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  • Inverting matrix then decomposing gives different quaternion than decomposing then inverting the quat

    - by Fraser
    I'm getting different signs when I convert a matrix to quaternion and invert that, versus when I invert a matrix and then get the quaternion from it: Quaternion a = Quaternion.Invert(getRotation(m)); Quaternion b = getRotation(Matrix.Invert(m)); I would expect a and b to be identical (or inverses of each other). However, it looks like q1 = (x, y, -z, -w) while q2 = (-x, -y, w, z). In other words, the Z and W components have been switched for some reason. Note: getRotation() decomposes the transform matrix and returns just the rotation part of it (I've tried normalizing the result; it does nothing). The matrix m is a complete transform matrix and contains a translation (and possibly a scale) as well as a rotation. I'm using D3DXMatrixDecompose to do the actual decomposition.

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  • Rotate sphere in Javascript / three.js while moving on x/z axes

    - by kaipr
    I have a sphere/ball in three.js which I want to "roll" arround on a x/z axis. For the z axe I could simply do this no matter what the current x and y rotation is: sphere.roll_z = function(distance) { sphere.position.z += distance; sphere.rotation.x += distance > 0 ? 0.05 : -0.05; } But how can I roll it along the x axe? And how could I properly do the roll_z? I've found a lot about quateration and matrixes, but I can't figure out how to use them properly to achieve my (rather simple) goal. I'm aware that I have to update multiple rotations and that I have to calculate how far to rotate the sphere to match the distance, but the "how" is the question. It's probably just lack of mathematical skills which I should train, but a working example/short explanation would help alot to start with.

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  • Repelling a rigidbody in the direction an object is rotating

    - by ndg
    Working in Unity, I have a game object which I rotate each frame, like so: void Update() { transform.Rotate(new Vector3(0, 1, 0) * speed * Time.deltaTime); } However, I'm running into problems when it comes to applying a force to rigidbodies that collide with this game objects sphere collider. The effect I'm hoping to achieve is that objects which touch the collider are thrown in roughly the same direction as the object is rotating. To do this, I've tried the following: Vector3 force = ((transform.localRotation * Vector3.forward) * 2000) * Time.deltaTime; collision.gameObject.rigidbody.AddForce(force, ForceMode.Impulse); Unfortunately this doesn't always match the rotation of the object. To debug the issue, I wrote a simple OnDrawGizmos script, which (strangely) appears to draw the line correctly oriented to the rotation. void OnDrawGizmos() { Vector3 pos = transform.position + ((transform.localRotation * Vector3.forward) * 2); Debug.DrawLine(transform.position, pos, Color.red); } You can see the result of the OnDrawGizmos function below: What am I doing wrong?

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  • rotating an object on an arc

    - by gardian06
    I am trying to get a turret to rotate on an arc, and have hit a wall. I have 8 possible starting orientations for the turrets, and want them to rotate on a 90 degree arc. I currently take the starting rotation of the turret, and then from that derive the positive, and negative boundary of the arc. because of engine restrictions (Unity) I have to do all of my tests against a value which is between [0,360], and due to numerical precision issues I can not test against specific values. I would like to write a general test without having to go in, and jury rig cases //my current test is: // member variables public float negBound; public float posBound; // found in Start() function (called immediately after construction) // eulerAngles.y is the the degree measure of the starting y rotation negBound = transform.eulerAngles.y-45; posBound = transform.eulerAngles.y+45; // insure that values are within bounds if(negBound<0){ negBound+=360; }else if(posBound>360){ posBound-=360; } // called from Update() when target not in firing line void Rotate(){ // controlls what direction if(transform.eulerAngles.y>posBound){ dir = -1; } else if(transform.eulerAngles.y < negBound){ dir = 1; } // rotate object } follows is a table of values for my different cases (please excuse my force formatting) read as base is the starting rotation of the turret, neg is the negative boundry, pos is the positive boundry, range is the acceptable range of values, and works is if it performs as expected with the current code. |base-|-neg-|-pos--|----------range-----------|-works-| |---0---|-315-|--45--|-315-0,0-45----------|----------| |--45--|---0---|--90--|-0-45,54-90----------|----x----| |-135-|---90--|-180-|-90-135,135-180---|----x----| |-180-|--135-|-225-|-135-180,180-225-|----x----| |-225-|--180-|-270-|-180-225,225-270-|----x----| |-270-|--225-|-315-|-225-270,270-315-|----------| |-315-|--270-|---0---|--270-315,315-0---|----------| I will need to do all tests from derived, or stored values, but can not figure out how to get all of my cases to work simultaneously. //I attempted to concatenate the 2 tests: if((transform.eulerAngles.y>posBound)&&(transform.eulerAngles.y < negBound)){ dir *= -1; } this caused only the first case to be successful // I attempted to store a opposite value, and do a void Rotate(){ // controlls what direction if((transform.eulerAngles.y > posBound)&&(transform.eulerAngles.y<oposite)){ dir = -1; } else if((transform.eulerAngles.y < negBound)&&(transform.eulerAngles.y>oposite)){ dir = 1; } // rotate object } this causes the opposite situation as indicated on the table. What am I missing here?

