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  • Using MVC with a retained mode renderer

    - by David Gouveia
    I am using a retained mode renderer similar to the display lists in Flash. In other words, I have a scene graph data structure called the Stage to which I add the graphical primitives I would like to see rendered, such as images, animations, text. For simplicity I'll refer to them as Sprites. Now I'm implementing an architecture which is becoming very similar to MVC, but I feel that that instead of having to create View classes, that the sprites already behave pretty much like Views (except for not being explicitly connected to the Model). And since the Model is only changed through the Controller, I could simply update the view together with the Model in the controller, as in the example below: Example 1 class Controller { Model model; Sprite view; void TeleportTo(Vector2 position) { model.Position = view.Position = position; } } The alternative, I think, would be to create View classes that wrap the sprites, make the model observable, and make the view react to changes on the model. This seems like a lot of extra work and boilerplate code, and I'm not seeing the benefits if I'm just going to have one view per controller. Example 2 class Controller { Model model; View view; void TeleportTo(Vector2 position) { model.Position = position; } } class View { Model model; Sprite sprite; View() { model.PropertyChanged += UpdateView; } void UpdateView() { sprite.Position = model.Position; } } So, how is MVC or more specifically, the View, usually implemented when using a retained-mode renderer? And is there any reason why I shouldn't stick with example 1?

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  • AIR2 NativeProcess to Java debugging

    - by dede
    I'm using AIR2 NativeProcess API to communicate to Java process, but I don't know how to debug Java process when AIR send something to java process input, I want to continue debugging in Java (Eclipse). Is that somehow possible? I think other developers will agree with me that this is really important question for AIR2 new API.

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  • Game Institute Math Courses

    - by W3Geek
    I'm 21 years old and I suck at math, I mean really bad. I don't have the necessary logic to apply it towards programming. I would like to learn the math and logic of applying it. I found Game Institute (http://www.gameinstitute.com) awhile back and heard a lot of praise about them. Are there Math courses any good? Thank you. Edit: My high school was terrible and did not prepare me for any math. I am fairly decent at programming, I just don't have the logic to apply any mathematics to programming, as an example I don't understand the algorithm of finding the size of a user's screen. Yes I have heard of KhanAcademy (http://www.khanacademy.org/) and I have completed a lot of maths on his website but I still don't have the logic to apply any of it to programming.

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  • Ruby and Forking

    - by Cory
    Quick question about Ruby forking - I ran across a bit of forking code in Resque earlier that was sexy as hell but tripped me up for a few. I'm hoping for someone to give me a little more detail about what's going on here. Specifically - it would appear that forking spawns a child (expected) and kicks it straight into the 'else' side of my condition (less expected. Is that expected behavior? A Ruby idiom? My IRB hack here: def fork return true if @cant_fork begin if Kernel.respond_to?(:fork) Kernel.fork else raise NotImplementedError end rescue NotImplementedError @cant_fork = true nil end end def do_something puts "Starting do_something" if foo = fork puts "we are forking from #{Process.pid}" Process.wait else puts "no need to fork, let's get to work: #{Process.pid} under #{Process.ppid}" puts "doing it" end end do_something

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  • How to spawn a character at certain point and walk to a set point

    - by Robert H.
    I am making a game where I have a background image of a neighborhood. Each location has a different number of customers that are generated to walk on sidewalks. They all walk to a specific location (like a stand or cart that sells stuff), after they get to location I want them to interact with the cart. However, if another customer is already in a sale interaction then the others get in line in order of arrival. After the transaction the customers walk off screen. Any information on how I can do this and what game engine would be needed? Any one have any idea where I should go for this. I already have my game done up through Eclipse/Java without any game engine.

