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  • Making a perfect map (not tile-based)

    - by Sri Harsha Chilakapati
    I would like to make a map system as in the GameMaker and the latest code is here. I've searched a lot in google and all of them resulted in tutorials about tile-maps. As tile maps do not fit for every type of game and GameMaker uses tiles for a different purpose, I want to make a "Sprite Based" map. The major problem I had experienced was collision detection being slow for large maps. So I wrote a QuadTree class here and the collision detection is fine upto 50000 objects in the map without PixelPerfect collision detection and 30000 objects with PixelPerferct collisions enabled. Now I need to implement the method "isObjectCollisionFree(float x, float y, boolean solid, GObject obj)". The existing implementation is becoming slow in Platformer games and I need suggestions on improvement. The current Implementation: /** * Checks if a specific position is collision free in the map. * * @param x The x-position of the object * @param y The y-position of the object * @param solid Whether to check only for solid object * @param object The object ( used for width and height ) * @return True if no-collision and false if it collides. */ public static boolean isObjectCollisionFree(float x, float y, boolean solid, GObject object){ boolean bool = true; Rectangle bounds = new Rectangle(Math.round(x), Math.round(y), object.getWidth(), object.getHeight()); ArrayList<GObject> collidables = quad.retrieve(bounds); for (int i=0; i<collidables.size(); i++){ GObject obj = collidables.get(i); if (obj.isSolid()==solid && obj != object){ if (obj.isAlive()){ if (bounds.intersects(obj.getBounds())){ bool = false; if (Global.USE_PIXELPERFECT_COLLISION){ bool = !GUtil.isPixelPerfectCollision(x, y, object.getAnimation().getBufferedImage(), obj.getX(), obj.getY(), obj.getAnimation().getBufferedImage()); } break; } } } } return bool; } Thanks.

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  • Fixed-Function vs Shaders: Which for beginner?

    - by Rob Hays
    I'm currently going to college for computer science. Although I do plan on utilizing an existing engine at some point to create a small game, my aim right now is towards learning the fundamentals: namely, 3D programming. I've already done some research regarding the choice between DirectX and OpenGL, and the general sentiment that came out of that was that whether you choose OpenGL or DirectX as your training-wheels platform, a lot of the knowledge is transferrable to the other platform. Therefore, since OpenGL is supported by more systems (probably a silly reason to choose what to learn), I decided that I'm going to learn OpenGL first. After I made this decision to learn OpenGL, I did some more research and found out about a dichotomy that I was somewhere unaware of all this time: fixed-function OpenGL vs. modern programmable shader-based OpenGL. At first, I thought it was an obvious choice that I should choose to learn shader-based OpenGL since that's what's most commonly used in the industry today. However, I then stumbled upon the very popular Learning Modern 3D Graphics Programming by Jason L. McKesson, located here: http://www.arcsynthesis.org/gltut/ I read through the introductory bits, and in the "About This Book" section, the author states: "First, much of what is learned with this approach must be inevitably abandoned when the user encounters a graphics problem that must be solved with programmability. Programmability wipes out almost all of the fixed function pipeline, so the knowledge does not easily transfer." yet at the same time also makes the case that fixed-functionality provides an easier, more immediate learning curve for beginners by stating: "It is generally considered easiest to teach neophyte graphics programmers using the fixed function pipeline." Naturally, you can see why I might be conflicted about which paradigm to learn: Do I spend a lot of time learning (and then later unlearning) the ways of fixed-functionality, or do I choose to start out with shaders? My primary concern is that modern programmable shaders somehow require the programmer to already understand the fixed-function pipeline, but I doubt that's the case. TL;DR == As an aspiring game graphics programmer, is it in my best interest to learn 3D programming through fixed-functionality or modern shader-based programming?

