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• How to highlight non-rectangular hotspots?

  - by HuseyinUslu

  So my question is highly related to Creating non-rectangular hotspots and detecting clicks. Yet again, I've irregular hot-spots (think the game Risk). So basically, we can detect clicks on these hot-spots easily using color key mapping as discussed in above question which I don't have any problems implementing (which is also covered here in details). The problem is about highlighting these irreguar hotspots. So let me explain the question a bit more - the above color key mapping guide uses this as a world map: Then the author color-maps the imaginary countries: Now we can now detect the country the pointer is over. In the same article author mentions outlining countries on mouse-over. Though to get the effect, he creates unique border assets for each country - like: For the game I'm working on I'm using the same color-key mapping idea to detect hot-spots, but I didn't like the way of highlighting hot-spots. Coloring all the hot-spots is already a time-consuming job for me - as I have 25+ hot-spots for each map. Further, the need to have 25 unique border/highlight asset per hot-spot doesn't sound right. Anyone have a better idea/suggestion on highlighting these hot-spots?

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• The practical cost of swapping effects

  - by sebf

  I use XNA for my projects and on those forums I sometimes see references to the fact that swapping an effect for a mesh has a relatively high cost, which surprises me as I thought to swap an effect was simply a case of copying the replacement shader program to the GPU along with appropriate parameters. I wondered if someone could explain exactly what is costly about this process? And put, if possible, 'relatively' into context? For example say I wanted to use a short shader to help with picking, I would: Change the effect on every object, calculting a unique color to identify it and providing it to the shader. Draw all the objects to a render target in memory. Get the color from the target and use it to look up the selected object. What portion of the total time taken to complete that process would be spent swapping the shaders? My instincts would say that rendering the scene again, no matter how simple the shader, would be an order of magnitude slower than any other part of the process so why all the concern over effects?

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• Rotate canvas along its center based on user touch - Android

  - by Ganapathy

  I want to rotate the canvas circularly on its center axis based on user touch. i want to rotate based on center but its rotating based on top left corner . so i am able to see only 1/4 for rotation of image. any idea.. Like a old phone dialer . I have tried like as follows onDraw(Canvas canvas){ canvas.save(); // do my rotation canvas.rotate(rotation,0,0); canvas.drawBitmap( ((BitmapDrawable)d).getBitmap(),0,0,p ); canvas.restore(); } @Override public boolean onTouchEvent(MotionEvent e) { float x = e.getX(); float y = e.getY(); updateRotation(x,y); mPreviousX = x; mPreviousY = y; invalidate(); } private void updateRotation(float x, float y) { double r = Math.atan2(x - centerX, centerY - y); rotation = (int) Math.toDegrees(r); }

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• Z-order with Alpha blending in a 3D world

  - by user41765

  I'm working on a game in a 3D world with 2D sprites only (like Don't Starve game). (OpenGL ES2 with C++) Currently, I'm ordering elements back to front before drawing them without batch (so 1 element = 1 drawcall). I would like to implement batching in my framework to decrease draw calls. Here is what I've got for the moment: Order all elements of my scene back to front. Send order list of elements to the Renderer. Renderer look in his batch manager if a batch exist for the given element with his Material. Batch didn't exist: create a new one. Batch exist for element with this Material: Add sprite to the batch. Compute big mesh with all sprite for each batch (1 material type = 1 batch). When all batches are ok, the batch manager compute draw commands for the renderer. Renderer process draw commands (bind shader, bind textures, bind buffers, draw element) Image with my problem here: Explication here But I've got some problems because objects can be behind another objects inside another batch. How can I do something like that? Thanks!