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  • Rotating wheel with touch adding velocity

    - by Lewis
    I have a wheel control in a game which is setup like so: - (void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; CGPoint location = [touch locationInView:[touch view]]; location = [[CCDirector sharedDirector] convertToGL:location]; if (CGRectContainsPoint(wheel.boundingBox, location)) { CGPoint firstLocation = [touch previousLocationInView:[touch view]]; CGPoint location = [touch locationInView:[touch view]]; CGPoint touchingPoint = [[CCDirector sharedDirector] convertToGL:location]; CGPoint firstTouchingPoint = [[CCDirector sharedDirector] convertToGL:firstLocation]; CGPoint firstVector = ccpSub(firstTouchingPoint, wheel.position); CGFloat firstRotateAngle = -ccpToAngle(firstVector); CGFloat previousTouch = CC_RADIANS_TO_DEGREES(firstRotateAngle); CGPoint vector = ccpSub(touchingPoint, wheel.position); CGFloat rotateAngle = -ccpToAngle(vector); CGFloat currentTouch = CC_RADIANS_TO_DEGREES(rotateAngle); wheelRotation += (currentTouch - previousTouch) * 0.6; //limit speed 0.6 } } I update the rotation of a the wheel in the update method by doing: wheel.rotation = wheelRotation; Now once the user lets go of the wheel I want it to rotate back to where it was before but not without taking into account the velocity of the swipe the user has done. This is the bit I really can't get my head around. So if the swipe generates a lot of velocity then the wheel will carry on moving slightly in that direction until the overall force which pulls the wheel back to the starting position kicks in. Any ideas/code snippets?

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  • Openlayers - LayerRedraw() / Feature rotation / Linestring coords

    - by Ozaki
    TLDR: I have an Openlayers map with a layer called 'track' I want to remove track and add track back in. Or figure out how to plot a triangle based off one set of coords & a heading(see below). I have an image 'imageFeature' on a layer that rotates on load to the direction being set. I want it to update this rotation that is set in 'styleMap' on a layer called 'tracking'. I set the var 'stylemap' to apply the external image & rotation. The 'imageFeature' is added to the layer at the coords specified. 'imageFeature' is removed. 'imageFeature' is added again in its new location. Rotation is not applied.. As the 'styleMap' applies to the layer I think that I have to remove the layer and add it again rather than just the 'imageFeature' Layer: var tracking = new OpenLayers.Layer.GML("Tracking", "coordinates.json", { format: OpenLayers.Format.GeoJSON, styleMap: styleMap }); styleMap: var styleMap = new OpenLayers.StyleMap({ fillOpacity: 1, pointRadius: 10, rotation: heading, }); Now wrapped in a timed function the imageFeature: map.layers[3].addFeatures(new OpenLayers.Feature.Vector( new OpenLayers.Geometry.Point(longitude, latitude), {rotation: heading, type: parseInt(Math.random() * 3)} )); Type refers to a lookup of 1 of 3 images.: styleMap.addUniqueValueRules("default", "type", lookup); var lookup = { 0: {externalGraphic: "Image1.png", rotation: heading}, 1: {externalGraphic: "Image2.png", rotation: heading}, 2: {externalGraphic: "Image3.png", rotation: heading} } I have tried the 'redraw()' function: but it returns "tracking is undefined" or "map.layers[2]" is undefined. tracking.redraw(true); map.layers[2].redraw(true); Heading is a variable: from a JSON feed. var heading = 13.542; But so far can't get anything to work it will only rotate the image onload. The image will move in coordinates as it should though. So what am I doing wrong with the redraw function or how can I get this image to rotate live? Thanks in advance -Ozaki Add: I managed to get map.layers[2].redraw(true); to sucessfully redraw layer 2. But it still does not update the rotation. I am thinking because the stylemap is updating. But it runs through the style map every n sec, but no updates to rotation and the variable for heading is updating correctly if i put a watch on it in firebug. If I were to draw a triangle with an array of points & linestring. How would I go about facing the triangle towards the heading. I have the Lon/lat of one point and the heading. var points = new Array( new OpenLayers.Geometry.Point(lon1, lat1), new OpenLayers.Geometry.Point(lon2, lat2), new OpenLayers.Geometry.Point(lon3, lat3) ); var line = new OpenLayers.Geometry.LineString(points); Looking for any way to solve this problem Image or Line anyone know how to do either added a 100rep bounty I am really stuck with this.

