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• About floating point precision and why do we still use it

  - by system_is_b0rken

  Floating point has always been troublesome for precision on large worlds. This article explains behind-the-scenes and offers the obvious alternative - fixed point numbers. Some facts are really impressive, like: "Well 64 bits of precision gets you to the furthest distance of Pluto from the Sun (7.4 billion km) with sub-micrometer precision. " Well sub-micrometer precision is more than any fps needs (for positions and even velocities), and it would enable you to build really big worlds. My question is, why do we still use floating point if fixed point has such advantages? Most rendering APIs and physics libraries use floating point (and suffer it's disadvantages, so developers need to get around them). Are they so much slower? Additionally, how do you think scalable planetary engines like outerra or infinity handle the large scale? Do they use fixed point for positions or do they have some space dividing algorithm?

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• Explaining Asteroids Movement code

  - by Moaz ELdeen

  I'm writing an Asteroids Atari clone, and I want to figure out how the AI for the asteroids is done. I have came across that piece of code, but I can't get what it does 100% if ((float)rand()/(float)RAND_MAX < 0.5) { m_Pos.x = -app::getWindowWidth() / 2; if ((float)rand()/(float)RAND_MAX < 0.5) m_Pos.x = app::getWindowWidth() / 2; m_Pos.y = (int) ((float)rand()/(float)RAND_MAX * app::getWindowWidth()); } else { m_Pos.x = (int) ((float)rand()/(float)RAND_MAX * app::getWindowWidth()); m_Pos.y = -app::getWindowHeight() / 2; if (rand() < 0.5) m_Pos.y = app::getWindowHeight() / 2; } m_Vel.x = (float)rand()/(float)RAND_MAX * 2; if ((float)rand()/(float)RAND_MAX < 0.5) { m_Vel.x = -m_Vel.x; } m_Vel.y =(float)rand()/(float)RAND_MAX * 2; if ((float)rand()/(float)RAND_MAX < 0.5) m_Vel.y = -m_Vel.y;

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• Can't export Blender model for use in jMonkeyEngine SDK

  - by Nathan Sabruka

  I have a scene rendered in blender called "civ1.blend" which contains multiple materials (for example, I have one called "white"). I want to use this model in jMonkeyEngine, so I used the OGRE exporter to create .scene and .material files. This gives me, for example, a civ1.scene file and a white.material file.However, when I then try to import civ1.scene into the jMonkeyEngine SDK, I get an error along the lines of "Cannot find material file 'civ1.material'". Like I said, I have a white.material file, but I do not have a civ1.material file. Did anyone encounter this problem? How do I fix this?

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• Recommended hardware for developing ios games?

  - by Matthew

  I know you have to have mac os x to use xcode and thus to develop/compile apps for the iphone. And I'm not exactly wanting to go the hackintosh way, so I'm looking at buying a used mac. What specs are recommended. If I buy a cheap mac mini that has only 1gb of ram would that be enough? (I'm not talking about using that to create the graphics/audio, I'll use my normal windows/ubuntu pc for that). I'm just talking about being able to use xcode and write applications. I'm trying to spend the least amount I can without running into problems developing the app.

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• Javascript A* path finding

  - by Veyha

  I am trying to learn A* path finding. I am using this library - https://github.com/qiao/PathFinding.js But there is one thing I don't understand how to do. To find a path from player.x/player.y (player.x and player.y are both 0) to 10/10 I use this code var path = finder.findPath(player.x, player.y, 10, 10, grid); This gives an array of where I need to move, but how do I apply this array to my player.x and player.y? The path structure looks like this path = [[0, 0], [1, 0], [1, 1], ..., [10, 10]]

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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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• XNA Drag Gestures - fractional delta values

  - by Den

  I have an issue with objects moving roughly twice as far as expected when dragging them. I am comparing my application to the standard TouchGestureSample sample from MSDN. For some reason in my application gesture samples have fractional positions and deltas. Both are using same Microsoft.Xna.Framework.Input.Touch.dll, v4.0.30319. I am running both apps using standard Windows Phone Emulator. I am setting my break point immediately after this line of code in a simple Update method: GestureSample gesture = TouchPanel.ReadGesture(); Typical values in my app: Delta = {X:-13.56522 Y:4.166667} Position = {X:184.6956 Y:417.7083} Typical values in sample app: Delta = {X:7 Y:16} Position = {X:497 Y:244} Have anyone seen this issue? Does anyone have any suggestions? Thank you.