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• Trouble with touch events on iPhone

  - by MrDatabase

  I'm making a simple 2D game for iPhone. Think of the game as a ball on the screen that goes up while the user is touching the screen and falls down when the user stops touching the screen. The ball starts moving up in touchesBegan:withEvent and starts moving down in touchesEnded:withEvent. This works fine almost all the time. However on occasion the ball will keep moving up after the user stops touching... or the ball will keep moving down while the user is touching. Why is this happening? Just fyi the ball is drawn on a UIWindow. The taps are handled by a UIImageview subclass that's clearColor and takes up the entire screen. This "touchLayer" is also moved to the front of the window in the game loop. Any idea why this control scheme occasionally fails? Perhaps the touch events just aren't firing? Or they're fired out of order? Cheers!

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• How do I draw a single Triangle with XNA and fill it with a Texture?

  - by Deukalion

  I'm trying to wrap my head around: http://msdn.microsoft.com/en-us/library/bb196409.aspx I'm trying to create a method in XNA that renders a single Triangle, then later make a method that takes a list of Triangles and renders them also. But it isn't working. I'm not understanding what all the things does and there's not enough information. My methods: // Triangle is a struct with A, B, C (didn't include) A, B, C = Vector3 public static void Render(GraphicsDevice device, List<Triangle> triangles, Texture2D texture) { foreach (Triangle triangle in triangles) { Render(device, triangle, texture); } } public static void Render(GraphicsDevice device, Triangle triangle, Texture2D texture) { BasicEffect _effect = new BasicEffect(device); _effect.Texture = texture; _effect.VertexColorEnabled = true; VertexPositionColor[] _vertices = new VertexPositionColor[3]; _vertices[0].Position = triangle.A; _vertices[1].Position = triangle.B; _vertices[2].Position = triangle.B; foreach (var pass in _effect.CurrentTechnique.Passes) { pass.Apply(); device.DrawUserIndexedPrimitives<VertexPositionColor> ( PrimitiveType.TriangleList, _vertices, 0, _vertices.Length, new int[] { 0, 1, 2 }, // example has something similiar, no idea what this is 0, 3 // 3 = gives me an error, 1 = works but no results ); } }

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• How do I adjust the origin of rotation for a group of sprites?

  - by Jon

  I am currently grouping sprites together, then applying a rotation transformation on draw: private void UpdateMatrix(ref Vector2 origin, float radians) { Vector3 matrixorigin = new Vector3(origin, 0); _rotationMatrix = Matrix.CreateTranslation(-matrixorigin) * Matrix.CreateRotationZ(radians) * Matrix.CreateTranslation(matrixorigin); } Where the origin is the Centermost point of my group of sprites. I apply this transformation to each sprite in the group. My problem is that when I adjust the point of origin, my entire sprite group will re-position itself on screen. How could I differentiate the point of rotation used in the transformation, from the position of the sprite group? Is there a better way of creating this transformation matrix? EDIT Here is the relevant part of the Draw() function: Matrix allTransforms = _rotationMatrix * camera.GetTransformation(); spriteBatch.Begin(SpriteSortMode.BackToFront, null, null, null, null, null, allTransforms); for (int i = 0; i < _map.AllParts.Count; i++) { for (int j = 0; j < _map.AllParts[0].Count; j++) { spriteBatch.Draw(_map.AllParts[i][j].Texture, _map.AllParts[i][j].Position, null, Color.White, 0, _map.AllParts[i][j].Origin, 1.0f, SpriteEffects.None, 0f); } } This all works fine, again, the problem is that when a rotation is set and the point of origin is changed, the sprite group's position is offset on screen. I am trying to figure out a way to adjust the point of origin without causing a shift in position. EDIT 2 At this point, I'm looking for workarounds as this is not working. Does anyone know of a better way to rotate a group of sprites in XNA? I need a method that will allow me to modify the point of rotation (origin) without affecting the position of the sprite group on screen.

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• How can I handle copyrighted music?

  - by David Dimalanta

  I have a curious question regarding on musics used in music rhythm game. In Guitar Hero for example, they used all different music albums in one program. Then, each album requires to ask permission to the owner, composer of the music, or the copyright owner of the music. Let's say, if you used 15 albums for the music rhythm game, then you have to contact 15 copyright owners and it might be that, for the game developer, that the profit earned goes to the copyright owner or owner of this music. For the independent game developers, was it okay if either used the copyright music by just mentioning the name of the singer included in the credits and in the music select screen or use the non-popular/old music that about 50 years ago? And, does still earn money for the indie game developers by making free downloadable game?

