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• scaling point sprites with distance

  - by Will

  How can you scale a point sprite by its distance from the camera? GLSL fragment shader: gl_PointSize = size / gl_Position.w; seems along the right tracks; for any given scene all sprites seem nicely scaled by distance. Is this correct? How do you compute the proper scaling for my vertex attribute size? I want each sprite to be scaled by the modelview matrix. I had played with arbitrary values and it seems that size is the radius in pixels at the camera, and is not in modelview scale. I've also tried: gl_Position = pMatrix * mvMatrix * vec4(vertex,1.0); vec4 v2 = pMatrix * mvMatrix * vec4(vertex.x,vertex.y+0.5*size,vertex.z,1.0); gl_PointSize = length(gl_Position.xyz-v2.xyz) * gl_Position.w; But this makes the sprites be bigger in the distance, rather than smaller:

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• Using a permutation table for simplex noise without storing it

  - by J. C. Leitão

  Generating Simplex noise requires a permutation table for randomisation (e.g. see this question or this example). In some applications, we need to persist the state of the permutation table. This can be done by creating the table, e.g. using def permutation_table(seed): table_size = 2**10 # arbitrary for this question l = range(1, table_size + 1) random.seed(seed) # ensures the same shuffle for a given seed random.shuffle(l) return l + l # see shared link why l + l; is a detail and storing it. Can we avoid storing the full table by generating the required elements every time they are required? Specifically, currently I store the table and call it using table[i] (table is a list). Can I avoid storing it by having a function that computes the element i, e.g. get_table_element(seed, i). I'm aware that cryptography already solved this problem using block cyphers, however, I found it too complex to go deep and implement a block cypher. Does anyone knows a simple implementation of a block cypher to this problem?

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• What is the XACT API?

  - by EddieV223

  I wanted to use DirectMusic in my game, but it's not in the June 2010 SDK, so I thought that I had to use DirectSound. Then I saw the XAudio2.h header in the SDK's include folder and found that XAudio2 is the replacement for DirectSound. Both are low-level. During my research I stumbled across the XACT API, but can't find a good explanation on it. Is XACT to XAudio2 what DirectMusic was to DirectSound? By which I mean, is the XACT API a high-level, easier-to-use API for playing sounds that abstracts away the details of XAudio2? If not, what is it?

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• Java Slick2d - Mouse picking how to take into account camera

  - by Corey

  When I move it it obviously changes the viewport so my mouse picking is off. My camera is just a float x and y and I use g.translate(-cam.cameraX+400, -cam.cameraY+300); to translate the graphics. I have the numbers hard coded just for testing purposes. How would I take into account the camera so my mouse picking works correctly. double mousetileX = Math.floor((double)mouseX/tiles.tileWidth); double mousetileY = Math.floor((double)mouseY/tiles.tileHeight); double playertileX = Math.floor(playerX/tiles.tileWidth); double playertileY = Math.floor(playerY/tiles.tileHeight); double lengthX = Math.abs((float)playertileX - mousetileX); double lengthY = Math.abs((float)playertileY - mousetileY); double distance = Math.sqrt((lengthX*lengthX)+(lengthY*lengthY)); if(input.isMousePressed(Input.MOUSE_LEFT_BUTTON) && distance < 4) { if(tiles.map[(int)mousetileX][(int)mousetileY] == 1) { tiles.map[(int)mousetileX][(int)mousetileY] = 0; } } That is my mouse picking code

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• Scaling Sound Effects and Physics with Framerate

