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• This code is of chess game. What is represented by 'DISTANCE' in code? [closed]

  - by rajeshverma423

  package chess; public class Evaluate { public static final int PIECE_KING = 0; public static final int PIECE_QUEEN = 1; public static final int PIECE_ROOK = 2; public static final int PIECE_BISHOP = 3; public static final int PIECE_KNIGHT = 4; public static final int PIECE_PAWN = 5; public static final int FULL_BIT_RANK = 4080; public static final int LAZY_MARGIN = 100; public static final int ISOLATED_PENALTY = 10; public static final int DOUBLE_PENALTY = 4; public static final int[] PIECE_VALUE = { 0, 9, 5, 3, 3, 1 }; public static final int[] PASS_PAWN = { 0, 35, 30, 20, 10, 5 }; public static final byte[] DISTANCE = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 5, 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 5, 4, 3, 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 7, 6, 5, 4, 3, 2, 3, 4, 5, 6, 7, 0, 0, 0, 0, 7, 6, 5, 4, 3, 2, 1, 2, 3, 4, 5, 6, 7, 0, 0, 7, 6, 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 5, 6, 7, 0, 0, 7, 6, 5, 4, 3, 2, 1, 2, 3, 4, 5, 6, 7, 0, 0, 0, 0, 7, 6, 5, 4, 3, 2, 3, 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 7, 6, 5, 4, 3, 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 5, 4, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 5, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 6, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7 };

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• How can we view 3d objects from top down view in TD game

  - by Syed

  I am making a tower defense game. I am working in x and y axis only. I have made a grid, snapped towers and made a pathfinding algo to run enemy. Initially I have worked with cubes and spheres in place of towers and enemies. Now I am going to place real towers (3D). Note that I haven't used z axis up till now. The user will analyze the game from top down view. I want the user to see towers placement with a little bit of 3d view but I have made my all code in 2d thing. Is there any solution to my problem that somewhat tower placement would view a 3D touch or you can say 2.5D ?? (like fieldrunners) or should I have to involve z axis and ignoring y axis ?

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• Problems running Java SWT application. Is this something to do with 64 vs 32-bit libraries?

  - by ?????

  I'm getting started with SWT Exception in thread "main" java.lang.UnsatisfiedLinkError: no swt-cocoa-3557 or swt-cocoa in swt.library.path, java.library.path or the jar file at org.eclipse.swt.internal.Library.loadLibrary(Unknown Source) at org.eclipse.swt.internal.Library.loadLibrary(Unknown Source) at org.eclipse.swt.internal.C.<clinit>(Unknown Source) at org.eclipse.swt.internal.cocoa.NSThread.isMainThread(Unknown Source) at org.eclipse.swt.graphics.Device.<init>(Unknown Source) at org.eclipse.swt.widgets.Display.<init>(Unknown Source) at org.eclipse.swt.widgets.Display.<init>(Unknown Source) at org.eclipse.swt.widgets.Display.getDefault(Unknown Source) at com.astrobetty.getotagdesktop.MainUIWindow.main(MainUIWindow.java:110) I've carefully followed the directions here http://www.eclipse.org/swt/eclipse.php I can see libswt-awt-cocoa-3557.jnilib, libswt-cocoa-3557.jnilib, libswt-pi-cocoa-3557.jnilib clearly listed under "Referenced Libraries" in my Eclipse package explorer. Presumably, that should make them available on the classpath when I select the java module that contains "main" and do a "run as" application. What's the problem? I suspect it may be related to 64-bit vs 32-bit VMs....

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• Please help with bounding box/sprite collision in darkBASIC pro

  - by user1601163

  So I just recently learned BASIC and figured I would try making a clone of pong on my own in darkBASIC pro, and I made everything else work just fine except for the part that makes the ball bounce off the paddle. And yes I'm aware that the game is not yet finished. The error is on lines 39-51 EVERYTHING IS 2D. /////////////////////////////////////////////////////////// // // Project: Pong // Created: Friday, August 31, 2012 // Code: Brandon Spaulding // Art: Brandon Spaulding // Made in CIS lab at CPAVTS // Pong art and code © Brandon Spaulding 2012-2013 // ////////////////////////////////////////////////////////// y=150 x=0 ay=150 ax=612 ballx=300 bally=200 ballx_DIR=1 bally_DIR=1 hide mouse set global collision on //objectnumber=10 //make object box objectnumber,5,150,0 do load image "media\paddle1.png",1 load image "media\paddle2.png",2 load image "media\ball.png",3 sprite 1,x,y,1 sprite 2,ax,ay,2 sprite 3,ballx,bally,3 if upkey()=1 then y = y - 4 if downkey()=1 then y = y + 4 //num_1 = sprite collision(1,0) //num_2 = sprite collision(2,0) num_3 = sprite collision(3,0) for t=1 to 2 //ball&paddle collision if num_3 > 0 if bally_DIR=1 bally_DIR=0 else bally_DIR=1 endif if ballx_DIR=0 ballx_DIR=1 else ballx_DIR=0 endif endif //if bally > 1 and bally < 500 then bally=bally + 2.5 if bally_DIR=1 bally=bally-2.5 if bally<-2.5 bally_DIR=0 endif else bally=bally+2.5 if bally>452.5 bally_DIR=1 endif endif if ballx_DIR=1 ballx=ballx-2.5 if ballx<-2.5 ballx_DIR=0 endif else ballx=ballx+2.5 if ballx>612 ballx_DIR=1 endif endif //bally = bally + t //if bally < 600 or bally > 1 then bally = bally - 2.5 //if ballx < 400 or ballx > 1 then ballx = ballx + 2.5 //move sprite 3,1 next t if escapekey()=1 then exit loop end Thank you in advance for the help.