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• Using copyrighted sprites

  - by Zertalx

  I was thinking about making a pacman clone, I know there is a similar question here Using Copyrighted Images , but I know i can't use the original art from the game because it belongs to Namco, so if I design a character that has the shape of the slice circle it will look exactly like pacman, maybe if I use green instead of yellow? Also if the game plays like the original pacman, it is wrong? I just want to make the game as a personal project and and publish it in my site without getting in trouble

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• XNA Skinned Animated Mesh Rendering Exported from Maya

  - by Devin Garner

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

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• Improving Click and Drag with C++

  - by Josh

  I'm currently using SFML 2.0 to develop a game in C++. I have a game sprite class that has a click and drag method. The method works, but there is a slight problem. If the mouse moves too fast, the object the user selected can't keep up and is left behind in the spot where the mouse left its bounds. I will share the class definition and the given function implementation. Definition: class codePeg { protected: FloatRect bounds; CircleShape circle; int xPos, yPos, xDiff, yDiff, once; int xBase, yBase; Vector2i mousePos; Vector2f circlePos; public: void init(RenderWindow& Window); void draw(RenderWindow& Window); void drag(RenderWindow& Window); void setPegPosition(int x, int y); void setPegColor(Color pegColor); void mouseOver(RenderWindow& Window); friend int isPegSelected(void); }; Implementation of the "drag" function: void codePeg::drag(RenderWindow& Window) { mousePos = Mouse::getPosition(Window); circlePos = circle.getPosition(); if(Mouse::isButtonPressed(Mouse::Left)) { if(mousePos.x > xPos && mousePos.y > yPos && mousePos.x - bounds.width < xPos && mousePos.y - bounds.height < yPos) { if(once) { xDiff = mousePos.x - circlePos.x; yDiff = mousePos.y - circlePos.y; once = 0; } xPos = mousePos.x - xDiff; yPos = mousePos.y - yDiff; circle.setPosition(xPos, yPos); } } else { once = 1; xPos = xBase; yPos = yBase; xDiff = 0; yDiff = 0; circle.setPosition(xBase, yBase); } Window.draw(circle); } Like I said, the function works, but to me, the code is very ugly and I think it could be improved and could be more efficient. The only thing I can think of as to why the object cannot keep up with the mouse is that there are too many function calls and/or checks. The user does not really have to mouse the mouse "fast" for it to happen, I would say at an average pace the object is left behind. How can I improve the code so that the object remains with the mouse when it is selected? Any help improving this code or giving advice is greatly appreciated.

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• Height Map Mapping to "Chunked" Quadrilateralized Spherical Cube

  - by user3684950

  I have been working on a procedural spherical terrain generator for a few months which has a quadtree LOD system. The system splits the six faces of a quadrilateralized spherical cube into smaller "quads" or "patches" as the player approaches those faces. What I can't figure out is how to generate height maps for these patches. To generate the heights I am using a 3D ridged multi fractals algorithm. For now I can only displace the vertices of the patches directly using the output from the ridged multi fractals. I don't understand how I generate height maps that allow the vertices of a terrain patch to be mapped to pixels in the height map. The only thing I can think of is taking each vertex in a patch, plug that into the RMF and take that position and translate into u,v coordinates then determine the pixel position directly from the u,v coordinates and determine the grayscale color based on the height. I feel as if this is the right approach but there are a few other things that may further complicate my problem. First of all I intend to use "height maps" with a pixel resolution of 192x192 while the vertex "resolution" of each terrain patch is only 16x16 - meaning that I don't have any vertices to sample for the RMF for most of the pixels. The main reason the height map resolution is higher so that I can use it to generate a normal map (otherwise the height maps serve little purpose as I can just directly displace vertices as I currently am). I am pretty much following this paper very closely. This is, essentially, the part I am having trouble with. Using the cube-to-sphere mapping and the ridged multifractal algorithm previously described, a normalized height value ([0, 1]) is calculated. Using this height value, the terrain position is calculated and stored in the first three channels of the positionmap (RGB) – this will be used to calculate the normalmap. The fourth channel (A) is used to store the height value itself, to be used in the heightmap. The steps in the first sentence are my primary problem. I don't understand how the pixel positions correspond to positions on the sphere and what positions are sampled for the RMF to generate the pixels if only vertices cannot be used.