  - by Thomas Bradsworth

  (I'm using XNA and C#) Currently, my game (a shooter) runs flawlessly with 60 FPS (which I developed around). However, if the framerate is changed, there are two major problems: Gunshot sound effects are slower Jumping gets messed up Here's how I play gunshot sounds: update(gametime) { if(leftMouseButton.down) { enqueueBulletForSend(); playGunShot(); } } Now, obviously, the frequency of playGunShot depends on the framerate. I can easily fix the issue if the FPS is higher than 60 FPS by capping the shooting rate of the gun, but what if the FPS is less than 60? At first I thought to just loop and play more gunshots per frame, but I found that this can cause audio clipping or make the bullets fire in "clumps." Now for the second issue: Here's how jumping works in my game: if(jumpKey.Down && canJump) { velocity.Y += 0.224f; } // ... (other code) ... if(!onGround) velocity.Y += GRAVITY_ACCELERATION * elapsedSeconds; position += velocity; The issue here is that at < 60 FPS, the "intermediate" velocity is lost and therefore the character jumps lower. At 60 FPS, the game adds more "intermediate" velocities, and therefore the character jumps higher. For example, at 60 FPS, the following occurs: Velocity increased to 0.224 Not on ground, so velocity decreased by X Position increased by (0.224 - X) <-- this is the "intermediate" velocity At 30 FPS, the following occurs: Velocity increased to 0.224 Not on ground, so velocity decreased by 2X Position increased by (0.224 - 2X) <-- the "intermediate" velocity was lost All help is appreciated!

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• Algorithm to shoot at a target in a 3d game

  - by Sebastian Bugiu

  For those of you remembering Descent Freespace it had a nice feature to help you aim at the enemy when shooting non-homing missiles or lasers: it showed a crosshair in front of the ship you chased telling you where to shoot in order to hit the moving target. I tried using the answer from http://stackoverflow.com/questions/4107403/ai-algorithm-to-shoot-at-a-target-in-a-2d-game?lq=1 but it's for 2D so I tried adapting it. I first decomposed the calculation to solve the intersection point for XoZ plane and saved the x and z coordinates and then solving the intersection point for XoY plane and adding the y coordinate to a final xyz that I then transformed to clipspace and put a texture at those coordinates. But of course it doesn't work as it should or else I wouldn't have posted the question. From what I notice the after finding x in XoZ plane and the in XoY the x is not the same so something must be wrong. float a = ENG_Math.sqr(targetVelocity.x) + ENG_Math.sqr(targetVelocity.y) - ENG_Math.sqr(projectileSpeed); float b = 2.0f * (targetVelocity.x * targetPos.x + targetVelocity.y * targetPos.y); float c = ENG_Math.sqr(targetPos.x) + ENG_Math.sqr(targetPos.y); ENG_Math.solveQuadraticEquation(a, b, c, collisionTime); First time targetVelocity.y is actually targetVelocity.z (the same for targetPos) and the second time it's actually targetVelocity.y. The final position after XoZ is crossPosition.set(minTime * finalEntityVelocity.x + finalTargetPos4D.x, 0.0f, minTime * finalEntityVelocity.z + finalTargetPos4D.z); and after XoY crossPosition.y = minTime * finalEntityVelocity.y + finalTargetPos4D.y; Is my approach of separating into 2 planes and calculating any good? Or for 3D there is a whole different approach? sqr() is square not sqrt - avoiding a confusion.

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• HLSL problem with divide by homogeneous component

  - by Berend

  When I try to divide my position.z by my position.w in HLSL I get as result always 1.0f or higher. Is this a common problem for some reason? When I divide my position.x or y by the w this works fine. But the divide for the z gives a wrong result. I use the view matrix for my camera and the projection matrix as i use it in the game because I want to create a depthmap from the cameraposition. Can anybody explain what I'm doing wrong? Do I need another view matrix?

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• Trouble with AABB collision response and physics