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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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  • Sprites rendering blurry with velocity

    - by ashes999
    After adding velocity to my game, I feel like my textures are twitching. I thought it was just my eyes, until I finally captured it in a screenshot: The one on the left is what renders in my game; the one on the right is the original sprite, pasted over. (This is a screenshot from Photoshop, zoomed in 6x.) Notice the edges are aliasing -- it looks almost like sub-pixel rendering. In fact, if I had not forced my sprites (which have position and velocity as ints) to draw using integer values, I would swear that MonoGame is drawing with floating point values. But it isn't. What could be the cause of these things appearing blurry? It doesn't happen without velocity applied. To be precise, my SpriteComponent class has a Vector2 Position field. When I call Draw, I essentially use new Vector2((int)Math.Round(this.Position.X), (int)Math.Round(this.Position.Y)) for the position. I had a bug before where even stationary objects would jitter -- that was due to me using the straight Position vector and not rounding the values to ints. If I use Floor/Ceiling instead of round, the sprite sinks/hovers (one pixel difference either way) but still draws blurry.

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  • How do I prevent other dynamic bodies from affecting the player's velocity with Box2D?

    - by Milo
    I'm working on my player object for my game. PhysicsBodyDef def; def.fixedRotation = true; def.density = 1.0f; def.position = Vec2(200.0f, 200.0f); def.isDynamic = true; def.size = Vec2(50.0f,200.0f); m_player.init(def,&m_physicsEngine.getWorld()); This is how he moves: b2Vec2 vel = getBody()->GetLinearVelocity(); float desiredVel = 0; if (m_keys[ALLEGRO_KEY_A] || m_keys[ALLEGRO_KEY_LEFT]) { desiredVel = -5; } else if (m_keys[ALLEGRO_KEY_D] || m_keys[ALLEGRO_KEY_RIGHT]) { desiredVel = 5; } else { desiredVel = 0; } float velChange = desiredVel - vel.x; float impulse = getBody()->GetMass() * velChange; //disregard time factor getBody()->ApplyLinearImpulse( b2Vec2(impulse,0), getBody()->GetWorldCenter(),true); This creates a few problems. First, to move the player at a constant speed he must be given a high velocity. The problem with this is if he just comes in contact with a small box, he makes it move a lot. Now, I can fix this by lowering his density, but then comes my main issue: I need other objects to be able to run into him, but when they do, he should be like a static wall and not move. I'm not sure how to do that without high density. I cannot use collision groups since I still need him to be solid toward other dynamic things. How can this be done? Essentially, how do I prevent other dynamic bodies from affecting the player's velocity?

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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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  • Wheel rotation, to change velocity of vehicle

    - by Lewis
    I update the velocity of my vehicle like so: [v setVelocity: ((2 * 3.14 * 100 * (wheel.getRotationValue / 360) / 30)) * gameSpeed]; // update on 60 fps this gets velocity on all frames divide by 60 for 1 frame. This is done in my update method in my world class. Now wheel.getRotationValue returns the rotation value which is worked out like this: - (void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; CGPoint location = [touch locationInView:[touch view]]; location = [[CCDirector sharedDirector] convertToGL:location]; if (CGRectContainsPoint(wheel.boundingBox, location)) { CGPoint firstLocation = [touch previousLocationInView:[touch view]]; CGPoint location = [touch locationInView:[touch view]]; CGPoint touchingPoint = [[CCDirector sharedDirector] convertToGL:location]; CGPoint firstTouchingPoint = [[CCDirector sharedDirector] convertToGL:firstLocation]; CGPoint firstVector = ccpSub(firstTouchingPoint, wheel.position); CGFloat firstRotateAngle = -ccpToAngle(firstVector); CGFloat previousTouch = CC_RADIANS_TO_DEGREES(firstRotateAngle); CGPoint vector = ccpSub(touchingPoint, wheel.position); CGFloat rotateAngle = -ccpToAngle(vector); CGFloat currentTouch = CC_RADIANS_TO_DEGREES(rotateAngle); float limit = 0.5; rotationValue += (currentTouch - previousTouch) * limit; } touching = YES; } Say I steer the vehicle to the far right of the screen, and want to move it to the far left, It wont start moving to the left of the screen until the rotationValue is past 0 degrees again (the wheel is in its center posistion) and is dragged past this value. Is there anyway to change the code I have above, so that movement on the wheel is recognised instantly and updates the velocity of v instantly too?