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• How do I draw anti-aliased holes in a bitmap

  - by gyozo kudor

  I have an artillery game (hobby-learning project) and when the projectile hits it leaves a hole in the ground. I want this hole to have antialiased edges. I'm using System.Drawing for this. I've tried with clipping paths, and drawing with a transparent color using gfx.CompositingMode = CompositingMode.SourceCopy, but it gives me the same result. If I draw a circle with a solid color it works fine, but I need a hole, a circle with 0 alpha values. I have enabled these but they work only with solid colors: gfx.CompositingQuality = CompositingQuality.HighQuality; gfx.InterpolationMode = InterpolationMode.HighQualityBicubic; gfx.SmoothingMode = SmoothingMode.AntiAlias; In the two pictures consider black as being transparent. This is what I have (zoomed in): And what I need is something like this (made with photoshop): This will be just a visual effect, in code for collision detection I still treat everything with alpha 128 as solid. Edit: I'm usink OpenTK for this game. But for this question I think it doesn't really matter probably it is gdi+ related.

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• How to remove seams from a tile map in 3D?

  - by Grimshaw

  I am using my OpenGL custom engine to render a tilemap made with Tiled, using a well spread tileset from the web. There is nothing fancy going on. I load the TMX file from Tiled and generate vertex arrays and index arrays to render the tilemap. I am rendering this tilemap as a wall in my 3D world, meaning that I move around with a fly camera in my 3D world and at Z=0 there is a plane showing me my tiles. Everything is working correctly but I get ugly seems between the tiles. I've tried orthographic and perspective cameras and with either I found particular sets of parameters for the projection and view matrices where the artifacts did not show, but otherwise they are there 99% of the time in multiple patterns, depending on the zoom and camera parameters like field of view. Here's a screenshot of the artifact being shown: http://i.imgur.com/HNV1g4M.png Here's the tileset I am using (which Tiled also uses and renders correctly): http://i.imgur.com/SjjHK4q.png My tileset has no mipmaps and is set to GL_NEAREST and GL_CLAMP_TO_EDGE values. I've looked around many articles in the internet and nothing helped. I tried uv correction so the uv fall at half of the texel, rather than the end of the texel to prevent interpolating with the neighbour value(which is transparency). I tried debugging with my geometry and I verified that with no texture and a random color in each tile, I don't seem to see any seams. All vertices have integer coordinates, i.e, the first tile is a quad from (0,0) to (1,1) and so on. Tried adding a little offset both to the UV and to the vertices to see if the gaps cease to exist. Disabled multisampling too. Nothing fixed it so far. Thanks.

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• Entity Component System for HUD and GUI

  - by Jason L.

  This is a very rough sketch of how I currently have things designed. It should, at least, give an idea of how my ECS is currently designed. If you notice in that diagram, I have basically split the HUD out of the ECS. They have their own set of things (HudLayer, HudComponent, etc) and are handled differently. This is where I'm struggling, though. There are many different instances in which the HUD will need to know about entities. Not just data changing (I have an event dispatcher for that), but the actual entity and all it encompasses. There are also situations where entities will need to be able to query the HUD for data. Let's take a couple examples: First, my equipment screen. On here I can change the equipment on a character (Entity). In order for this to happen, I need to know about the entity. At least I think I do? How can I handle this? The second scenario involves my Systems needing to query a HudComponent for data. A specific example would be my battle system. Each "team" is given a 3x3 grid they can move around in. See here: Skills target these cells, and not the player, so I would need a way for my systems to determine which cells are occupied and which are not. Basically I need a way for two way communication between Systems and my HUD. I know it's recommended (by some people, anyways) to take your HUD out of the ECS. Is that appropriate in my case?