  - by WCM

  I have been racking my brain trying to figure out a problem I am having with physics and basic AABB collision response. I am fairly close as the physics are mostly right. Gravity feels good and movement is solid. The issue I am running into is that when I land on the test block in my project, I can jump off of it most of the time. If I repeatedly jump in place, I will eventually get stuck one or two pixels below the surface of the test block. If I try to jump, I can become free of the other block, but it will happen again a few jumps later. I feel like I am missing something really obvious with this. I have two functions that support the detection and function to return a vector for the overlap of the two rectangle bounding boxes. I have a single update method that is processing the physics and collision for the entity. I feel like I am missing something very simple, like an ordering of the physics vs. collision response handling. Any thoughts or help can be appreciated. I apologize for the format of the code, tis prototype code mostly. The collision detection function: public static bool Collides(Rectangle source, Rectangle target) { if (source.Right < target.Left || source.Bottom < target.Top || source.Left > target.Right || source.Top > target.Bottom) { return false; } return true; } The overlap function: public static Vector2 GetMinimumTranslation(Rectangle source, Rectangle target) { Vector2 mtd = new Vector2(); Vector2 amin = source.Min(); Vector2 amax = source.Max(); Vector2 bmin = target.Min(); Vector2 bmax = target.Max(); float left = (bmin.X - amax.X); float right = (bmax.X - amin.X); float top = (bmin.Y - amax.Y); float bottom = (bmax.Y - amin.Y); if (left > 0 || right < 0) return Vector2.Zero; if (top > 0 || bottom < 0) return Vector2.Zero; if (Math.Abs(left) < right) mtd.X = left; else mtd.X = right; if (Math.Abs(top) < bottom) mtd.Y = top; else mtd.Y = bottom; // 0 the axis with the largest mtd value. if (Math.Abs(mtd.X) < Math.Abs(mtd.Y)) mtd.Y = 0; else mtd.X = 0; return mtd; } The update routine (gravity = 0.001f, jumpHeight = 0.35f, moveAmount = 0.15f): public void Update(GameTime gameTime) { Acceleration.Y = gravity; Position += new Vector2((float)(movement * moveAmount * gameTime.ElapsedGameTime.TotalMilliseconds), (float)(Velocity.Y * gameTime.ElapsedGameTime.TotalMilliseconds)); Velocity.Y += Acceleration.Y; Vector2 previousPosition = new Vector2((int)Position.X, (int)Position.Y); KeyboardState keyboard = Keyboard.GetState(); movement = 0; if (keyboard.IsKeyDown(Keys.Left)) { movement -= 1; } if (keyboard.IsKeyDown(Keys.Right)) { movement += 1; } if (Position.Y + 16 > GameClass.Instance.GraphicsDevice.Viewport.Height) { Velocity.Y = 0; Position = new Vector2(Position.X, GameClass.Instance.GraphicsDevice.Viewport.Height - 16); IsOnSurface = true; } if (Collision.Collides(BoundingBox, GameClass.Instance.block.BoundingBox)) { Vector2 mtd = Collision.GetMinimumTranslation(BoundingBox, GameClass.Instance.block.BoundingBox); Position += mtd; Velocity.Y = 0; IsOnSurface = true; } if (keyboard.IsKeyDown(Keys.Space) && !previousKeyboard.IsKeyDown(Keys.Space)) { if (IsOnSurface) { Velocity.Y = -jumpHeight; IsOnSurface = false; } } previousKeyboard = keyboard; } This is also a full download to the project. https://www.box.com/s/3rkdtbso3xgfgc2asawy P.S. I know that I could do this with the XNA Platformer Starter Kit algo, but it has some deep flaws that I am going to try to live without. I'd rather go the route of collision response via an overlay function. Thanks for any and all insight!

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• How to properly do weapon cool-down reload timer in multi-player laggy environment?

  - by John Murdoch

  I want to handle weapon cool-down timers in a fair and predictable way on both client on server. Situation: Multiple clients connected to server, which is doing hit detection / physics Clients have different latency for their connections to server ranging from 50ms to 500ms. They want to shoot weapons with fairly long reload/cool-down times (assume exactly 10 seconds) It is important that they get to shoot these weapons close to the cool-down time, as if some clients manage to shoot sooner than others (either because they are "early" or the others are "late") they gain a significant advantage. I need to show time remaining for reload on player's screen Clients can have clocks which are flat-out wrong (bad timezones, etc.) What I'm currently doing to deal with latency: Client collects server side state in a history, tagged with server timestamps Client assesses his time difference with server time: behindServerTimeNs = (behindServerTimeNs + (System.nanoTime() - receivedState.getServerTimeNs())) / 2 Client renders all state received from server 200 ms behind from his current time, adjusted by what he believes his time difference with server time is (whether due to wrong clocks, or lag). If he has server states on both sides of that calculated time, he (mostly LERP) interpolates between them, if not then he (LERP) extrapolates. No other client-side prediction of movement, e.g., to make his vehicle seem more responsive is done so far, but maybe will be added later So how do I properly add weapon reload timers? My first idea would be for the server to send each player the time when his reload will be done with each world state update, the client then adjusts it for the clock difference and thus can estimate when the reload will be finished in client-time (perhaps considering also for latency that the shoot message from client to server will take as well?), and if the user mashes the "shoot" button after (or perhaps even slightly before?) that time, send the shoot event. The server would get the shoot event and consider the time shot was made as the server time when it was received. It would then discard it if it is nowhere near reload time, execute it immediately if it is past reload time, and hold it for a few physics cycles until reload is done in case if it was received a bit early. It does all seem a bit convoluted, and I'm wondering whether it will work (e.g., whether it won't be the case that players with lower ping get better reload rates), and whether there are more elegant solutions to this problem.