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  • Correct Rotation and Translation with a 4x4 matrix

    - by sFuller
    I am using a 4x4 matrix to transform verts in a shader. I multiply an identity matrix by a rotation matrix by a translation matrix. I am trying to first rotate the verts and then translate them, however in my result, it appears that the verts are being transformed and then rotated. My matrix looks something like this: m00 m01 m02 tx m10 m11 m12 ty m20 m21 m22 tz --- --- --- 1 I am not using OpenGL's fixed function pipeline, I am multiplying matrices on the client side, and uploading the matrix to a GLSL shader. If it helps, I am using my own matrix multiplication code, but I have recreated this problem using matrices on my graphing calculator, so I don't believe my matrix code has errors.. I'll include a visual aid if needed.

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  • convert orientation vec3 to a rotation matrix

    - by lapin
    I've got a normalized vec3 that represents an orientation. Each frame of animation, an object's orientation changes slightly, so I add a delta vector to the orientation vector and then normalize to find the new orientation. I'd like to convert the vec3 that represents an orientation into a rotation matrix that I can use to orient my object. If it helps, my object is a cone, and I'd like to rotate it about the pointy end, not from its center :) PS I know I should use quaternions because of the gimbal lock problem. If someone can explain quats too, that'd be great :)

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  • How to Disable Screen Auto-Rotation in Windows 8

    - by Taylor Gibb
    Windows 8 is strongly aimed at tablets, most of which allow use in both landscape and portrait orientations. Depending on your personal preference, you may wish to disable this auto-rotating behavior. Here’s how to do it. Note: While testing out devices we noticed that the setting to disable screen rotation isn’t available on all devices, so we have provided a way to disable it in the registry as well. How To Use USB Drives With the Nexus 7 and Other Android Devices Why Does 64-Bit Windows Need a Separate “Program Files (x86)” Folder? Why Your Android Phone Isn’t Getting Operating System Updates and What You Can Do About It

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  • Bitmap rotation jitter around pivot

    - by Manderin87
    I am working on a asteriods clone and I have the ship graphic loaded as a 96x96 bitmap. When the player rotates the ship I rotate the bitmap by degree (float). rotation function: if(m_Matrix == null) { m_Matrix = new Matrix(); } else { m_Matrix.reset(); } m_Matrix.setRotate(degree, m_BaseImage.getWidth() / 2, m_BaseImage.getHeight() / 2); m_RotatedImage = Bitmap.createBitmap(m_BaseImage, 0, 0, m_BaseImage.getWidth(), m_BaseImage.getHeight(), m_Matrix, true); draw function: m_Paint.setAntiAlias(true); m_Paint.setFilterBitmap(true); m_Paint.setDither(true); canvas.drawBitmap(m_RotatedImage, (int) posX - m_RotatedImage.getWidth() / 2, (int) posY - m_RotatedImage.getHeight() / 2, m_Paint); When the bitmap is drawn, the bitmap jitters slightly around the pivot. Can anyone fix or tell me why the bitmap is jittering around the pivot? It needs to be smooth.

