I want to draw a Circle with Letter punched out of it. to do this, I need to stroke the circle clockwise and the letter counterclockwise.
That is all good and well, but when I get the letter path using Core Text I can't figure out how to essentially reverse the path. NOT MIRROR or ROTATE or anything...that is straightforward enough. I want the point stroke order to be counterclockwise.
it is actually hilariously difficult. I've had entirely too many visual 'off by one' errors.
About all I can think of is to call CGPathApply on the path and save information about all of the points, and then redraw the path in the opposite direction. Remember to call CGPathCloseSubpath when you're done.
iOS 6 introduced -bezierPathByReversingPath
It had some issues at first but it seems to be the answer to this question.
Related
I have stumbled upon an interesting problem and I am not sure how to solve it. I have a line graph on which data points are marked with circular dots. At the moment I am creating one CAShapeLayer for the line itself and also CAShapeLayer for each dot.
The line is being animated with the strokeEnd animation key path. And it is working. However, the slightly negative effect is that once I open the graph I see all the data points already drawn and then a line is being animated through them.
Ideally I would like to change this behaviour in such a way that at the beginning nothing is shown and as the line gets animated data points are being drawn once the line passes through them.
I was thinking about this problem for some time now and I cannot find an elegant way of solving it. It seems to me that there should be a fairly easy way of achieving what I want. Maybe I should create a compounded path (but then how do I specify that a line needs to be stroked whereas dots need to be filled?).
Could anyone please guide me in the right direction?
There are lots of ways to handle this.
Assuming that the X increments of your graph are constant, and you're using linear timing, you could simply divide the total animation time by the number of data-points, and calculate the times when you need to add points to the graph when the line progresses to that X position. Simply add dot shape layers to the parent view's layer at the appropriate time intervals.
You could also change your drawing method to add new line segments to your graph path one at a time, on a timer, and add dot shapes at the same time. That would give you a step-by-step animation rather than a smooth line drawing.
I am currently trying to label lines that I draw in my Map (in my iOS app, but I guess it applies to all maps).
So what I currently am doing, I simplify my path so that I get rid of most small curves and then just draw my glyphs along that line. Currently that looks like this:
On some parts of the line that's already ok. If the line is quite straight and the corners aren't too spiky.
But in some parts you can just not read anything... So what are strategies to make that look nicer?
Does anybody know an algorithm or a strategy on how to make my path look like the red line here:
I am happy about any ideas on how to improve my drawing :)
I do it, in my commercial map rendering system, by finding a portion of the line without sharp corners. There is no way to make the label look good if it turns corners of a right angle or greater. If there's no section long enough I abbreviate the label (e.g., Link Road becomes Link Rd), or split it on to two lines. If there's still nowhere to draw the label I don't draw it.
Another thing that's important is to adjust the spacing so that ascenders and descenders don't clash, so you need to look at the bounding box of each adjacent pair of letters as you draw the text and add small amounts of space as necessary.
I don't bother to smooth my lines, as you suggest with your red line. It really doesn't seem to matter, at least with street labelling.
I need to be able to interact with a representation of a cilinder that has many different parts in it. When the users taps over on of the small rectangles, I need to display a popover related to the specific piece (form).
The next image demonstrates a realistic 3d approach. But, I repeat, I need to solve the problem, the 3d is NOT required (would be really cool though). A representation that complies the functional needs will suffice.
The info about the parts to make the drawing comes from an API (size, position, etc)
I dont need it to be realistic really. The simplest aproximation would be to show a cilinder in a 2d representation, like a rectangle made out of interactable small rectangles.
So, as I mentioned, I think there are (as I see it) two opposite approaches: Realistic or Simplified
Is there a way to achieve a nice solution in the middle? What libraries, components, frameworks that I should look into?
My research has led me to SceneKit, but I still dont know if I will be able to interact with it. Interaction is a very important part as I need to display a popover when the user taps on any small rectangle over the cylinder.
Thanks
You don't need any special frameworks to achieve an interaction like this. This effect can be achieved with standard UIKit and UIView and a little trigonometry. You can actually draw exactly your example image using 2D math and drawing. My answer is not an exact formula but involves thinking about how the shapes are defined and break the problem down into manageable steps.
A cylinder can be defined by two offset circles representing the end pieces, connected at their radii. I will use an orthographic projection meaning the cylinder doesn't appear smaller as the depth extends into the background (but you could adapt to perspective if needed). You could draw this with CoreGraphics in a UIView drawRect.
A square slice represents an angle piece of the circle, offset by an amount smaller than the length of the cylinder, but in the same direction, as in the following diagram (sorry for imprecise drawing).
This square slice you are interested in is the area outlined in solid red, outside the radius of the first circle, and inside the radius of the imaginary second circle (which is just offset from the first circle by whatever length you want the slice).
To draw this area you simply need to draw a path of the outline of each arc and connect the endpoints.