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  • Queries regarding Geometry Shaders

    - by maverick9888
    I am dealing with geometry shaders using GL_ARB_geometry_shader4 extension. My code goes like : GLfloat vertices[] = { 0.5,0.25,1.0, 0.5,0.75,1.0, -0.5,0.75,1.0, -0.5,0.25,1.0, 0.6,0.35,1.0, 0.6,0.85,1.0, -0.6,0.85,1.0, -0.6,0.35,1.0 }; glProgramParameteriEXT(psId, GL_GEOMETRY_INPUT_TYPE_EXT, GL_TRIANGLES); glProgramParameteriEXT(psId, GL_GEOMETRY_OUTPUT_TYPE_EXT, GL_TRIANGLE_STRIP); glLinkProgram(psId); glBindAttribLocation(psId,0,"Position"); glEnableVertexAttribArray (0); glVertexAttribPointer(0, 3, GL_FLOAT, 0, 0, vertices); glDrawArrays(GL_TRIANGLE_STRIP,0,4); My vertex shader is : #version 150 in vec3 Position; void main() { gl_Position = vec4(Position,1.0); } Geometry shader is : #version 150 #extension GL_EXT_geometry_shader4 : enable in vec4 pos[3]; void main() { int i; vec4 vertex; gl_Position = pos[0]; EmitVertex(); gl_Position = pos[1]; EmitVertex(); gl_Position = pos[2]; EmitVertex(); gl_Position = pos[0] + vec4(0.3,0.0,0.0,0.0); EmitVertex(); EndPrimitive(); } Nothing is rendered with this code. What exactly should be the mode in glDrawArrays() ? How does the GL_GEOMETRY_OUTPUT_TYPE_EXT parameter will affect glDrawArrays() ? What I expect is 3 vertices will be passed on to Geometry Shader and using those we construct a primitive of size 4 (assuming GL_TRIANGLE_STRIP requires 4 vertices). Can somebody please throw some light on this ?

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  • Handling different screen densities in Android Devices?

    - by DevilWithin
    Well, i know there are plenty of different-sized screens in devices that run Android. The SDK I code with deploys to all major desktop platforms and android. I am aware i must have special cares to handle the different screen sizes and densities, but i just had an idea that would work in theory, and my question is exactly about that method, How could it FAIL ? So, what I do is to have an ortho camera of the same size for all devices, with possible tweaks, but anyway that would grant the proper positioning of all elements in all devices, right? We can assume everything is drawn in OpenGLES and input handling is converted to the proper camera coordinates. If you need me to improve the question, please tell me.

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  • Can I become a Game Designer? [on hold]

    - by user32721
    This is my first time posting something on a forum in 4 years. I am posting this because I want to adjust my expectations and goals regarding game design. I am in college in Morocco (Al Akhawayn university). just started my junior year. I am a communications major (school of humanities) and a gender studies minor. I want to become a video game designer. It is the only career that I am interested in. I have been playing ever since I was 5 and haven't stopped yet. Currently I don't have any noteworthy skills to become a designer. I don't know how to program (don't really have the patience for it) and I can't draw to save my life. I haven't tried visual software like MAYA or MAX so I can't comment on graphic design. So I basically want to know whether my current education is capable of helping me reach my goal. If not then should I take a master's in game design (in the U.S?) or switch my minor to computer science? I am sorry that this post is long! I look forward to hearing your advice!