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• Keeping player aligned to grid in Pacman

  - by user17577

  I am making a Pacman game using XNA. The game is tile based, with each tile being 32 pixels. As the player moves, I need to know whenever it is perfectly on a tile (ie position of 32, 64, etc...) so that I can check to see if the next tile is free. I am using the following logic to test this. if (position.X % 32 == 0 && position.Y %32 == 0) { onTile = true; } I figure that I need to make the player's speed evenly divide 32. Everything works fine if I make the player's speed an integer such as 4 or 8. But if I make the speed something like 6.4, I end up with positions such as 64.00001, and my if statement no longer works correctly. How can I keep the player aligned with the grid, while allowing a wider range of player speeds than 1, 2, 4, 8, 16, and 32? Or is there some better way to go about this? Thanks

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• Animation API vs frame animation

  - by Max

  I'm pretty far down the road in my game right now, closing in on the end. And I'm adding little tweaks here and there. I used custom frame animation of a single image with many versions of my sprite on it, and controlled which part of the image to show using rectangles. But I'm starting to think that maybe I should've used the Animation API that comes with android instead. Will this effect my performance in a negative way? Can I still use rectangles to draw my bitmap? Could I add effects from the Animation API to my current frame-controlled animation? like the fadeout-effect etc? this would mean I wont have to change my current code. I want some of my animations to fade out, and just noticed that using the Animation API makes things alot easier. But needless to say, I would prefer not having to change all my animation-code. I'm bad at explaining, so Ill show a bit of how I do my animation: private static final int BMP_ROWS = 1; //I use top-view so only need my sprite to have 1 direction private static final int BMP_COLUMNS = 3; public void update(GameControls controls) { if (sprite.isMoving) { currentFrame = ++currentFrame % BMP_COLUMNS; } else { this.setFrame(1); } } public void draw(Canvas canvas, int x, int y, float angle) { this.x=x; this.y=y; canvas.save(); canvas.rotate(angle , x + width / 2, y + height / 2); int srcX = currentFrame * width; int srcY = 0 * height; Rect src = new Rect(srcX, srcY, srcX + width, srcY + height); Rect dst = new Rect(x, y, x + width, y + height); canvas.drawBitmap(bitmap, src, dst, null); canvas.restore(); }

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• Android Swipe In Unity 3D World with AR

  - by Christian

  I am working on an AR application using Unity3D and the Vuforia SDK for Android. The way the application works is a when the designated image(a frame marker in our case) is recognized by the camera, a 3D island is rendered at that spot. Currently I am able to detect when/which objects are touched on the model by raycasting. I also am able to successfully detect a swipe using this code: if (Input.touchCount > 0) { Touch touch = Input.touches[0]; switch (touch.phase) { case TouchPhase.Began: couldBeSwipe = true; startPos = touch.position; startTime = Time.time; break; case TouchPhase.Moved: if (Mathf.Abs(touch.position.y - startPos.y) > comfortZoneY) { couldBeSwipe = false; } //track points here for raycast if it is swipe break; case TouchPhase.Stationary: couldBeSwipe = false; break; case TouchPhase.Ended: float swipeTime = Time.time - startTime; float swipeDist = (touch.position - startPos).magnitude; if (couldBeSwipe && (swipeTime < maxSwipeTime) && (swipeDist > minSwipeDist)) { // It's a swiiiiiiiiiiiipe! float swipeDirection = Mathf.Sign(touch.position.y - startPos.y); // Do something here in reaction to the swipe. swipeCounter.IncrementCounter(); } break; } touchInfo.SetTouchInfo (Time.time-startTime,(touch.position-startPos).magnitude,Mathf.Abs (touch.position.y-startPos.y)); } Thanks to andeeeee for the logic. But I want to have some interaction in the 3D world based on the swipe on the screen. I.E. If the user swipes over unoccluded enemies, they die. My first thought was to track all the points in the moved TouchPhase, and then if it is a swipe raycast into all those points and kill any enemy that is hit. Is there a better way to do this? What is the best approach? Thanks for the help!

