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• View matrix question (rotate by 180 degrees)

  - by King Snail

  I am using a third party rendering API on top of OpenGL code and I cannot get my matrices correct. The API states this: We're right handed by default, and we treat y as up by convention. Since IwGx's coordinate system has (0,0) as the top left, you typically need a 180 degree rotation around Z in your view matrix. I think the viewer does this by default. In my OpenGL app I have access to the view and projection matrices separately. How can I convert them to fit the criteria used by my third party rendering API? I don't understand what they mean to rotate 180 degrees around Z, is that in the view matrix itself or something in the camera before making the view matrix. Any code would be helpful, thanks.

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• 3D Vector "End Point" Calculation for procedural Vector Graphics

  - by FrostFlame64

  Alright, So I need some help with some Vector Math. I've developing some game Engines that have Procedural Fractal Generation for Some Graphics, such as using Lindenmayer Systems for generating Trees and Plants. L-Systems, are drawn by using Turtle Graphics, which is a form of Vector graphics. I first created a system to draw in 2D Graphics, which works perfectly fine. But now I want to make a 3D equivalent, and I’ve run into an issue. For my 2D Version, I created a Method for quickly determining the “End Point” of a Vector-like movement. Given a starting point (X, Y), a direction (between 0 and 360 degrees), and a distance, the end point is calculated by these formulas: newX = startX + distance * Sin((PI * direction) / 180) newY = startY + distance * Cos((PI * direction) / 180) Now I need something Similarly Equivalent for performing this Calculation in 3D, But I haven’t been able to Google anything that could show me how to do this. I'm flexible enough to get whatever required information is needed for this method calculation, in any reasonable form (Vector3, Quaternion, ect). To summarize: Given a starting point/vector position in 3D space (X, Y, Z), a Direction in 3D space (Vector3, Quaternion, ect), and a Distance, I need to find the “End Point” in 3D Space. Thank you for your time and help.

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• In an Entity-Component-System Engine, How do I deal with groups of dependent entities?

  - by John Daniels

  After going over a few game design patterns, I have settle with Entity-Component-System (ES System) for my game engine. I've reading articles (mainly T=Machine) and review some source code and I think I got enough to get started. There is just one basic idea I am struggling with. How do I deal with groups of entities that are dependent on each other? Let me use an example: Assume I am making a standard overhead shooter (think Jamestown) and I want to construct a "boss entity" with multiple distinct but connected parts. The break down might look like something like this: Ship body: Movement, Rendering Cannon: Position (locked relative to the Ship body), Tracking\Fire at hero, Taking Damage until disabled Core: Position (locked relative to the Ship body), Tracking\Fire at hero, Taking Damage until disabled, Disabling (er...destroying) all other entities in the ship group My goal would be something that would be identified (and manipulated) as a distinct game element without having to rewrite subsystem form the ground up every time I want to build a new aggregate Element. How do I implement this kind of design in ES System? Do I implement some kind of parent-child entity relationship (entities can have children)? This seems to contradict the methodology that Entities are just empty container and makes it feel more OOP. Do I implement them as separate entities, with some kind of connecting Component (BossComponent) and related system (BossSubSystem)? I can't help but think that this will be hard to implement since how components communicate seem to be a big bear trap. Do I implement them as one Entity, with a collection of components (ShipComponent, CannonComponents, CoreComponent)? This one seems to veer way of the ES System intent (components here seem too much like heavy weight entities), but I'm know to this so I figured I would put that out there. Do I implement them as something else I have mentioned? I know that this can be implemented very easily in OOP, but my choosing ES over OOP is one that I will stick with. If I need to break with pure ES theory to implement this design I will (not like I haven't had to compromise pure design before), but I would prefer to do that for performance reason rather than start with bad design. For extra credit, think of the same design but, each of the "boss entities" were actually connected to a larger "BigBoss entity" made of a main body, main core and 3 "Boss Entities". This would let me see a solution for at least 3 dimensions (grandparent-parent-child)...which should be more than enough for me. Links to articles or example code would be appreciated. Thanks for your time.

