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• Android Swipe In Unity 3D World with AR

  - by Christian

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

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• Sluggish/unresponsive trackpad on pre-unibody MacBook Pro

  - by Art

  I am running Ubuntu Natty Narwhal on pre-unibody MacBook Pro (2007 I believe). There seems to be a problem with trackpad - it barely works, in order to move cursor you have to move your finger a lot, and it terminates the 'gestures' abruptly - say you are moving the cursor with your finger and out of the blue it just stops, although the finger is still in contact with the surface of the trackpad. Those issues seem to dissapear as soon as I boot Mac OS X, so I suspect it is something Ubuntu-specific. Also, if I try to move the cursor with not just fingertip but increase the contact area, it seems to work just fine, although it is hardly convenient.

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• Image 1 becomes image 2 with sliding effect from left to right?

  - by Paul

  I would like to show a second image appearing while a "door" is closing on my character. I've got my character in the middle of the screen and a door coming from the left. When the door passes my character, I would like to have this second image appearing little by little. So far, I've gotten by with fadingOut the character and then fadingIn my second image of the character at the same position when the door is completely closed, but I would like to have both of them at the same time. (the effect that image 1 becomes image 2 when the door is sliding from left to right). Would you know how to do this with Cocos2d? Here are the images : at first, the character is blue, and the door is coming from the left : Then, behind the black door, the character becomes red, but only behind this door, so it stays blue when the door is not on him, and will become completely red when the door passes the character : EDIT : with this code, the black door hides the red and blue rectangles : (And if i add each of my layers at a different depth, and only use GL_LESS, same thing) blue.position = ccp( size.width*0.5 , size.height/2 ); red.position = ccp( size.width*0.46 , size.height/2 ); black.position = ccp( size.width*0.1 , size.height/2 ); glEnable(GL_DEPTH_TEST); [batch addChild:red z:0]; [batch addChild:black z:2]; glDepthFunc(GL_GREATER); [batch addChild:blue z:1]; glDepthFunc(GL_LESS); id action1 = [CCMoveTo actionWithDuration:3 position:ccp(size.width,size.height/2)]; [black runAction: [CCSequence actions:action1, nil]];

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• XNA clip plane effect makes models black

  - by user1990950

  When using this effect file: float4x4 World; float4x4 View; float4x4 Projection; float4 ClipPlane0; void vs(inout float4 position : POSITION0, out float4 clipDistances : TEXCOORD0) { clipDistances.x = dot(position, ClipPlane0); clipDistances.y = 0; clipDistances.z = 0; clipDistances.w = 0; position = mul(mul(mul(position, World), View), Projection); } float4 ps(float4 clipDistances : TEXCOORD0) : COLOR0 { clip(clipDistances); return float4(0, 0, 0, 0); } technique { pass { VertexShader = compile vs_2_0 vs(); PixelShader = compile ps_2_0 ps(); } } all models using this are rendered black. Is it possible to render them correctly?

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• XNA shield effect with a Primative sphere problem