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• Unity custom shaders and z-fighting

  - by Heisenbug

  I've just readed a chapter of Unity iOS Essential by Robert Wiebe. It shows a solution for handling z-figthing problem occuring while rendering a street on a plane with the same y offset. Basically it modified Normal-Diffuse shader provided by Unity, specifing the (texture?) offset in -1, -1. Here's basically what the shader looks like: Shader "Custom/ModifiedNormalDiffuse" { Properties { _Color ("Main Color", Color) = (1,1,1,1) _MainTex ("Base (RGB)", 2D) = "white" {} } SubShader { Offset -1,-1 //THIS IS THE ADDED LINE Tags { "RenderType"="Opaque" } LOD 200 CGPROGRAM #pragma surface surf Lambert sampler2D _MainTex; fixed4 _Color; struct Input { float2 uv_MainTex; }; void surf (Input IN, inout SurfaceOutput o) { half4 c = tex2D (_MainTex, IN.uv_MainTex) *_Color; o.Albedo = c.rgb; o.Alpha = c.a; } ENDCG } FallBack "Diffuse" } Ok. That's simple and it works. The author says about it: ...we could use a copy of the shader that draw the road at an Offset of -1, -1 so that whenever the two textures are drawn, the road is always drawn last. I don't know CG nor GLSL, but I've a little bit of experience with HLSL. Anyway I can't figure out what exactly is going on. Could anyone explain me what exactly Offset directly does, and how is solves z-fighting problems?

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• BlitzMax - generating 2D neon glowing line effect to png file

  - by zanlok

  Originally asked on StackOverflow, but it became tumbleweed. I'm looking to create a glowing line effect in BlitzMax, something like a Star Wars lightsaber or laserbeam. Doesn't have to be realtime, but just to TImage objects and then maybe saved to PNG for later use in animation. I'm happy to use 3D features, but it will be for use in a 2D game. Since it will be on black/space background, my strategy is to draw a series of white blurred lines with color and high transparency, then eventually central lines less blurred and more white. What I want to draw is actually bezier curved lines. Drawing curved lines is easy enough, but I can't use the technique above to create a good laser/neon effect because it comes out looking very segmented. So, I think it may be better to use a blur effect/shader on what does render well, which is a 1-pixel bezier curve. The problems I've been having are: Applying a shader to just a certain area of the screen where lines are drawn. If there's a way to do draw lines to a texture and then blur that texture and save the png, that would be great to hear about. There's got to be a way to do this, but I just haven't gotten the right elements working together yet. Any help from someone familiar with this stuff would be greatly appreciated. Using just 2D calls could be advantageous, simpler to understand and re-use. It would be very nice to know how to save a PNG that preserves the transparency/alpha stuff. p.s. I've reviewed this post (and many many others on the Blitz site), have samples working, and even developed my own 5x5 frag shaders. But, it's 3D and a scene-wide thing that doesn't seem to convert to 2D or just a certain area very well. I'd rather understand how to apply shading to a 2D scene, especially using the specifics of BlitzMax.

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• Something other than Vertex Welding with Texture Atlas?

  - by Tim Winter

  What options (in C# with XNA) would there be for texture usage in a procedural generated 3D world made of cubes to increase performance? Yes, it's like Minecraft. I've been doing a texture atlas and rendering faces individually (4 vertices per face), but I've also read in a couple places about using texture wrapping with two 1D atlases to merge adjacent faces with the same texture. If two or more adjacent faces share the same image, it'd be quite easy to wrap in this way reducing vertices by a large amount. My problem with this is having too many textures, swapping too often, and many image related things like non-power of 2 images. Is there a middle ground option between the 1D texture atlas trick and rendering 4 vertices per cube face? This is a picture of what I have currently (in wireframe). 4 vertices per face seems extremely inefficient to me.

