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caradk milk

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since Nov 15, 2009
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Recent posts by caradk milk

Augmented reality is somehow a technology that makes scenes generated by computer to merge with scenes captured from the real world. Such as if you capture your own picture or video, which is an object in the real world, and you create a computer-generated background or 3D objects, such as in a deep ocean with fishes swimming around. And using the augmented reality software tool you can merge them, which results a video or a picture that looks so real, that you can hardly differentiate between what is real and what is generated by the computer.

Open source augmented reality software tools have existed on the desktop computers for quite some times. Now there is a version of these AR tools available for the iPhone, called ARToolKit v4.4, which makes your iPhone capable of creating AR videos for you on the fly.

The ARToolKit v4.4 is the first fully-featured AR framework that supports native operation on Apple iPhone, which lets you create applications with sample real world imagery captured with your iPhone camera, and merges them with software-generated 3D objects. The ARToolKit is also well integrated with the accelerometer of the iPhone, which allows it to automatically detect movements from the iPhone, and impose those movements on 3D images instantaneously.

This AR software also allows iPhone to track multiple points simultaneously, and you can easily place new objects in the virtual world using the iPhone’s multi-touch interface.
14 years ago
iOS
We implemented our own custom Spring scope. A lot of our code works at a relatively low level, close to the database, and we maintain a conceptual level on top of that with its own object model of data sources, links, attributes etc.

Anyway, a lot of beans require a so-called StorageDictionary (an encapsulation of this object graph) to do their work. When we make non-trivial changes to the object graph, the dictionary sometimes needs to be blown away and recreated. Consequently, we implemented a custom scope for objects that were dictionary scoped, and part of the invalidation of a given dictionary involves clearing this custom scope. This lets Spring handle a nice form of automatic caching for these objects. You get the same object back every time up until the dictionary is invalidated, at which point you get a new object.

This helps not only with consistency but also allows the objects themselves to cache references to entities within the dictionary, safe within the knowledge that the cache will be valid for as long as they themselves are retrievable by Spring. This in turn lets us build these as immutable objects (so long as they can be wired via constructor injection), which is a very good thing to do anyway wherever possible.

This technique won't work everywhere and does depend heavily on the characteristics of the software (e.g. if the dictionary was modified regularly this would be horribly inefficient, and if it was updated never this would be unnecessary and slightly less efficient than direct access). However, it has definitely helped us pass off this management of lifecycle to Spring in a way that is conceptually straightforward and in my opinion quite elegant.
14 years ago
WSS4J can be used for securing web services deployed in virtually any application server, but it includes special support for Axis. WSS4J ships with handlers that can be used in Axis-based web services for an easy integration. These handlers can be added to the service deployment descriptor (wsdd file) to add a WS-Security layer to the web service. This is a step by step tutorial for deploying a simple service with Username Token.
14 years ago