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  • Getting the number of fragments which passed the depth test

    - by Etan
    In "modern" environments, the "NV Occlusion Query" extension provides a method to get the number of fragments which passed the depth test. However, on the iPad / iPhone using OpenGL ES, the extension is not available. What is the most performant approach to implement a similar behaviour in the fragment shader? Some of my ideas: Render the object completely in white, then count all the colors together using a two-pass shader where first a vertical line is rendered and for each fragment the shader computes the sum over the whole row. Then, a single vertex is rendered whose fragment sums all the partial sums of the first pass. Doesn't seem to be very efficient. Render the object completely in white over a black background. Downsample recursively, abusing the hardware linear interpolation between textures until being at a reasonably small resolution. This leads to fragments which have a greyscale level depending on the number of white pixels where in their corresponding region. Is this even accurate enough? Use mipmaps and simply read the pixel on the 1x1 level. Again the question of accuracy and if it is even possible using non-power-of-two textures. The problem wit these approaches is, that the pipeline gets stalled which results in major performance issues. Therefore, I'm looking for a more performant way to accomplish my goal. Using the EXT_OCCLUSION_QUERY_BOOLEAN extension Apple introduced EXT_OCCLUSION_QUERY_BOOLEAN in iOS 5.0 for iPad 2. "4.1.6 Occlusion Queries Occlusion queries use query objects to track the number of fragments or samples that pass the depth test. An occlusion query can be started and finished by calling BeginQueryEXT and EndQueryEXT, respectively, with a target of ANY_SAMPLES_PASSED_EXT or ANY_SAMPLES_PASSED_CONSERVATIVE_EXT. When an occlusion query is started with the target ANY_SAMPLES_PASSED_EXT, the samples-boolean state maintained by the GL is set to FALSE. While that occlusion query is active, the samples-boolean state is set to TRUE if any fragment or sample passes the depth test. When the occlusion query finishes, the samples-boolean state of FALSE or TRUE is written to the corresponding query object as the query result value, and the query result for that object is marked as available. If the target of the query is ANY_SAMPLES_PASSED_CONSERVATIVE_EXT, an implementation may choose to use a less precise version of the test which can additionally set the samples-boolean state to TRUE in some other implementation dependent cases." The first sentence hints on a behavior which is exactly what I'm looking for: getting the number of pixels which passed the depth test in an asynchronous manner without much performance loss. However, the rest of the document describes only how to get boolean results. Is it possible to exploit this extension to get the pixel count? Does the hardware support it so that there may be hidden API to get access to the pixel count? Other extensions which could be exploitable would be debugging features like the number of times the fragment shader was invoked (PSInvocations in DirectX - not sure if something simila is available in OpenGL ES). However, this would also result in a pipeline stall.

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  • SDL 1.2 reports wrong screen size

    - by Aaron Digulla
    I have a multi-monitor setup with two displays, both 1920x1200. In games, I can only select resolutions 1920x1200 (like 2560x1200) which makes games unusable. Full screen doesn't work either because it switches one display to 800x600 which means I can't reach the close button... I have to kill the game and then, I have to restore my desktop because all windows are moved/resized. How can I force SDL to use any resolution that I want?

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  • library for octree or kdtree

    - by Will
    Are there any robust performant libraries for indexing objects? It would need frustum culling and visiting objects hit by a ray as well as neighbourhood searches. I can find lots of articles showing the math for the component parts, often as algebra rather than simple C, but nothing that puts it all together (apart from perhaps Ogre, which has rather more involved and isn't so stand-alone). Surely hobby game makers don't all have to make their own octrees? (Python or C/C++ w/bindings preferred)

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  • Implmenting RLE into a tilemap or how to create a large 3D array?

    - by Smallbro
    Currently I've been using a 3D array for my tiles in a 2D world but the 3D side comes in when moving down into caves and whatnot. Now this is not memory efficient and I switched over to a 2D array and can now have much larger maps. The only issue I'm having now is that it seems that my tiles cannot occupy the same space as a tile on the same z level. My current structure means that each block has its own z variable. This is what it used to look like: map.blockData[x][y][z] = new Block(); however now it works like this map.blockData[x][y] = new Block(z); I'm not sure why but if I decide to use the same space on say the floor below it wont allow me to. Does anyone have any ideas on how I can add a z-axis to my 2D array? I'm using java but I reckon the concept carries across different languages. Edit: As Will posted, RLE sounds like the best method for achieving a fast 3D array. However I'm struggling to understand how I would even start to implement it? Would I create a 4D array the 4th being something which controls how many to skip? Or would the x-axis simply change altogether and have large gaps in between - for example [5][y][z] would skip 5 tiles? Is there something really obvious here which I am missing? The number of z levels I'm trying to have is around 66, it would be preferably that I can have up to or more than 1000 in x and y.

