I've been programming the iphone for a couple of months now and have 3 apps in the store already.
However, I have not done any kind of graphics programming in the platform.
Given that I'm planning on starting my 5th app (the 4th is under Apple's review) I wanted to ask for some pointers as to where to get information for this (been googling for a while but nothing matches what I'm looking for)
I need to create an App where I can 'drop' some shapes from a menu (a rectangle, circle, squares, and then some complex shapes) onto a main window.
the idea is that the user can drag them around. BUT, I want them to 'snap' to each other (kind of like in a CAD package where a circle has quadrants on the edges that snap to any other geometry entity in the drawing).
So if I had a circle on the left of the screen and a rectangle on the right and then I move the circle around, it would stop moving to the right If I hit the rectangles edges. Not completely stop but giving some sort of 'resistance' to the continuity of the movement.
Also, if I have several overlapping drawings, is there a way to 'divide' them (any overlapping becomes a shape on itself but is removed from any other shape composing the overlap)?
The reason for this is that I need to calculate the area of the drawing (along with other properties)
I'm thinking of CALayer 1, 2, 3,..., n on of top of the other, each one with a drawing (with CGPath?), that may or may not overlap the others.
Then I need to somehow obtain information of the 'projection' of all those on a single CALayer.
I'm clueless here.
Should I look into Quartz2D? is CALayer and CGPath enough for this?
this is not for a game. Just an engineering application I have in mind.
Any help is appreciated.
regards
dh
iPhone Application Programming Guide has a chapter on drawing.
You might get some ideas where to start by looking at the appropriate lectures from iPhone Application Programming lectures at Stanford. They include hight quality video lectures (filmed by Apple) over at iTunesU, slides and example source code.
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I'm looking for an efficient way to draw curved lines and to make an object follow them in Unity.
I also need to draw them using a custom image and not a solid color.
And on top of that I would like to apply an outer glow to them, and not to the rest of the scene.
I don't ask for a copy/paste solution for each of these elements, I list them all to give some context.
I did something similar in a web app using the html5 canvas to draw text progressively. Here a gif showing you the render:
I only used small lines to draw what you see above. Here a very big letter with thinker lines so lines are more visible:
Of course it's not perfect, but the goal was to keep it simple and efficient. And spaces on the outer edges are not very visible in normal size.
This is used in an educational game working on mobile as a progressive app. In real world usage I attach a particles emitter to it for better effect :
And it runs smoothly even on low end devices.
I don't want to recreate this exact effect on Unity but the core functionality is very close.
Because of how I did it the first time, I thought about creating a big list of segments to draw manually, but unity may have better tools to create this kind of stuff, maybe working directly with bezier curves.
I a beginner in Unity so I don't really know what is the most efficient way to do it.
I looked at the line renderer which seemed (at first) to be a good choice but I'm a little bit worried about performances with a list of 500+ points (considering mobiles are a target).
Also, the glow I would like to add may impact on the technique to choose.
Do you have any advice or direction to give me?
Thank you very much.
I am trying to draw a box that can help someone understand the dimensions of an item, but I keep having the issue that since I first need to recognize a plane when I put my physical item on top of the plane, my box gets drawn in front of the item.
Is it possible to somehow overcome this?
#John Scalo is right, your problem is not having to first detect a plane, but it's that your render engine doesn't know that part of your green box frame is occluded (hidden) by a real-world object.
"…to somehow overcome this"
Yes, and by doing so you might be "solving" your original problem—help someone understand the dimensions of an item.
(Depending on your choice of render engine, e.g. SceneKit) You can add an invisible 3D object that has the same dimensions as the real-world object; so the render engine will "know" that some parts of your box frame are behind this (for the user invisible) 3D object. Therefor, you can tell it not to draw those parts of your box frame, which will give the illusion (borrowing from Apple here) that your soda can has the box around it.
These workarounds are inaccurate, but maybe their accuracy is enough for the level of realism you are trying to achieve:
Option 1: 1. After detecting the desk surface, place a semi-transparent 3D object over the soda can and then resize it (gestures/buttons your choice) until it's about the dimensions of the soda can. 2. Confirm that you're done, and just don't draw a texture on it at all just let it occlude the green box frame.
Option 2: Hold your device near the edges of the soda can and add "enough" ARAnchors to be able to create a "bounding shape" that (again) can be used to capture the real-word object and occlude that.
Option 3: (intense, and perhaps the least accurate) Use your finger to "brush" over the object from various angles, and on each touch perform a hit test (hopefully the top/nearest hit is a part of your soda can) and build up a "bounding shape" that way.
Option X: any combination of 1 - 2 - 3.
Good luck, there's lots of people trying to work around this device/ARKit limitation at them moment, so keep your eyes open for good ideas.