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• What is wrong with my game loop/mechanic?

  - by elias94xx

  I'm currently working on a 2d sidescrolling game prototype in HTML5 canvas. My implementations so far include a sprite, vector, loop and ticker class/object. Which can be viewed here: http://elias-schuett.de/apps/_experiments/2d_ssg/js/ So my game essentially works well on todays lowspec PC's and laptops. But it does not on an older win xp machine I own and on my Android 2.3 device. I tend to get ~10 FPS with these devices which results in a too high delta value, which than automaticly gets fixed to 1.0 which results in a slow loop. Now I know for a fact that there is a way to implement a super smooth 60 or 30 FPS loop on both devices. Best example would be: http://playbiolab.com/ I don't need all the chunk and debugging technology impact.js offers. I could even write a super simple game where you just control a damn square and it still wouldn't run on a equally fast 30 or 60 fps. Here is the Loop class/object I'm using. It requires a requestAnimationFrame unify function. Both devices I've tested my game on support requestAnimationFrame, so there is no interval fallback. var Loop = function(callback) { this.fps = null; this.delta = 1; this.lastTime = +new Date; this.callback = callback; this.request = null; }; Loop.prototype.start = function() { var _this = this; this.request = requestAnimationFrame(function(now) { _this.start(); _this.delta = (now - _this.lastTime); _this.fps = 1000/_this.delta; _this.delta = _this.delta / (1000/60) > 2 ? 1 : _this.delta / (1000/60); _this.lastTime = now; _this.callback(); }); }; Loop.prototype.stop = function() { cancelAnimationFrame(this.request); };

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• What 2D game engines are there available for C++?

  - by dysoco

  I just realized there are not C++ 2D Game Engines that I know of. For example, something like Pygame in Python, or Slick2D in Java. We have the following: SDL - Too low level, not a Game Engine SFML - Handles more things than SDL and it's more modern, but still not a Game Engine. I like it, but I have found it a little bit buggy with the 2.0 version. Irrlitch - It's a Game Engine, but 3D focused. Ogre3D - Same as Irrlitch Allegro - This is a Game Engine, but it's C based, I'd like a modern C++ library. Monocle Engine - This looks like what I need... but sadly there is no Documentation, no community... nothing, all I have is the Github repo. So, do you know any ? I'd like to use C++, not C#, not Java: I'm just more comfortable with C++.

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• Component-based Rendering

  - by Kikaimaru

  I have component Renderer, that Draws Texture2D (or sprite) According to component-based architecture i should have only method OnUpdate, and there should be my rendering code, something like spriteBatch.Draw(Texture, Vector2.Zero, Color.White) But first I need to do spriteBatch.Begin();. Where should i call it? And how can I make sure it's called before any Renderer components OnUpdate method? (i need to do more stuff then just Begin() i also need to set right rendertarget for camera etc.)

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• std::vector::size with glDrawElements crashes?