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  • Map and fill texture using PBO (OpenGL 3.3)

    - by NtscCobalt
    I'm learning OpenGL 3.3 trying to do the following (as it is done in D3D)... Create Texture of Width, Height, Pixel Format Map texture memory Loop write pixels Unmap texture memory Set Texture Render Right now though it renders as if the entire texture is black. I can't find a reliable source for information on how to do this though. Almost every tutorial I've found just uses glTexSubImage2D and passes a pointer to memory. Here is basically what my code does... (In this case it is generating an 1-byte Alpha Only texture but it is rendering it as the red channel for debugging) GLuint pixelBufferID; glGenBuffers(1, &pixelBufferID); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pixelBufferID); glBufferData(GL_PIXEL_UNPACK_BUFFER, 512 * 512 * 1, nullptr, GL_STREAM_DRAW); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0); GLuint textureID; glGenTextures(1, &textureID); glBindTexture(GL_TEXTURE_2D, textureID); glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, 512, 512, 0, GL_RED, GL_UNSIGNED_BYTE, nullptr); glBindTexture(GL_TEXTURE_2D, 0); glBindTexture(GL_TEXTURE_2D, textureID); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pixelBufferID); void *Memory = glMapBuffer(GL_PIXEL_UNPACK_BUFFER, GL_WRITE_ONLY); // Memory copied here, I know this is valid because it is the same loop as in my working D3D version glUnmapBuffer(GL_PIXEL_UNPACK_BUFFER); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0); And then here is the render loop. // This chunk left in for completeness glUseProgram(glProgramId); glBindVertexArray(glVertexArrayId); glBindBuffer(GL_ARRAY_BUFFER, glVertexBufferId); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 20, 0); glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 20, 12); GLuint transformLocationID = glGetUniformLocation(3, 'transform'); glUniformMatrix4fv(transformLocationID , 1, true, somematrix) // Not sure if this is all I need to do glBindTexture(GL_TEXTURE_2D, pTex->glTextureId); GLuint textureLocationID = glGetUniformLocation(glProgramId, "texture"); glUniform1i(textureLocationID, 0); glDrawArrays(GL_TRIANGLES, Offset*3, Triangles*3); Vertex Shader #version 330 core in vec3 Position; in vec2 TexCoords; out vec2 TexOut; uniform mat4 transform; void main() { TexOut = TexCoords; gl_Position = vec4(Position, 1.0) * transform; } Pixel Shader #version 330 core uniform sampler2D texture; in vec2 TexCoords; out vec4 fragColor; void main() { // Output color fragColor.r = texture2D(texture, TexCoords).r; fragColor.g = 0.0f; fragColor.b = 0.0f; fragColor.a = 1.0; }

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  • Can't remove JPanel from JFrame while adding new class into it

    - by A.K.
    Basically, I have my Frame class, which instantiates all the properties for the JFrame, and draws a JLabel with an image (my title screen). Then I made a separate JPanel with a start button on it, and made a mouse listener that will allow me to remove these objects while adding in a new Board() class (Which paints the main game). *Note: The JLabel is SEPARATE from the JPanel, but it still gets moved to the side by it. Problem: Whenever I click the button though, it only shows a little square of what I presume is my board class trying to run. Code below for the Frame Class: package OurPackage; //Made By A.K. 5/24/12 //Contains Frame. import java.awt.BorderLayout; import java.awt.Color; import java.awt.Container; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.GridBagLayout; import java.awt.GridLayout; import java.awt.Image; import java.awt.Rectangle; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyEvent; import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import java.awt.event.MouseListener; import javax.swing.*; import javax.swing.plaf.basic.BasicOptionPaneUI.ButtonActionListener; public class Frame implements MouseListener { public static boolean StartGame = false; ImageIcon img = new ImageIcon(getClass().getResource("/Images/ActionJackTitle.png")); ImageIcon StartImg = new ImageIcon(getClass().getResource("/Images/JackStart.png")); public Image Title; JLabel TitleL = new JLabel(img); public JPanel panel = new JPanel(); JButton StartB = new JButton(StartImg); JFrame frm = new JFrame("Action-Packed Jack"); public Frame() { TitleL.setPreferredSize(new Dimension(1200, 420)); frm.add(TitleL); frm.setLayout(new GridBagLayout()); frm.add(panel); panel.setSize(new Dimension(220, 45)); panel.setLayout(new GridBagLayout ()); panel.add(StartB); StartB.addMouseListener(this); StartB.setPreferredSize(new Dimension(220, 45)); frm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frm.setSize(1200, 420); frm.setVisible(true); frm.setResizable(false); frm.setLocationRelativeTo(null); } public static void main(String[] args) { new Frame(); } public void mouseClicked(MouseEvent e) { StartB.setContentAreaFilled(false); panel.remove(StartB); frm.remove(panel); frm.remove(TitleL); //frm.setLayout(null); frm.add(new Board()); //Add Game "Tiles" Or Content. x = 1200 frm.validate(); System.out.println("Hit!"); } @Override public void mouseEntered(MouseEvent arg0) { // TODO Auto-generated method stub } @Override public void mouseExited(MouseEvent arg0) { // TODO Auto-generated method stub } @Override public void mousePressed(MouseEvent arg0) { // TODO Auto-generated method stub } @Override public void mouseReleased(MouseEvent arg0) { // TODO Auto-generated method stub } }