  - by Sparky41

  I'm having issue with a shield effect i'm trying to develop. I want to do a shield effect that surrounds part of a model like this: http://i.imgur.com/jPvrf.png I currently got this: http://i.imgur.com/Jdin7.png (The red likes are a simple texture a black background with a red cross in it, for testing purposes: http://i.imgur.com/ODtzk.png where the smaller cross in the middle shows the contact point) This sphere is drawn via a primitive (DrawIndexedPrimitives) This is how i calculate the pieces of the sphere using a class i've called Sphere (this class is based off the code here: http://xbox.create.msdn.com/en-US/education/catalog/sample/primitives_3d) public class Sphere { // During the process of constructing a primitive model, vertex // and index data is stored on the CPU in these managed lists. List vertices = new List(); List indices = new List(); // Once all the geometry has been specified, the InitializePrimitive // method copies the vertex and index data into these buffers, which // store it on the GPU ready for efficient rendering. VertexBuffer vertexBuffer; IndexBuffer indexBuffer; BasicEffect basicEffect; public Vector3 position = Vector3.Zero; public Matrix RotationMatrix = Matrix.Identity; public Texture2D texture; /// <summary> /// Constructs a new sphere primitive, /// with the specified size and tessellation level. /// </summary> public Sphere(float diameter, int tessellation, Texture2D text, float up, float down, float portstar, float frontback) { texture = text; if (tessellation < 3) throw new ArgumentOutOfRangeException("tessellation"); int verticalSegments = tessellation; int horizontalSegments = tessellation * 2; float radius = diameter / 2; // Start with a single vertex at the bottom of the sphere. AddVertex(Vector3.Down * ((radius / up) + 1), Vector3.Down, Vector2.Zero);//bottom position5 // Create rings of vertices at progressively higher latitudes. for (int i = 0; i < verticalSegments - 1; i++) { float latitude = ((i + 1) * MathHelper.Pi / verticalSegments) - MathHelper.PiOver2; float dy = (float)Math.Sin(latitude / up);//(up)5 float dxz = (float)Math.Cos(latitude); // Create a single ring of vertices at this latitude. for (int j = 0; j < horizontalSegments; j++) { float longitude = j * MathHelper.TwoPi / horizontalSegments; float dx = (float)(Math.Cos(longitude) * dxz) / portstar;//port and starboard (right)2 float dz = (float)(Math.Sin(longitude) * dxz) * frontback;//front and back1.4 Vector3 normal = new Vector3(dx, dy, dz); AddVertex(normal * radius, normal, new Vector2(j, i)); } } // Finish with a single vertex at the top of the sphere. AddVertex(Vector3.Up * ((radius / down) + 1), Vector3.Up, Vector2.One);//top position5 // Create a fan connecting the bottom vertex to the bottom latitude ring. for (int i = 0; i < horizontalSegments; i++) { AddIndex(0); AddIndex(1 + (i + 1) % horizontalSegments); AddIndex(1 + i); } // Fill the sphere body with triangles joining each pair of latitude rings. for (int i = 0; i < verticalSegments - 2; i++) { for (int j = 0; j < horizontalSegments; j++) { int nextI = i + 1; int nextJ = (j + 1) % horizontalSegments; AddIndex(1 + i * horizontalSegments + j); AddIndex(1 + i * horizontalSegments + nextJ); AddIndex(1 + nextI * horizontalSegments + j); AddIndex(1 + i * horizontalSegments + nextJ); AddIndex(1 + nextI * horizontalSegments + nextJ); AddIndex(1 + nextI * horizontalSegments + j); } } // Create a fan connecting the top vertex to the top latitude ring. for (int i = 0; i < horizontalSegments; i++) { AddIndex(CurrentVertex - 1); AddIndex(CurrentVertex - 2 - (i + 1) % horizontalSegments); AddIndex(CurrentVertex - 2 - i); } //InitializePrimitive(graphicsDevice); } /// <summary> /// Adds a new vertex to the primitive model. This should only be called /// during the initialization process, before InitializePrimitive. /// </summary> protected void AddVertex(Vector3 position, Vector3 normal, Vector2 texturecoordinate) { vertices.Add(new VertexPositionNormal(position, normal, texturecoordinate)); } /// <summary> /// Adds a new index to the primitive model. This should only be called /// during the initialization process, before InitializePrimitive. /// </summary> protected void AddIndex(int index) { if (index > ushort.MaxValue) throw new ArgumentOutOfRangeException("index"); indices.Add((ushort)index); } /// <summary> /// Queries the index of the current vertex. This starts at /// zero, and increments every time AddVertex is called. /// </summary> protected int CurrentVertex { get { return vertices.Count; } } public void InitializePrimitive(GraphicsDevice graphicsDevice) { // Create a vertex declaration, describing the format of our vertex data. // Create a vertex buffer, and copy our vertex data into it. vertexBuffer = new VertexBuffer(graphicsDevice, typeof(VertexPositionNormal), vertices.Count, BufferUsage.None); vertexBuffer.SetData(vertices.ToArray()); // Create an index buffer, and copy our index data into it. indexBuffer = new IndexBuffer(graphicsDevice, typeof(ushort), indices.Count, BufferUsage.None); indexBuffer.SetData(indices.ToArray()); // Create a BasicEffect, which will be used to render the primitive. basicEffect = new BasicEffect(graphicsDevice); //basicEffect.EnableDefaultLighting(); } /// <summary> /// Draws the primitive model, using the specified effect. Unlike the other /// Draw overload where you just specify the world/view/projection matrices /// and color, this method does not set any renderstates, so you must make /// sure all states are set to sensible values before you call it. /// </summary> public void Draw(Effect effect) { GraphicsDevice graphicsDevice = effect.GraphicsDevice; // Set our vertex declaration, vertex buffer, and index buffer. graphicsDevice.SetVertexBuffer(vertexBuffer); graphicsDevice.Indices = indexBuffer; graphicsDevice.BlendState = BlendState.Additive; foreach (EffectPass effectPass in effect.CurrentTechnique.Passes) { effectPass.Apply(); int primitiveCount = indices.Count / 3; graphicsDevice.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, vertices.Count, 0, primitiveCount); } graphicsDevice.BlendState = BlendState.Opaque; } /// <summary> /// Draws the primitive model, using a BasicEffect shader with default /// lighting. Unlike the other Draw overload where you specify a custom /// effect, this method sets important renderstates to sensible values /// for 3D model rendering, so you do not need to set these states before /// you call it. /// </summary> public void Draw(Camera camera, Color color) { // Set BasicEffect parameters. basicEffect.World = GetWorld(); basicEffect.View = camera.view; basicEffect.Projection = camera.projection; basicEffect.DiffuseColor = color.ToVector3(); basicEffect.TextureEnabled = true; basicEffect.Texture = texture; GraphicsDevice device = basicEffect.GraphicsDevice; device.DepthStencilState = DepthStencilState.Default; if (color.A < 255) { // Set renderstates for alpha blended rendering. device.BlendState = BlendState.AlphaBlend; } else { // Set renderstates for opaque rendering. device.BlendState = BlendState.Opaque; } // Draw the model, using BasicEffect. Draw(basicEffect); } public virtual Matrix GetWorld() { return /*world */ Matrix.CreateScale(1f) * RotationMatrix * Matrix.CreateTranslation(position); } } public struct VertexPositionNormal : IVertexType { public Vector3 Position; public Vector3 Normal; public Vector2 TextureCoordinate; /// <summary> /// Constructor. /// </summary> public VertexPositionNormal(Vector3 position, Vector3 normal, Vector2 textCoor) { Position = position; Normal = normal; TextureCoordinate = textCoor; } /// <summary> /// A VertexDeclaration object, which contains information about the vertex /// elements contained within this struct. /// </summary> public static readonly VertexDeclaration VertexDeclaration = new VertexDeclaration ( new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0), new VertexElement(12, VertexElementFormat.Vector3, VertexElementUsage.Normal, 0), new VertexElement(24, VertexElementFormat.Vector2, VertexElementUsage.TextureCoordinate, 0) ); VertexDeclaration IVertexType.VertexDeclaration { get { return VertexPositionNormal.VertexDeclaration; } } } A simple call to the class to initialise it. The Draw method is called in the master draw method in the Gamecomponent. My current thoughts on this are: The direction of the weapon hitting the ship is used to get the middle position for the texture Wrap a texture around the drawn sphere based on this point of contact Problem is i'm not sure how to do this. Can anyone help or if you have a better idea please tell me i'm open for opinion? :-) Thanks.