  - by NoobScratcher

  ( win32 / OpenGL 3.3 / GLSL 330 ) I decided after a long time of trying to do a graphical user interface using just opengl graphics to go back to a gui toolkit and so in the process have had to port alot of my code to win32. But I have a problem with my glDrawElement function. my program compiles and runs fine until it gets to glDrawElements then crashes.. which is rather annoying right. so I was trying to figure out why and I found out its std::vector::size member not returning the correct amount of faces in the unsigned interger vector eg, "vector<unsigned int>faces; " so when I use cout << faces.size() << endl; I got 68 elements???? instead of 24 as you can see here in this .obj file: # Blender v2.61 (sub 0) OBJ File: '' # www.blender.org v 1.000000 -1.000000 -1.000000 v 1.000000 -1.000000 1.000000 v -1.000000 -1.000000 1.000000 v -1.000000 -1.000000 -1.000000 v 1.000000 1.000000 -0.999999 v 0.999999 1.000000 1.000001 v -1.000000 1.000000 1.000000 v -1.000000 1.000000 -1.000000 s off f 1 2 3 4 f 5 8 7 6 f 1 5 6 2 f 2 6 7 3 <--- 24 Faces not 68? f 3 7 8 4 f 5 1 4 8 I'm using a parser I created to get the faces/vertexes in my .obj file: char modelbuffer [20000]; int MAX_BUFF = 20000; unsigned int face[3]; FILE * pfile; pfile = fopen(szFileName, "rw"); while(fgets(modelbuffer, MAX_BUFF, pfile) != NULL) { if('v') { Point p; sscanf(modelbuffer, "v %f %f %f", &p.x, &p.y, &p.z); points.push_back(p); cout << " p.x = " << p.x << " p.y = " << p.y << " p.z = " << p.x << endl; } if('f') { sscanf(modelbuffer, "f %d %d %d %d", &face[0], &face[1], &face[2], &face[3]); cout << "face[0] = " << face[0] << " face[1] = " << face[1] << " face[2] = " << face[2] << " face[3] = " << face[3] << "\n"; faces.push_back(face[0] - 1); faces.push_back(face[1] - 1); faces.push_back(face[2] - 1); faces.push_back(face[3] - 1); cout << face[0] - 1 << face[1] - 1 << face[2] - 1 << face[3] - 1 << endl; } } using this struct to store the x,y,z positions also this vector was used with Point: vector<Point>points; struct Point { float x, y, z; }; If someone could tell me why its not working and how to fix it that would be awesome I also provide a pastebin to the full source code if you want a closer look. http://pastebin.com/gznYLVw7

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• How to derive euler angles from matrix or quaternion?

  - by KlashnikovKid

  Currently working on steering behavior for my AI and just hit a little mathematical bump. I'm in the process of writing an align function, which basically tries to match the agent's orientation with a target orientation. I've got a good source material for implementing this behavior but it uses euler angles to calculate the rotational delta, acceleration, and so on. This is nice, however I store orientation as a quaternion and the math library I'm using doesn't provide any functionality for deriving the euler angles. But if it helps I also have rotational matrices at my disposal too. What would be the best way to decompose the quaternion or rotational matrix to get the euler information? I found one source for decomposing the matrix, but I'm not quite getting the correct results. I'm thinking it may be a difference of column/row ordering of my matrices but then again, math isn't my strong point. http://nghiaho.com/?page_id=846

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• Projective texture and deferred lighting