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  • How To Approach 360 Degree Snake

    - by Austin Brunkhorst
    I've recently gotten into XNA and must say I love it. As sort of a hello world game I decided to create the classic game "Snake". The 90 degree version was very simple and easy to implement. But as I try to make a version of it that allows 360 degree rotation using left and right arrows, I've come into sort of a problem. What i'm doing now stems from the 90 degree version: Iterating through each snake body part beginning at the tail, and ending right before the head. This works great when moving every 100 milliseconds. The problem with this is that it makes for a choppy style of gameplay as technically the game progresses at only 6 fps rather than it's potential 60. I would like to move the snake every game loop. But unfortunately because the snake moves at the rate of it's head's size it goes way too fast. This would mean that the head would need to move at a much smaller increment such as (2, 2) in it's direction rather than what I have now (32, 32). Because I've been working on this game off and on for a couple of weeks while managing school I think that I've been thinking too hard on how to accomplish this. It's probably a simple solution, i'm just not catching it. Here's some pseudo code for what I've tried based off of what makes sense to me. I can't really think of another way to do it. for(int i = SnakeLength - 1; i > 0; i--){ current = SnakePart[i], next = SnakePart[i - 1]; current.x = next.x - (current.width * cos(next.angle)); current.y = next.y - (current.height * sin(next.angle)); current.angle = next.angle; } SnakeHead.x += cos(SnakeAngle) * SnakeSpeed; SnakeHead.y += sin(SnakeAngle) * SnakeSpeed; This produces something like this: Code in Action. As you can see each part always stays behind the head and doesn't make a "Trail" effect. A perfect example of what i'm going for can be found here: Data Worm. Not the viewport rotation but the trailing effect of the triangles. Thanks for any help!

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  • per pixel based collision detection.

    - by pengume
    I was wondering if anyone had any ideas on how to get per pixel collision detection for the android. I saw that the andEngine has great collision detection on rotation as well but couldn't see where the actual detection happened per pixel. Also noticed a couple solutions for java, could these be replicated for use with the Android SDK? Maybe someone here has a clean piece of code I could look at to help understand what is going on with per pixel detection and also why when rotating it is a different process.

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  • Camera not staying behind model while moving in circle

    - by ChocoMan
    I have a camera behind a model (3rd Person) and I'm having problems KEEPING it behind the model. When I first start my game, you see the back of the model. If the model moves forward, backward or strafe left or right, the camera moves along accordingly. When the model rotates (stationary), the camera rotates accordingly with the model still pointing at the model's back. So far, so good. The problem comes when the player is BOTH moving and rotating at the same time. Take for example a model moving in a circular pattern like running around a track. As the model moves in this motion, the model rotates slightly more with each complete rotation. Eventually, instead of looking at the model's back, eventually you will see the model in a profile view and before you know it, the model's front is facing the camera. And when you stop moving the model, the model stays in that position. So, as long as my model is stationary and rotating in one place, the camera rotates correctly. But as soon as there is any sort movement while rotating, the model is offset by a mysterious increasing amount. How can I keep the camera maintaining the same view no matter how I move AND rotate at the same time? // Rotates model and pitches camera on its own axis public void modelRotMovement(GamePadState pController) { /* For rotating the model left or right. * Camera maintains distance from model * throughout rotation and if model moves * to a new position. */ Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(speedAngleMAX); AddRotation = Quaternion.CreateFromAxisAngle(Vector3.Up, yaw); //AddRotation = Quaternion.CreateFromYawPitchRoll(Yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); Pitch = pController.ThumbSticks.Right.Y * MathHelper.ToRadians(speedAngleMAX); AddPitch = Quaternion.CreateFromAxisAngle(Vector3.Up, pitch); ModelLoad.CRotation *= AddPitch; COrientation = Matrix.CreateFromQuaternion(ModelLoad.CRotation); } // Orbit (yaw) Camera around model public void cameraYaw(float yaw) { Vector3 yawAngle = ModelLoad.CameraPos - ModelLoad.camTarget; Vector3 axisYaw = Vector3.Up; ModelLoad.CameraPos = Vector3.Transform(yawAngle, Matrix.CreateFromAxisAngle(axisYaw, yaw)) + ModelLoad.camTarget; }