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• Errors compiling XNA project Windows 8?

  - by ChocoMan

  I'm using Visual Studio 2012 have just installed Windows 8 on my computer and tried to compile a game Im working on in XNA. When the game tried to build, I got the following errors: Error 12 Could not copy the file "C:\Users\Computer\Documents\Visual Studio 2012\Projects\WindowsGame1\WindowsGame1\WindowsGame1\bin\x86\Debug\Content\SkyDome\skycirrus01.xnb" because it was not found. Error 13 Could not copy the file "C:\Users\Computer\Documents\Visual Studio 2012\Projects\WindowsGame1\WindowsGame1\WindowsGame1\bin\x86\Debug\Content\Fonts\Arial.xnb" because it was not found. Error 14 Could not copy the file "C:\Users\Computer\Documents\Visual Studio 2012\Projects\WindowsGame1\WindowsGame1\WindowsGame1\bin\x86\Debug\Content\Fonts\ISOCP2.xnb" because it was not found. skycirrus01.xnb is actually a .fbx. *Arial.xmb* and ISOCP2.xmb are my spritefonts within my project. Prior to installing Windows 8 (store bought) my project compiled. Does anyone know how to convert these to .xnb files? I'm assuming that will make them compatible.

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• How to render 2D particles as fluid?

  - by luke

  Suppose you have a nice way to move your 2D particles in order to simulate a fluid (like water). Any ideas on how to render it? This is for a 2D game, where the perspective is from the side, like this. The water will be contained in boxes that can be broken in order to let it fall down and interact with other objects. The simplest way that comes to my mind is to use a small image for each particle. I am interested in hearing more ways of rendering water.

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• Decal implementation

  - by dreta

  I had issues finding information about decals, so maybe this question will help others. The implementation is for a forward renderer. Could somebody confirm if i got decal implementation right? You define a cube of any dimension that'll define the projection volume in common space. You check for triangle intersection with the defined cube to recieve triangles that the projection will affect. You clip these triangles and save them. You then use matrix tricks to calculate UV coordinates for the saved triangles that'll reference the texture you're projecting. To do this you take the vectors representing height, width and depth of the cube in common space, so that f.e. the bottom left corner is the origin. You put that in a matrix as the i, j, k unit vectors, set the translation for the cube, then you inverse this matrix. You multiply the vertices of the saved triangles by this matrix, that way you get their coordinates inside of a 0 to 1 size cube that you use as the UV coordinates. This way you have the original triangles you're projecting onto and you have UV coordinates for them (the UV coordinates are referencing the texture you're projecting). Then you rerender the saved triangles onto the scene and they overwrite the area of projection with the projected image. Now the questions that i couldn't find answers for. Is the last point right? I've never done software clipping, but it seems error prone enough, due to limited precision, that the'll be some z fighting occuring for the projected texture. Also is the way of getting UV coordinates correct?

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• Tile-based 2D collision detection problems

  - by Vee

  I'm trying to follow this tutorial http://www.tonypa.pri.ee/tbw/tut05.html to implement real-time collisions in a tile-based world. I find the center coordinates of my entities thanks to these properties: public float CenterX { get { return X + Width / 2f; } set { X = value - Width / 2f; } } public float CenterY { get { return Y + Height / 2f; } set { Y = value - Height / 2f; } } Then in my update method, in the player class, which is called every frame, I have this code: public override void Update() { base.Update(); int downY = (int)Math.Floor((CenterY + Height / 2f - 1) / 16f); int upY = (int)Math.Floor((CenterY - Height / 2f) / 16f); int leftX = (int)Math.Floor((CenterX + Speed * NextX - Width / 2f) / 16f); int rightX = (int)Math.Floor((CenterX + Speed * NextX + Width / 2f - 1) / 16f); bool upleft = Game.CurrentMap[leftX, upY] != 1; bool downleft = Game.CurrentMap[leftX, downY] != 1; bool upright = Game.CurrentMap[rightX, upY] != 1; bool downright = Game.CurrentMap[rightX, downY] != 1; if(NextX == 1) { if (upright && downright) CenterX += Speed; else CenterX = (Game.GetCellX(CenterX) + 1)*16 - Width / 2f; } } downY, upY, leftX and rightX should respectively find the lowest Y position, the highest Y position, the leftmost X position and the rightmost X position. I add + Speed * NextX because in the tutorial the getMyCorners function is called with these parameters: getMyCorners (ob.x+ob.speed*dirx, ob.y, ob); The GetCellX and GetCellY methods: public int GetCellX(float mX) { return (int)Math.Floor(mX / SGame.Camera.TileSize); } public int GetCellY(float mY) { return (int)Math.Floor(mY / SGame.Camera.TileSize); } The problem is that the player "flickers" while hitting a wall, and the corner detection doesn't even work correctly since it can overlap walls that only hit one of the corners. I do not understand what is wrong. In the tutorial the ob.x and ob.y fields should be the same as my CenterX and CenterY properties, and the ob.width and ob.height should be the same as Width / 2f and Height / 2f. However it still doesn't work. Thanks for your help.