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• Data Transformation Pipeline

  - by davenewza

  I have create some kind of data pipeline to transform coordinate data into more useful information. Here is the shell of pipeline: public class PositionPipeline { protected List<IPipelineComponent> components; public PositionPipeline() { components = new List<IPipelineComponent>(); } public PositionPipelineEntity Process(Position position) { foreach (var component in components) { position = component.Execute(position); } return position; } public PositionPipeline RegisterComponent(IPipelineComponent component) { components.Add(component); return this; } } Every IPipelineComponent accepts and returns the same type - a PositionPipelineEntity. Code: public interface IPipelineComponent { PositionPipelineEntity Execute(PositionPipelineEntity position); } The PositionPipelineEntity needs to have many properties, many which are unused in certain components and required in others. Some properties will also have become redundant at the end of the pipeline. For example, these components could be executed: TransformCoordinatesComponent: Parse the raw coordinate data into a Coordinate type. DetermineCountryComponent: Determine and stores country code. DetermineOnRoadComponent: Determine and store whether coordinate is on a road. Code: pipeline .RegisterComponent(new TransformCoordinatesComponent()) .RegisterComponent(new DetermineCountryComponent()) .RegisterComponent(new DetermineOnRoadComponent()); pipeline.Process(positionPipelineEntity); The PositionPipelineEntity type: public class PositionPipelineEntity { // Only relevant to the TransformCoordinatesComponent public decimal RawCoordinateLatitude { get; set; } // Only relevant to the TransformCoordinatesComponent public decimal RawCoordinateLongitude { get; set; } // Required by all components after TransformCoordinatesComponent public Coordinate CoordinateLatitude { get; set; } // Required by all components after TransformCoordinatesComponent public Coordinate CoordinateLongitude { get; set; } // Set in DetermineCountryComponent, not required anywhere. // Requires CoordinateLatitude and CoordinateLongitude (TransformCoordinatesComponent) public string CountryCode { get; set; } // Set in DetermineOnRoadComponent, not required anywhere. // Requires CoordinateLatitude and CoordinateLongitude (TransformCoordinatesComponent) public bool OnRoad { get; set; } } Problems: I'm very concerned about the dependency that a component has on properties. The way to solve this would be to create specific types for each component. The problem then is that I cannot chain them together like this. The other problem is the order of components in the pipeline matters. There is some dependency. The current structure does not provide any static or runtime checking for such a thing. Any feedback would be appreciated.

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• Camera movement and threshold not working

  - by irish guy mcconagheh

  I have a platformer that is in progress, part of this has a camera which I only want to move when the character moves out of a certain threshold, to try to accomplish this I have the following if statement: if(((Mathf.Abs(target.transform.position.x))-(Mathf.Abs(transform.position.x)))>thres){ x = moveTo(transform.position.x, target.position.x, trackSpeed); } in unity/c#. In pseudocode it means if((absolute value of player x) - (absolute value of camera x) is greater than the threshold){ move { however this does not seem to work correctly. it appears to work for the first couple of times the threshold is reached, however the distance between the camera and the player has to increase every time for the camera to move. I do not believe the movement of the camera is the problem, however the code for it is as follows: private float moveTo(float n, float target, float accel) { if (n == target) { return n; } else { float dir = Mathf.Sign(target - n); n += accel * Time.deltaTime * dir; return (dir == Mathf.Sign(target-n))? n: target; } } }

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• Help understand GLSL directional light on iOS (left handed coord system)

  - by Robse

  I now have changed from GLKBaseEffect to a own shader implementation. I have a shader management, which compiles and applies a shader to the right time and does some shader setup like lights. Please have a look at my vertex shader code. Now, light direction should be provided in eye space, but I think there is something I don't get right. After I setup my view with camera I save a lightMatrix to transform the light from global space to eye space. My modelview and projection setup: - (void)setupViewWithWidth:(int)width height:(int)height camera:(N3DCamera *)aCamera { aCamera.aspect = (float)width / (float)height; float aspect = aCamera.aspect; float far = aCamera.far; float near = aCamera.near; float vFOV = aCamera.fieldOfView; float top = near * tanf(M_PI * vFOV / 360.0f); float bottom = -top; float right = aspect * top; float left = -right; // projection GLKMatrixStackLoadMatrix4(projectionStack, GLKMatrix4MakeFrustum(left, right, bottom, top, near, far)); // identity modelview GLKMatrixStackLoadMatrix4(modelviewStack, GLKMatrix4Identity); // switch to left handed coord system (forward = z+) GLKMatrixStackMultiplyMatrix4(modelviewStack, GLKMatrix4MakeScale(1, 1, -1)); // transform camera GLKMatrixStackMultiplyMatrix4(modelviewStack, GLKMatrix4MakeWithMatrix3(GLKMatrix3Transpose(aCamera.orientation))); GLKMatrixStackTranslate(modelviewStack, -aCamera.position.x, -aCamera.position.y, -aCamera.position.z); } - (GLKMatrix4)modelviewMatrix { return GLKMatrixStackGetMatrix4(modelviewStack); } - (GLKMatrix4)projectionMatrix { return GLKMatrixStackGetMatrix4(projectionStack); } - (GLKMatrix4)modelviewProjectionMatrix { return GLKMatrix4Multiply([self projectionMatrix], [self modelviewMatrix]); } - (GLKMatrix3)normalMatrix { return GLKMatrix3InvertAndTranspose(GLKMatrix4GetMatrix3([self modelviewProjectionMatrix]), NULL); } After that, I save the lightMatrix like this: [self.renderer setupViewWithWidth:view.drawableWidth height:view.drawableHeight camera:self.camera]; self.lightMatrix = [self.renderer modelviewProjectionMatrix]; And just before I render a 3d entity of the scene graph, I setup the light config for its shader with the lightMatrix like this: - (N3DLight)transformedLight:(N3DLight)light transformation:(GLKMatrix4)matrix { N3DLight transformedLight = N3DLightMakeDisabled(); if (N3DLightIsDirectional(light)) { GLKVector3 direction = GLKVector3MakeWithArray(GLKMatrix4MultiplyVector4(matrix, light.position).v); direction = GLKVector3Negate(direction); // HACK -> TODO: get lightMatrix right! transformedLight = N3DLightMakeDirectional(direction, light.diffuse, light.specular); } else { ... } return transformedLight; } You see the line, where I negate the direction!? I can't explain why I need to do that, but if I do, the lights are correct as far as I can tell. Please help me, to get rid of the hack. I'am scared that this has something to do, with my switch to left handed coord system. My vertex shader looks like this: attribute highp vec4 inPosition; attribute lowp vec4 inNormal; ... uniform highp mat4 MVP; uniform highp mat4 MV; uniform lowp mat3 N; uniform lowp vec4 constantColor; uniform lowp vec4 ambient; uniform lowp vec4 light0Position; uniform lowp vec4 light0Diffuse; uniform lowp vec4 light0Specular; varying lowp vec4 vColor; varying lowp vec3 vTexCoord0; vec4 calcDirectional(vec3 dir, vec4 diffuse, vec4 specular, vec3 normal) { float NdotL = max(dot(normal, dir), 0.0); return NdotL * diffuse; } ... vec4 calcLight(vec4 pos, vec4 diffuse, vec4 specular, vec3 normal) { if (pos.w == 0.0) { // Directional Light return calcDirectional(normalize(pos.xyz), diffuse, specular, normal); } else { ... } } void main(void) { // position highp vec4 position = MVP * inPosition; gl_Position = position; // normal lowp vec3 normal = inNormal.xyz / inNormal.w; normal = N * normal; normal = normalize(normal); // colors vColor = constantColor * ambient; // add lights vColor += calcLight(light0Position, light0Diffuse, light0Specular, normal); ... }

