In iOS, I'd like to have a series of items in "space" similar to the way Time Machine works. The "space" would be navigated by a scroll bar like feature on the side of the page. So if the person scrolls up, it would essentially zoom in in the space and objects that were further away will be closer to the reference point. If one zooms out, then those objects will fade into the back and whatever is behind the frame of refrence will come into view. Kind of like this.
I'm open to a variety of solutions. I imagine there's a relatively easy solution within openGL, I just don't know where to begin.
Check out Nick Lockwood's iCarousel on github. It's a very good component. The example code he provides uses a custom carousel style very much like what you describe. You should get there with just a few tweaks.
As you said, in OpenGL(ES) is relatively easy to accomplish what you ask, however it may not be equally easy to explain it to someone that is not confident with OpenGL :)
First of all, I may suggest you to take a look at The Red Book, the reference guide to OpenGL, or at the OpenGL Wiki.
To begin, you may do some practice using GLUT; it will help you taking confidence with OpenGL, providing some high-level API that will let you skip the boring side of setting up an OpenGL context, letting you go directly to the drawing part.
OpenGL ES is a subset of OpenGL, so essentially has the same structure. Once you understood how to use OpenGL shouldn't be so difficult to use OpenGL ES. Of course Apple documentation is a very important resource.
Now that you know a lot of stuff about OpenGL you should be able to easily understand how your program should be structured.
You may, for example, keep your view point fixed and translate the world (or viceversa). There is not (of course) a universal solution, especially because the only thing that matters is the final result.
Another solution (maybe equally good, it depends on your needs), may be to simply scale up and down images (representing the objects of your world) to simulate the movement through the object itself.
For example you may use an array to store all of your images and use a slider to set (increase/decrease) the dimension of your image. Once the image becomes too large for the display you may gradually decrease alpha, so that the image behind will slowly appear. Take a look at UIImageView reference, it contains all the API's you need for it.
This may lead you to the loss of 3-dimensionality, but it's probably a simpler/faster solution than learn OpenGL.
Related
I’m building a program where you control a small avatar (this is a basic circle geometry or plane) that traverses through a scene filled with 3D Models and shapes. I’d like to achieve an effect similar to those found in many video games where you can see some sort of indication that the avatar is behind the various models and shapes. For example, here is an image to explain what i mean:
Example image to show desired effect
It doesn’t necessarily need to be the outline of the shape like in the example image. I’m open to any effect really that shows some sort of indication that the avatar is behind something but also cant be too performance heavy as I'd like to get this program running on mobile. Being able to customise the effect somewhat (e.g. color, thickness, etc) is also highly desirable. Any advice or suggestions would be greatly appreciated. There really doesn't seem to be much information that I can find to achieve an effect like this.
Also I thought it was worth mentioning that thus far I have attempted two things on my own. One is just rendering the avatar above everything. That turned out to look really silly and confusing. The other thing I attempted was to use an Outline post processing effect (from this library https://github.com/vanruesc/postprocessing). Which actually looked pretty great but proved to be too performance heavy to run optimally at all times (not to mention other problems with color blending and transparent / see-through shapes and models).
I understand this is kind of a shot in the dark but thought it didn't hurt to ask.
I have some quads that have a texture with transparency and some objects behind these quads. However, these don't seem to be shown. I know it's something about GL_BLEND but I can't manage to make the objects behind show.
I've tried with:
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);
but still not working. What I basically have is:
// I paint the object
draw_ac3d_file([actualObject getCurrentObject3d]);
// I paint the quad
paintQuadWithAlphaTexture();
There are two common scenarios that create this situation, and it is difficult to tell which one your program is doing, if either at all.
Draw Order
First, make sure you are drawing your objects in the correct order. You must draw from back-to-front or else the models will not be blended properly.
http://www.opengl.org/wiki/Transparency_Sorting
note as Arne Bergene Fossaa pointed out, front-to-back is the proper way to render objects that are not transparent from a performance stand point. Because of this, most renderers first draw all the models that have no transparency front-to-back, and then they go back and render all models that have transparency back-to-front. This is covered in most 3D-graphic texts out there.
back-to-front
front-to-back
image credit to Geoff Leach at RMIT University
Lighting
The second most common issue is improper use of lighting. Normally in this case if you were using the fixed-function pipeline, people would advise you to simply call glDisable(GL_LIGHTING);
Now this should work (if it is the cause at all) but what if you want lighting? Then you would either have to employ custom shaders or set up proper material settings for the models.
A discussion of using the material properties can be found at http://www.opengl.org/discussion_boards/ubbthreads.php?ubb=showflat&Number=285889
So I want to have a view (NSView, NSOpenGLView, something CG related?) which basically displays a map. Such as:
http://dump.tanaris4.com/map.png
Obviously that looks horrible, but I did it using an NSView, and it draws SO slow. Clearly not designed for this.
