Drawing Part of a UIImage

Happy Thanksgiving, and sorry for the relative lack of posts here lately. Things are crazier than ever and it's been a challenge finding time to shower, let alone blog.I do have something to share, today, though. No, it's not the next chapter of OpenGL ES 2.0 for iOS. It's a category that some of you may find useful: a method that allows you to draw only part of a UIImage rather than the entire thing.On the Mac, NSImage has a handy instance method called drawInRect:fromRect:operation:fraction: that lets you specify exactly which part of an image to draw. On UIImage, we've only got the ability to draw the entire image either unless we drop down to Core Graphics calls. We don't have a nice, easy, convenient way using just UIImage to draw a portion of the image it represents.I needed this ability...

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Posted in: Categories,source code,UIImage

OpenGL ES Course on iTunes University

Those of you waiting for the next chapter of OpenGL ES 2.0 for iOS can do yourselves a favor by checking out this course on iTunes University. It's an Advanced iOS Development course taught by Brad Larsson at the Madison Area Technical College, and the most recent lesson is on OpenGL ES. You can also find the course notes he...

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Posted in: OpenGL ES,tutorials

OpenGL ES Update

Sorry for the silence around here lately.Unfortunately, the next chapter of OpenGL ES 2.0 I plan to release contains detailed, step-by-step instructions based on Xcode 4 (mostly written around the time of DP2) which is still under NDA. As a result, this chapter is going to take a little longer to scrub, and I haven't had much time to scrub lately. In the meantime, I realized that I've never linked to the PowerVR Insider SDK, so I'm rectifying that. The company that makes the GPU in all iOS devices has an SDK you can download - in fact, they have several versions of it for different platforms, including iOS. Most of the code is fairly generic C++ with just enough Objective-C around them to work, but there's a metric buttload of good code there for doing all sorts of things. Definitely worth...

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Posted in: OpenGL ES,Power VR

NSExpression

The relatively new NSExpression class is incredibly powerful, yet not really used very often. Part of that is that it's not very well documented. Although the API documentation for NSExpression is fairly well detailed, the listed "companion guide" (Introduction to Predicates Programming) has very little information about how to actually use NSExpression.NSExpression deserves to be better documented, because it brings to predicate programming (including Core Data), a lot of features from the relational database world that people often complain are missing, like unioning, intersecting, and subtracting resultsets and performing aggregate operations without loading managed objects or faults into memory.The aggregates functionality is especially important on iOS given the limited memory on most...

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Posted in: category,Core Data,NSExpression,NSPreciate,Sample Code

OpenGL ES 2.0 for iOS, Chapter 4 - Introducing the Programmable Pipeline

The code for this chapter can be found here.I've mentioned OpenGL ES 2.0's programmable pipeline, but it may not be clear to you exactly what that term means. If that's the case, let's clear it up now. The term “pipeline” refers to the entire sequence of events, starting from when you tell OpenGL ES to draw something (usually called rendering), through the point where the objects submitted have been fully drawn. Typically, an OpenGL ES program is repeatedly drawing as the program runs, with each completed image begin referred to as a frame.Versions of OpenGL ES prior to 2.0 (including 1.1, which is supported by all iOS devices) used what's called a fixed rendering pipeline, which means that the final image was generated by OpenGL ES without...

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Posted in: Book project,OpenGL ES