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• Jittery Movement, Uncontrollably Rotating + Front of Sprite?

  - by Vipar

  So I've been looking around to try and figure out how I make my sprite face my mouse. So far the sprite moves to where my mouse is by some vector math. Now I'd like it to rotate and face the mouse as it moves. From what I've found this calculation seems to be what keeps reappearing: Sprite Rotation = Atan2(Direction Vectors Y Position, Direction Vectors X Position) I express it like so: sp.Rotation = (float)Math.Atan2(directionV.Y, directionV.X); If I just go with the above, the sprite seems to jitter left and right ever so slightly but never rotate out of that position. Seeing as Atan2 returns the rotation in radians I found another piece of calculation to add to the above which turns it into degrees: sp.Rotation = (float)Math.Atan2(directionV.Y, directionV.X) * 180 / PI; Now the sprite rotates. Problem is that it spins uncontrollably the closer it comes to the mouse. One of the problems with the above calculation is that it assumes that +y goes up rather than down on the screen. As I recorded in these two videos, the first part is the slightly jittery movement (A lot more visible when not recording) and then with the added rotation: Jittery Movement So my questions are: How do I fix that weird Jittery movement when the sprite stands still? Some have suggested to make some kind of "snap" where I set the position of the sprite directly to the mouse position when it's really close. But no matter what I do the snapping is noticeable. How do I make the sprite stop spinning uncontrollably? Is it possible to simply define the front of the sprite and use that to make it "face" the right way?

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• Design pattern for an automated mechanical test bench

  - by JJS

  Background I have a test fixture with a number of communication/data acquisition devices on it that is used as an end of line test for a product. Because of all the various sensors used in the bench and the need to run the test procedure in near real-time, I'm having a hard time structuring the program to be more friendly to modify later on. For example, a National Instruments USB data acquisition device is used to control an analog output (load) and monitor an analog input (current), a digital scale with a serial data interface measures position, an air pressure gauge with a different serial data interface, and the product is interfaced through a proprietary DLL that handles its own serial communication. The hard part The "real-time" aspect of the program is my biggest tripping point. For example, I need to time how long the product needs to go from position 0 to position 10,000 to the tenth of a second. While it's traveling, I need to ramp up an output of the NI DAQ when it reaches position 6,000 and ramp it down when it reaches position 8,000. This sort of control looks easy from browsing NI's LabVIEW docs but I'm stuck with C# for now. All external communication is done by polling which makes for lots of annoying loops. I've slapped together a loose Producer Consumer model where the Producer thread loops through reading the sensors and sets the outputs. The Consumer thread executes functions containing timed loops that poll the Producer for current data and execute movement commands as required. The UI thread polls both threads for updating some gauges indicating current test progress. Unsure where to start Is there a more appropriate pattern for this type of application? Are there any good resources for writing control loops in software (non-LabVIEW) that interface with external sensors and whatnot?

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• Interpolation between two 3D points?

  - by meds

  I'm working with some splines which define a path a character follows (you can see a gameplay video here to get a better understanding of what's going on: http://www.youtube.com/watch?v=BndobjOiZ6g). Basically the characters 'forward' look direction is set to the 'forward' direction of the spline and when players tilt their phone left and right the character is strafed along its 'right' coordinate. The issue with this is (rather obviously) in performance, interpolating over a spline to find the nearest position and tangent relative to the player is an incredibly costly operation. To get by this I cache a finite number of positions in what I call 'SplineDetails', the class is as follows: public class SplineDetails { public SplineDetails() { Forward = Vector3.forward; Position = Vector3.one * float.MaxValue; Alpha = -1; } public float Alpha; // [0,1] measured along length of spline where 0 is the initial point and 1 is the end point of the spline public Vector3 Position; // the point of the spline at this alpha public Vector3 Forward; // the forward tangent of the spline at this alpha } I populate this with say 30 coordinates and I can give a rough estimate of a coordinate and 'forward' based on a position past in. It's not as accurate but it's much faster. But now I'd like to make the system work better by estimating positions and 'forward' directions by interpolating between two of the cached points though I'm stuck trying to figure out some logic. My first problem is, how can I determine between which two points the object is? Given each point can be placed at different intervals along the spline it could mean that two points in front or behind the object can be closer to the object. The other problem is to figure out the proportion between the two paths it's between, i.e. if there is a point a at coordinate (0,0,0) and point b at coordinate (1,0,0) if the object is at position (0.5,0,0) then the result it should give is '0.5' (as it is equal distance away from point a and point b). That's a simple example, but what if the object is at coordinate (0.5,3,0) for example?