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• Efficiently rendering to 3D texture

  - by TravisG

  I have an existing depth texture and some other color textures, and want to process the information in them by rendering to a 3D texture (based on the depth contained in the depth texture, i.e. a point at (x/y) in the depth texture will be rendered to (x/y/texture(depth,uv)) in the 3D texture). Simply doing one manual draw call for each slice of the 3D texture (via glFramebufferTextureLayer) is terribly slow, since I don't know beforehand to what slice of the 3D texture a given texel from one of the color textures or the depth texture belongs. This means the entire process is effectively for each slice for each texel in depth texture process color textures and render to slice So I have to sample the depth texture completely per each slice, and I also have to go through the processing (at least until to discard;) for all texels in it. It would be much faster if I could rearrange the process to for each texel in depth texture figure out what slice it should end up in process color textures and render to slice Is this possible? If so, how? What I'm actually trying to do: the color textures contain lighting information (as seen from light view, it's a reflective shadow map). I want to accumulate that information in the 3D texture and then later use it to light the scene. More specifically I'm trying to implement Cryteks Light Propagation Volumes algorithm.

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• Kinect joint coordinates and XNA animation

  - by Sweta Dwivedi

  I have written a program to record the x,y,z coordinated of the Hand joint and I want to animate my models 2D or 3D according to these coordinates. . .However the output of the x,y,z coordinates are fluctuating from -0 to 1 but not more than that.. So i assume I will need to multiply them back with the screen width and height, however it still doesnt seem to animate according to the original x,y,z points Any transformations I might be missing out? while ((line = r.ReadLine()) != null) { string[] temp = line.Split(','); int x = (int) float.Parse(temp[0]))* maxWidth); int y = (int) float.Parse(temp[1])) * maxHeight); }

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• Check if an object is facing another based on angles

  - by Isaiah

  I already have something that calculates the bearing angle to get one object to face another. You give it the positions and it returns the angle to get one to face the other. Now I need to figure out how tell if on object is facing toward another object within a specified field and I can't find any information about how to do this. The objects are obj1 and obj2. Their angles are at obj1.angle and obj2.angle. Their vectors are at obj1.pos and obj2.pos. It's in the format [x,y]. The angle to have one face directly at another is found with direction(obj1.pos,obj2.pos). I want to set the function up like this: isfacing(obj1,obj2,area){...} and return true/false depending if it's in the specified field area to the angle to directly see it. I've got a base like this: var isfacing = function (obj1,obj2,area){ var toface = direction(obj1.pos,obj2.pos); if(toface+area >= obj1.angle && ob1.angle >= toface-area){ return true; } return false; } But my problem is that the angles are in 360 degrees, never above 360 and never below 0. How can I account for that in this? If the first object's angle is say at 0 and say I subtract a field area of 20 or so. It'll check if it's less than -20! If I fix the -20 it becomes 340 but x < 340 isn't what I want, I'd have to x 340 in that case. Is there someone out there with more sleep than I that can help a new dev pulling an all-nighter just to get enemies to know if they're attacking in the right direction? I hope I'm making this harder than it seems. I'd just make them always face the main char if the producer didn't want attacks from behind to work while blocking. In which case I'll need the function above anyways. I've tried to give as much info as I can think would help. Also this is in 2d.