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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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• 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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• Light shaped like a line

  - by Michael

  I am trying to figure out how line-shaped lights fit into the standard point light/spotlight/directional light scheme. The way I see it, there are two options: Seed the line with regular point lights and just deal with the artifacts. Easy, but seems wasteful. Make the line some kind of emissive material and apply a bloom effect. Sounds like it could work, but I can't test it in my engine yet. Is there a standard way to do this? Or for non-point lights in general?

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• Software design of a browser-based strategic MMO game

  - by Mehran

  I wonder if there are any known tested software designs for Travian-like browser-based strategic MMO games? I mean how would they implement the server of such games or what is stored in database and what is stored in RAM? Is the state of the world stored in one piece or is it distributed among a number of storage? Does anyone know a resource to study the problems and solutions of creating such games? [UPDATE] Suggested in comments, I'm going to give an example how would I design such a project. Even though I'm not sure if I'm proposing the right one. Having stored the world state in a MongoDB, I would implement an event collection in which all the changes to the world will register. Changes that are meant to happen in the future will come with an action date set to the future and those that are to be carried out immediately will be set to now. Having this datastore as the central point of the system, players will issue their actions as events inserted in datastore. At the other end of the system, I'll have a constant-running software taking out events out of the datastore which are due to be carried out and not done yet. Executing an event means apply some update on the world's state and thus the datastore. As scalable as this design sounds, I'm not sure if it will be worth implementing. For one, it is pointless to cache the datastore as most of updates happen once without any follow ups. For instance if you have the growth of resources in your game, you'll be updating the whole world state periodically in which case, having incorporated a cache, you are keeping the whole world in RAM (which most likely is impossible). So can someone come up with a better design?

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• Dynamic Dijkstra

  - by Dani

  I need dynamic dijkstra algorithm that can update itself when edge's cost is changed without a full recalculation. Full recalculation is not an option. I've tryed to "brew" my own implemantion with no success. I've also tryed to find on the Internet but found nothing. A link to an article explaining the algorithm or even it's name will be good. Edit: Thanks everyone for answering. I managed to make algorithm of my own that runs in O(V+E) time, if anyone wishes to know the algorithm just say so and I will post it.

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• How can I resolve collisions at different speeds, depending on the direction?

  - by Raven Dreamer

  I have, for all intents and purposes, a Triangle class that objects in my scene can collide with (In actuality, the right side of a parallelogram). My collision detection and resolution code works fine for the purposes of preventing a gameobject from entering into the space of the Triangle, instead directing the movement along the edge. The trouble is, the maximum speed along the x and y axis is not equivalent in my game, and moving along the Y axis (up or down) should take twice as long as an equivalent distance along the X axis (left or right). Unfortunately, these speeds apply to the collision resolution too, and movement along the blue path above progresses twice as fast. What can I do in my collision resolution to make sure that the speedlimit for Y axis movement is obeyed in the latter case? Collision Resolution for this case below (vecInput and velocity are the position and velocity vectors of the game object): // y = mx+c // solve for y. M = 2, x = input's x coord, c = rightYIntercept lowY = 2*vecInput.x + parag.rightYIntercept ; ... else { // y = mx+c // vecInput.y = 2(x) + RightYIntercept // (vecInput.y - RightYIntercept) / 2 = x; //if velocity.Y (positive) greater than velocity.X (negative) //pushing from bottom, so push right. if(velocity.y > -1*velocity.x) { //change the input vector's x position to match the //y position on the shape's edge. Formula for line: Y = MX+C // M is 2, C is rightYIntercept, y is the input y, solve for X. vecInput = new Vector2((vecInput.y - parag.rightYIntercept)/2, vecInput.y); Debug.Log("adjusted rightwards"); } else { vecInput = new Vector2( vecInput.x, lowY); Debug.Log("adjusted downwards"); } }

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• Repeat a part of spritesheet as background

  - by Moiblpadde

  So I'm trying to repeat a part of my spritesheet as a background (js, canvas). My code so far: var canvas = $("#board")[0], ctx = canvas.getContext("2d"), sprite = new Image(); sprite.src = "spritesheet.png"; sprite.onload = function(){ ctx.fillStyle = ctx.createPattern(spriteBg, "repeat"); ctx.fillRect(0, 25, 500, 500); } This is fine, but as you can see, it repeat the whole sprite, not just a part of it, and I just can't figure out how to do it D:

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• 2d shapes in XNA 4.0?