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• Character Stats and Power

  - by Stephen Furlani

  I'm making an RPG game system and I'm having a hard time deciding on doing detailed or abstract character statistics. These statistics define the character's natural - not learned - abilities. For example: Mass Effect: 0 (None that I can see) X20 (Xtreme Dungeon Mastery): 1 "STAT" Diablo: 4 "Strength, Magic, Dexterity, Vitality" Pendragon: 5 "SIZ, STR, DEX, CON, APP" Dungeons & Dragons (3.x, 4e): 6 "Str, Dex, Con, Wis, Int, Cha" Fallout 3: 7 "S.P.E.C.I.A.L." RIFTS: 8 "IQ, ME, MA, PS, PP, PE, PB, Spd" Warhammer Fantasy Roleplay (1st ed?): 12-ish "WS, BS, S, T, Ag, Int, WP, Fel, A, Mag, IP, FP" HERO (5th ed): 14 "Str, Dex, Con, Body, Int, Ego, Pre, Com, PD, ED, Spd, Rec, END, STUN" The more stats, the more complex and detailed your character becomes. This comes with a trade-off however, because you usually only have limited resources to describe your character. D&D made this infamous with the whole min/max-ing thing where strong characters were typically not also smart. But also, a character with a high Str typically also has high Con, Defenses, Hit Points/Health. Without high numbers in all those other stats, they might as well not be strong since they wouldn't hold up well in hand-to-hand combat. So things like that force trade-offs within the category of strength. So my original (now rejected) idea was to force players into deciding between offensive and defensive stats: Might / Body Dexterity / Speed Wit / Wisdom Heart Soul But this left some stat's without "opposites" (or opposites that were easily defined). I'm leaning more towards the following: Body (Physical Prowess) Mind (Mental Prowess) Heart (Social Prowess) Soul (Spiritual Prowess) This will define a character with just 4 numbers. Everything else gets based off of these numbers, which means they're pretty important. There won't, however, be ways of describing characters who are fast, but not strong or smart, but absent minded. Instead of defining the character with these numbers, they'll be detailing their character by buying skills and powers like these: Quickness Add a +2 Bonus to Body Rolls when Dodging. for a character that wants to be faster, or the following for a big, tough character Body Building Add a +2 Bonus to Body Rolls when Lifting, Pushing, or Throwing objects. [EDIT - removed subjectiveness] So my actual questions is what are some pitfalls with a small stat list and a large amount of descriptive powers? Is this more difficult to port cross-platform (pen&paper, PC) for example? Are there examples of this being done well/poorly? Thanks,

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• Level Design V.S. Modeler

  - by Ecurbed

  From what I understand being a level designer and a character/environment/object/etc Modeler are two different jobs, yet sometimes it feels like a Modeler can also do the job of the level designer. I know this also depends on the scale of the game. For small games maybe they are one and the same, but for bigger games they become two different jobs. I understand a background in some modeling could not hurt when it comes to level design, but the question I have is: Do jobs prefer people who can model for level designing? This way they can kill two birds with one stone and have someone to create the assets and design the level. What is your opinion of the training? Does level design contain skill sets that make them completely different from what a modeler can do, or is this an easy transition for a modeler to become a level designer? Can you be a bad level designer but a good modeler and vice versa?

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• Does XNA 4 support 3D affine transformations for 2D images?

  - by Paul Baker Salt Shaker

  Looooong story short I'm essentially trying to code Mode 7 in XNA. Before I continue bashing my brains out in research and various failed matrix math equations; I just want to make sure that XNA supports this just out-of-the-box (so to speak). I'd prefer not to have to import other libraries, because I want to learn how it works myself that way I understand the whole thing better. However that's all for naught if it won't work at all. So no opengl, directx, etc if possible (will eventually do it just to optimize everything, but not for now). tl;dr: Can I has Mode 7 in XNA?

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• WebGL CORS error loading simple texture in Chrome

  - by mathacka

  Here's my code: function loadTexture() { textureImage = new Image(); textureImage.onload = function() { setupTexture(); } textureImage.src = "jumper2.png"; } function setupTexture() { texture = gl.createTexture(); gl.bindTexture(gl.TEXTURE_2D, texture); gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true); // this next line has the error: Uncaught SecurityError: An attempt was made to break through the security policy of the user agent. gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, textureImage); gl.texParameteri(gl.TEXTURE_2D, gl.OES_TEXTURE_FLOAT_LINEAR, gl.NEAREST); if (!gl.isTexture(texture)) { alert("Error: Texture is invalid"); } glProgram.samplerUniform = gl.getUniformLocation(glProgram, "uSampler"); gl.uniform1i(glProgram.samplerUniform, 0); } I've researched it and it is a CORS error a "Cross-origin resource sharing" error, but it's a local file! I can't figure out what's wrong. I did make the picture using gimp, and I'm not sure the coding was right on the export, but I eliminated a previous error using "gl.OES_TEXTURE_FLOAT_LINEAR".