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  • How do I implement smooth movement in a Box2D platform game?

    - by Romeo
    I have implemented a character in JBox2D which moves with the help of a wheel rotating at the bottom of it. The movement is the best result I've had 'till now but it's a little glitchy when the character stands on the edge. So I am thinking should I use five smaller wheels instead of a big wheel. The wheel/wheels will not be visible in the finished product, now they are drawn for debugging. Here is a video. Is there a better way to do this using JBox2D?

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  • 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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  • What's the difference between Canvas and WebGL?

    - by gadr90
    I'm thinking about using CAAT as a part of a HTML5 game engine. One of it's features is the ability to render to Canvas and WebGL without changing anything in the client code. That is a good thing, but I haven't found precisely: what are the differences between those two technologies? I would specially like to know the differences of Canvas and WebGL in the following regards: Framerate Desktop browser support Mobile browser support Futureproofability (TM)

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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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  • Pygame: Save a list of objects/classes/surfaces

    - by Sam Tubb
    I am working on a game, in which you can create mazes. You place blocks on a 16x16 grid, while choosing from a variety of block to make the level with. Whenever you create a block, it adds this class: class Block(object): def __init__(self,x,y,spr): self.x=x self.y=y self.sprite=spr self.rect=self.sprite.get_rect(x=self.x,y=self.y) to a list called instances. I tried shelving it to a .bin file, but it returns some error dealing with surfaces. How can I go about saving and loading levels? Any help is appreciated! :) Here is the whole code for reference: import pygame from pygame.locals import * #initstuff pygame.init() screen=pygame.display.set_mode((640,480)) pygame.display.set_caption('PiMaze') instances=[] #loadsprites menuspr=pygame.image.load('images/menu.png').convert() b1spr=pygame.image.load('images/b1.png').convert() b2spr=pygame.image.load('images/b2.png').convert() currentbspr=b1spr curspr=pygame.image.load('images/curs.png').convert() curspr.set_colorkey((0,255,0)) #menu menuspr.set_alpha(185) menurect=menuspr.get_rect(x=-260,y=4) class MenuItem(object): def __init__(self,pos,spr): self.x=pos[0] self.y=pos[1] self.sprite=spr self.pos=(self.x,self.y) self.rect=self.sprite.get_rect(x=self.x,y=self.y) class Block(object): def __init__(self,x,y,spr): self.x=x self.y=y self.sprite=spr self.rect=self.sprite.get_rect(x=self.x,y=self.y) while True: #menu items b1menu=b1spr.get_rect(x=menurect.left+32,y=48) b2menu=b2spr.get_rect(x=menurect.left+64,y=48) menuitems=[MenuItem(b1menu,b1spr),MenuItem(b2menu,b2spr)] screen.fill((20,30,85)) mse=pygame.mouse.get_pos() key=pygame.key.get_pressed() placepos=((mse[0]/16)*16,(mse[1]/16)*16) if key[K_q]: if mse[0]<260: if menurect.right<255: menurect.right+=1 else: if menurect.left>-260: menurect.left-=1 else: if menurect.left>-260: menurect.left-=1 for e in pygame.event.get(): if e.type==QUIT: exit() if menurect.right<100: if e.type==MOUSEBUTTONUP: if e.button==1: to_remove = [i for i in instances if i.rect.collidepoint(placepos)] for i in to_remove: instances.remove(i) if not to_remove: instances.append(Block(placepos[0],placepos[1],currentbspr)) for i in instances: screen.blit(i.sprite,i.rect) if not key[K_q]: screen.blit(curspr,placepos) screen.blit(menuspr,menurect) for item in menuitems: screen.blit(item.sprite,item.pos) if item.rect.collidepoint(mse): if pygame.mouse.get_pressed()==(1,0,0): currentbspr=item.sprite pygame.draw.rect(screen, ((255,0,0)), item, 1) pygame.display.flip()