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• Multithreading 2D gravity calculations

  - by Postman

  I'm building a space exploration game and I've currently started working on gravity ( In C# with XNA). The gravity still needs tweaking, but before I can do that, I need to address some performance issues with my physics calculations. This is using 100 objects, normally rendering 1000 of them with no physics calculations gets well over 300 FPS (which is my FPS cap), but any more than 10 or so objects brings the game (and the single thread it runs on) to its knees when doing physics calculations. I checked my thread usage and the first thread was killing itself from all the work, so I figured I just needed to do the physics calculation on another thread. However when I try to run the Gravity.cs class's Update method on another thread, even if Gravity's Update method has nothing in it, the game is still down to 2 FPS. Gravity.cs public void Update() { foreach (KeyValuePair<string, Entity> e in entityEngine.Entities) { Vector2 Force = new Vector2(); foreach (KeyValuePair<string, Entity> e2 in entityEngine.Entities) { if (e2.Key != e.Key) { float distance = Vector2.Distance(entityEngine.Entities[e.Key].Position, entityEngine.Entities[e2.Key].Position); if (distance > (entityEngine.Entities[e.Key].Texture.Width / 2 + entityEngine.Entities[e2.Key].Texture.Width / 2)) { double angle = Math.Atan2(entityEngine.Entities[e2.Key].Position.Y - entityEngine.Entities[e.Key].Position.Y, entityEngine.Entities[e2.Key].Position.X - entityEngine.Entities[e.Key].Position.X); float mult = 0.1f * (entityEngine.Entities[e.Key].Mass * entityEngine.Entities[e2.Key].Mass) / distance * distance; Vector2 VecForce = new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle)); VecForce.Normalize(); Force = Vector2.Add(Force, VecForce * mult); } } } entityEngine.Entities[e.Key].Position += Force; } } Yeah, I know. It's a nested foreach loop, but I don't know how else to do the gravity calculation, and this seems to work, it's just so intensive that it needs its own thread. (Even if someone knows a super efficient way to do these calculations, I'd still like to know how I COULD do it on multiple threads instead) EntityEngine.cs (manages an instance of Gravity.cs) public class EntityEngine { public Dictionary<string, Entity> Entities = new Dictionary<string, Entity>(); public Gravity gravity; private Thread T; public EntityEngine() { gravity = new Gravity(this); } public void Update() { foreach (KeyValuePair<string, Entity> e in Entities) { Entities[e.Key].Update(); } T = new Thread(new ThreadStart(gravity.Update)); T.IsBackground = true; T.Start(); } } EntityEngine is created in Game1.cs, and its Update() method is called within Game1.cs. I need my physics calculation in Gravity.cs to run every time the game updates, in a separate thread so that the calculation doesn't slow the game down to horribly low (0-2) FPS. How would I go about making this threading work? (any suggestions for an improved Planetary Gravity system are welcome if anyone has them) I'm also not looking for a lesson in why I shouldn't use threading or the dangers of using it incorrectly, I'm looking for a straight answer on how to do it. I've already spent an hour googling this very question with little results that I understood or were helpful. I don't mean to come off rude, but it always seems hard as a programming noob to get a straight meaningful answer, I usually rather get an answer so complex I'd easily be able to solve my issue if I understood it, or someone saying why I shouldn't do what I want to do and offering no alternatives (that are helpful). Thank you for the help!

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• Disappearring instances of VertexPositionColor using MonoGame

  - by Rosko

  I am a complete beginner in graphics developing with XNA/Monogame. Started my own project using Monogame 3.0 for WinRT. I have this unexplainable issue that some of the vertices disappear while doing some updates on them. Basically, it is a game with balls who collide with the walls and with each other and in certain conditions they explode. When they explode they disappear. Here is a video demonstrating the issue. I used wireframes so that it is easier to see how vertices are missing. The perfect exploding balls are the ones which are result by user input with mouse clicking. Thanks for the help. The situations is: I draw user primitives with triangle strips using like this graphicsDevice.DrawUserPrimitives<VertexPositionColor>(PrimitiveType.TriangleStrip, circleVertices, 0, primitiveCount); All of the primitives are in the z-plane (z = 0), I thought that it is the culling in action. I tried setting the culling mode to none but it did not help. Here is the code responsible for the explosion private void Explode(GameTime gameTime, ref List<Circle> circles) { if (this.isExploding) { for (int i = 0; i < this.circleVertices.Length; i++) { if (this.circleVertices[i] != this.circleCenter) { if (Vector3.Distance(this.circleVertices[i].Position, this.circleCenter.Position) < this.explosionRadius * precisionCoefficient) { var explosionVector = this.circleVertices[i].Position - this.circleCenter.Position; explosionVector.Normalize(); explosionVector *= explosionSpeed; circleVertices[i].Position += explosionVector * (float)gameTime.ElapsedGameTime.TotalSeconds; } else { circles.Remove(this); } } } } } I'd be really greatful if anyone has suggestions about how to fix this issue.

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• How to get a point to the left/right of a vector

  - by MulletDevil

  I have a position vector of a point in space and a quaternion for it's rotation. What i'm trying to calculate is a point too the left and a point to the right. I have the position and rotation(quaternion) of the red dot. What I want is to get the position of the green dots. I have a float value for the distance I want these points to be. With only the position and rotation is it possible to get a unit direction vector pointing left/right which I can multiply by my float value? Edit: I also know the original direction vector.

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• Moving 2d camera in the y direction

  - by Alex

  I'm developing a simple game for the iphone and am struggling to work out the best way for the camera to follow the main character. The following picture hightlights the three main components: There are 3 components to this: Circle - the main character Green line - terrain Black background The terrain is simply made from an array of points (approx 20 points per screen width). The terrain is moved in the x direction relative to the black background in order to keep the circle in its position shown. The distance to move the terrain is simply: movex = circle.position.x - terrain.position.x with a constant to fix the circle at some distance from the left of the screen. I am struggling to determine the best way to position the terrain in the y plane keep the focus in the character. I want to move the terrain in the y direction smoothly and not fix it to the position of the circle, so the circle can move in the y plane. If I take the same approach as the x positioning, the character is fixed at a point on the screen and the terrain moves. I could sample some terrain points either side of the character and produce an average, but in my implementation this was not smooth. I thought another approach might be to create a camera 'line' that is a smooth version of the terrain line and make the camerea follow this, but I'm not sure if this is the optimum solution. Any advice is much appreciated!