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• iOS - pass UIImage to shader as texture

  - by martin pilch

  I am trying to pass UIImage to GLSL shader. The fragment shader is: varying highp vec2 textureCoordinate; uniform sampler2D inputImageTexture; uniform sampler2D inputImageTexture2; void main() { highp vec4 color = texture2D(inputImageTexture, textureCoordinate); highp vec4 color2 = texture2D(inputImageTexture2, textureCoordinate); gl_FragColor = color * color2; } What I want to do is send images from camera and do multiply blend with texture. When I just send data from camera, everything is fine. So problem should be with sending another texture to shader. I am doing it this way: - (void)setTexture:(UIImage*)image forUniform:(NSString*)uniform { CGSize sizeOfImage = [image size]; CGFloat scaleOfImage = [image scale]; CGSize pixelSizeOfImage = CGSizeMake(scaleOfImage * sizeOfImage.width, scaleOfImage * sizeOfImage.height); //create context GLubyte * spriteData = (GLubyte *)malloc(pixelSizeOfImage.width * pixelSizeOfImage.height * 4 * sizeof(GLubyte)); CGContextRef spriteContext = CGBitmapContextCreate(spriteData, pixelSizeOfImage.width, pixelSizeOfImage.height, 8, pixelSizeOfImage.width * 4, CGImageGetColorSpace(image.CGImage), kCGImageAlphaPremultipliedLast); //draw image into context CGContextDrawImage(spriteContext, CGRectMake(0.0, 0.0, pixelSizeOfImage.width, pixelSizeOfImage.height), image.CGImage); //get uniform of texture GLuint uniformIndex = glGetUniformLocation(__programPointer, [uniform UTF8String]); //generate texture GLuint textureIndex; glGenTextures(1, &textureIndex); glBindTexture(GL_TEXTURE_2D, textureIndex); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); //create texture glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, pixelSizeOfImage.width, pixelSizeOfImage.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, textureIndex); //"send" to shader glUniform1i(uniformIndex, 1); free(spriteData); CGContextRelease(spriteContext); } Uniform for texture is fine, glGetUniformLocation function do not returns -1. The texture is PNG file of resolution 2000x2000 pixels. PROBLEM: When the texture is passed to shader, I have got "black screen". Maybe problem are parameters of the CGContext or parameters of the function glTexImage2D Thank you

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• Movement prediction for non-shooters