  - by Lautaro

  Having some experience of XNA but none of 3D programming. I have an idea i want to realize but i have not decided to do it in 3d or 2d. Im not sure which one will be best in XNA. I want to have a shape like a blob that can reshape depending on input. The morphing does not need to be very advanced. It could be a circle (2d) or globe (3d) that just has one point that moves slightly in a random direction. In ASP.NET i have made this through the 2d Draw classes where i can make lines, circles, squares etc and then modify the points that makes them up. But it seems to me that XNA does not have classes for making 2d shapes (can i get this confirmed?). If it had, then this would be the quickest solution for me.

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• Android Loading Screen: How do I use a stack to load elements?

  - by tom_mai78101

  I have some problems with figuring out what value I should put in the function: int value_needed_to_figure_out = X; ProgressBar.incrementProgressBy(value_needed_to_figure_out); I've been researching about loading screens and how to use them. Some examples I've seen have implemented Thread.sleep() in a Handler.post(new Runnable()) function. To me, I got most of that concept of using the Handler to update the ProgressBar, while pretending to do some heavy crunching work. So, I kept looking. I have read this thread here: How do I load chunks of data from an assest manager during a loading screen? It said that I can try using a stack it needs to load, and adding a size counter as I add elements to the stack. What does it mean? This is the part where I'm totally stumped. If anyone would provide some hints, I'll gladly appreciate it. Thanks in advance.

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• How to keep balance / Unlock items / achievement rules

  - by Mark Knol

  I'm working on an engine for a game, too learn javascript and just because its fun. I'm a flashdeveloper, I know how to build websites. Now making games is a different challenge, javascript is a challenge, but I'd love to learn how to structure code and what patterns are common. I dont mind if the game ever finish, I'm mostly interested in the programming part of it. I dont have a particular endresult in mind, so I'll see where it takes me. I currently have a system where you can buy items. The items cost a specified amount of gold, silver, diamonds etc. When you have selected and bought the item, it takes time before getting rewarded. When time is over, you are getting rewarded with other properties (gold, energy, diamonds). For example, you can buy an apple for 50gold, It takes a minute, you get rewarded with 75energy. Or if you take a run, it cost 50energy, it takes 5minutes, reward is 25gold and 25silver. These definitions is what i call actions. Currently I already have a system where this already works and I can define as much actions with as much properties as I want. The definitions I have kinda looks like this: {id:101, category:544, onInit:{gold:-75}, onComplete:{energy:75}, time:2000, name:"Apple", locked: false} {id:102, category:544, onInit:{gold:-135}, onComplete:{energy:145}, time:2000, name:"Banana", locked: false} {id:106, category:302, onInit:{energy:-50, power: -25}, onComplete:{gold:100, diamonds:2}, time:10000, name:"Run", locked: false} {id:107, category:302, onInit:{energy:-70, silver: -55}, onComplete:{gold:100}, time:10000, name:"Dance", locked: false} {id:108, category:302, onInit:{energy:-230, power: -355}, onComplete:{gold:70, silver:70}, time:10000, name:"Fitness", locked: false} Now, I would love to add a system where I can lock/unlock the actions using achievement rules. Lets say, if you buy 10 apples, you unlock a new action, like bananas which cost more, and reward more. In the future I maybe want to restrict achievements and actions to levels. I am kinda stuck how to structure this. I have 2 questions: Which patterns are used to define achievements? How/where are they defined? Should it be part of the action, or should it be a separate controller? Is it a good idea to register all completed actions to it? I think I want multiple types of achievement rules, Id love to hear some ideas how to develop it. How do you create/find a good balance, so the user does not get stuck or can cheat by repeat a pattern of actions to get too much rewards. I know there is not a simple answer and i'm lacking of a good game-concept, but I wonder if anyone created such a game and how you dealed and played with it.

