I've set out to make a rotating roller uipicker like these. I know how to rotate a UILabel but I need help with the math to know how to progressively rotate the UILabel's based on their position on a circle of x circumference? Any math whizzes out there or am I over-thinking it?
What I'm thinking so far:
I need to find the angle of the tangent of a circle at a particular degree so I know which angle to rotate the label (this shouldn't be hard)
Hard bit will be working out the x/y coordinates and working how how much space to put between each value
EDIT
I'm thinking it might be easier to treat it as a half octagon and I can tweak the angles manually until it looks good. Then the only problem is working out how to animate between the positions but that won't be hard as it is just a rotate/move animation.
Here's a good tutorial on how to implement it.
http://www.raywenderlich.com/9864/how-to-create-a-rotating-wheel-control-with-uikit
Related
Say my camera is rotated around the X axis 60 degrees and looking down on a 9x9 block chess board. As we adjust board size, I want to zoom out the camera. Say for arguments sake the camera's position is (4,20,-7) and like this the whole board is visible and taking up the full screen.
If I adjust my board size to say 11x11 blocks I will now need to zoom out the camera. Say I want to maintain the same 60 degree angle and want the board to fill as much of the screen as it did before. What should the camera's new position be and how do you calculate it?
The X part is easy since you simple give the camera the same X position as the middle of the board. I'm not sure about how to calculate the new Y and Z positions though.
Any advice appreciated. Thanks.
edit: and if i wanted to change the angle of the camera as well as zoom out, is that possible to calculate? this is less important since i'll probably stick with the same angle, but i'm interested to know the maths behind it anyway.
Transform.Translate() method will move the transform according to the rotation. So you don't have to worry about the direction where your camera is looking at, just
yourCamera.transform.Translate(Vector3.forward * moveAmount);
will move your camera forward, which means zoom in. If you want to zoom out, just change the sign of the value to minus.
When I didn't know this, I used Mathf.Sin() and Mathf.Cos() to calculate each y and z world coordinates, which sucks.
I've been doing some research on online for a project I'm doing but so far haven't been able to quite get it working. I want to be able to slide my finger over a UIImage and delete part of it, kind of like an eraser. I'm able to draw lines on the screen but can't figure out how to do this. Any help would be greatly appreciated.
Can you mask the image and when you draw on it, it adds the lines to the mask (in white, rest of mask is black) and then it should make those spots transparent
http://iosdevelopertips.com/cocoa/how-to-mask-an-image.html
There are two parts to this problem-
a) Determining the curve along which the finger was moved
b) Drawing the curve (which is really a combination of short lines) with the white color
For part (a), have a look at UIPanGestureRecognizer. Using the touchesBegan: & touchesMoved methods, you will be notified every time the finger moves even the smallest distance, and the source and destination co-ordinates, say (x1, y1) & (x2, y2).
Part (b), As you know how to draw a line, now you need to draw a line from the source to the destination with the line's width (thickness) equal to the finger's. For that you can set the line's width using CGContextSetLineWidth.
Maybe I'm asking this too soon in my research, but I'd better know if this is possible sooner than later.
Imagine I have the following square printed on a paper on top of a table:
The table is brown, so it does not match with any of the colors in the square. Is there a way for me, from a common iPhone camera (non-stereo view), to figure out the distance and angle from which Im looking at the square in the table?
In the end what I'm looking for is being able to draw a 3D square on top of this one using the camera image, but I'm not sure if I am going to be able to figure out the distance and position of the object in space using only a 2D image. Any hints are well appreciated.
Short answer: http://weblog.bocoup.com/javascript-augmented-reality
Big answer:
First posterize, Then vectorize, With the vectors in your power you may need to do some math tricks to define, based on the vectors position, the perspective and then the camera position.
Maybe this help:
www.pixastic.com/lib/docs/actions/posterize/
github.com/selead/cl-vectorizer
vectormagic.com/home
autotrace.sourceforge.net
www.scipy.org/PyLab
raphaeljs.com/
technabob.com/blog/2007/12/29/video-games-get-vectorized/
superuser.com/questions/88415/is-there-an-open-source-alternative-to-vector-magic
Oughta be possible. Scan the image for the red/blue/yellow pattern, then do edge detection to figure out how warped the squares are (they'll be parallelograms in anything but straight-on view). Distance would depend on the camera's zoom setting and scan resolution. But basically you'd count how many pixels are visible in each of the squares, run that past the camera's specs and you should be able to determine a rough distance.
I'm attempting to get an object to rotate about the origin point (0,0,0)
I'm following some guidelines from this blog and was able to get the basic rotation about the Z axis and it makes a very tight circle about the Z azis.
When I change it to the X or Y axis the triangle I made goes behind me and then shows up from the other side.
The basic effect I'm hoping to achieve is to have it spin right infront of the camera.
I understand that I would have to rotate it by the amount I want and then translate it back to the origin, but I'm not quite sure on how to figure out how much to translate it by.
Can someone give me a push in the right direction about this especially the formula I would need to use to translate it properly?
Hard to answer without seeing your code, but it sounds like you want to first translate the center of the triangle to the origin, rotate, then translate back to the triangle's original position. glRotate() rotates around the origin, not an arbitrary point.
So, effectively,
glTranslatef(centerX, centerY, centerZ);
glRotatef(angle, 0, 0, 1);
glTranslatef(-centerX, -centerY, -centerZ);
Remember that OpenGL transformations are applied in reverse order that they are specified in the code, so the above translates by -(centerX, centerY, centerZ), then rotates, then translates back by (centerX, centerY, centerZ).
Check out Chapter 3 of the OpenGL Programming Guide for more information.
I am wondering if there is a way to translate the underlying matrix of a layer much like you can in ActionScript3.
In AS3 I can get the transform of a layer and shift it to, let's say, make the center of the layer the anchor point, rather than the upper-left corner.
The reason I ask is because I am trying to rotate a layer (containing a square) along a diagonal axis. I thought it might be easy if I could rotate the matrix by 45 degrees, then I could just rotate around the X-axis and be done.
But I cannot figure out how to do that.
Any help, greatly appreciate, as always.
Cheers,
Chris
Use a CGAffineTransform.
Edit:
I am afraid I don't know what you mean by "rotating an object along a diagonal axis". What you most likely need to do is to concatenate two or more transforms.
See figure 5-8 in Quartz 2D programming Guide The concatenation of two transforms creates the appearance of the image rotating around its lower left corner.