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• Cocos2d update leaking memory

  - by Andrey Chernukha

  I have a weird issue - my app is leaking memory on device only, not on a simulator. It is leaking if i schedule update method anywhere, on any scene. It is leaking despite update method is empty, there's nothing inside it except NSLog. How can it be? I have even scheduled update on the very first scene where it seems there's nothing to leak, and scheduled another empty and it's leaking or not leaking but allocating something, the result is the same - the volume of the memory consumed is increasing and my app is crashing soon. I can detect the leakage via using Instruments-Memory-Activity Monitor or with help of following function: void report_memory(void) { struct task_basic_info info; mach_msg_type_number_t size = sizeof(info); kern_return_t kerr = task_info(mach_task_self(), TASK_BASIC_INFO, (task_info_t)&info, &size); if( kerr == KERN_SUCCESS ) { NSLog(@"Memory in use (in bytes): %u", info.resident_size); } else { NSLog(@"Error with task_info(): %s", mach_error_string(kerr)); } } Can anyone explain me what's going on?

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• Calculate vector direction

  - by Starkers

  Is the direction angle always measured from the plus x axis? Does a vector in the +,+ quadrant always have a direction between 0 and 90, and in -,+ between 90 and 180 and in -,- between 180 and 270 and in -,+ between 270 and 360 ? Also, how should we calculate the direction using tan? Would that mean nested if statements to find out what quadrant we're in, and then applying the appropriate "work arounds"? E.g. If we were in the -,+ (like in the diagram) would we find the angle from the + axis would be 90 + tan^-1(y/x), the 90 + only used because we're in the -,+ quadrant. Also, that's just a quick solution, may be off, I just want to know if we use nested if statements to get the angle from the + x axis. Finally, should we find the distance in degrees or radians?

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• How does Minecraft render its sunset and sky?

  - by Nick

  In Minecraft, the sunset looks really beautiful and I've always wanted to know how they do it. Do they use several skyboxes rendered over eachother? That is, one for the sky (which can turn dark and light depending on the time of the day), one for the sun and moon, and one for the orange horizon effect? I was hoping someone could enlighten me... I wish I could enter wireframe or something like that but as far as I know that is not possible.

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• Heightmap and Textures

  - by Robert

  Im trying to find the "best way" to apply a texture to a heightmap with opengl 3.x. Its really hard to find something on google because tutorials are olds and they're all using different methods, im really lost and i dont know what to use at all. Here is my code that generates the heightmap (its basic) float[] vertexes = null; float[] textureCoords = null; for(int x = 0; x < this.m_size.width; x++) { for(int y = 0; y < this.m_size.height; y++) { vertexes ~= [x, 1.0f, y]; textureCoords ~= [cast(float)x / 50, cast(float)y / 50]; } } As you can see, i dont know how to apply the texture at all (i was using / 50 for my tests). Result of that code : I would like to have something very basic like : (you can find more pics in his blog) Edit : my texture size is 1024x1024.

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• Using a Vertex Buffer and DrawUserIndexedPrimitives?

  - by MattMcg

  Let's say I have a large but static world and only a single moving object on said world. To increase performance I wish to use a vertex and index buffer for the static part of the world. I set them up and they work fine however if I throw in another draw call to DrawUserIndexedPrimitives (to draw my one single moving object) after the call to DrawIndexedPrimitives, it will error out saying a valid vertex buffer must be set. I can only assume the DrawUserIndexedPrimitive call destroyed/replaced the vertex buffer I set. In order to get around this I must call device.SetVertexBuffer(vertexBuffer) every frame. Something tells me that isn't correct as that kind of defeats the point of a buffer? To shed some light, the large vertex buffer is the final merged mesh of many repeated cubes (think Minecraft) which I manually create to reduce the amount of vertices/indexes needed (for example two connected cubes become one cuboid, the connecting faces are cut out), and also the amount of matrix translations (as it would suck to do one per cube). The moving objects would be other items in the world which are dynamic and not fixed to the block grid, so things like the NPCs who move constantly. How do I go about handling the large static world but also allowing objects to freely move about?