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  • Simple question about a cocos2d based game template

    - by Zishan
    I am learning a cocos2d based Game template tutorial from here and now I am at this point of the tutorial. My question is, how can i run 30 different scenes in 30 different levels of 5 chapter? Now I am using this switch (gameData.selectedLevel) { case 1: [SceneManager goChapter1Level1Scene]; break; (... snip a whole lot of lines...) case 30: [SceneManager goChapter5Level6Scene]; break; default: break; } in the "- (void) onPlay: (CCMenuItemImage*) sender" method. But it work only for 6 levels scene of chapter1. Other 4 chapters levels are show as same as 1st chapter levels scene. they are not show their own level scene. can any one please teach me, how can I do this stuff using this game template?

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  • what making a good soundtrack for social game

    - by Maged
    there are many successful social games in Facebook and other social sites like brain buddies, who has the biggest brain and word challenge.both of them have a great soundtrack while playing and in the beginning of the game . my question is how to find a good soundtrack or what's i should look for to find a good soundtrack like this that's help to attract the user specially for games that need concentration ?

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  • Overriding component behavior

    - by deft_code
    I was thinking of how to implement overriding of behaviors in a component based entity system. A concrete example, an entity has a heath component that can be damaged, healed, killed etc. The entity also has an armor component that limits the amount of damage a character receives. Has anyone implemented behaviors like this in a component based system before? How did you do it? If no one has ever done this before why do you think that is. Is there anything particularly wrong headed about overriding component behaviors? Below is rough sketch up of how I imagine it would work. Components in an entity are ordered. Those at the front get a chance to service an interface first. I don't detail how that is done, just assume it uses evil dynamic_casts (it doesn't but the end effect is the same without the need for RTTI). class IHealth { public: float get_health( void ) const = 0; void do_damage( float amount ) = 0; }; class Health : public Component, public IHealth { public: void do_damage( float amount ) { m_damage -= amount; } private: float m_health; }; class Armor : public Component, public IHealth { public: float get_health( void ) const { return next<IHealth>().get_health(); } void do_damage( float amount ) { next<IHealth>().do_damage( amount / 2 ); } }; entity.add( new Health( 100 ) ); entity.add( new Armor() ); assert( entity.get<IHealth>().get_health() == 100 ); entity.get<IHealth>().do_damage( 10 ); assert( entity.get<IHealth>().get_health() == 95 ); Is there anything particularly naive about the way I'm proposing to do this?

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  • Prevent oversteering catastrophe in racing games

    - by jdm
    When playing GTA III on Android I noticed something that has been annoying me in almost every racing game I've played (maybe except Mario Kart): Driving straight ahead is easy, but curves are really hard. When I switch lanes or pass somebody, the car starts swiveling back and forth, and any attempt to correct it makes it only worse. The only thing I can do is to hit the brakes. I think this is some kind of oversteering. What makes it so irritating is that it never happens to me in real life (thank god :-)), so 90% of the games with vehicles inside feel unreal to me (despite probably having really good physics engines). I've talked to a couple of people about this, and it seems either you 'get' racing games, or you don't. With a lot of practice, I did manage to get semi-good at some games (e.g. from the Need for Speed series), by driving very cautiously, braking a lot (and usually getting a cramp in my fingers). What can you do as a game developer to prevent the oversteering resonance catastrophe, and make driving feel right? (For a casual racing game, that doesn't strive for 100% realistic physics) I also wonder what games like Super Mario Kart exactly do differently so that they don't have so much oversteering? I guess one problem is that if you play with a keyboard or a touchscreen (but not wheels and pedals), you only have digital input: gas pressed or not, steering left/right or not, and it's much harder to steer appropriately for a given speed. The other thing is that you probably don't have a good sense of speed, and drive much faster than you would (safely) in reality. From the top of my head, one solution might be to vary the steering response with speed.