I just need to allow users to click on the individual (x,y) coordinates to make changes, and zoom into a certain area (to see it better).
Should I go the OpenGL route? And if so - any suggestions as to how to get started? (I was able to follow the guide to draw a triangle, so that's good).
I did find this post on zooming in an NSView: How to implement zoom/scale in a Cocoa AppKit-application
My concern is if I'm drawing over 6000 coordinates and the lines connecting them, this isn't efficient at all.
I don't think using OpenGL would be of any good here. The problem does not seem to be the actual painting, but rather the rendering strategy. You would need a scene graph of some kind to dynamically handle level of detail and culling.
Qt has all this packaged in a nice class class QGraphicsScene (see http://doc.qt.nokia.com/latest/qgraphicsscene.html for reference, and http://doc.qt.nokia.com/main-snapshot/demos-chip.html for an example).
Some basic concepts you should consider using:
http://en.wikipedia.org/wiki/Scene_graph
http://en.wikipedia.org/wiki/Quadtree
http://en.wikipedia.org/wiki/Level_of_detail
Try using core graphics for this, really there is so much that could be done. Watch the video Practical Drawing for iOS Developers from WWDC 2011 and it should give an over view of what can be done with CG.
I believe even CoreGraphics will suffice for what you want to achieve, and that should work under a UIView if you draw the rectangle of your view completely under the DrawRect method of your UIView (you must overload this method). Please see the UIView Class Reference. I have a mobile application that logs points on the UIMapKit, kind of like Nike+, and it certainly works well for massive amounts of points/line segments. There is no reason why this simple approach cannot work for you as well.
I just wanted to know how you could implement a bookcase, like in iBooks, into your iPhone app.
I presume you would need to use a UIScrollView, but then I read somewhere that you need to use a UITableView. Which is it?!
You'd use code that others have already written, such as AQGridView.
I'm not sure if there's a better way, but you could create multiple small views or images (these would represent each book) then add these small views/images to the subview of a larger view in a linear format (leaving a space between each element). Then just set the background of your larger view as an image of a bookcase. Sorry I don't know of a better way.
And for the above solution I would use a UIScrollView.
You can implement it anyway you like, but it seems to me that a UITableView would be the easiest (which will scroll anyway). All of the magic will happen in your UITableViewDataSource, which is where you will decide what books are placed on what row.
Once you have decided which books to display you will have create a custom tableview cell that draws the appropriate objects.
To be honest, while not too difficult of a task, it will take a lot of effort to get looking right. If you are not comfortable with custom drawing then be prepared to spend time learning about the various image/graphic APIs.
Imagine I have a rectangle say 400px x 300px. Then let’s say I want to load an image in that. All of this is very easy using Sytem.Drawing.DrawImage.
Rectangle http://img576.imageshack.us/img576/2363/rectangle.gif
But then I want to leave the left hand side as 300px but change the right hand side to 250 px. I can draw the box using 4 DrawLines but I don’t know how to squash the image into the new shape. I want the right hand side of the shape to be 250, the left size 300 and the top and bottom 400px.
Resized http://img85.imageshack.us/img85/3479/rectangle2.gif
I can’t use DrawImage as it expects the left and right sizes to be the same. Is there a way to manipulate the image into the new shape?
I've looked at other questions, but they only apply where the left and right hand side is equal.
Any thoughts on how to squash an image into a shape which did not have parallel sides?
(If it helps, I'm happy to sacrifice image quality to fit the right shape.)
Disclaimer: I work for Atalasoft.
Our DotImage product has a command called QuadrilateralWarpCommand that can do this. It's in DotImage Photo.
What you want to do is non-trivial (but also very powerful).
#Heinzi is correct, the general class is called warp transformations. What you're trying to do is specifically a perspective transformation. At a high level, it involves running the individual coordinates through a transformation matrix to get their new positions, and then doing interpolation between pixel values based on the old and new locations.
This article talks about some transformations, one of them being a sheer, so it might be helpful overall. I'm not sure, I haven't read it closely. In general, you want to google for something approximately like "c# image transformation" or "c# image perspective transform".
Depending on what you're planning on using it for, buying a library might be the best way to go about it, although there is a lot to learn about image manipulation by doing it yourself.
I did not find a solution to your problem, but I have some information which might help you along:
What you want is called a warp transformation.
As far as I know, the .net framework natively supports this kind of transformation only for a GraphicsPath, namely, the GraphicsPath.Warp method. Unfortunately, I don't think that this will help you, unless you are willing to redraw your image using a .net GraphicsPath object.
If you need the transformation directly in the UI layer, your UI library might help: Silverlight, for example, includes the PlaneProjection class, which can be used for such effects; in WPF, the 3D engine might be useful for this (requiring more programming effort, through).