The problem you're dealing with is called occlusion, and ARKit doesn't (currently?) include occlusion support. Maybe some day soon iPhones and iPads will begin to ship with LIDAR (or similar), in which case ARKit will be able to detect objects in the scene, making occlusion much easier.
I am working on a iOS 5 iPhone project where users can choose an image on their device, then trace an object inside of the picture (trace an apple out of a picture of a fruit basket), and then the picture needs to be uploaded with the "tagged" object so it can be pulled down later. Other people will then pull down the image and try to find where the tagged object is in the picture (Think "Where's Waldo?").
I have been trying to figure out the best way of tracing the object. Before, I had a user press the top left, top right, bottom left, and bottom right points around the object and create a square view around the object. The info for that view was uploaded and then pulled down for the user to find the object. The downside is that all objects are obviously not squares/rectangles so I need to do a free form shape.
I was thinking of allowing the user to draw over the object and then somehow I need to be able to tell what is inside of the trace (For example, inside of a circle that they traced), but a problem I forsee is making sure the trace they made is closed so I can fill in the shape (which is a whole not problem).
Any advice welcome on the best way of starting this.
Thanks!
UIBezierPath might be a very useful friend here. It allows you to create any shape you need, and it supports both drawing and hit-detection. I recently did an implementation for a storybook where I could trace out a shape with their finger, freeze it, and then use the shape for tap detection.
The basic idea is this:
When your finger touches the screen, start recording positions. Discard any positions that are too close to the previous position (eg, only record a point if it is >min-distance from the last recorded point). While doing this, you can draw the UIBezierPath so you can see what you are tracing out. Modify the UIBezierPath by adding points to it, instead of recreating it every time.* When you lift your finger, close the bezier path. Quite simple.
Now, this will result in a polygon (ie, straight edges). If your min-distance is low enough or if you are using it for hit-detection (as you say), it won't really matter. However, if you want to smooth the path, you have to use the curve-to methods, which slightly complicate it - but should you wish to follow up on this more, read up on splines and spline generation from a point series.
*note: otherwise you'll get lag while drawing large shapes because recreating a bezier path from an increasingly large series of points gets expensive. Modifying the existing path makes it much, much, much faster.
How do you create filled flat circles (say white) that build out from each other in random overlap to fill the iPhone screen but ease-dissolve so that the screen never gets filled - on touch? On touch release they stop being created as they continue to ease transparency to 0 and are cleared from memory.
An example in code would be killer.
What you're doing shouldn't be too hard to do, but it would take some time to actually code. I'd be surprised but impressed if anyone were to make an example for you.
You could probably figure this out for yourself and learn some pretty good coding lessons on the way.
In order to do what you want, you need a pretty good handle on some concepts such as these:
(Cocos2d)
Touch Detection
Drawing Shapes
Random Numbers
Opacity
Timed Fade Animation (Your "Ease-Dissolve")
and utmost important:
**memory management!**
I'm currently trying to write an app, that would be able to show the effects of glas, as seen through the iPhone Camera.
I'm not talking about simple, uniform glas but glass like this:
Now I already broke this into two problems:
1) Apply some Image Filter to the 2D-frames presented by the iPhone Camera. This has been done and seems possible, e.g. in the app: faceman
2) I need to get the individual lighting properties of a sheet of glas that my client supplies me with. Now basicly, there must be a way to read the information about how the glas distorts ands skews the image. I think It might be somehow possible to make a high-res picture of the plate of glasplate, laid on a checkerboard-image and somehow analyze this.
Now, I'm mostly searching for literature, weblinks on how you guys think I could start at 2. It doesn't need to be exact, in the end I just need something that looks approximately like the sheet of glass I want to show. And I'm don't even know where to search, Physics, Image Filtering or Comupational Photography books.
EDIT: I'm currently thinking, that one easy solution could be bump-mapping the texture on top of the camera-feed, I asked another question on this here.
You need to start with OpenGL. You want to effectively have a texture - similar to the one you've got above - displace the texture below it (the live camera view) to give the impression of depth and distortion. This is a 'non-trivial' problem, in that whilst it's a fairly standard problem in its field if you're coming from a background with no graphics or OpenGL experience you can expect a very steep learning curve.
So in short, the only way you can achieve this realistically on iOS is to use OpenGL, and that should be your starting point. Apple have a few guides on the matter, but you'll be better off looking elsewhere. There are some useful books such as the OpenGL ES 2.0 Programming Guide that can get you off on the right track, but where you start would depend on how comfortable you are with 3D graphics and C.
Just wanted to add that I solved this old answer using the refraction example in the Khronos OpenGl ES SDK.
Wrote a blog-entry with pictures about it :
simulating windows with refraction