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  • Rotate/Translate object in local space

    - by Mathias Hölzl
    I am just trying to create a movementcontroller class for game entities. These class should transform the entity affected by the mouse and keyboard input. I am able to calculate the changed rotation and the new globalPosition. Then I multiply: newGlobalMatrix = changedRotationMatrix * oldGlobalMatrix; newGlobalMatrix = MatrixSetPosition(newPosition); The problem is that the object rotates around the global axis and not around the local axis. I use XNAMath for the matrix calculation.

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  • Stop a rotating object at a specified angle?

    - by Krummelz
    I'm working in JavaScript with HTML5 and the canvas. I have an object which is rotating at a certain speed, and I need the object's rotation to slow down gradually and the front of the object to stop at a specified angle. (I'm using radians, not degrees.) I have a variable to keep track of the angle which the object is facing, as it rotates. How would I go about getting the object to come to rest, facing the direction I want it to?

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  • Simple thruster like behaviour when rotating sprite

    - by ensamgud
    I'm prototyping some 2D game concepts with XNA and have added some basic keyboard inputs to control a triangle sprite. When I press key up the sprite accelerates in it's current facing direction, when I release the key it brakes down. For rotation, when I press left/right keys I rotate the sprite. Currently the sprite immedately changes direction when I rotate it. What I want is for it to keep moving in the same direction when I rotate, until I hit key up, adding thrust in whatever direction the sprite is pointing at. This would simulate thrusters on a classic space shooter like Asteroids. I'm adding an image to describe the behaviour I'm after and some code samples of how I'm doing things at the moment. This is my player struct, holding information of the sprite. public struct PlayerData { public Vector2 Position; // where to draw the sprite public Vector2 Direction; // travel direction of sprite public float Angle; // rotation of sprite public float Velocity; public float Acceleration; public float Decelleration; public float RotationAcceleration; public float RotationDecceleration; public float TopSpeed; public float Scale; } This is how I'm currently handling thrusting / braking (when pressing/releasing key up) (simplified, removed some bounds checking etc): player.Velocity += player.Acceleration * 0.1f; player.Velocity -= player.Acceleration * 0.1f; And when I rotate the sprite left and right: player.Angle -= player.RotationAcceleration * 0.1f; player.Angle += player.RotationAcceleration * 0.1f; This runs in the update loop, keeps the direction updated and updates the position: Vector2 up = new Vector2(0f, -1f); Matrix rotMatrix = Matrix.CreateRotationZ(player.Angle); player.Direction = Vector2.Transform(up, rotMatrix); player.Direction *= player.Velocity; player.Position += player.Direction; I am following along various beginner tutorials and haven't found any describing this, but I have tried some on my own without success. Do I need to change my velocity and acceleration fields to Vectors instead of floats to accomplish this type of movement? I realise my Angle and the Direction vector is currently tied together and I need to disconnect these somehow to be able to rotate freely without changing the direction of the movement, but I can't quite figure out how to do this while keeping the acceleration/decceleration functional. Would appreciate an explanation rather than pure code samples. Thanks,

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  • Rotating Sprite around Y-Axis (2D)

    - by Bruce Collie
    I'm going to be creating a game soon, and part of it involves spinning sprites. The sprites will be spinning around the Y-Axis (imagine a spinning plate on top of a stick, where the stick stands up vertically. The main way I've thought of is to have a series of sprites for various rotation values that I blur between as the 'plate' rotates (the sprite is more complex than a plate, though). The game will be for iPhone, but I'm open to using any 2D gave development library for it.

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  • How do I apply multiple rotation transforms on a Raphael text object?

    - by Pridkett
    I have a Raphael text object that I would like to rotate around an axis some distance away and also rotate the text accordingly so it stays horizontal. I know this is possible using SVG transformation matrices, but the author of Raphael has stated that they won't be a part of the toolkit anytime soon. Here's some code of what I'd like to do: txt_obj = paper.text(100, 0, "Hello!"); txt_obj.rotate(90, 100, 100); // rotate text so it is sideways at (200,100) txt_obj.rotate(-90); // rotate text back to horizontal Unfortunately, the second rotate command obliterates the translation and rotation accomplished by the first. Ideally I'd like to animate the operation, but I'll take it one step at a time for right now.