  - by ShadowChaser

  I'm working on an isometric 2D game with moderate-scale multiplayer, approximately 20-30 players connected at once to a persistent server. I've had some difficulty getting a good movement prediction implementation in place. Physics/Movement The game doesn't have a true physics implementation, but uses the basic principles to implement movement. Rather than continually polling input, state changes (ie/ mouse down/up/move events) are used to change the state of the character entity the player is controlling. The player's direction (ie/ north-east) is combined with a constant speed and turned into a true 3D vector - the entity's velocity. In the main game loop, "Update" is called before "Draw". The update logic triggers a "physics update task" that tracks all entities with a non-zero velocity uses very basic integration to change the entities position. For example: entity.Position += entity.Velocity.Scale(ElapsedTime.Seconds) (where "Seconds" is a floating point value, but the same approach would work for millisecond integer values). The key point is that no interpolation is used for movement - the rudimentary physics engine has no concept of a "previous state" or "current state", only a position and velocity. State Change and Update Packets When the velocity of the character entity the player is controlling changes, a "move avatar" packet is sent to the server containing the entity's action type (stand, walk, run), direction (north-east), and current position. This is different from how 3D first person games work. In a 3D game the velocity (direction) can change frame to frame as the player moves around. Sending every state change would effectively transmit a packet per frame, which would be too expensive. Instead, 3D games seem to ignore state changes and send "state update" packets on a fixed interval - say, every 80-150ms. Since speed and direction updates occur much less frequently in my game, I can get away with sending every state change. Although all of the physics simulations occur at the same speed and are deterministic, latency is still an issue. For that reason, I send out routine position update packets (similar to a 3D game) but much less frequently - right now every 250ms, but I suspect with good prediction I can easily boost it towards 500ms. The biggest problem is that I've now deviated from the norm - all other documentation, guides, and samples online send routine updates and interpolate between the two states. It seems incompatible with my architecture, and I need to come up with a better movement prediction algorithm that is closer to a (very basic) "networked physics" architecture. The server then receives the packet and determines the players speed from it's movement type based on a script (Is the player able to run? Get the player's running speed). Once it has the speed, it combines it with the direction to get a vector - the entity's velocity. Some cheat detection and basic validation occurs, and the entity on the server side is updated with the current velocity, direction, and position. Basic throttling is also performed to prevent players from flooding the server with movement requests. After updating its own entity, the server broadcasts an "avatar position update" packet to all other players within range. The position update packet is used to update the client side physics simulations (world state) of the remote clients and perform prediction and lag compensation. Prediction and Lag Compensation As mentioned above, clients are authoritative for their own position. Except in cases of cheating or anomalies, the client's avatar will never be repositioned by the server. No extrapolation ("move now and correct later") is required for the client's avatar - what the player sees is correct. However, some sort of extrapolation or interpolation is required for all remote entities that are moving. Some sort of prediction and/or lag-compensation is clearly required within the client's local simulation / physics engine. Problems I've been struggling with various algorithms, and have a number of questions and problems: Should I be extrapolating, interpolating, or both? My "gut feeling" is that I should be using pure extrapolation based on velocity. State change is received by the client, client computes a "predicted" velocity that compensates for lag, and the regular physics system does the rest. However, it feels at odds to all other sample code and articles - they all seem to store a number of states and perform interpolation without a physics engine. When a packet arrives, I've tried interpolating the packet's position with the packet's velocity over a fixed time period (say, 200ms). I then take the difference between the interpolated position and the current "error" position to compute a new vector and place that on the entity instead of the velocity that was sent. However, the assumption is that another packet will arrive in that time interval, and it's incredibly difficult to "guess" when the next packet will arrive - especially since they don't all arrive on fixed intervals (ie/ state changes as well). Is the concept fundamentally flawed, or is it correct but needs some fixes / adjustments? What happens when a remote player stops? I can immediately stop the entity, but it will be positioned in the "wrong" spot until it moves again. If I estimate a vector or try to interpolate, I have an issue because I don't store the previous state - the physics engine has no way to say "you need to stop after you reach position X". It simply understands a velocity, nothing more complex. I'm reluctant to add the "packet movement state" information to the entities or physics engine, since it violates basic design principles and bleeds network code across the rest of the game engine. What should happen when entities collide? There are three scenarios - the controlling player collides locally, two entities collide on the server during a position update, or a remote entity update collides on the local client. In all cases I'm uncertain how to handle the collision - aside from cheating, both states are "correct" but at different time periods. In the case of a remote entity it doesn't make sense to draw it walking through a wall, so I perform collision detection on the local client and cause it to "stop". Based on point #2 above, I might compute a "corrected vector" that continually tries to move the entity "through the wall" which will never succeed - the remote avatar is stuck there until the error gets too high and it "snaps" into position. How do games work around this?

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• Issue with multiplayer interpolation

  - by Ben Cracknell

  In a fast-paced multiplayer game I'm working on, there is an issue with the interpolation algorithm. You can see it clearly in the image below. Cyan: Local position when a packet is received Red: Position received from packet (goal) Blue: Line from local position to goal when packet is received Black: Local position every frame As you can see, the local position seems to oscillate around the goals instead of moving between them smoothly. Here is the code: // local transform position when the last packet arrived. Will lerp from here to the goal private Vector3 positionAtLastPacket; // location received from last packet private Vector3 goal; // time since the last packet arrived private float currentTime; // estimated time to reach goal (also the expected time of the next packet) private float timeToReachGoal; private void PacketReceived(Vector3 position, float timeBetweenPackets) { positionAtLastPacket = transform.position; goal = position; timeToReachGoal = timeBetweenPackets; currentTime = 0; Debug.DrawRay(transform.position, Vector3.up, Color.cyan, 5); // current local position Debug.DrawLine(transform.position, goal, Color.blue, 5); // path to goal Debug.DrawRay(goal, Vector3.up, Color.red, 5); // received goal position } private void FrameUpdate() { currentTime += Time.deltaTime; float delta = currentTime/timeToReachGoal; transform.position = FreeLerp(positionAtLastPacket, goal, currentTime / timeToReachGoal); // current local position Debug.DrawRay(transform.position, Vector3.up * 0.5f, Color.black, 5); } /// <summary> /// Lerp without being locked to 0-1 /// </summary> Vector3 FreeLerp(Vector3 from, Vector3 to, float t) { return from + (to - from) * t; } Any idea about what's going on?

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• Textures do not render on ATI graphics cards?

