rotation

问题 I want to rotate a shape in opengl, but I want to rotate it at a point. Namely I have a cylinder and I want to rotate it so it looks like it is spinning at the bottom and the spin 'size' increases until the object falls to the ground. How would I do this kind of rotation in opengl? 回答1: Translate to the origin Rotate Translate back So, if you want to rotate around (a,b,c), you would translate (-a,-b,-c) in step 1, and (a,b,c) in step 3. (Don't be afraid of the number of operations, by the way

问题 I want to rotate a shape in opengl, but I want to rotate it at a point. Namely I have a cylinder and I want to rotate it so it looks like it is spinning at the bottom and the spin 'size' increases until the object falls to the ground. How would I do this kind of rotation in opengl? 回答1: Translate to the origin Rotate Translate back So, if you want to rotate around (a,b,c), you would translate (-a,-b,-c) in step 1, and (a,b,c) in step 3. (Don't be afraid of the number of operations, by the way

问题 I'm trying to rotate the contents of an NSView ( NSButton ) in-place (I.e. from the center. I want to convert - into | ). This can be done with setFrameCenterRotation: … However, I'm trying to animate this, and [[myview animator] setFrameCenterRotation: 90]; causes the control to first jump to the right, and then rotate around the bottom-left corner (0,0) back to the original location. Some people have suggested first setting the anchorPoint : [[myview layer] setAnchorPoint: NSMakePoint(0.5,

问题 I want to rotate a UIBarButtonItem . I have been able to do this with UIButton s using setTransform:CGAffineTransformMakeRotation(…) , but UIBarButtonItem does not have this property. I know the Camera-app does this, so it should be achieveable. How can I achieve this? Thanks. 回答1: Have you tried using a custom view inside the UIBarButtonItem that you then transform any way you want? 回答2: UIBarButtonItem does not extend UIView, so it cannot be transformed directly. You can add the

问题 I'm trying to get the change in orientation between two deviceorientation events along the left-right axis, and top-bottom axis, those axis being usually defined as the phone x and y axis (https://developer.mozilla.org/en-US/docs/Web/Guide/Events/Orientation_and_motion_data_explained) ie between instants t1 and t2 where those phone axis move from (x1, y1) to (x2, y2) , It'd like to get (angle(x2-x1), angle(y1-y2)) . When the device is in portrait mode (in opposition to landscape mode), those

问题 I'm having some difficulty presenting a ModalViewController in landscape mode. Basically it shows up in the proper interface orientation and rotates only when the device is held in landscape mode but the viewcontroller acts as if it is in portrait mode. I'm presenting the modal like this - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]; // Override point

问题 I'm implementing a kind of a "compass arrow" that follows destination depending on physical orientation of the device using magnetic field sensor. Suddenly I faced with a little problem. Obtaining bearing and azimuth is OK, but performing a realistic animation turned into a really hard task. I tried to use different interpolators to make animation more "physical" (i. e. as in real compass, which arrow oscillate after hairpin rotation, accelerate and decelerate during movement etc). Now I'm

问题 Please help out a beginner iOS developer here! :) So, I have a timer which gets the latitude and longitude of a bus periodically from a xml sheet which provides real-time locations of the bus. I was able to setup the parser, animate the bus movement and setup a custom (arrow) image for the bus. However, the problem is, I'm not able to able to rotate the bus-annotation everytime I get new values for the latitude and longitude. The busAnnotation rotates only when the program starts, but not

问题 I have to rotate a view circularly on finger touch...I mean like dialing the old phones number...and the touch should be only on corners.....can any one help me...i have tried it a lot...but was not successes 回答1: You need to define the UIRotationGestureRecognize on the view that you want to rotate and than add a selector method and implement it like this. Add this to you viewDidLoad method UIRotationGestureRecognizer *rotate = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:

问题 From my experiments, the angle returned by RotatedRect's angle variable goes from -90 to 0 degrees, which is not sufficient to determine if the object is leaned to the left or right. For example, if the angle is -45 degrees, we cannot say if we need to rotate +45 or -45 degrees to deskew it. An excerpt of the code I'm using: RotatedRect rotated_rect = minAreaRect(contour); float blob_angle_deg = rotated_rect.angle; Mat mapMatrix = getRotationMatrix2D(center, blob_angle_deg, 1.0); Leaning the