TILE_SIZE static int (based on screen pixels). What I think is heavily confusing me is using a 2d orthogonal projection in opengl which maps (0,0) to the top left of the screen and (SCREEN_SIZE_X, SCREEN_SIZE_Y) to the bottom right of the screen. gl.glMatrixMode(GL.GL_PROJECTION); gl.glLoadIdentity(); glu.gluOrtho2D(0, getActualWidth(), getActualHeight(), 0); gl.glMatrixMode(GL.GL_MODELVIEW); gl.glLoadIdentity(); The map tiles are set so that the (0,0) in the array is the bottom left. And the player has to be in the middle on the screen (SCREEN_SIZE_X/2, SCREEN_SIZE_Y/2). What I've been doing so far is trying to render 1-2 tiles more all around what would be displayed on the screen so that I don't have to worry about figuring out rendering half a tile from the top left, depending where the player is. It seems like such an easy problem but after spending about 40+hours on it rewriting it many times I think I'm at a point where I just can't think clearly anymore... Any help would be appreciated. It would be great if someone can provide some very basic pseudo code on keeping the player in the middle when your projection is mapped to screen coordinates and only rendering basically the tiles that you would be any be see. Thanks!

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• Whole continent simulation [on hold]

  - by user2309021

  Let's suppose I am planning to create a simulation of an entire continent at some point in the past (let's say, around 0 A.D). Is it feasible to spawn a hundred million actors that interact with each other and their environments? Having them reproduce, extract resources, etc? The fact is that I actually want to create a simulation that allows me to zoom in from a view of the entire continent up to a single village, and interact with it. (Think as if you could keep zooming in the campaign map of any Total War game and the transition to the battle map was seamless, not a change of the "game mode"). By the way, I have never made a game in my entire life (I have programmed normal desktop applications, though), so I am really having trouble wrapping my head around how to implement such a thing. Even while thinking about how to implement a simple population simulator, without a graphical interface, I think that the O(n) complexity of traversing an array and telling all people to get one year older each time the program ticks is kind of stupid. Any kind help would be greatly appreciated :) EDIT: After being put on hold, I shall specify a question. How would you implement a simulation of all basic human dynamics (reproduction, resource consumption) in an entire continent (with millions of people)?

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• Setting uniform value of a vertex shader for different sprites in a SpriteBatch

  - by midasmax

  I'm using libGDX and currently have a simple shader that does a passthrough, except for randomly shifting the vertex positions. This shift is a vec2 uniform that I set within my code's render() loop. It's declared in my vertex shader as uniform vec2 u_random. I have two different kind of Sprites -- let's called them SpriteA and SpriteB. Both are drawn within the same SpriteBatch's begin()/end() calls. Prior to drawing each sprite in my scene, I check the type of the sprite. If sprite instance of SpriteA: I set the uniform u_random value to Vector2.Zero, meaning that I don't want any vertex changes for it. If sprite instance of SpriteB, I set the uniform u_random to Vector2(MathUtils.random(), MathUtils.random(). The expected behavior was that all the SpriteA objects in my scene won't experience any jittering, while all SpriteB objects would be jittering about their positions. However, what I'm experiencing is that both SpriteA and SpriteB are jittering, leading me to believe that the u_random uniform is not actually being set per Sprite, and being applied to all sprites. What is the reason for this? And how can I fix this such that the vertex shader correctly accepts the uniform value set to affect each sprite individually? passthrough.vsh attribute vec4 a_color; attribute vec3 a_position; attribute vec2 a_texCoord0; uniform mat4 u_projTrans; uniform vec2 u_random; varying vec4 v_color; varying vec2 v_texCoord; void main() { v_color = a_color; v_texCoord = a_texCoord0; vec3 temp_position = vec3( a_position.x + u_random.x, a_position.y + u_random.y, a_position.z); gl_Position = u_projTrans * vec4(temp_position, 1.0); } Java Code this.batch.begin(); this.batch.setShader(shader); for (Sprite sprite : sprites) { Vector2 v = Vector2.Zero; if (sprite instanceof SpriteB) { v.x = MathUtils.random(-1, 1); v.y = MathUtils.random(-1, 1); } shader.setUniformf("u_random", v); sprite.draw(this.batch); } this.batch.end();