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• Applying Textures to Hexagonal Tiles Seamlessly

  - by PATRY

  I'm doing a tactical game (X-Com / Fallout style) for fun. I've decided to use a hexagonal map, but I'm having a graphic problem. My current map display is HUD-like, with only the border of the map cells displayed, without any texture. it's simple and allow for display of different types of informations by varying the color of the border. For exemple the "danger view mode" displays the borders with a color going from green (no damage possible) to red (prob of damage 90%). Now, It's a bit hard to differentiate the kind of tile the player is on. I could put a plain color (green is grass, pale blue is water...), but this is going to limit the possibilities. Thus, i would like to display a texture on my tiles. Since the map are generated, i can not use a picture for the whole map with the HUD over. So, my question is : does any one knows how i could generate the sealess hexagonal textures (algo or plugin), or if there is a site with some hexagonal tiles ?

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• Self learning automated movement

  - by Super1

  I am trying to make a small demo in Javascript, I have a black border and a car the car travels randomly and a line is drawn of its trail. When the user click inside the area it creates an object (we'll call this the wall). If the car hits the wall then it goes back 3 paces and tries a different route. When its hit the wall it needs to log down its location so it does NOT make that mistake again. Here is my example: http://jsfiddle.net/Jtq3E/ How can I get the car to move by itself and create a trail?

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• How to proceed on the waypoint path?

  - by Alpha Carinae

  I'm using Dijkstra algorithm to find shortest path and I'm drawing this path on the screen. As the character object moves on, path updates itself(shortens as the object approaches the target and gets longer as the object moves away from it.) I tried to visualize my problem. This is the beginning state. 'A' node is the target, path is the blue and the object is the green one. I draw this path, from object to the closest node. In this case my problem occurs. Because 'D' node is more closer to the object than 'C' node, something like this happens: So, how can i decide that the object passed the 'D' node? Path should be look like this: One thing comes to my mind is that I use some distance variables between the two closest nodes in the route path. (In this example these are 'C' and 'D' nodes.) As the object approaches 'C' and moves away from the 'D' node at the same time, this means character passed the 'D'. However, I think there are some standardized and easy ways to solve this. What approach should I take?

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• DX9 Deferred Rendering, GBuffer displays as clear color only

  - by Fire31

  I'm trying to implement Catalin Zima's Deferred Renderer in a very lightweight c++ DirectX 9 app (only renders a skydome and a model), at this moment I'm trying to render the gbuffer, but I'm having a problem, the screen shows only the clear color, no matter how much I move the camera around. However, removing all the render target operations lets the app render the scene normally, even if the models are being applied the renderGBuffer effect. Any ideas of what I'm doing wrong?

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• Isometric Screen View to World View

  - by Sleepy Rhino

  I am having trouble working out the math to transform the screen coordinates to the Grid coordinates. The code below is how far I have got but it is totally wrong any help or resources to fix this issue would be great, had a complete mind block with this for some reason. private Point ScreenToIso(int mouseX, int mouseY) { int offsetX = WorldBuilder.STARTX; int offsetY = WorldBuilder.STARTY; Vector2 startV = new Vector2(offsetX, offsetY); int mapX = offsetX - mouseX; int mapY = offsetY - mouseY + (WorldBuilder.tileHeight / 2); mapY = -1 * (mapY / WorldBuilder.tileHeight); mapX = (mapX / WorldBuilder.tileHeight) + mapY; return new Point(mapX, mapY); }

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• 1136: Incorrect number of arguments. Expected 0 AS3 Flash CS5.5 [on hold]

