I drew a lot points in my program with webgl. Now I want to pick any point and move this point new position. The case is I don't know how to select point. So am I supposed to add actionlistener to each point?
WebGL is a rasterization library. It has no concept of movable, clickable position or points. It just draws pixels where you ask it to.
If you want to move things it's up to you to make your own data, use that data to decide if the mouse was clicked on something, update the data to reflect how the mouse changed it, and finally use WebGL to re-render something based on the data.
Notice none of those steps except the last one involve WebGL. WebGL has no concept of an actionlistener since WebGL has no actions you could listen to. It just draws pixels based on what you ask it to do. That's it. Everything else is up to you and outside the scope of WebGL.
Maybe you're using some library like three.js or X3D or Unity3d but in that case your question would be about that specific library as all input/mouse/object position related issues would be specific to that library (because again, WebGL just draws pixels)
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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.
I'm looking for a library/framework/toolkit that will allow me to render a 2D map from real GeoSpatial data and draw objects on the 2D map.
Requirements:
Map Tiling (when I zoom into the map, i want a more detailed image)
Pan (ability to use the mouse to move around the map)
Read various Geospatial images (satellite, street, etc)
Ability to draw objects onto the map (based on lat/longs) and have them move. For example, I want to be able to put an image of a bird on the map and have it move and rotate correctly.
Primitive shapes. It would be nice if it had built in ability to draw lines, circles, etc.
Complex drawing. For example, I want to draw a compass and have it show the heading of the current heading of the bird.
Mouse input. I want to be able to right click on the map and have a context menu appear. I want to click and hold an shape I draw on the map and drag it easily.
What I have looked at:
OpenSceneGraph with osgEarth. It's great, and fulfills my reqs, but is really slow and I had to do a lot of weird things to get things to work (especially with dragging objects on the map).
Cesium: looks promising, but somewhat slow, and I need it to work as a desktop application. I've seen online that some have managed to use Cesium inside Qt's Webkit, but I'm not sure I would want to take that risk.
EDIT:
I really want to stay away from a web-based framework if possible.
http://imgur.com/52DaJtQ
Here is a primitive picture of what I'm want to achieve. The aircraft icon should move and the degree circle along with it. I want to be able to drag the green waypoints and have the lines redraw as I move a waypoint. The red sensor footprint should adjust to what the aircraft can see.
http://imgur.com/52DaJtQ
Google Maps, Open Street Map, Bing Maps.
I use OpenSceneGraph/osgEarth extensively and am not dissatisfied with its performance.
What kind of weird things did you need to do?
If you want, you can contact me privately to troubleshoot your situation. Me website is AlphaPixel.com and there's a contact form there.
I need to draw an interactive map for an iOs application. For example it can be the map of the US showing the states. It will need to show all the states in different colors ( I'll get this from a delegate colorForStateNo: ) It will need to allow the user to select a state by touching it, when the color will change, and a "stick out" effect should be shown, maybe even a symbol animated to appear over the selected state. Also the color of some states will need to change depending on external events. This color change will mean an animation like a circle starting in the middle of the state and progressing towards the edges changing the color from the current one to the one inside the circle.
Can this be done ,easily in core-graphics? Or is it only possible with Open GL ES? What is the easiest way to do this? I have worked with core graphics and it doesn't seem to handle animation very well, I just redraw the entire screen when something needed to move... Also how could I use an external image to draw the map? Setting up a lot of drawLineToPoint seems like , a lot of work to draw only one state let alone the whole map ...
You could create the map using vector graphics and then have that converted to OpenGL calls.
Displaying SVG in OpenGL without intermediate raster
EDIT: The link applies to C++, but you may be able to find a similar solution.
I understand that I have to draw everything in draw(), and it's looping continuously.
But I don't want to draw texture again and again, for example I want to create a texture, draw something to texture (not spritebatch). than I will only draw that texture in draw().
Is it possible?
What can I use?
You have to draw again and again, as in short, if you dont it wont show. A wise man once wrote in a windows development book
Ask not why the text on your windows has to be constantly drawn, ask why it never used to be in DOS/Unix command line.
If something is placed over the area you're drawing too, and you dont redraw it, it just simply wont be there. You need to keep drawing it for it to be sustained on screen. Its done very quickly and wont hurt anything (especially if you're thinking in terms of background)
Not drawing it again is a performance optimisation. You should only do that if you really need to.
If you do need to do this, create a render target, draw your scene to the render target, and then draw your render target to the screen each frame (using SpriteBatch makes this easy) instead of your scene.
Take a look at this question about caching drawing using render targets.
In my application I want to draw polygons using Windows Create Graphics method and later edit the polygon by allowing the user to select the points of the polygon and allowing to re-position them.
I use moue move event to get the new position of the point to get the new coordinates of the point being moved and use Paint event to re-draw the polygon. The application is working but when a point is moved the movement is not smooth. This is probably due to large numbe of mouse move and paint events firing while moving the point.
I dont know weather the mouse move or the paint event the performance hindrance.
Can anyone make a suggestion as to how to improve this?
look at double buffering in c#. this can speed thing up greatly.
From my Win32 expirience (not a .NET) the fastest vector graphic is Metafile. I dont know if the C# System.Drawing.Imaging.Metafile is as fast as Win32 one. Could be as fast as your video 2D hardware.