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• How do I use D3DXVec3Unproject with D3D11?

  - by Miguel P

  I'm having a small issue with D3DXVec3Unproject. I'm currently using Direct3D 11 and not 10, and the signature for this function is: D3DXVECTOR3 *pOut, CONST D3DXVECTOR3 *pV, CONST D3D10_VIEWPORT *pViewport, CONST D3DXMATRIX *pProjection, CONST D3DXMATRIX *pView, CONST D3DXMATRIX *pWorld As you may have noticed, it requires a D3D10_VIEWPORT, and I'm using a Direct3D 11 viewport, D3D11_VIEWPORT. Do you have any ideas how I can use D3DXVec3Unproject with Direct3D 11?

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• Coordinate and positioning problem on iOS with cocos2d-x

  - by Vexille

  I'm using cocos2d-x alongside with Marmalade and running some tests and tutorials before starting an actual project with them. So far things are working reasonably well on the windows simulator, Android and even on Blackberry's Playbook, but on iOS devices (iPhone and iPad) the positioning seems to be off. To make things clearer, I put together a scene that just draws an image in the middle of the screen. It worked as expected on everything else, but this is the result I got on an iPhone: To get the coordinates for the center of the screen I'm using the VisibleRect class from the TestCpp sample. It just uses sharedOpenGLView to get the visible size and visible origin, and calculate the center from that. CCSprite* test = CCSprite::create("Ball.png", CCRectMake(0, 0, 80, 80) ); test->setPosition( ccp(VisibleRect::center().x, VisibleRect::center().y) ); this->addChild(test); Also I have a noBorder policy set on AppDelegate: CCEGLView::sharedOpenGLView()->setDesignResolutionSize(designSize.width, designSize.height, kResolutionNoBorder); One funny thing is that I tried to deploy the TestCpp sample project to some iOS devices and it worked reasonably well on the iPhone, but on the iPad the application was only being drawn on a small portion of the screen - just like what happened on the iPhone when I tried using the ShowAll policy.

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• Bad texture on model with different GPU

  - by Pacha

  I have some kind of distortion on the texture of my 3D model. It works perfectly well on an AMD GPU, but when testing on a integrated Intel HD graphics card it has a weird issue. I don't have a problem with the rest of my entities as they are not scaled. The models with the problems are scaled, as my engine supports different sizes for the platforms. I am using Ogre3D as rendering engine, and GLSL as shader language. Vertex shader: #version 120 varying vec2 UV; void main() { UV = gl_MultiTexCoord0; gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; } Fragment shader: #version 120 varying vec2 UV; uniform sampler2D diffuseMap; void main(void) { gl_FragColor = texture(diffuseMap, UV); } Screenshot (the error is on the right and left side, the top and bottom part are rendered perfectly well):

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• Working out of a vertex array for destrucible objects

  - by bobobobo

  I have diamond-shaped polygonal bullets. There are lots of them on the screen. I did not want to create a vertex array for each, so I packed them into a single vertex array and they're all drawn at once. | bullet1.xyz | bullet1.rgb | bullet2.xyz | bullet2.rgb This is great for performance.. there is struct Bullet { vector<Vector3f*> verts ; // pointers into the vertex buffer } ; This works fine, the bullets can move and do collision detection, all while having their data in one place. Except when a bullet "dies" Then you have to clear a slot, and pack all the bullets towards the beginning of the array. Is this a good approach to handling lots of low poly objects? How else would you do it?

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• Why are trees shining in background?

  - by Kinected

  Currently I am creating a forest scene in the dark, and the trees are shining far away, but when I get close they are fine. I have the shaders set to "Nature/Tree Soft Occlusion [bark/leaves]", but they are still rendering strange far away, but close they are fine. I tried placing the trees in a folder named "Ambient-Occlusion" like said here, but no luck. Also fog is turned off. Thanks in advance.