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• Direct3D - Zooming into Mouse Position

  - by roohan

  I'm trying to implement my camera class for a simulation. But I cant figure out how to zoom into my world based on the mouse position. I mean the object under the mouse cursor should remain at the same screen position. My zooming looks like this: VOID ZoomIn(D3DXMATRIX& WorldMatrix, FLOAT const& MouseX, FLOAT const& MouseY) { this->Position.z = this->Position.z * 0.9f; D3DXMatrixLookAtLH(&this->ViewMatrix, &this->Position, &this->Target, &this->UpDirection); } I passed the world matrix to the function because I had the idea to move my drawing origin according to the mouse position. But I cant find out how to calculate the offset in to move my drawing origin. Anyone got an idea how to calculate this? Thanks in advance. SOLVED Ok I solved my problem. Here is the code if anyone is interested: VOID CAMERA2D::ZoomIn(FLOAT const& MouseX, FLOAT const& MouseY) { // Get the setting of the current view port. D3DVIEWPORT9 ViewPort; this->Direct3DDevice->GetViewport(&ViewPort); // Convert the screen coordinates of the mouse to world space coordinates. D3DXVECTOR3 VectorOne; D3DXVECTOR3 VectorTwo; D3DXVec3Unproject(&VectorOne, &D3DXVECTOR3(MouseX, MouseY, 0.0f), &ViewPort, &this->ProjectionMatrix, &this->ViewMatrix, &WorldMatrix); D3DXVec3Unproject(&VectorTwo, &D3DXVECTOR3(MouseX, MouseY, 1.0f), &ViewPort, &this->ProjectionMatrix, &this->ViewMatrix, &WorldMatrix); // Calculate the resulting vector components. float WorldZ = 0.0f; float WorldX = ((WorldZ - VectorOne.z) * (VectorTwo.x - VectorOne.x)) / (VectorTwo.z - VectorOne.z) + VectorOne.x; float WorldY = ((WorldZ - VectorOne.z) * (VectorTwo.y - VectorOne.y)) / (VectorTwo.z - VectorOne.z) + VectorOne.y; // Move the camera into the screen. this->Position.z = this->Position.z * 0.9f; D3DXMatrixLookAtLH(&this->ViewMatrix, &this->Position, &this->Target, &this->UpDirection); // Calculate the world space vector again based on the new view matrix, D3DXVec3Unproject(&VectorOne, &D3DXVECTOR3(MouseX, MouseY, 0.0f), &ViewPort, &this->ProjectionMatrix, &this->ViewMatrix, &WorldMatrix); D3DXVec3Unproject(&VectorTwo, &D3DXVECTOR3(MouseX, MouseY, 1.0f), &ViewPort, &this->ProjectionMatrix, &this->ViewMatrix, &WorldMatrix); // Calculate the resulting vector components. float WorldZ2 = 0.0f; float WorldX2 = ((WorldZ2 - VectorOne.z) * (VectorTwo.x - VectorOne.x)) / (VectorTwo.z - VectorOne.z) + VectorOne.x; float WorldY2 = ((WorldZ2 - VectorOne.z) * (VectorTwo.y - VectorOne.y)) / (VectorTwo.z - VectorOne.z) + VectorOne.y; // Create a temporary translation matrix for calculating the origin offset. D3DXMATRIX TranslationMatrix; D3DXMatrixIdentity(&TranslationMatrix); // Calculate the origin offset. D3DXMatrixTranslation(&TranslationMatrix, WorldX2 - WorldX, WorldY2 - WorldY, 0.0f); // At the offset to the cameras world matrix. this->WorldMatrix = this->WorldMatrix * TranslationMatrix; } Maybe someone has even a better solution than mine.