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• Flickering when accessing texture by offset

  - by TravisG

  I have this simple compute shader that basically just takes the input from one image and writes it to another. Both images are 128/128/128 in size and glDispatchCompute is called with (128/8,128/8,128/8). The source images are cleared to 0 before this compute shader is executed, so no undefined values should be floating around in there. (I have the appropriate memory barrier on the C++ side set before the 3D texture is accessed). This version works fine: #version 430 layout (location = 0, rgba16f) uniform image3D ping; layout (location = 1, rgba16f) uniform image3D pong; layout (local_size_x = 8, local_size_y = 8, local_size_z = 8) in; void main() { ivec3 sampleCoord = gl_GlobalInvocationID.xyz; imageStore(pong, imageLoad(ping,sampleCoord)); } Reading values from pong shows that it's just a copy, as intended. However, when I load data from ping with an offset: #version 430 layout (location = 0, rgba16f) uniform image3D ping; layout (location = 1, rgba16f) uniform image3D pong; layout (local_size_x = 8, local_size_y = 8, local_size_z = 8) in; void main() { ivec3 sampleCoord = gl_GlobalInvocationID.xyz; imageStore(pong, imageLoad(ping,sampleCoord+ivec3(1,0,0))); } The data that is written to pong seems to depend on the order of execution of the threads within the work groups, which makes no sense to me. When reading from the pong texture, visible flickering occurs in some spots on the texture. What am I doing wrong here?

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• Turn-based JRPG battle system architecture resources

  - by BenoitRen

  The past months I've been busy programming a 2D JRPG (Japanese-style RPG) in C++ using the SDL library. The exploration mode is more or less done. Now I'm tackling the battle mode. I have been unable to find any resources about how a classic turn-based JRPG battle system is structured. All I find are discussions about damage formula. I've tried googling, searching gamedev.net's message board, and crawling through C++-related questions here on Stack Exchange. I've also tried reading source code of existing open source RPGs, but without a guide of some sort it's like trying to find a needle in a haystack. I'm not looking for a set of rules like D&D or anything similar. I'm talking purely about code and object structure design. A battle system asks the player for input using menus. Next the battle turn is executed as the heroes and the enemies execute their actions. Can anyone point me in the right direction? Thanks in advance.

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• How does Starcraft 2 load it's metadata?

  - by chobok

  Lets say you are playing Starcraft 2 melee map. The game loads the map. Melee maps have the following dependencies: Liberty (Mod) Liberty Multi (Mod) I think the game engine will load the data from Liberty (Mod) first, then from Liberty Multi (Mod). For data that exists in both dependencies, the engine will use the one from Liberty Multi (Mod). Is this correct? Liberty Multi (Mod) is updated with each patch of Starcraft 2. Does the game engine load just the latest version of Liberty Multi (Mod)? or Does the game engine load all the versions and overwrite duplicate data with the latest version?

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• C# and Unity - Learning to Develop a game by developing the game I want to develop

  - by 97s

  So I am pretty new to C#, I have some python and javascript experience, but nothing substantial. I have read a lot about C# and Unity and I know they are the tools I want to use. My question is: Should I be reading books about C# or should I just start hacking in unity and piecing the game together part by part? Right now I am going through the book, HeadFirst C#, and it is very good, but I taught myself web design and javascript by just creating and hacking until I got the results I wanted then looked at other code to see ways they did it and improved my code. The issue is that with the browser I got immediate results and it was all under one roof, where developing games is a completely different monster. I am just wondering if my time would be better spent buying a book that uses C# to teach you unity, and doing that instead, or if the time spent in HeadFirst book is going to be valuable. Thanks a ton, I am having difficulties using my time, and I just want to maximize it as I don't have a lot of free time. Edit: Hopefully this isn't to broad? If it is, I will delete and go elsewhere just let me know. Thanks.