  - by Erick

  how do I solve this error? I've been trying to get the answer online but have not been successful. I'm trying to learn As3 for flash so I decided to try making a preloader for a game. Preloader.as package com.game.moran { import flash.display.LoaderInfo; import flash.display.MovieClip; import flash.events.*; public class ThePreloader extends MovieClip { private var fullWidth:Number; public var ldrInfo:LoaderInfo; public function ThePreloader (fullWidth:Number = 0, ldrInfo:LoaderInfo = null) { this.fullWidth = fullWidth; this.ldrInfo = ldrInfo; addEventListener(Event.ENTER_FRAME, checkLoad); } private function checkLoad (e:Event) : void { if (ldrInfo.bytesLoaded == ldrInfo.bytesTotal && ldrInfo.bytesTotal !=0) { dispatchEvent (new Event ("loadComplete")); phaseOut(); } updateLoader (ldfInfo.bytesLoaded / ldrInfo.bytesTotal); } private function updateLoader(num:Number) : void { mcPreloaderBar.Width = num * fullWidth; } private function phaseOut() : void { removeEventListener (Event.ENTER_FRAME, checkLoad); phaseComplete(); } private function phaseComplete() : void { dispatchEvent (new Event ("preloaderFinished")); } } } Engine.as package com.game.moran { import flash.display.MovieClip; import flash.display.Sprite; import flash.events.Event; public class Engine extends MovieClip { private var preloader:ThePreloader; public function Engine() { preloader = new ThePreloader(732, this.loaderInfo); stage.addChild(preloader); preloader.addEventListener("loadComplete", loadAssets); preloader.addEventListener("preloaderFinished", showSponsors); } private function loadAssets (e:Event) : void { this.play(); } private function showSponsors(e:Event) : void { stage.removeChild(preloader); trace("show sponsors") } } } The line being flagged as an error is line 13 in Engine.as.

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• How can I dynamically load the correct sprite from a sprite sheet?

  - by Leonard Challis

  I am making a simple card game in unity. The game is based on a standard 52-card pack, with identical backs for unique faces. In my particular game different cards are worth different values and have various special abilities. The game will have 52 cards on the table (on the draw position or in the face-down deck or in someone's hand) at all times, so this number won't change. I thought that making a Card prefab and instantiating 52 of these manually would be a bad idea. Even doing it in code, I thought, would be a bit OTT, and that I should just instantiate visual cards when they are face-up to the player. I have a sprite sheet of the 52 cards and the back, which is imported as a Sprite in multiple mode, sliced in to a grid containing all the cards needed to play the game. The problem I now face is that, through my GameController script I want to generate a shuffled pack of cards, deal some to each player and then show those cards to a player. However, I am not sure of the best way, or even if it's possible, to do this dynamically with the sprite sheets as they are. For instance if I have the following: private CardRank rank; private CardSuite suite; private void Start() { this.rank = CardRank.Ace; this.suite = CardSuite.Spades; } This class would be instantiated by the game manager. I would have 52 of these in code. Whenever I have to visually show a card in the scene, I would use a card prefab, which is essentially a game object with a SpriteRenderer on it. I would need to dynamically load the correct sprite for this object from the spritesheet. The sliced sprites from the sprite sheet actually have names in the format AS (Ace of Spades), 7H (Seven of Hearts), etc - though this was a manual thing I did myself of course. I have also tried various alternative solutions, including creating animations, having separate sprites not in a spritesheet and having an array of available sprites in an array with a specific index for each card, but none seem as elegant as trying to load the correct sprite at runtime, as I'm trying to. So, how do I load a specific sprite from a spritesheet at runtime? I'm open to suggestions, even those that make me think differently about how to approach the problem.

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• Automatically zoom out the camera to show all players

  - by user36159

  I am building a game in XNA that takes place in a rectangular arena. The game is multiplayer and each player may go where they like within the arena. The camera is a perspective camera that looks directly downwards. The camera should be automatically repositioned based on the game state. Currently, the xy position is a weighted sum of the xy positions of important entities. I would like the camera's z position to be calculated from the xy coordinates so that it zooms out to the point where all important entities are visible. My current approach is to: hw = the greatest x distance from the camera to an important entity hh = the greatest y distance from the camera to an important entity Calculate z = max(hw / tan(FoVx), hh / tan(FoVy)) My code seems to almost work as it should, but the resulting z values are always too low by a factor of about 4. Any ideas?

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• Opposite Force to Apply to a Collided Rigid Body?