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• Component based design, but components rely on eatchother

  - by MintyAnt

  I've begun stabbing at a "Component Based" game system. Basically, each entity holds a list of components to update (and render) I inherit the "Component" class and break each game system into it. Examples: RenderComponent - Draws the entity MovementComponent - Moves the entity, deals with velocity and speed checks DamageComponent - Deals with how/if the entity gets damaged... So. My system has this: MovementComponent InputComponent Now maybe my design is off, but the InputComponent should say things like if (w key is down) add y speed to movement if (x key is down) Trigger primary attack This means that the InputComponent sort of relies on these other components. I have to do something alone the lines of: if (w key is down) { MovementComponent* entityMovement = mEntity->GetMovement(); if (entityMovement != NULL) add y speed to movement } which seems kinda crappy every update. Other options? Better design? Is this the best way? Thanks!

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• What is the recommended way to output values to FBO targets? (OpenGL 3.3 + GLSL 330)

  - by datSilencer

  I'll begin by apologizing for any dumb assumptions you might find in the code below since I'm still pretty much green when it comes to OpenGL programming. I'm currently trying to implement deferred shading by using FBO's and their associated targets (textures in my case). I have a simple (I think :P) geometry+fragment shader program and I'd like to write its Fragment Shader stage output to three different render targets (previously bound by a call to glDrawBuffers()), like so: #version 330 in vec3 WorldPos0; in vec2 TexCoord0; in vec3 Normal0; in vec3 Tangent0; layout(location = 0) out vec3 WorldPos; layout(location = 1) out vec3 Diffuse; layout(location = 2) out vec3 Normal; uniform sampler2D gColorMap; uniform sampler2D gNormalMap; vec3 CalcBumpedNormal() { vec3 Normal = normalize(Normal0); vec3 Tangent = normalize(Tangent0); Tangent = normalize(Tangent - dot(Tangent, Normal) * Normal); vec3 Bitangent = cross(Tangent, Normal); vec3 BumpMapNormal = texture(gNormalMap, TexCoord0).xyz; BumpMapNormal = 2 * BumpMapNormal - vec3(1.0, 1.0, -1.0); vec3 NewNormal; mat3 TBN = mat3(Tangent, Bitangent, Normal); NewNormal = TBN * BumpMapNormal; NewNormal = normalize(NewNormal); return NewNormal; } void main() { WorldPos = WorldPos0; Diffuse = texture(gColorMap, TexCoord0).xyz; Normal = CalcBumpedNormal(); } If my render target textures are configured as: RT1:(GL_RGB32F, GL_RGB, GL_FLOAT, GL_TEXTURE0, GL_COLOR_ATTACHMENT0) RT2:(GL_RGB32F, GL_RGB, GL_FLOAT, GL_TEXTURE1, GL_COLOR_ATTACHMENT1) RT3:(GL_RGB32F, GL_RGB, GL_FLOAT, GL_TEXTURE2, GL_COLOR_ATTACHMENT2) And assuming that each texture has an internal format capable of contaning the incoming data, will the fragment shader write the corresponding values to the expected texture targets? On a related note, do the textures need to be bound to the OpenGL context when they are Multiple Render Targets? From some Googling, I think there are two other ways to output to MRTs: 1: Output each component to gl_FragData[n]. Some forum posts say this method is deprecated. However, looking at the latest OpenGL 3.3 and 4.0 specifications at opengl.org, the core profiles still mention this approach. 2: Use a typed output array variable for the expected type. In this case, I think it would be something like this: out vec3 [3] output; void main() { output[0] = WorldPos0; output[1] = texture(gColorMap, TexCoord0).xyz; output[2] = CalcBumpedNormal(); } So which is then the recommended approach? Is there a recommended approach at all if I plan to code on top of OpenGL 3.3? Thanks for your time and help!