To check if a touch is inside one of these square slices:
Check if the touch point is between angle a from the origin at a.
Check if the touch point is outside the radius of the inside circle.
Check if the touch point is inside the radius of the outside circle. (Note what this means if the circles are more than a radius apart.)
To find a point to display the popover you could average the end points on the slice or find the middle angle between the two edges and offset by half the distance.
Theoretically, doing this in Scene Kit with either SpriteKit or UIKit Popovers is ideal.
However Scene Kit (and Sprite Kit) seem to be in a state of flux wherein nobody from Apple is communicating with users about the raft of issues folks are currently having with both. From relatively stable and performant Sprite Kit in iOS 8.4 to a lot of lost performance in iOS 9 seems common. Scene Kit simply doesn't seem finished, and the documentation and community are both nearly non-existent as a result.
That being said... the theory is this:
Material IDs are what's used in traditional 3D apps to define areas of an object that have different materials. Somehow these Material IDs are called "elements" in SceneKit. I haven't been able to find much more about this.
It should be possible to detect the "element" that's underneath a touch on an object, and respond accordingly. You should even be able to change the state/nature of the material on that element to indicate it's the currently selected.
When wanting a smooth, well rounded cylinder as per your example, start with a cylinder that's made of only enough segments to describe/define the material IDs you need for your "rectangular" sections to be touched.
Later you can add a smoothing operation to the cylinder to make it round, and all the extra smoothing geometry in each quadrant of unique material ID should be responsive, regardless of how you add this extra detail to smooth the presentation of the cylinder.
Idea for the "Simplified" version:
if this representation is okey, you can use a UICollectionView.
Each cell can have a defined size thanks to
collectionView:layout:sizeForItemAtIndexPath:
Then each cell of the collection could be a small rectangle representing a
touchable part of the cylinder.
and using
collectionView:(UICollectionView *)collectionView
didSelectItemAtIndexPath:(NSIndexPath *)indexPath
To get the touch.
This will help you to display the popover at the right place:
CGRect rect = [collectionView layoutAttributesForItemAtIndexPath:indexPath].frame;
Finally, you can choose the appropriate popover (if the app has to work on iPhone) here:
https://www.cocoacontrols.com/search?q=popover
Not perfect, but i think this is efficient!
Yes, SceneKit.
When user perform a touch event, that mean you knew the 2D coordinate on screen, so your only decision is to popover a view or not, even a 3D model is not exist.
First, we can logically split the requirement into two pieces, determine the touching segment, showing right "color" in each segment.
I think the use of 3D model is to determine which piece of data to show in your case if I don't get you wrong. In that case, the SCNView's hit test method will do most of work for you. What you should do is to perform a hit test, take out the hit node and the hit's local 3D coordinate of this node, you can then calculate which segment is hit by this touch and do the decision.
Now how to draw the surface of the cylinder would be the only left question, right? There are various ways to do, for example simply paint each image you need and programmatically and attach it to the cylinder's material or have your image files on disk and use as material for the cylinder ...
I think the problem would be basically solved.
Although I am quite experienced with most frameworks in iOS, I have no clue when it comes to 3D modelling. I even worked with SpriteKit, but never with something like SceneKit.
Now a customer wants a very ambitious menu involving a 3D object, an 'icosahedron' to be exact. I want it to look something like this:
So I just want to draw the lines, and grey out the 'see-through' lines on the back. Eventually I want the user to be able to freely rotate the object in 3D.
I already found this question with an example project attached, but this just draws a simple cube: Stroke Width with a SceneKit line primitive type
I have no clue how to approach a more complex shape.
Any help in the right direction would be appreciated! I don't even need to use SceneKit, but it seemed like the best approach to me. Any other suggestions are welcome.
to build an icosahedron you can use SCNSphere and set its geodesic property to YES.
Using shader modifiers to draw the wireframe (as described in Stroke Width with a SceneKit line primitive type) is a good idea.
But in your case lines are not always plain or dotted — it depends on the orientation of the icosahedron. To solve that you can rely on gl_FrontFacing to determine whether the edge belongs to a front-facing or back-facing triangle.
I have two UIViews, each one has draw a car(vectorgraph), now if a car(A) behind another car(B), then I want the overlaps in A be dashed.
the car was drawn by UIBezierPath, I want the overlaps in A's path become dashed, how can I do this?
Thank you for your helping!
I don't think there is any way to do this automatically. You would need to calculate the bounding rectangle of the intersection of the 2 views, and then manually parse the path of car A into 2 parts, the part that's covered and the part that's not, and draw the covered part using dashed lines.
This is original development that you would have to do yourself.
Erica Sadun's outstanding "iOS Developer's Cookbook" series has a recipe that shows how to parse a bezier path segment by segment. Figuring out the portion of the path that is inside the intersection range will involve some tricky programming.