  - by Vodácek

  In my previous question, I asked whether it is possible to do projective texturing with deferred lighting. Now (more than half a year later) I have a problem with my implementation of the same thing. I am trying to apply this technique in light pass. (my projector doesn't affect albedo). I have this projector View a Projection matrix: Matrix projection = Matrix.CreateOrthographicOffCenter(-halfWidth * Scale, halfWidth * Scale, -halfHeight * Scale, halfHeight * Scale, 1, 100000); Matrix view = Matrix.CreateLookAt(Position, Target, Vector3.Up); Where halfWidth and halfHeight is are half of the texture's width and height, Position is the Projector's position and target is the projector's target. This seems to be ok. I am drawing full screen quad with this shader: float4x4 InvViewProjection; texture2D DepthTexture; texture2D NormalTexture; texture2D ProjectorTexture; float4x4 ProjectorViewProjection; sampler2D depthSampler = sampler_state { texture = <DepthTexture>; minfilter = point; magfilter = point; mipfilter = point; }; sampler2D normalSampler = sampler_state { texture = <NormalTexture>; minfilter = point; magfilter = point; mipfilter = point; }; sampler2D projectorSampler = sampler_state { texture = <ProjectorTexture>; AddressU = Clamp; AddressV = Clamp; }; float viewportWidth; float viewportHeight; // Calculate the 2D screen position of a 3D position float2 postProjToScreen(float4 position) { float2 screenPos = position.xy / position.w; return 0.5f * (float2(screenPos.x, -screenPos.y) + 1); } // Calculate the size of one half of a pixel, to convert // between texels and pixels float2 halfPixel() { return 0.5f / float2(viewportWidth, viewportHeight); } struct VertexShaderInput { float4 Position : POSITION0; }; struct VertexShaderOutput { float4 Position :POSITION0; float4 PositionCopy : TEXCOORD1; }; VertexShaderOutput VertexShaderFunction(VertexShaderInput input) { VertexShaderOutput output; output.Position = input.Position; output.PositionCopy=output.Position; return output; } float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0 { float2 texCoord =postProjToScreen(input.PositionCopy) + halfPixel(); // Extract the depth for this pixel from the depth map float4 depth = tex2D(depthSampler, texCoord); //return float4(depth.r,0,0,1); // Recreate the position with the UV coordinates and depth value float4 position; position.x = texCoord.x * 2 - 1; position.y = (1 - texCoord.y) * 2 - 1; position.z = depth.r; position.w = 1.0f; // Transform position from screen space to world space position = mul(position, InvViewProjection); position.xyz /= position.w; //compute projection float3 projection=tex2D(projectorSampler,postProjToScreen(mul(position,ProjectorViewProjection)) + halfPixel()); return float4(projection,1); } In first part of pixel shader is recovered position from G-buffer (this code I am using in other shaders without any problem) and then is tranformed to projector viewprojection space. Problem is that projection doesn't appear. Here is an image of my situation: The green lines are the rendered projector frustum. Where is my mistake hidden? I am using XNA 4. Thanks for advice and sorry for my English. EDIT: Shader above is working but projection was too small. When I changed the Scale property to a large value (e.g. 100), the projection appears. But when the camera moves toward the projection, the projection expands, as can bee seen on this YouTube video.

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• PHP city-sim castle layout

  - by Gert

  I am currently contemplating the layout system for my php based game but i've run into a couple of worries. So my idea is a 9X9 grid where the center 3X3 are inner castle. The inner castle will be 6X6 if you enter it(click on it). and with the option to expand the inner castle converting one of the 9X9 tiles to a 4X4 inner castle tile. So here is my question: What is the best way to tackle this type of layout? my original idea was a 18X18 grid and saving it in the db as (idCastle, Y, X) where X is a string of 18 numbers long telling me if the tile is an inner/outer tile or a inner/outer building. but i am not really fond of this idea and would like to hear some other ideas on how to tackle this. Thanks in Advance, Gert

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• Unity3D Android - Move your character to a specific x position

  - by user3666251

  Im making a new game for android and I wanted to move my character (which is a cube for now) to a specific x location (on top of a flying floor/ground thingy) but I've been having some troubles with it.I've been using this script : var jumpSpeed: float = 3.5; var distToGround: float; function Start(){ // get the distance to ground distToGround = collider.bounds.extents.y; } function IsGrounded(): boolean { return Physics.Raycast(transform.position, -Vector3.up, distToGround + 0.1); } function Update () { // Move the object to the right relative to the camera 1 unit/second. transform.Translate(Vector3.forward * Time.deltaTime); if (Input.anyKeyDown && IsGrounded()){ rigidbody.velocity.x = jumpSpeed; } } And this is the result (which is not what I want) : https://www.youtube.com/watch?v=Fj8B6eI4dbE&feature=youtu.be Anyone has any idea how to do this ? Im new in unity and scripting.Im using java btw. Ty.

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• Unable to Call Instantiate in Class Member Function

  - by onguarde

  The following javascript is attached to a gameObject. var instance : GameObject; class eg_class { function eg_func(){ var thePrefab : GameObject; instance = Instantiate(thePrefab); } } Error, Unknown identifier: 'instance'. Unknown identifier: 'Instantiate'. Questions, 1) Why is it that "instance" cannot be accessed within a class? Isn't it supposed to be a public variable? 2) "Instantiate" function works in Start()/Update() root functions. Is there a way to make it work from within member functions? Thanks in advance!