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• Re-sizing the form without scaling the GUI

  - by Bmoore

  I am writing a turn based strategy game in C#. My GUI implementation consists of class that extends Form containing a class that extends Panel. When I render the GUI I draw to the paint method in the panel. I am trying to figure out what is the best way for handling form re-size events. I know I want a minimum window size, but I would prefer to not have a maximum or a set size. Ideally the GUI would reveal more/less of the map as the user changes the window size. I would like to avoid scaling the graphics if at all possible. What is the best way to handle re-size events?

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• How can I cleanly and elegantly handle data and dependancies between classes

  - by Neophyte

  I'm working on 2d topdown game in SFML 2, and need to find an elegant way in which everything will work and fit together. Allow me to explain. I have a number of classes that inherit from an abstract base that provides a draw method and an update method to all the classes. In the game loop, I call update and then draw on each class, I imagine this is a pretty common approach. I have classes for tiles, collisions, the player and a resource manager that contains all the tiles/images/textures. Due to the way input works in SFML I decided to have each class handle input (if required) in its update call. Up until now I have been passing in dependencies as needed, for example, in the player class when a movement key is pressed, I call a method on the collision class to check if the position the player wants to move to will be a collision, and only move the player if there is no collision. This works fine for the most part, but I believe it can be done better, I'm just not sure how. I now have more complex things I need to implement, eg: a player is able to walk up to an object on the ground, press a key to pick it up/loot it and it will then show up in inventory. This means that a few things need to happen: Check if the player is in range of a lootable item on keypress, else do not proceed. Find the item. Update the sprite texture on the item from its default texture to a "looted" texture. Update the collision for the item: it might have changed shape or been removed completely. Inventory needs to be updated with the added item. How do I make everything communicate? With my current system I will end up with my classes going out of scope, and method calls to each other all over the place. I could tie up all the classes in one big manager and give each one a reference to the parent manager class, but this seems only slightly better. Any help/advice would be greatly appreciated! If anything is unclear, I'm happy to expand on things.

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• Random enemy placement on a 2d grid

  - by Robb

  I want to place my items and enemies randomly (or as randomly as possible). At the moment I use XNA's Random class to generate a number between 800 for X and 600 for Y. It feels like enemies spawn more towards the top of the map than in the middle or bottom. I do not seed the generator, maybe that is something to consider. Are there other techniques described that can improve random enemy placement on a 2d grid?

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• Prevent collisions between mobs/npcs/units piloted by computer AI : How to avoid mobile obstacles?

  - by Arthur Wulf White

  Lets says we have character a starting at point A and character b starting at point B. character a is headed to point B and character b is headed to point A. There are several simple ways to find the path(I will be using Dijkstra). The question is, how do I take preventative action in the code to stop the two from colliding with one another? case2: Characters a and b start from the same point in different times. Character b starts later and is the faster of the two. How do I make character b walk around character a without going through it? case3:Lets say we have m such characters in each side and there is sufficient room to pass through without the characters overlapping with one another. How do I stop the two groups of characters from "walking on top of one another" and allow them pass around one another in a natural organic way. A correct answer would be any algorithm, that given the path to the destination and a list of mobile objects that block the path, finds an alternative path or stops without stopping all units when there is sufficient room to traverse.

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• Mouse pointer position to screen space

  - by Ylisar

  If I have a mouse pointer position in pixels of canvas, I can easily convert it to the -1..1 range for both X & Y by lerping by dividing with canvas dimensions. However, the problem is what I should put in Z & W if I want my screen space position to be on the near plane? The step afterwards would be for me to multiply by the inverse of view-projection to take me to world space, where I easily can construct a ray from the cameras world space position.

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• LWJGL GL_QUADS texture artifact

  - by Dajgoro Labinac

  I managed to get working lwjgl in Java, and i loaded a test image(tv test card), but i keep getting weird artifacts outside the image. Image link: http://tinypic.com/r/vhv9g/6 Code: glBegin(GL_QUADS); glTexCoord2f(0, 0); glVertex2i(10, 10); glTexCoord2f(1, 0); glVertex2i(500, 10); glTexCoord2f(1, 1); glVertex2i(500, 500); glTexCoord2f(0, 1); glVertex2i(10, 500); glEnd(); What could be the cause?