  - by Mathias Lykkegaard Lorenzen

  I'm rendering textured quads to an orthographic view in XNA through hardware instancing. On Nvidia graphics cards, this all works, tested on 3 machines. On ATI cards, it doesn't work at all, tested on 2 machines. How come? Culling perhaps? My orthographic view is set up like this: Matrix projection = Matrix.CreateOrthographicOffCenter(0, graphicsDevice.Viewport.Width, -graphicsDevice.Viewport.Height, 0, 0, 1); And my elements are rendered with the Z-coordinate 0. Edit: I just figured out something weird. If I do not call this spritebatch code above doing my textured quad rendering code, then it won't work on Nvidia cards either. Could that be due to culling information or something like that? Batch.Instance.SpriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.LinearClamp, DepthStencilState.Default, RasterizerState.CullNone); ... spriteBatch.End(); Edit 2: Here's the full code for my instancing call. public void DrawTextures() { Batch.Instance.SpriteBatch.Begin(SpriteSortMode.Texture, BlendState.AlphaBlend, SamplerState.LinearClamp, DepthStencilState.Default, RasterizerState.CullNone, textureEffect); while (texturesToDraw.Count > 0) { TextureJob texture = texturesToDraw.Dequeue(); spriteBatch.Draw(texture.Texture, texture.DestinationRectangle, texture.TintingColor); } spriteBatch.End(); #if !NOTEXTUREINSTANCING // no work to do if (positionInBufferTextured > 0) { device.BlendState = BlendState.Opaque; textureEffect.CurrentTechnique = textureEffect.Techniques["Technique1"]; textureEffect.Parameters["Texture"].SetValue(darkTexture); textureEffect.CurrentTechnique.Passes[0].Apply(); if ((textureInstanceBuffer == null) || (positionInBufferTextured > textureInstanceBuffer.VertexCount)) { if (textureInstanceBuffer != null) textureInstanceBuffer.Dispose(); textureInstanceBuffer = new DynamicVertexBuffer(device, texturedInstanceVertexDeclaration, positionInBufferTextured, BufferUsage.WriteOnly); } if (positionInBufferTextured > 0) { textureInstanceBuffer.SetData(texturedInstances, 0, positionInBufferTextured, SetDataOptions.Discard); } device.Indices = textureIndexBuffer; device.SetVertexBuffers(textureGeometryBuffer, new VertexBufferBinding(textureInstanceBuffer, 0, 1)); device.DrawInstancedPrimitives(PrimitiveType.TriangleStrip, 0, 0, textureGeometryBuffer.VertexCount, 0, 2, positionInBufferTextured); // now that we've drawn, it's ok to reset positionInBuffer back to zero, // and write over any vertices that may have been set previously. positionInBufferTextured = 0; } #endif }

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• Is there any difference between storing textures and baked lighting for environment meshes?

  - by Ben Hymers

  I assume that when texturing environments, one or several textures will be used, and the UVs of the environment geometry will likely overlap on these textures, so that e.g. a tiling brick texture can be used by many parts of the environment, rather than UV unwrapping the entire thing, and having several areas of the texture be identical. If my assumption is wrong, please let me know! Now, when thinking about baking lighting, clearly this can't be done the same way - lighting in general will be unique to every face so the environment must be UV unwrapped without overlap, and lighting must be baked onto unique areas of one or several textures, to give each surface its own texture space to store its lighting. My questions are: Have I got this wrong? If so, how? Isn't baking lighting going to use a lot of texture space? Will the geometry need two UV sets, one used for the colour/normal texture and one for the lighting texture? Anything else you'd like to add? :)

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• Create bullet physics rigid body along the vertices of a blender model