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• OpenGL ES, orthopgraphics projection and viewport

  - by DarkDeny

  I want to make some simple 2D game on iOS to familiarize myself with OpenGL ES. I started with Ray Wenderlich tutorial (How To Create A Simple 2D iPhone Game with OpenGL ES 2.0 and GLKit). That tutorial is quite good, but I miss some parts of a puzzle. Ray creates orthographic projection using some magic numbers like 480 and 320. It is not clear to me why did he take these numbers, and as far as I can see - sprite is not mapped to the ipad simulator screen one-to-one pixel. I tried to play with parameters with which ortho matrix is created, but I cannot figure out what math is here. How can I calculate numbers (bottom, top, left, right, close, far) which will be parameters to orthographic projection matrix creation and have sprite on the screen shown in its original size?

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• AndEngine Box2d game

  - by OneMoreVladimir

  I'm developing a 2d survival shooter using Box2d extension and I've got some questions: I have two AnalogOnScreenControls. Their listeners modify both sprites and bodies. I receive TouchEventPool was exhausted and as their number grows the game crashes accidently. I've tried to put the modification of the bodies and sprites on the UpdateThread but that does not solve the problem. What could be the cause? I have a class that at the beginnig of the game loads all the textures. After I relaunch the game activity several times I receive Unable to find Phys Addr for and "green color" interface. But that doesn't happen if I clear the memory manually through the Task Manager before relaunch What could be the cause? I unload my atlas at the end of the game. The game sometimes crashes at start with NullPointerException in onResumeGame. The solution suggested is to set android:configChanges="orientation|screenSize" but my device is API 10 so it doesn't have screenSize property and orientation only does not seem to help, because the game starts in portrait mode at times (though landscape is set in the code)

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• 2D Animation Smoothness - Delta time vs. Kinematics

  - by viperld002

  I'm animating a sprite in 2D with key frames of rotation and xy-positions. I've recently had a discussion with someone saying that when the device (happens to be an iPad using cocos2D) hits a performance bump due to whatever else the user may be doing, lag will arise and that the best way to fight it is to not use actual positions, but velocities, accelerations and torques with kinematics. His message is to evaluate the positions and rotations from these speeds at the current point in time. I've never experienced a situation where I've heard of using kinematics to stem lag in 2D animations and am not sure of how effective it could be. Also, it seems to be overkill. The application is not networked so it's all running on a local device. The desired effect is that the animation always plays as closely as it can to the target frame rate. Wouldn't the technique suffer the same problems as just using the time since the last frame or a fixed time step since the kinematics would also require some time value to perform the calculation? What techniques could you suggest to best achieve the desired effect? EDIT 1 Thank you for your responses, they are very illuminating. I want to clarify my question before choosing an answer however, to make sure that this post really serves it's purpose. I have a sprite of a ball, and a text file with 3 arrays worth of information (rotation,translations x, translations y) with each unit of information existing as a key frame to be stepped through (0 to 49 and back to 0 to replay it again). I have this playing by interpolating from the current key frame to the next, every n-units of time. The animation is visibly correct when compared to a video I was given of it, and it is smooth because of the interpolations between the key frames. This is the existing state of the project. There are no physics simulated, only a static animation of a ball moving in a way an artist specifically designed. Should I, instead of rotation in degrees and translations by positions in space, derive velocities, accelerations and torques to express this static animation as a function of time? As in, position now = foo(time now), where foo uses kinematics.