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• Information about rendering, batches, the graphical card, performance etc. + XNA?

  - by Aidiakapi

  I know the title is a bit vague but it's hard to describe what I'm really looking for, but here goes. When it comes to CPU rendering, performance is mostly easy to estimate and straightforward, but when it comes to the GPU due to my lack of technical background information, I'm clueless. I'm using XNA so it'd be nice if theory could be related to that. So what I actually wanna know is, what happens when and where (CPU/GPU) when you do specific draw actions? What is a batch? What influence do effects, projections etc have? Is data persisted on the graphics card or is it transferred over every step? When there's talk about bandwidth, are you talking about a graphics card internal bandwidth, or the pipeline from CPU to GPU? Note: I'm not actually looking for information on how the drawing process happens, that's the GPU's business, I'm interested on all the overhead that precedes that. I'd like to understand what's going on when I do action X, to adapt my architectures and practices to that. Any articles (possibly with code examples), information, links, tutorials that give more insight in how to write better games are very much appreciated. Thanks :)

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• android shut-down errors / thread problems

  - by iQue

  Im starting to deal with some stuff in my game that I thought were "minor problems" and one of these are that I get an error every time I shut down my game that looks like this: 09-05 21:40:58.320: E/AndroidRuntime(30401): FATAL EXCEPTION: Thread-4898 09-05 21:40:58.320: E/AndroidRuntime(30401): java.lang.NullPointerException 09-05 21:40:58.320: E/AndroidRuntime(30401): at nielsen.happy.shooter.MainGamePanel.render(MainGamePanel.java:94) 09-05 21:40:58.320: E/AndroidRuntime(30401): at nielsen.happy.shooter.MainThread.run(MainThread.java:101) on these lines is my GameViews rendering-method and the line in my Thread that calls my GameViews rendering-method. Im guessing Something in my surfaceDestroyed(SurfaceHolder holder) is wrong, or maybe Im not ending the tread in the right place. My surfaceDestroyed-method: public void surfaceDestroyed(SurfaceHolder holder) { Log.d(TAG, "Surface is being destroyed"); boolean retry = true; ((MainThread)thread).setRunning(false); while (retry) { try { ((MainThread)thread).join(); retry = false; } catch (InterruptedException e) { } } Log.d(TAG, "Thread was shut down cleanly"); } Also, In my activity for this View my onPaus, onDestoy and onStop are empty, do I maybe need to add something there? The crash occurs when I press my home-button on the phone, or any other button that makes the game stop. But as I understand it the onPaus is called when you press the Home-button.. This is really new territory for me so Im sorry if im missing something obvious or something really big. adding my surfaceCreated method asweel since that is where I start this thread: public void surfaceCreated(SurfaceHolder holder) { controls = new GameControls(this); setOnTouchListener(controls); timer1.schedule(new Task(this), 0, delay1); thread.setRunning(true); thread.start(); } and aslong as this is running, my game is rendering and updating.

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• Why wont the LibGDX's main class Initialize on Android Launcher?

  - by BluFire

  So I was searching for different ways that could suit me in programming and came across LibGDX. Naturally I looked at the tutorial. As I was doing it, I was following the steps word for word, except naming the classes. In the end, I was able to create the desktop launcher for the game but not the android launcher. The following error is my error: Cannot instantiate the type Game (Game is the name of the class) I got the tutorial from http://steigert.blogspot.com.au/2012/02/1-libgdx-tutorial-introduction.html The link in the tutorial is the original but it uses jogl instead of lwjgl.

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• How to set sprite source coordinates?