  - by Krishnabhadra

  I am working on my first 3D game, for iphone, and I am using Blender to create models, Cocos3D game engine and Bullet for physics simulation. I am trying to learn the use of physics engine. What I have done I have created a small model in blender which contains a Cube (default blender cube) at the origin and a UVSphere hovering exactly on top of this cube (without touching the cube) I saved the file to get MyModel.blend. Then I used File -> Export -> PVRGeoPOD (.pod/.h/.cpp) in Blender to export the model to .pod format to use along with Cocos3D. In the coding side, I added necessary bullet files to my Cocos3D template project in XCode. I am also using a bullet objective C wrapper. -(void) initializeScene { _physicsWorld = [[CC3PhysicsWorld alloc] init]; [_physicsWorld setGravity:0 y:-9.8 z:0]; /*Setup camera, lamp etc.*/ .......... ........... /*Add models created in blender to scene*/ [self addContentFromPODFile: @"MyModel.pod"]; /*Create OpenGL ES buffers*/ [self createGLBuffers]; /*get models*/ CC3MeshNode* cubeNode = (CC3MeshNode*)[self getNodeNamed:@"Cube"]; CC3MeshNode* sphereNode = (CC3MeshNode*)[self getNodeNamed:@"Sphere"]; /*Those boring grey colors..*/ [cubeNode setColor:ccc3(255, 255, 0)]; [sphereNode setColor:ccc3(255, 0, 0)]; float *cVertexData = (float*)((CC3VertexArrayMesh*)cubeNode.mesh).vertexLocations.vertices; int cVertexCount = (CC3VertexArrayMesh*)cubeNode.mesh).vertexLocations.vertexCount; btTriangleMesh* cTriangleMesh = new btTriangleMesh(); // for (int i = 0; i < cVertexCount * 3; i+=3) { // printf("\n%f", cVertexData[i]); // printf("\n%f", cVertexData[i+1]); // printf("\n%f", cVertexData[i+2]); // } /*Trying to create a triangle mesh that curresponds the cube in 3D space.*/ int offset = 0; for (int i = 0; i < (cVertexCount / 3); i++){ unsigned int index1 = offset; unsigned int index2 = offset+6; unsigned int index3 = offset+12; cTriangleMesh->addTriangle( btVector3(cVertexData[index1], cVertexData[index1+1], cVertexData[index1+2] ), btVector3(cVertexData[index2], cVertexData[index2+1], cVertexData[index2+2] ), btVector3(cVertexData[index3], cVertexData[index3+1], cVertexData[index3+2] )); offset += 18; } [self releaseRedundantData]; /*Create a collision shape from triangle mesh*/ btBvhTriangleMeshShape* cTriMeshShape = new btBvhTriangleMeshShape(cTriangleMesh,true); btCollisionShape *sphereShape = new btSphereShape(1); /*Create physics objects*/ gTriMeshObject = [_physicsWorld createPhysicsObjectTrimesh:cubeNode shape:cTriMeshShape mass:0 restitution:1.0 position:cubeNode.location]; sphereObject = [_physicsWorld createPhysicsObject:sphereNode shape:sphereShape mass:1 restitution:0.1 position:sphereNode.location]; sphereObject.rigidBody->setDamping(0.1,0.8); } When I run the sphere and cube shows up fine. I expect the sphere object to fall directly on top of the cube, since I have given it a mass of 1 and the physics world gravity is given as -9.8 in y direction. But What is happening the spere rotates around cube three or times and then just jumps out of the scene. Then I know I have some basic misunderstanding about the whole process. So my question is, how can I create a physics collision shape which corresponds to the shape of a particular mesh model. I may need complex shapes than cube and sphere, but before going into them I want to understand the concepts.

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• Interesting/Innovative Open Source tools for indie games

  - by Gastón

  Just out of curiosity, I want to know opensource tools or projects that can add some interesting features to indie games, preferably those that could only be found on big-budget games. EDIT: As suggested by The Communist Duck and Joe Wreschnig, I'm putting the examples as answers. EDIT 2: Please do not post tools like PyGame, Inkscape, Gimp, Audacity, Slick2D, Phys2D, Blender (except for interesting plugins) and the like. I know they are great tools/libraries and some would argue essential to develop good games, but I'm looking for more rare projects. Could be something really specific or niche, like generating realistic trees and plants, or realistic AI for animals.

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• [JOGL] My program is too slow, how can I profile with Eclipse?

  - by nkint

  My simple opengl program is really toooo slow and not fluid. I'm rendering 30 sphere with simple illumination and simple materials. The only complex computing stuff I do is a collision detection between ray-mouse and spheres (that works ok and i do it only in mouseMoved) I'm not using any threads, just an animator to move spheres. How can I profile my jogl project? Or maybe (most probable...) I have some opengl instructions that I don't understand and make render particular accurate (or back face rendering that I don't need or whatever I don't know exactly I'm just entering the opengl world)

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• Is finding graph minors without single node pinch points possible?

  - by Alturis

  Is it possible to robustly find all the graph minors within an arbitrary node graph where the pinch points are generally not single nodes? I have read some other posts on here about how to break up your graph into a Hamiltonian cycle and then from that find the graph minors but it seems to be such an algorithm would require that each "room" had "doorways" consisting of single nodes. To explain a bit more a visual aid is necessary. Lets say the nodes below are an example of the typical node graph. What I am looking for is a way to automatically find the different colored regions of the graph (or graph minors)

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• Slick and Timers?

  - by user3491043

  I'm making a game where I need events to happen in a precise amount of time. Explanation : I want that event A happens at 12000ms, and event B happens every 10000ms. So "if"s should looks like this. //event A if(Ticks == 12000) //do things //even B if(Ticks % 10000 == 0) //do stuff But now how can I have this "Ticks" value ? I tried to declare an int and then increasing it in the update method, I tried 2 ways of increasing it : Ticks++; It doesn't works because the update method is not always called every microseconds. Ticks += delta; It's kinda good but the delta is not always equals to 1, so I can miss the precise values I need in the if statements So if you know how can I do events in a precise amount of time please tell me how can I do this

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