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• Deploy from NetBeans IDE by Twisting an External Dial

  - by Geertjan

  Via this code in a NetBeans module, i.e., a registered NetBeans ModuleInstall class, you can twist the Tinkerforge Rotary Poti Bricklet to deploy the current application in the IDE: import com.tinkerforge.BrickMaster; import com.tinkerforge.BrickletLCD20x4; import com.tinkerforge.BrickletRotaryPoti; import com.tinkerforge.IPConnection; import javax.swing.Action; import javax.swing.JMenuItem; import org.netbeans.api.project.Project; import org.netbeans.api.project.ProjectUtils; import org.openide.awt.Actions; import org.openide.modules.ModuleInstall; import org.openide.util.Utilities; public class Installer extends ModuleInstall { private static final String HOST = "localhost"; private static final int PORT = 4223; private static final String MASTERBRICKUID = "abc"; private static final String LCDUID = "abc"; private static final String ROTIUID = "abc"; private static IPConnection ipc; private static BrickMaster master = new BrickMaster(MASTERBRICKUID); private static BrickletLCD20x4 lcd = new BrickletLCD20x4(LCDUID); private static BrickletRotaryPoti poti = new BrickletRotaryPoti(ROTIUID); @Override public void restored() { try { ipc = new IPConnection(HOST, PORT); ipc.addDevice(master); ipc.addDevice(lcd); ipc.addDevice(poti); poti.setPositionCallbackPeriod(50); poti.addListener(new BrickletRotaryPoti.PositionListener() { @Override public void position(final short position) { lcd.backlightOn(); lcd.clearDisplay(); final Action runAction = Actions.forID("Project","org.netbeans.modules.project.ui.RunMainProject"); //The action must be invoked from menu item or toolbar button, //see line 147 in org.netbeans.modules.project.ui.actions.LookupSensitiveAction: JMenuItem jmi = new JMenuItem(runAction); //When position is 100 (range is -150 to 150), deploy the app //and print info about the project to the LCD display: if (position == 100) { jmi.doClick(); Project p = Utilities.actionsGlobalContext().lookup(Project.class); lcd.writeLine((short) 0, (short) 0, "Deployed:"); lcd.writeLine((short) 1, (short) 0, ProjectUtils.getInformation(p).getDisplayName()); } else { lcd.writeLine((short) 0, (short) 0, "Position: " + position); } } }); } catch (Exception e) { } } }

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• How to do the transition from project manager to product manager? [on hold]

  - by E. Topp

  I'm working as project manager / head of software for a small software company and was working on my own previously to this position. I want to however make the transition to product manager from my current position. You could ask about position differences, pitfalls of using project management processes and decision making as a product manager. What skill sets you need for the product manager job What are the position differences? What are the pitfalls of using project management processes and decision making as a product manager? What skill set is required for the product manager job? Is the transition easier for a project manager?

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• LINQ and ArcObjects

  - by Marko Apfel

  Motivation LINQ (language integrated query) is a component of the Microsoft. NET Framework since version 3.5. It allows a SQL-like query to various data sources such as SQL, XML etc. Like SQL also LINQ to SQL provides a declarative notation of problem solving – i.e. you don’t need describe in detail how a task could be solved, you describe what to be solved at all. This frees the developer from error-prone iterator constructs. Ideally, of course, would be to access features with this way. Then this construct is conceivable: var largeFeatures = from feature in features where (feature.GetValue("SHAPE_Area").ToDouble() > 3000) select feature; or its equivalent as a lambda expression: var largeFeatures = features.Where(feature => (feature.GetValue("SHAPE_Area").ToDouble() > 3000)); This requires an appropriate provider, which manages the corresponding iterator logic. This is easier than you might think at first sight - you have to deliver only the desired entities as IEnumerable<IFeature>. LINQ automatically establishes a state machine in the background, whose execution is delayed (deferred execution) - when you are really request entities (foreach, Count (), ToList (), ..) an instantiation processing takes place, although it was already created at a completely different place. Especially in multiple iteration through entities in the first debuggings you are rubbing your eyes when the execution pointer jumps magically back in the iterator logic. Realization A very concise logic for constructing IEnumerable<IFeature> can be achieved by running through a IFeatureCursor. You return each feature via yield. For an easier usage I have put the logic in an extension method Getfeatures() for IFeatureClass: public static IEnumerable<IFeature> GetFeatures(this IFeatureClass featureClass, IQueryFilter queryFilter, RecyclingPolicy policy) { IFeatureCursor featureCursor = featureClass.Search(queryFilter, RecyclingPolicy.Recycle == policy); IFeature feature; while (null != (feature = featureCursor.NextFeature())) { yield return feature; } //this is skipped in unit tests with cursor-mock if (Marshal.IsComObject(featureCursor)) { Marshal.ReleaseComObject(featureCursor); } } So you can now easily generate the IEnumerable<IFeature>: IEnumerable<IFeature> features = _featureClass.GetFeatures(RecyclingPolicy.DoNotRecycle); You have to be careful with the recycling cursor. After a delayed execution in the same context it is not a good idea to re-iterated on the features. In this case only the content of the last (recycled) features is provided and all the features are the same in the second set. Therefore, this expression would be critical: largeFeatures.ToList(). ForEach(feature => Debug.WriteLine(feature.OID)); because ToList() iterates once through the list and so the the cursor was once moved through the features. So the extension method ForEach() always delivers the same feature. In such situations, you must not use a recycling cursor. Repeated executions of ForEach() is not a problem, because for every time the state machine is re-instantiated and thus the cursor runs again - that's the magic already mentioned above. Perspective Now you can also go one step further and realize your own implementation for the interface IEnumerable<IFeature>. This requires that only the method and property to access the enumerator have to be programmed. In the enumerator himself in the Reset() method you organize the re-executing of the search. This could be archived with an appropriate delegate in the constructor: new FeatureEnumerator<IFeatureclass>(_featureClass, featureClass => featureClass.Search(_filter, isRecyclingCursor)); which is called in Reset(): public void Reset() { _featureCursor = _resetCursor(_t); } In this manner, enumerators for completely different scenarios could be implemented, which are used on the client side completely identical like described above. Thus cursors, selection sets, etc. merge into a single matter and the reusability of code is increasing immensely. On top of that in automated unit tests an IEnumerable could be mocked very easily - a major step towards better software quality. Conclusion Nevertheless, caution should be exercised with these constructs in performance-relevant queries. Because of managing a state machine in the background, a lot of overhead is created. The processing costs additional time - about 20 to 100 percent. In addition, working without a recycling cursor is fast a performance gap. However declarative LINQ code is much more elegant, flawless and easy to maintain than manually iterating, compare and establish a list of results. The code size is reduced according to experience an average of 75 to 90 percent! So I like to wait a few milliseconds longer. As so often it has to be balanced between maintainability and performance - which for me is gaining in priority maintainability. In times of multi-core processors, the processing time of most business processes is anyway not dominated by code execution but by waiting for user input. Demo source code The source code for this prototype with several unit tests, you can download here: https://github.com/esride-apf/Linq2ArcObjects. .