  - by ChaosDev

  I am creating own sprite drawer with DX11 on C++. Works fine but I dont know how to apply source rectangle to texture coordinates of rendering surface(for animation sprite sheets) //source = (0,0,32,64); //RECT D3DXVECTOR2 t0 = D3DXVECTOR2( 1.0f, 0.0f); D3DXVECTOR2 t1 = D3DXVECTOR2( 1.0f, 1.0f); D3DXVECTOR2 t2 = D3DXVECTOR2( 0.0f, 1.0f); D3DXVECTOR2 t3 = D3DXVECTOR2( 0.0f, 1.0f); D3DXVECTOR2 t4 = D3DXVECTOR2( 0.0f, 0.0f); D3DXVECTOR2 t5 = D3DXVECTOR2( 1.0f, 0.0f); VertexPositionColorTexture vertices[] = { { D3DXVECTOR3( dest.left+dest.right, dest.top, z),D3DXVECTOR4(1,1,1,1), t0}, { D3DXVECTOR3( dest.left+dest.right, dest.top+dest.bottom, z),D3DXVECTOR4(1,1,1,1), t1}, { D3DXVECTOR3( dest.left, dest.top+dest.bottom, z),D3DXVECTOR4(1,1,1,1), t2}, { D3DXVECTOR3( dest.left, dest.top+dest.bottom, z),D3DXVECTOR4(1,1,1,1), t3}, { D3DXVECTOR3( dest.left , dest.top, z),D3DXVECTOR4(1,1,1,1), t4}, { D3DXVECTOR3( dest.left+dest.right, dest.top, z),D3DXVECTOR4(1,1,1,1), t5}, };

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• Box2Dweb very slow on node.js

  - by Peteris

  I'm using Box2Dweb on node.js. I have a rotated box object that I apply an impulse to move around. The timestep is set at 50ms, however, it bumps up to 100ms and even 200ms as soon as I add any more edges or boxes. Here are the edges I would like to use as bounds around the playing area: // Computing the corners var upLeft = new b2Vec2(0, 0), lowLeft = new b2Vec2(0, height), lowRight = new b2Vec2(width, height), upRight = new b2Vec2(width, 0) // Edges bounding the visible game area var edgeFixDef = new b2FixtureDef edgeFixDef.friction = 0.5 edgeFixDef.restitution = 0.2 edgeFixDef.shape = new b2PolygonShape var edgeBodyDef = new b2BodyDef; edgeBodyDef.type = b2Body.b2_staticBody edgeFixDef.shape.SetAsEdge(upLeft, lowLeft) world.CreateBody(edgeBodyDef).CreateFixture(edgeFixDef) edgeFixDef.shape.SetAsEdge(lowLeft, lowRight) world.CreateBody(edgeBodyDef).CreateFixture(edgeFixDef) edgeFixDef.shape.SetAsEdge(lowRight, upRight) world.CreateBody(edgeBodyDef).CreateFixture(edgeFixDef) edgeFixDef.shape.SetAsEdge(upRight, upLeft) world.CreateBody(edgeBodyDef).CreateFixture(edgeFixDef) Can box2d really become this slow for even two bodies or is there some pitfall? It would be very surprising given all the demos which successfully use tens of objects.

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• In 3D camera math, calculate what Z depth is pixel unity for a given FOV