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• Dynamically load images inside jar

  - by Rahat Ahmed

  I'm using Slick2d for a game, and while it runs fine in Eclipse, i'm trying to figure out how to make it work when exported to a runnable .jar. I have it set up to where I load every image located in the res/ directory. Here's the code /** * Loads all .png images located in source folders. * @throws SlickException */ public static void init() throws SlickException { loadedImages = new HashMap<>(); try { URI uri = new URI(ResourceLoader.getResource("res").toString()); File[] files = new File(uri).listFiles(new FilenameFilter(){ @Override public boolean accept(File dir, String name) { if(name.endsWith(".png")) return true; return false; } }); System.out.println("Naming filenames now."); for(File f:files) { System.out.println(f.getName()); FileInputStream fis = new FileInputStream(f); Image image = new Image(fis, f.getName(), false); loadedImages.put(f.getName(), image); } } catch (URISyntaxException | FileNotFoundException e) { System.err.println("UNABLE TO LOAD IMAGES FROM RES FOLDER!"); e.printStackTrace(); } font = new AngelCodeFont("res/bitmapfont.fnt",Art.get("bitmapfont.png")); } Now the obvious problem is the line URI uri = new URI(ResourceLoader.getResource("res").toString()); If I pack the res folder into the .jar there will not be a res folder on the filesystem. How can I iterate through all the images in the compiled .jar itself, or what is a better system to automatically load all images?

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• Creating a voxel chunk with a VBO - How to translate the coordinates of each block and add it to the VBO chunk?

  - by sunsunsunsunsun

  Im trying to make a voxel engine similar to minecraft as a little learning experience and a way to learn some opengl. I have created a chunk class and I want to put all of the vertices for the whole chunk into a single VBO. I was previously only putting each block into a vbo and making a call to render each block. Anyways, I am a bit confused about how I can translate the coordinates of each block in the chunk when I'm putting all vertices into one vbo. This is what I have at the moment. public void putVertices(float tx, float ty, float tz) { float l_length = 1.0f; float l_height = 1.0f; float l_width = 1.0f; vertexPositionData.put(new float[]{ xOffset + l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, l_height + ty,zOffset + l_width + tz, xOffset + -l_length + tx, -l_height + ty,zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, -l_height + ty,zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + -l_length + tx, l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, -l_height + ty, zOffset + -l_width + tz, xOffset + -l_length + tx, -l_height + ty,zOffset + l_width + tz, xOffset + l_length + tx, l_height + ty,zOffset + -l_width + tz, xOffset + l_length + tx, l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + l_width + tz, xOffset + l_length + tx, -l_height + ty, zOffset + -l_width + tz }); } public void createChunk() { vertexPositionData = BufferUtils.createFloatBuffer((24*3)*activateBlocks); Random random = new Random(); for (int x = 0; x < CHUNK_SIZE; x++) { for (int y = 0; y < CHUNK_SIZE; y++) { for (int z = 0; z < CHUNK_SIZE; z++) { if(blocks[x][y][z].getActive()) { putVertices(x*2.0f, y*2.0f, z*2.0f); } } } } Whats any easy way to translate the vertices of each block into its correct position? I was previously using glTranslatef with each call to render block but this wont work now. What I am doing now also does not work, the blocks all render in stacks on top of each other and it looks like this: http://i.imgur.com/NyFtBTI.png Thanks

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• Simple 3D Physics engine as a part of graduation project [on hold]

  - by Eugene Kolesnikov

  I am working on my graduation project and one part of it is to simulate the motion of a rigid body in 3D space. I can use either already written physics engine or to write it myself. It's quite an interesting challenge for me, so I would like to do it myself. I am able to use either C++ or Java for programming (prefer C++). I am using Mac OS X and Debian 7. Could you suggest any guides or tutorials how to do it, can't find it anywhere... More precisely, I need a very simple engine, without collision detection, and many other things that I do not know, I just need to calculate the forces and move my body, depending on the resultant force. If you think that this task is still very difficult or there is no such tutorial, please suggest me some good and simple engine.

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• vector collision on polygon in 3d space detection/testing?

  - by LRFLEW

  In the 3d fps in java I'm working on, I need a bullet to be fired and to tell if it hit someone. All visual objects in the game are defined through OpenGL, so the object it can be colliding with can be any drawable polygon (although they will most likely be triangles and rectangles anyways). The bullet is not an object, but will be treated as a vector that instantaneously moves all the way across the map (like the snipper riffle in Halo). What's the best way to detect/test collisions with the polygon and the vector. I have access to OpenCL, however I have absolutely no experience with it. I am very early in the developmental stage, so if you think there's a better way of going about this, feel free to tell me (I barley have a player model to collide with anyways, so I'm flexible with it). Thanks

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