  - by Milo

  I'm working on the physics for my GTA2-like game so I can learn more about game physics. The collision detection and resolution are working great. I'm now just unsure how to compute the force to apply to a body after it collides with a wall. My rigid body looks like this: /our simulation object class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private float mass; private Vector2D v = new Vector2D(); //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; private Matrix mat = new Matrix(); private float[] Vector2Ds = new float[2]; private Vector2D tangent = new Vector2D(); private static Vector2D worldRelVec = new Vector2D(); private static Vector2D relWorldVec = new Vector2D(); private static Vector2D pointVelVec = new Vector2D(); private static Vector2D acceleration = new Vector2D(); public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; setLayer(LAYER_OBJECTS); } protected void rectChanged() { if(getWorld() != null) { getWorld().updateDynamic(this); } } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position.x,position.y, getWidth(), getHeight(), angle); rectChanged(); } public Vector2D getPosition() { return getRect().getCenter(); } @Override public void update(float timeStep) { doUpdate(timeStep); } public void doUpdate(float timeStep) { //integrate physics //linear acceleration.x = forces.x / mass; acceleration.y = forces.y / mass; velocity.x += (acceleration.x * timeStep); velocity.y += (acceleration.y * timeStep); //velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); v.x = getRect().getCenter().getX() + (velocity.x * timeStep); v.y = getRect().getCenter().getY() + (velocity.y * timeStep); setCenter(v.x, v.y); forces.x = 0; //clear forces forces.y = 0; //angular float angAcc = torque / inertia; angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { mat.reset(); Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); relWorldVec.x = Vector2Ds[0]; relWorldVec.y = Vector2Ds[1]; return relWorldVec; } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { mat.reset(); Vector2Ds[0] = world.x; Vector2Ds[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vector2Ds); worldRelVec.x = Vector2Ds[0]; worldRelVec.y = Vector2Ds[1]; return worldRelVec; } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { tangent.x = -worldOffset.y; tangent.y = worldOffset.x; pointVelVec.x = (tangent.x * angularVelocity) + velocity.x; pointVelVec.y = (tangent.y * angularVelocity) + velocity.y; return pointVelVec; } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces.x += worldForce.x; forces.y += worldForce.y; //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } public Vector2D getVelocity() { return velocity; } public void setVelocity(Vector2D velocity) { this.velocity = velocity; } } The way it is given force is by the applyForce method, this method considers angular torque. I'm just not sure how to come up with the vectors in the case where: RigidBody hits static entity RigidBody hits other RigidBody that may or may not be in motion. Would anyone know a way (without too complex math) that I could figure out the opposite force I need to apply to the car? I know the normal it is colliding with and how deep it collided. My main goal is so that say I hit a building from the side, well the car should not just stay there, it should slowly rotate out of it if I'm more than 45 degrees. Right now when I hit a wall I only change the velocity directly which does not consider angular force. Thanks!

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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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• 3D Paint tool in Maya

  - by Joris

  Hey everyone, could someone help me out on this question? When I am trying to texture objects in maya (for example a barrel) I want to texture it with a brush. When I try to use the 3D painting tool it al gets black even when I have a image file selected. Also the resolution is very very low of the models and textures in maya, though the texture image is very high quality. Can someone please help me? Thanks so much for helping.

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• "has no motion" warnings

  - by Adam R. Grey

  When I reimport my project's Library, I get lots of warnings such as State combat.Ghoul Attack has no motion but I have no idea why. In this specific case, I looked up Ghoul Attack. Here's the state in which it appears, in the only animator controller that includes anything called Ghoul Attack: State: m_ObjectHideFlags: 3 m_PrefabParentObject: {fileID: 0} m_PrefabInternal: {fileID: 0} m_Name: Ghoul Attack m_Speed: 1 m_CycleOffset: 0 m_Motions: - {fileID: 7400000, guid: 0db269712a91fd641b6dd5e0e4c6d507, type: 3} - {fileID: 0} m_ParentStateMachine: {fileID: 110708233} m_Position: {x: 492, y: 132, z: 0} m_IKOnFeet: 1 m_Mirror: 0 m_Tag: I thought perhaps that second one - {fileID: 0} was throwing up the warning incorrectly, so I removed it. There was no effect, I still get warnings about Ghoul Attack. So given that the only state I know of with that name does in fact have motion, what is this warning actually trying to tell me?

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