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• geomipmapping using displacement mapping (and glVertexAttribDivisor)

  - by Will

  I wake up with a clear vision, but sadly my laptop card doesn't do displacement mapping nor glVertexAttribDivisor so I can't test it out; I'm left sharing here: With geomipmapping, the grid at any factor is transposable - if you pass in an offset - say as a uniform - you can reuse the same vertex and index array again and again. If you also pass in the offset into the heightmap as a uniform, the vertex shader can do displacement mapping. If the displacement map is mipmapped, you get the advantages of trilinear filtering for distant maps. And, if the scenery is closer, rather than exposing that the you have a world made out of quads, you can use your transposable grid vertex array and indices to do vertex-shader interpolation (fancy splines) to do super-smooth infinite zoom? So I have some questions: does it work? In theory, in practice? does anyone do it? Does this technique have a name? Papers, demos, anything I can look at? does glVertexAttribDivisor mean that you can have a single glMultiDrawElementsEXT or similar approach to draw all your terrain tiles in one call rather than setting up the uniforms and emitting each tile? Would this offer any noticeable gains? does a heightmap that is GL_LUMINANCE take just one byte per pixel(=vertex)? (On mainstream cards, obviously. Does storage vary in practice?) Does going to the effort of reusing the same vertices and indices mean that you can basically fill the GPU RAM with heightmap and not a lot else, giving you either bigger landscapes or more detailed landscapes/meshes for the same bang? is mipmapping the displacement map going to work? On future cards? Is it going to introduce unsurmountable inaccuracies if it is enabled?

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• Circular motion on low powered hardware

  - by Akroy

  I was thinking about platforms and enemies moving in circles in old 2D games, and I was wondering how that was done. I understand parametric equations, and it's trivial to use sin and cos to do it, but could an NES or SNES make real time trig calls? I admit heavy ignorance, but I thought those were expensive operations. Is there some clever way to calculate that motion more cheaply? I've been working on deriving an algorithm from trig sum identities that would only use precalculated trig, but that seems convoluted.

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• How AlphaBlend Blendstate works in XNA 4 when accumulighting light into a RenderTarget?

  - by cubrman

  I am using a Deferred Rendering engine from Catalin Zima's tutorial: His lighting shader returns the color of the light in the rgb channels and the specular component in the alpha channel. Here is how light gets accumulated: Game.GraphicsDevice.SetRenderTarget(LightRT); Game.GraphicsDevice.Clear(Color.Transparent); Game.GraphicsDevice.BlendState = BlendState.AlphaBlend; // Continuously draw 3d spheres with lighting pixel shader. ... Game.GraphicsDevice.BlendState = BlendState.Opaque; MSDN states that AlphaBlend field of the BlendState class uses the next formula for alphablending: (source × Blend.SourceAlpha) + (destination × Blend.InvSourceAlpha), where "source" is the color of the pixel returned by the shader and "destination" is the color of the pixel in the rendertarget. My question is why do my colors are accumulated correctly in the Light rendertarget even when the new pixels' alphas equal zero? As a quick sanity check I ran the following code in the light's pixel shader: float specularLight = 0; float4 light4 = attenuation * lightIntensity * float4(diffuseLight.rgb,specularLight); if (light4.a == 0) light4 = 0; return light4; This prevents lighting from getting accumulated and, subsequently, drawn on the screen. But when I do the following: float specularLight = 0; float4 light4 = attenuation * lightIntensity * float4(diffuseLight.rgb,specularLight); return light4; The light is accumulated and drawn exactly where it needs to be. What am I missing? According to the formula above: (source x 0) + (destination x 1) should equal destination, so the "LightRT" rendertarget must not change when I draw light spheres into it! It feels like the GPU is using the Additive blend instead: (source × Blend.One) + (destination × Blend.One)

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