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  • In a 2D platform game, how to ensure the player moves smoothly over sloping ground?

    - by Kovsa
    See image: http://i41.tinypic.com/huis13.jpg I'm developing a physics engine for a 2D platform game. I'm using the separating axis theorem for collision detection. The ground surface is constructed from oriented bounding boxes, with the player as an axis aligned bounding box. (Specifically, I'm using the algorithm from the book "Realtime Collision Detection" which performs swept collision detection for OBBs using SAT). I'm using a fairly small (close to zero) restitution coefficient in the collision response, to ensure that the dynamic objects don't penetrate the environment. The engine mostly works fine, it's just that I'm concerned about some edge cases that could possibly occur. For example, in the diagram, A, B and C are the ground surface. The player is heading left along B towards A. It seems to me that due to inaccuracy, the player box could be slightly below the box B as it continues up and left. When it reaches A, therefore, the bottom left corner of the player might then collide with the right side of A, which would be undesirable (as the intention is for the player to move smoothly over the top of A). It seems like a similar problem could happen when the player is on top of box C, moving left towards B - the most extreme point of B could collide with the left side of the player, instead of the player's bottom left corner sliding up and left above B. Box2D seems to handle this problem by storing connectivity information for its edge shapes, but I'm not really sure how it uses this information to solve the problem, and after looking at the code I don't really grasp what it's doing. Any suggestions would be greatly appreciated.

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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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  • Understanding how OpenGL blending works

    - by yuumei
    I am attempting to understand how OpenGL (ES) blending works. I am finding it difficult to understand the documentation and how the results of glBlendFunc and glBlendEquation effect the final pixel that is written. Do the source and destination out of glBlendFunc get added together with GL_FUNC_ADD by default? This seems wrong because "basic" blending of GL_ONE, GL_ONE would output 2,2,2,2 then (Source giving 1,1,1,1 and dest giving 1,1,1,1). I have written the following pseudo-code, what have I got wrong? struct colour { float r, g, b, a; }; colour blend_factor( GLenum factor, colour source, colour destination, colour blend_colour ) { colour colour_factor; float i = min( source.a, 1 - destination.a ); // From http://www.khronos.org/opengles/sdk/docs/man/xhtml/glBlendFunc.xml switch( factor ) { case GL_ZERO: colour_factor = { 0, 0, 0, 0 }; break; case GL_ONE: colour_factor = { 1, 1, 1, 1 }; break; case GL_SRC_COLOR: colour_factor = source; break; case GL_ONE_MINUS_SRC_COLOR: colour_factor = { 1 - source.r, 1 - source.g, 1 - source.b, 1 - source.a }; break; // ... } return colour_factor; } colour blend( colour & source, colour destination, GLenum source_factor, // from glBlendFunc GLenum destination_factor, // from glBlendFunc colour blend_colour, // from glBlendColor GLenum blend_equation // from glBlendEquation ) { colour source_colour = blend_factor( source_factor, source, destination, blend_colour ); colour destination_colour = blend_factor( destination_factor, source, destination, blend_colour ); colour output; // From http://www.khronos.org/opengles/sdk/docs/man/xhtml/glBlendEquation.xml switch( blend_equation ) { case GL_FUNC_ADD: output = add( source_colour, destination_colour ); case GL_FUNC_SUBTRACT: output = sub( source_colour, destination_colour ); case GL_FUNC_REVERSE_SUBTRACT: output = sub( destination_colour, source_colour ); } return output; } void do_pixel() { colour final_colour; // Blending if( enable_blending ) { final_colour = blend( current_colour_output, framebuffer[ pixel ], ... ); } else { final_colour = current_colour_output; } } Thanks!

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  • Game engines and monetization of indie games

    - by Extrakun
    Does the game engine you use affect monetization of indie games? Of course, targeting difficult platforms is one of the issues. Besides that, how would the game engine used impact monetization of games, assuming cases where the developers is going through a portal and handling the online distribution themselves? As an example, if I make a game in DarkBASIC, will it be harder to sell it than one made with Popcaps Framework or ClanLib etc.?