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  • Can anyone recommend an AI sandbox?

    - by user19433
    I'm passionate person, who has been around AI from a long time [1] but never going in deep enough. Now it's time! I've been really looking for some way to concentrate on AI coding but couldn't succeeded to find an AI environment I can focus on. I just want to use an AI sandbox environment which would let me have tools like: visibility information character controller able to easily define a level, with obstacles of course physics collider management triggers management don't need to be a shiny, eye candy graphical render : this is about pathfinding, tactical reasoning, etc.. I have tried : Unreal Dev Kit : while the new release announce is about C++ coding, this is about external tools and will be released in 2013 Cry Engine : really interesting as AI is presents here but coding with it appears to be an hell: did I got it wrong ? Half Life source, C4, Torque, Dx Studio : either quite old, not very useful or costly these imply to dig in documentation (when provided) to code everything, graphics included. Unity 3D : the most promising platform. While you also need to create your own environment, there are lot of examples. The disadvantage is, in addition to spend time to have this env. working, is the languages choice : C#, Javascript or Boo. C# is not that hard, but this implies you'll allways have to convert papers (I love those from Lars Linden) books codes, or anything you can have in Aigamedev are most often in C++. This is extra work. I've look at "Simple Path", the very good Arong Greenberg work but no source provided and AngryAnt work. AI Sandbox : this seems to be exactly what as AI coder I want to use. I saw some preview but from 2009 we still don't know what it will be about precisely, will it be opensource or free (I strongly doubt), will I be able to buy it? will it really provide me tools I need to focus on AI ? That being said, what is the best environment to be able to focus on AI coding only, is it even possible?

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  • Regulating how much to draw based on how much was drawn last frame.

    - by Mike Howard
    I have a 3D game world on an iPhone (limited graphics speed), and I'm already regulating whether I draw each shape on the screen based on it's size and distance from the camera. Something like... if (how_big_it_looks_from_the_camera > constant) then draw What I want to do now is also take into account how many shapes are being drawn, so that in busier areas of the game world I can draw less than I otherwise would. I tried to do this by dividing how_big_it_looks by the number of shapes that were drawn last frame (well, the square root of this but I'm simplifying - the problem is the same). if (how_big_it_looks / shapes_drawn > constant2) then draw But the check happens at the level of objects which represent many drawn shapes, and if an object containing many shapes is switched on, it increases shapes_drawn lots and switches itself back off the next frame. It flickers on and off. I tried keeping a kind of weighted average of previous values, by each frame doing something like shapes_drawn_recently = 0.9 * shapes_drawn_recently + 0.1 * shapes_just_drawn, but of course it only slows the flickering down because of the nature of the feedback loop. Is there a good way of solving this? My project is in Objective-C, but a general algorithm or pseudo-code is good too. Thanks.

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  • Absorbtion 2d image effect

    - by Ed.
    I want to create a specyfic 2d image effect. It consists in modifying a sprite so it looks like it is being zoomed to a point or "absorbed" by that point. I'm not really sure what is the technical name of this effect so I cannot explain it correctly. Here you can see a video of what I'm talking about, it is the effect when the character absorbs the three glyphs. http://www.youtube.com/watch?v=PIo-GddsMcU&t=4m45s What is the name of this effect? How can I implement it with XNA for 2D textures/sprites?

