On Seven Inches

Tim Bray has a year-end blog post up that's worth a read. In case you don't know, Tim Bray is Google's Android Evangelist. As you might expect from someone who would take that job, he's as enthusiastic about the Android platform as I am about iOS. Although his perspective colors his view (as does mine), his analysis is usually pretty good.He's got one assertion in this most recent post, however, that doesn't seem to ring true to my ear.Apple will totally do a 7" device. Anyone who’s spent quality time reading books or playing games on the Galaxy Tab knows; there’s a great big hole in the ecosystem that needs something bigger than a handset but that still fits in one hand and you can use for four hours in a row sitting up. This argument is over.John Gruber seems similarly skeptical, opining...

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Posted in: Android,Apple,Rant

More Animation Curves than You Can Shake a Stick at

Core Animation is awesome. It makes doing a lot of complex, fancy animations downright easy. One of the really nice built-in features of Core Animation is the ability to use animation curves. These curves let you specify whether the animation happens linearly (at the same pace throughout the animation), or whether the animation eases in, eases out, or does both.When you have to go closer to the metal and use OpenGL ES, you're not so lucky. We don't have animation curves provided for us in OpenGL ES. We have to interpolate ourselves. Fortunately, the math behind animation curves is straightforward. Plus, there are far more curves than just the four Apple offers. I haven't run across a good library for generating animation curves, so I've decided...

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Posted in: Animation,Core Animation,OpenGL ES,Sample Code

The Little Grashopper Blog

Well, I'm not sure how I never ran across it before, but Philip Rideout, author of O'Reilly's iPhone 3D (a book I recommended last week), has a hell of a blog for people interested in OpenGL. A lot of the posts are specific to desktop OpenGL (and recent versions of OpenGL at that!), but there's tons of great information that applies to OpenGL ES as well. It's a veritable treasure trove of advanced graphics goodness from a guy who's been doing it for yea...

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Posted in: OpenGL ES,Other blogs

More Math Resources

After posting about the free Linear Algebra book, I was told about another resource for learning math via Twitter. The Khan Academy is a not-for-profit website providing online video courses on a number of topics. They don't just cover math, but they do cover math extensively. They have well over 100 video lessons on linear algebra alone. Definitely a great resource I'm happy to pass alo...

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Non-Deterministic Problems aka Finding Talent

As programmers, we usually deal with deterministic systems. To state it simplistically, deterministic systems are systems where the same inputs always results in the same output. Unless we intentionally introduce randomness¹ or have a relatively rare kind of bug in our code, the same inputs to our programs will always yield the same output. It could very well be the wrong result if our algorithm is bad, but it should be the same wrong result every time, which is a trait we rely on heavily.In the real world, most things we encounter are non-deterministic. There are always factors we can't control or measure, and most systems have a human element. We are at the mercy of whim and emotion, and that's hard for a lot of programmers to deal with. Our fellow humans's decisions are decidedly non-deterministic...

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Posted in: Contracting,Developers,Rant

Free Course in Linear Algebra

Computer graphics programming uses linear algebra so heavily, you could basically say it's based on it. Yet, many people — perhaps most — who develop an interest in graphics programming don't have a background in Linear Algebra. At most universities, it is taught as an upper-level (300 or 400) mathematics course, which means that the majority of students who aren't majoring or minoring in math or certain hard sciences, typically don't take them. Even if you have studied it, if you've gone a period of time without using it, you very likely have forgotten it.Yet, if you want to go beyond a certain level in graphics programming, you need to understand it.Today, I stumbled across a free course in Linear Algebra, and it looks to be quite good. It's dense but, hey, this is higher math we're talking...

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OpenGL ES Book Recommendation

Since canceling my OpenGL ES 2.0 for iOS 4 book, I've had several people request book recommendations to use instead of my book. Honestly, I didn't really have one to give before today, partially because I intentionally avoided reading competing books while working on mine.Today, while stuck on a train, I checked out Philip Rideout's iPhone 3D Programming by O'Reilly. Now, it's never easy to give an objective opinion on a book that competes with one you're writing, and even though my book is currently not on a production schedule and I have no time to work on it, I tend to still think of myself as working on an OpenGL ES book. Although there are several things that I would have done differently, I also know it's unfair to judge a book that way. Deciding what to include and what not to include...

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Posted in: Book project,Books,OpenGL ES

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