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  • How would I balance a multiplayer competitive game

    - by Simon
    I'm looking at my first foray into developing a game, and would love to know whether you guys have any thoughts on game balancing on limited multiplayer games. The game I have in mind involves a neutral player that has to achieve a goal, with two supporting "deity" players who are one of 'good' and 'evil' - One of the deity players would try to help the player achieve their goal, while the other would try to thwart them. Any thoughts or pointers on how I can ensure the deities are balanced? If you want me to expand, I will, just didn't want to give away too much of the game play before I finish it.

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  • Customize Colors for Sprites in Web Game

    - by NateDSaint
    So I'm working on an html5/javascript/css3-based game. Without going into too much detail, I'm thinking of having the characters be simple 8 or 16-bit style sprites, but I'd like to allow the user to customize the colors of their character. Here are some examples of what I'm talking about : http://jsfiddle.net/simurai/CGmCe/light/ http://www.splashnology.com/article/sprite-animation-in-css3/1485/ So the problem I'm having is two-fold: 1) Should I use something other than a sprite map for my characters, like actually draw them as shapes and animate them in a canvas element? That way I can fill the sprite with colors of the user's choosing? My fear there is that this would be inefficient as far as resources and also waste a lot of time hand-drawing everything, but could allow other customization (like height/width etc). 2) Are there potentially some web apis that would allow you to alter colors inside of a sprite? I suppose I could do it on the back-end with GD, but I'm trying to make it entirely in-browser (including local storage). It's not a definitive one-answer only question, but I'm hoping someone can suggest something they've seen that approaches the same problem from another angle or gives us a way to customize the sprites or manipulate them in some manner. Or avoid them altogether, and use a different method.

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  • Error in my Separating Axis Theorem collision code

    - by Holly
    The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; int x; int y; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } public void update(int xPos, int yPos){ x = xPos; y = yPos; } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(new Vect(vertices[0].x+x, vertices[0].y+y)); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(new Vect(vertices[i].x+x, vertices[i].y+y)); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if(y > other.x && other.y > x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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  • How to create an extensible rope in Box2D?

    - by Thomas
    Let's say I'm trying to create a ninja lowering himself down a rope, or pulling himself back up, all whilst he might be swinging from side to side or hit by objects. Basically like http://ninja.frozenfractal.com/ but with Box2D instead of hacky JavaScript. Ideally I would like to use a rope joint in Box2D that allows me to change the length after construction. The standard Box2D RopeJoint doesn't offer that functionality. I've considered a PulleyJoint, connecting the other end of the "pulley" to an invisible kinematic body that I can control to change the length, but PulleyJoint is more like a rod than a rope: it constrains maximum length, but unlike RopeJoint it constrains the minimum as well. Re-creating a RopeJoint every frame using a new length is rather inefficient, and I'm not even sure it would work properly in the simulation. I could create a "chain" of bodies connected by RotationJoints but that is also less efficient, and less robust. I also wouldn't be able to change the length arbitrarily, but only by adding and removing a whole number of links, and it's not obvious how I would connect the remainder without violating existing joints. This sounds like something that should be straightforward to do. Am I overlooking something?

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  • Where can I find free or buy "next-gen" 3D Assets?

    - by Valmond
    Usually I buy 3D Assets from sites like turbosquid.com or similar. My problem is that I have lately implemented glow, normal maps, specular (and specular power) maps and reflection maps and I can't find any models that use those techniques. So where can I find / buy "next gen" assets (at least models/items with a normal map)? I have checked for similar posts but those I found are about either free only or 2D or 'ordinary' 3D so I hope this is not a duplicate.

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  • Render full-screen gradient or texture

    - by Filip Skakun
    What's the simplest way to fill the background of the screen with a gradient or a texture in Direct3D 10/11? I'm building a Windows 8 metro app in which the camera never moves and I render some content in D3D, but I need to fill the background with something else than a solid color. Do I need to figure out the size and position of a rectangle and position it in 3D space or can I have some simpler solution? I don't care about depth at all, I don't use any depth buffer since all my content is sorted back to front, so I could just start by drawing to the background.

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