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  • Visual artifacts on UIView rotation with tiled background image.

    - by Halbanonym
    I have an iPad app with a standard UIViewController/UIView setup - all rotations are allowed. The UIView draws some tiled image as background (the tile is 256*256 pixels): - (void)drawRect:(CGRect)rect { [[UIImage imageNamed: @"Background.png"] drawAsPatternInRect: rect]; } When I turn my iPad I can see that during the rotation the image pattern of the original orientation is scaled to fit the new orientation. Then - immediately after the animation is finished - the view redraws its background pattern with the final configuration which is unscaled. The switching from a scaled to an unscaled pattern looks a bit ugly. Is there a way to circumvent (or hide) this strecthing of the background pattern?

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  • UIRotationGestureRecognizer minimum rotation value

    - by dc
    Is it possible to set a minimum rotation value necessary for a UIRotationGestureRecognizer to transition into UIGestureRecognizerStateRecognized? I'm using multiple recognizers, and my UIRotationGestureRecognizer keeps getting called with a very small rotation (Between 1 and 15 degrees either direction) rather than my UIPinchGestureRecognizer. What I'd like to do is only have the rotation be called if the rotation is within a certain range, otherwise cancel it and let the pinch be called.

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  • Wheel rotation, to change velocity of vehicle

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

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  • GLSL billboard move center of rotation

    - by Jacob Kofoed
    I have successfully set up a billboard shader that works, it can take in a quad and rotate it so it always points toward the screen. I am using this vertex-shader: void main(){ vec4 tmpPos = (MVP * bufferMatrix * vec4(0.0, 0.0, 0.0, 1.0)) + (MV * vec4( vertexPosition.x * 1.0 * bufferMatrix[0][0], vertexPosition.y * 1.0 * bufferMatrix[1][1], vertexPosition.z * 1.0 * bufferMatrix[2][2], 0.0) ); UV = UVOffset + vertexUV * UVScale; gl_Position = tmpPos; BufferMatrix is the model-matrix, it is an attribute to support Instance-drawing. The problem is best explained through pictures: This is the start position of the camera: And this is the position, looking in from 45 degree to the right: Obviously, as each character is it's own quad, the shader rotates each one around their own center towards the camera. What I in fact want is for them to rotate around a shared center, how would I do this? What I have been trying to do this far is: mat4 translation = mat4(1.0); translation = glm::translate(translation, vec3(pos)*1.f * 2.f); translation = glm::scale(translation, vec3(scale, 1.f)); translation = glm::translate(translation, vec3(anchorPoint - pos) / vec3(scale, 1.f)); Where the translation is the bufferMatrix sent to the shader. What I am trying to do is offset the center, but this might not be possible with a single matrix..? I am interested in a solution that doesn't require CPU calculations each frame, but rather set it up once and then let the shader do the billboard rotation. I realize there's many different solutions, like merging all the quads together, but I would first like to know if the approach with offsetting the center is possible. If it all seems a bit confusing, it's because I'm a little confused myself.

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  • Offset Forward vector of object based on Rotation

    - by Taylor
    I'm using the Bullet 3D physics engine in a iOS application running openGL ES 1.1 Currently I'm accepting info from the gyroscope to allow the user to "look around" a 3d world that follows a bouncing ball (note: it only takes in the yaw to look around 360 degrees). Im also accepting information from the accelerometer based on the tilt to push the ball. As of right now, to move forward, the user tilts the devise forward (using the accelerometer); to move to the right, the user tilts the devise to the right and so on. The forward vector is currently along it's local Z-axis. The problem is that I want to change the ball bounce based on where the user has changed the view. If I change the view, the ball bounces in the fixed direction. I want to change the forward facing direction so that when a user changes the view (say to the look at the right of the world, the user rotates the device), tilting the devise forward will result in a forward force in that direction. Basically, I want the forward vector to take the rotation into consideration. Sorry if I didn't explain the issue well enough, its kind of confusing to write down.

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