  - by badweasel

  I am working in iOS and OpenGL ES 2.0. Through trial and error I've figured out a frustum to where at a specific z depth pixels drawn are 1 to 1 with my source textures. So 1 pixel in my texture is 1 pixel on the screen. For 2d games this is good. Of course it means that I also factor in things like the size of the quad and the size of the texture. For example if my sprite is a quad 32x32 pixels. The quad size is 3.2 units wide and tall. And the texcoords are 32 / the size of the texture wide and tall. Then the frustum is: matrixFrustum(-(float)backingWidth/frustumScale,(float)backingWidth/frustumScale, -(float)backingHeight/frustumScale, (float)backingHeight/frustumScale, 40, 1000, mProjection); Where frustumScale is 800 for a retina screen. Then at a distance of 800 from camera the sprite is pixel for pixel the same as photoshop. For 3d games sometimes I still want to be able to do this. But depending on the scene I sometimes need the FOV to be different things. I'm looking for a way to figure out what Z depth will achieve this same pixel unity for a given FOV. For this my mProjection is set using: matrixPerspective(cameraFOV, near, far, (float)backingWidth / (float)backingHeight, mProjection); With testing I found that at an FOV of 45.0 a Z of 38.5 is very close to pixel unity. And at an FOV of 30.0 a Z of 59.5 is about right. But how can I calculate a value that is spot on? Here's my matrixPerspecitve code: void matrixPerspective(float angle, float near, float far, float aspect, mat4 m) { //float size = near * tanf(angle / 360.0 * M_PI); float size = near * tanf(degreesToRadians(angle) / 2.0); float left = -size, right = size, bottom = -size / aspect, top = size / aspect; // Unused values in perspective formula. m[1] = m[2] = m[3] = m[4] = 0; m[6] = m[7] = m[12] = m[13] = m[15] = 0; // Perspective formula. m[0] = 2 * near / (right - left); m[5] = 2 * near / (top - bottom); m[8] = (right + left) / (right - left); m[9] = (top + bottom) / (top - bottom); m[10] = -(far + near) / (far - near); m[11] = -1; m[14] = -(2 * far * near) / (far - near); } And my mView is set using: lookAtMatrix(cameraPos, camLookAt, camUpVector, mView); * UPDATE * I'm going to leave this here in case anyone has a different solution, can explain how they do it, or why this works. This is what I figured out. In my system I use a 10th scale unit to pixels on non-retina displays and a 20th scale on retina displays. The iPhone is 640 pixels wide on retina and 320 pixels wide on non-retina (obsolete). So if I want something to be the full screen width I divide by 20 to get the OpenGL unit width. Then divide that by 2 to get the left and right unit position. Something 32 units wide centered on the screen goes from -16 to +16. Believe it or not I have an excel spreadsheet do all this math for me and output all the vertex data for my sprite sheet. It's an arbitrary thing I made up to do .1 units = 1 non-retina pixel or 2 retina pixels. I could have made it .01 units = 2 pixels and someday I might switch to that. But for now it's the other. So the width of the screen in units is 32.0, and that means the left most pixel is at -16.0 and the right most is at 16.0. After messing a bit I figured out that if I take the [0] value of an identity modelViewProjection matrix and multiply it by 16 I get the depth required to get 1:1 pixels. I don't know why. I don't know if the 16 is related to the screen size or just a lucky guess. But I did a test where I placed a sprite at that calculated depth and varied the FOV through all the valid values and the object stays steady on screen with 1:1 pixels. So now I'm just calculating the unityDepth that way. If someone gives me a better answer I'll checkmark it.

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• Scene transitions

  - by Mars

  It's my first time working with actual scenes/states, aka DrawableGameComponents, which work separate from one another. I'm now wondering what's the best way to make transitions between them, and how to affect them from other scenes. Lets say I wanted to "push" one screen to the right, with another one coming in at the same time. Naturally I'd have to keep drawing both, until the transition is complete. And I'd have to adjust the coordinates I'm drawing at while doing it. Is there a way around specifically handling this special case in every single scene? Or of I wanted to fade one into the other. Basically the question stays the same, how would you do that without having to handle it in every single scene? While writing this I'm realizing it will be the same thing for all kinds of transitions. Maybe a central Draw method in the manager could be a solution, where parameters and effects are applied when necessary. But this wouldn't work if objects that are drawn have their own method, and aren't drawn within the scene, or if an effect has to be applied to the whole scene. That means, maybe scenes have to be drawn to their own rendertarget? That way one call to the base class after the normal drawing could be enough, to apply the effects, while drawing it to the main render target. But I once heard there are problems when switching from target to target, back and forth. So is that even a viable option? As you can see, I have some basic ideas how it might work... but nothing specific. I'd like to learn what's the common way to achieve such things, a general way to apply all kinds of transitions.

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• How do I interpolate air drag with a variable time step?