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• View space lighting in deferred shading

  - by kochol

  I implemented a simple deferred shading renderer. I use 3 G-Buffer for storing position (R32F), normal (G16R16F) and albedo (ARGB8). I use sphere map algorithm to store normals in world space. Currently I use inverse of view * projection matrix to calculate the position of each pixel from stored depth value. First I want to avoid per pixel matrix multiplication for calculating the position. Is there another way to store and calculate position in G-Buffer without the need of matrix multiplication Store the normal in view space Every lighting in my engine is in world space and I want do the lighting in view space to speed up my lighting pass. I want an optimized lighting pass for my deferred engine.

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• Movement prediction for non-shooters

  - by ShadowChaser

  I'm working on an isometric (2D) game with moderate-scale multiplayer - 20-30 players. I've had some difficulty getting a good movement prediction implementation in place. Right now, clients are authoritative for their own position. The server performs validation and broad-scale cheat detection, and I fully realize that the system will never be fully robust against cheating. However, the performance and implementation tradeoffs work well for me right now. Given that I'm dealing with sprite graphics, the game has 8 defined directions rather than free movement. Whenever the player changes their direction or speed (walk, run, stop), a "true" 3D velocity is set on the entity and a packet it sent to the server with the new movement state. In addition, every 250ms additional packets are transmitted with the player's current position for state updates on the server as well as for client prediction. After the server validates the packet, it gets automatically distributed to all of the other "nearby" players. Client-side, all entities with non-zero velocity (ie/ moving entities) are tracked and updated by a rudimentary "physics" system - basically nothing more than changing the position by the velocity according to the elapsed time slice (40ms or so). What I'm struggling with is how to implement clean movement prediction. I have the nagging suspicion that I've made a design mistake somewhere. I've been over the Unreal, Half-life, and all other movement prediction/lag compensation articles I could find, but they all seam geared toward shooters: "Don't send each control change, send updates every 120ms, server is authoritative, client predicts, etc". Unfortunately, that style of design won't work well for me - there's no 3D environment so each individual state change is important. 1) Most of the samples I saw tightly couple movement prediction right into the entities themselves. For example, storing the previous state along with the current state. I'd like to avoid that and keep entities with their "current state" only. Is there a better way to handle this? 2) What should happen when the player stops? I can't interpolate to the correct position, since they might need to walk backwards or another strange direction if their position is too far ahead. 3) What should happen when entities collide? If the current player collides with something, the answer is simple - just stop the player from moving. But what happens if two entities take up the same space on the server? What if the local prediction causes a remote entity to collide with the player or another entity - do I stop them as well? If the prediction had the misfortune of sticking them in front of a wall that the player has gone around, the prediction will never be able to compensate and once the error gets to high the entity will snap to the new position.

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• Moving an object using its velocity on a closed curve

  - by Futaro

  I want that an object follows a path, in Peggle game there are some pegs that have movement in a closed path. How can i get the same result? I guess that I can use parametric curve but I need use the velocity and not the position (x, y). I use NAPE and I have this in my gameloop: //circunference angle = angle + 1*(Math.PI / 180); movableBall.position.x = radius * Math.cos(angle)+ h; movableBall.position.y = radius * Math.sin(angle)+ k; it's works but I can not control the velocity, each movableBall must have its own velocity. Besides, from docs of NAPE:"Setting the position of a body is equivalent to simply teleporting the body; for instance moving a kinematic body by position is not the way to go about things.." I want to use: movableBall.velocity.x =?? movableBall.velocity.y = ?? The final idea is to follow others paths like the Lemniscate of Bernoulli. Thanks!

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• What is a useful pattern to maintaining an object state in a one to many relationship?

  - by ahenderson

  I am looking for a design for my application, here are the players(classes) involved. struct Transform { // Uses a matrix to transform the position. // Also acts acts as the state of a Dialog. Position transform(Position p); //other methods. }; struct Dialog { // There are multiple dialog for the user to transform the output. Transform& t; void ChangeTranformation(){t.rotate(360);} } struct Algorithm { //gives us a position based on an implementation. For example this can return points on a circle or line. Transform& t; Position m_p; Dialog& d; Position GetCurrentPosition(){ return t.transform(m_p);} //other methods. } Properties I need: Each algorithms has one dialog and each dialog can have many algorithms associated with it. When the user selects an algorithm a dialog associated with that algorithm is displayed. If the user selects a different algorithm then re-selects back the state is restored in the dialog. Basically I want a good design pattern to maintain the state of the dialog given that many algorithms use it and they can be switched back and forth. Does anyone have any suggestions? Here is a use case: Dialog1 has a single edit box to control the radius. Algorithm1 generates points on a unit circle. Algorithm2 is the same as Algorithm1. The user has selected Algorithm1 and entered 2 into the edit box. This will generate points on a circle of radius 2. The user then selects Algorithm2 and enters 10 into the edit box of Dialog1. This will generate points on a circle of radius 10. Finally Algorithm1 is selected again. The edit box of Dialog1 should show 2 and points on a circle of radius 2 should be generated.