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  • Dynamic Terrain Texture

    - by lgrevenl
    I've been looking at a 2D physics game called 'Hill Climb Racing' (Android and iOS) and was wondering how they went about texturing the terrain? I've had a think about it and I've come up with nothing and finding a resource on the web has proved impossible. Please help. The game mentioned uses Cocos2d. Would it be just as doable in a different environment? EDIT: I was looking at another question: Drawing large 2D sidescroller level terrain The end result is what I'm looking for, but in my mind I was thinking that there would be some way to add this effect (using small textures) to some terrain specified by vertices rather than making a very large image to match whatever is seen in the level.

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  • Play audio in javascript with a good performance

    - by João
    I'm developing a browser game where the player can shoot. Everytime he shoots it play a sound. Currently i'm using this code to play sounds in JavaScript: var audio = document.createElement("audio"); audio.src = "my_sound.mp3"; audio.play(); I'm worried about performance here. Will 10 simultaneous sounds impact my game performance too much? Will all audio objects stay in memory even after they are played?

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  • In-Game Encyclopedias

    - by SHiNKiROU
    There are some games where there is an in-game encyclopedia where you can know many things about characters and settings of the game. For example, the Codex in Mass Effect. I want to know if it is exclusive to Bioware, and get inspired about other encyclopedia systems. What are some other examples of in-game encyclopedias? How effective is it? I also want some examples where the in-game encyclopedia is not effective at all or an ignored feature

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  • box2d resize bodies arround point

    - by philipp
    I have a compound object, consisting of a b2Body, vector-graphics and a list polygons which describe the b2body's shapes. This object has its own transformation matrix to centralize the storage of transformations. So far everything is working quiet fine, even scaling works, but not if i scale around a point. In the initialization phase of the object it is scaled around a point. This happens in this order: transform the main matrix transform the vector graphics and the polygons recreate the b2Body After this function ran, the shapes and all the graphics are exactly where they should be, BUT: after the first steps of the b2World the graphical stuff moves away from the body. When I ran the debugger I found out that the position of the body is 0/0 the red dot shows the center of scaling. the first image shows the basic setup and the second the final position of the graphics. This distance stays constant for the rest of the simulation. If I set the position via myBody.SetPosition( sx, sy ); the whole scenario just plays a bit more distant for the origin. Any Idea how to fix this? EDIT:: I came deeper down to the problem and it lies in the fact that i must not scale the transform matrix for the b2body shapes around the center, but set the b2body's position back to the point after scaling. But how can I calculate that point? EDIT 2 :: I came ever deeper down to it, even solved it, but this is a slow solution and i hope that there is somebody who understands what formula I need. assuming to have a set polygons relative to an origin as basis shapes for a b2body: scaling the whole object around a certain point is done in the following steps: i scale everything around the center except the polygons i create a clone of the polygons matrix i scale this clone around the point i calculate dx, dy as difference of clone.tx - original.tx and clone.ty - original.ty i scale the original polygon matrix NOT around the point i recreate the body i create the fixture i set the position of the body to dx and dy done! So what i an interested in is a formula for dx and dy without cloning matrices, scaling the clone around a point, getting dx and dy and finally scale the vertex matrix.

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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 teach game programming at school ?

    - by jokoon
    I'm in this private school right now, and apart from my progressive stoppage of anti-depressants, I'm having an hard time focusing on what the school wants me to do. The school has a professional contract for a game we have to do with Unity. I don't really learn anything new while using unity, so I don't like using it. We recently learned how to use DirectX, and we have to do some sort of Gradius-precursor clone (Parsec) with directX, in 3D: this annoys me, and I'm currently learning to use Ogre3D by myself by making some game. The teacher is an engineer, and all of us won't be engineers. How would you teach game programming ?

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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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