  - by Valentin Krummenacher

  So I have a little game which works with small steps, however those steps vary in time, so for example I sometimes have 10 Steps/second and then I have 20 Steps/second. This changes automatically depending on how many steps the user's computer can take. To avoid inaccurate positioning of the game's player object I use y=v0*dt+g*dt^2/2 to determine my objects y-position, where dt is the time since the last step, v0 is the velocity of my object in the beginning of my step and g is the gravity. To calculate the velocity in the end of a step I use v=v0+g*dt what also gives me correct results, independent of whether I use 2 steps with a dt of for example 20ms or one step with a dt of 40ms. Now I would like to introduce air drag. For simplicity's sake I use a=k*v^2 where a is the air drag's acceleration (I am aware that it would usually result in a force, but since I assume 1kg for my object's mass the force is the same as the resulting acceleration), k is a constant (in this case I'm using 0.001) and v is the speed. Now in an infinitely small time interval a is k multiplied by the velocity in this small time interval powered by 2. The problem is that v in the next time interval would depend on the drag of the last which again depends on the v of the last interval and so on... In other words: If I use a=k*v^2 I get different results for my position/velocity when I use 2 steps of 20ms than when I use one step of 40ms. I used to have this problem for my position too, but adding +g*dt^2/2 to the formula for my position fixed the problem since it takes into account that the position depends on the velocity which changes slightly in every infinitely small time interval. Does something like that exist for air drag too? And no, I dont mean anything like Adding air drag to a golf ball trajectory equation or similar, for that kind of method only gives correct results when all my steps are the same. (I hope you can understand my intermediate english, it's not my main language so I would like to say sorry for all the silly mistakes I might have made in my question)

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• Which API for cross platform mobile audio?

  - by deft_code

  This question focuses on the API's available on phones. I'd been planning to use OpenAL in my game for maximum portability. It runs great on Linux so I can quickly develop the Game and leverage it's superior debugging tools. However I've recently heard that Android doesn't support OpenAL well. Instead they've gone with a OpenSL ES library. What I'm looking for is a free Audio library that I can use with minimal custom code on iPhone, Android, and my Linux desktop. Does such an API exists? Some extra details: The game is written in C++ with custom minimal front ends. ObjC for iPhone, Java for Android, and SFML for Desktops. I'm using OpenGL ES for portability as iPhone doesn't support the more advanced OpenGL APIs.

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• libGDX using Stage and Actor produces different camera angles on desktop and Android Phone

  - by Brandon

  libGDX using Stage and Actor produces different camera angles on desktop and Android Phone. Here are pictures demonstrating the problem: http://brandonyuh.minus.com/mFpdTSgN17VUq On the desktop version, the image takes up most all the screen. On the Android phone it only takes up a bit of the screen. Here's the code (not my actual project but I isolated the problem): package com.me.mygdxgame2; import com.badlogic.gdx.*; import com.badlogic.gdx.graphics.*; import com.badlogic.gdx.graphics.Texture.TextureFilter; import com.badlogic.gdx.graphics.g2d.*; import com.badlogic.gdx.scenes.scene2d.*; public class MyGdxGame2 implements ApplicationListener { private Stage stage; public void create() { stage = new Stage(); stage.addActor(new ActorHi()); } public void render() { Gdx.gl.glClearColor(0, 1, 0, 1); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); stage.draw(); } public void dispose() {} public void resize(int width, int height) {} public void pause() {} public void resume() {} public class ActorHi extends Actor { private Sprite sprite; public ActorHi() { Texture texture = new Texture(Gdx.files.internal("data/hi.png")); texture.setFilter(TextureFilter.Linear, TextureFilter.Linear); sprite = new Sprite(new TextureRegion(texture, 0, 0, 128, 128)); sprite.setBounds(0, 0, 300.0f, 300.0f); } public void draw(SpriteBatch batch, float parentAlpha) { sprite.draw(batch); } } } hi.png is included in the above link Thank you very much for answering my question. I've spent 3 days trying to figure it out.

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