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• How do I interpolate air drag with a variable time step?

  - by Valentin Krummenacher

  So I have a little game which works with small steps, however those steps vary in time, so for example I sometimes have 10 Steps/second and then I have 20 Steps/second. This changes automatically depending on how many steps the user's computer can take. To avoid inaccurate positioning of the game's player object I use y=v0*dt+g*dt^2/2 to determine my objects y-position, where dt is the time since the last step, v0 is the velocity of my object in the beginning of my step and g is the gravity. To calculate the velocity in the end of a step I use v=v0+g*dt what also gives me correct results, independent of whether I use 2 steps with a dt of for example 20ms or one step with a dt of 40ms. Now I would like to introduce air drag. For simplicity's sake I use a=k*v^2 where a is the air drag's acceleration (I am aware that it would usually result in a force, but since I assume 1kg for my object's mass the force is the same as the resulting acceleration), k is a constant (in this case I'm using 0.001) and v is the speed. Now in an infinitely small time interval a is k multiplied by the velocity in this small time interval powered by 2. The problem is that v in the next time interval would depend on the drag of the last which again depends on the v of the last interval and so on... In other words: If I use a=k*v^2 I get different results for my position/velocity when I use 2 steps of 20ms than when I use one step of 40ms. I used to have this problem for my position too, but adding +g*dt^2/2 to the formula for my position fixed the problem since it takes into account that the position depends on the velocity which changes slightly in every infinitely small time interval. Does something like that exist for air drag too? And no, I dont mean anything like Adding air drag to a golf ball trajectory equation or similar, for that kind of method only gives correct results when all my steps are the same. (I hope you can understand my intermediate english, it's not my main language so I would like to say sorry for all the silly mistakes I might have made in my question)

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• box2d and constant movement

  - by Arnas

  i'm developing a game with a top down view, the players body is a circle. To move the character you need to tap on the screen and it moves to the spot. To achieve this i'm saving the coordinate of the touch and call a method every frame which applies linear velocity to the body with a vector of the direction the body should go _body->SetLinearVelocity(b2Vec2((a.x - currPos.x)/SPEED_RATIO,(size.height - a.y - currPos.y)/SPEED_RATIO)); //click position - current position, screen height - click position (since the y axis is flipped, (0,0) is in the bottom left ) - current position = vector of the direction we want to go now the problem with this is that the body slows down until it finally stops when getting closer to the point we want it to go, since the closer we are to that point the lenght of the vector gets smaller. Besides that i've read that it's bad practice to set linear velocity in box2d and i should use apply force instead, but that way the forces would add up and overshoot the target where it's supposed to stop. So what i'm asking is how to move a box2d body to a coordinate in constant speed.

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• Stumbling Through: Visual Studio 2010 (Part II)

  I would now like to expand a little on what I stumbled through in part I of my Visual Studio 2010 post and touch on a few other features of VS 2010.  Specifically, I want to generate some code based off of an Entity Framework model and tie it up to an actual data source.  Im not going to take the easy way and tie to a SQL Server data source, though, I will tie it to an XML data file instead.  Why?  Well, why not?  This is purely for learning, there are probably much better ways to get strongly-typed classes around XML but it will force us to go down a path less travelled and maybe learn a few things along the way.  Once we get this XML data and the means to interact with it, I will revisit data binding to this data in a WPF form and see if I cant get reading, adding, deleting, and updating working smoothly with minimal code.  To begin, I will use what was learned in the first part of this blog topic and draw out a data model for the MFL (My Football League) - I dont want the NFL to come down and sue me for using their name in this totally football-related article.  The data model looks as follows, with Teams having Players, and Players having a position and statistics for each season they played: Note that when making the associations between these entities, I was given the option to create the foreign key but I only chose to select this option for the association between Player and Position.  The reason for this is that I am picturing the XML that will contain this data to look somewhat like this: <MFL> <Position/> <Position/> <Position/> <Team>     <Player>         <Statistic/>     </Player> </Team> </MFL> Statistic will be under its associated Player node, and Player will be under its associated Team node no need to have an Id to reference it if we know it will always fall under its parent.  Position, however, is more of a lookup value that will not have any hierarchical relationship to the player.  In fact, the Position data itself may be in a completely different xml file (something Id like to play around with), so in any case, a player will need to reference the position by its Id. So now that we have a simple data model laid out, I would like to generate two things based on it:  A class for each entity with properties corresponding to each entity property An IO class with methods to get data for each entity, either all instances, by Id or by parent. Now my experience with code generation in the past has consisted of writing up little apps that use the code dom directly to regenerate code on demand (or using tools like CodeSmith).  Surely, there has got to be a more fun way to do this given that we are using the Entity Framework which already has built-in code generation for SQL Server support.  Lets start with that built-in stuff to give us a base to work off of.  Right click anywhere in the canvas of our model and select Add Code Generation Item: So just adding that code item seemed to do quite a bit towards what I was intending: It apparently generated a class for each entity, but also a whole ton more.  I mean a TON more.  Way too much complicated code was generated now that code is likely to be a black box anyway so it shouldnt matter, but we need to understand how to make this work the way we want it to work, so lets get ready to do some stumbling through that text template (tt) file. When I open the .tt file that was generated, right off the bat I realize there is going to be trouble there is no color coding, no intellisense no nothing!  That is going to make stumbling through more like groping blindly in the dark while handcuffed and hopping on one foot, which was one of the alternate titles I was considering for this blog.  Thankfully, the community comes to my rescue and I wont have to cast my mind back to the glory days of coding in VI (look it up, kids).  Using the Extension Manager (Available under the Tools menu), I did a quick search for tt editor in the Online Gallery and quickly found the Tangible T4 Editor: Downloading and installing this was a breeze, and after doing so I got some color coding and intellisense while editing the tt files.  If you will be doing any customizing of tt files, I highly recommend installing this extension.  Next, well see if that is enough help for us to tweak that tt file to do the kind of code generation that we wantDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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