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• How to display image in second layer in Cocos2d

  - by PeterK

  I am very new at Cocos2d and is testing to displaying an image over the "Hello World" text on a second layer and need help to get it work. I guess it is some basic stuff here and appreciate any tips etc. with this. I know that if i put the display-code (myLayer1) in the "init" it work or do the call [self goHere] from the "init" in myLayer1 it works but i want to call the "goHere" directly. I have the following code: HelloWorld.m: #import "HelloWorldLayer.h" #import "myLayer1.h" // HelloWorldLayer implementation @implementation HelloWorldLayer +(CCScene *) scene { // 'scene' is an autorelease object. CCScene *scene = [CCScene node]; // 'layer' is an autorelease object. HelloWorldLayer *layer = [HelloWorldLayer node]; myLayer1 *layer1 = [myLayer1 node]; // add layer as a child to scene [scene addChild: layer]; [scene addChild: layer1]; // return the scene return scene; } // on "init" you need to initialize your instance -(id) init { // always call "super" init // Apple recommends to re-assign "self" with the "super" return value if( (self=[super init])) { // create and initialize a Label CCLabelTTF *label = [CCLabelTTF labelWithString:@"Hello World" fontName:@"Marker Felt" fontSize:64]; // ask director the the window size CGSize size = [[CCDirector sharedDirector] winSize]; // position the label on the center of the screen label.position = ccp( size.width /2 , size.height/2 ); // add the label as a child to this Layer [self addChild: label]; myLayer1 *a1 = [myLayer1 new]; [a1 goHere]; [myLayer1 release]; } return self; } myLayer1.m: #import "myLayer1.h" @implementation myLayer1 -(void)goHere { NSLog(@">>>>goHere<<<<"); CGSize size = [[CCDirector sharedDirector] winSize]; CCSprite *vv = [CCSprite spriteWithFile:@"hand.png"]; vv.position = ccp( size.width /2 , size.height/2 ); [self addChild:vv z:3]; } -(id) init { // always call "super" init // Apple recommends to re-assign "self" with the "super" return value if( (self=[super init])) { } return self; } @end

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• Circle physics and collision using vectors

  - by Joe Hearty

  This is a problem I've been having, When making a set number of filled circles at random locations on a JPanel and applying a gravity (a negative change in the y), each of the circles collide. I want them to have collision detection and push in the opposite direction using vectors but I don't know how to apply that to my scenario could someone help? public void drawballs(Graphics g){ g.setColor (Color.white); //displays circles for(int i = 0; i<xlocationofcircles.length-1; i++){ g.fillOval( (int) xlocationofcircles[i], (int) (ylocationofcircles[i]) ,16 ,16 ); ylocationofcircles[i]+=.2; //gravity if(ylocationofcircles[i] > 550) //stops gravity at bottom of screen ylocationofcircles[i]-=.2; //Check distance between circles(i think..) float distance =(xlocationofcircles[i+1]-xlocationofcircles[i]) + (ylocationofcircles[i+1]-xlocationofcircles[i]); if( Math.sqrt(distance) <16) ...

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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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• Geometry Shader : points + Triangles

  - by CmasterG

  I have different Shaders and for each Shader a instance of the ShaderClass class, which initializes the Shaders, Renders the Shaders, etc. I use most of the Shaderclasses without Geometry Shader, but in one Shader Class i also use a Geometry Shader. The problem is, that when I render one object with the Shaderclass that uses the Geometry shader, all other object are rendered with the same geometry that I create in the Geometry Shader. Can you help me? Is it possible that I have to use a Geometry Shader for each object, when I use one for one object? I use DirectX 11 with C++.

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• DirectX 11 Constant Buffers vs Effect Framework

  - by Alex

  I'm having some trouble understanding the differences between using constant buffers or using the effect framework of DirectX11 for updating shader constants. From what I understand they both do exactly the same thing, although from reading the documentation it appears as if using effects is meant to be 'easier'. However they seem the same to me, one uses VSSetConstantBuffers and the other GetConstantBufferByName. Is there something I'm missing here?

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