Emerald Blog

Notes from the developers at Emerald Sequoia LLC

Leap Seconds

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The latest versions in the store of our digital timekeeping apps, Emerald Time and Emerald Timestamp, support leap seconds. We had a chance to test them during the leap second at the end of last month. You can see a movie we took of the apps running here

Supporting the Retina iPad

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Version 3.8 of Emerald Chronometer HD has just been approved for the App Store, and fully supports the new iPad’s Retina display.

Just as with support for the iPhone 4’s Retina display, adding this support required new artwork at double the resolution in each dimension, for a total of 4 times the pixels of the prior ECHD version.

And just as before, that means that the app download got a lot bigger; it’s now 164 MB to hold all of the new artwork. For comparison, here’s the artwork for the three kinds of display devices we support:

First the non-Retina iPhone and iPod touch:
Old display 'parts list' or texture atlas

Next the Retina iPhone and iPod touch in Chronometer, and the iPad in Chronometer HD:

Finally, the Retina iPad in Chronometer HD:

We hope you enjoy it! As before, we sympathize with those of you on slow connections, but we used the same logic as before and decided we wanted this to be a free upgrade for ECHD users, which meant all ECHD users needed to upgrade.

Thanks for your support.

We’ve just added our 16th watch to Emerald Chronometer and Emerald Chronometer HD: “Babylon” is a full-month calendar watch, with an unusual mechanism.

The mechanism (which is one of our most complicated “mechanically”) consists of three stacked wheels and a series of covers that slide in and out. You can read more about it here.

We hope you enjoy it!

Just a quick note that there is a total lunar eclipse today: http://eclipse.gsfc.nasa.gov/LEdecade/LEdecade2011.html

It’s the longest and deepest lunar eclipse of the decade, but unfortunately most of our customers will miss it because the moon will be below the horizon. You’ll be able to see a bit of the ends in Europe and Australia, but only India and eastern Africa (and a bit of central Asia) will get the whole show.

You can still see the effects in Emerald Observatory and Emerald Chronometer/Emerald Geneva (the back of the Geneva watch has an eclipse indicator dial), even if the eclipse isn’t visible at your location.

We’ve gotten a lot of requests for this, and we’ve finally put it in the can: We’ve just hit the App Store with an iPad version of Emerald Chronometer, called “Emerald Chronometer HD”. You can see the press release here, some images here, and the App Store page here.

Once again this was more work than you might think, because of the way the app works with its OpenGL implementation. Something as simple as rotation, which is trivial on a simple app with standard UIKit views, becomes a lot more complicated when you have an OpenGL view and UIKit views and you want to animate it all smoothly during an orientation change. Watch carefully what happens when you rotate the device while grid mode is up; that represents a week of development effort. 🙂 We did get to make use of the higher-resolution images we developed for the Retina display, however.

Anyway, we’re pretty happy with the way it looks, in both portrait and landscape modes. And in grid mode with 2-4 watches, all of the watches are the same size as they are in Emerald Chronometer on the iPhone (or larger), so it’s a nice way to see more than one watch at once and still be able to read each one.

The new app is priced at USD $5, the same price as Emerald Chronometer has been since it entered the store. At the same time, we are reducing the price of Emerald Chronometer to USD $2; this reflects both an overall downward trend in app pricing in the past three years and also the additional value (and development effort) associated with the iPad app.

We hope you like the new app!


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There will be a lunar eclipse later this month, visible in the Americas (a total eclipse, around midnight on the night of Dec 20-21, weather willing) and parts of Australia (partial eclipse just after sunset on the 21st) and Great Britain (partial eclipse just before sunrise on the 21st).

Emerald Chronometer (and Emerald Geneva) have had the capability to model eclipses for some time now, and there’s a web page about it in the Help and online. But we thought Emerald Observatory should have some of the fun, too. So we took that display from Geneva, simplified it a bit and shrunk it into the spot in Emerald Observatory previously occupied by the leap-year indicator:

Eclipse simulator in Emerald Observatory

Eclipse Simulator in Emerald Observatory

The outer ring shows things that are apparently rotating around the Earth, namely the Sun, the Moon, the shadow of the Earth, and the nodal points of the lunar orbit, which are the points where it intersects the apparent orbit of the Sun. When the Moon and the Sun are at the same point on the display’s ring, there is a new moon. A new moon does not always result in an eclipse, but if the new moon happens near a “nodal point” (red line on the ring), it means the orbital paths of the Sun and Moon are close to intersecting and a solar eclipse is possible. Similarly, when the Moon is opposite the Sun on the ring, it will be at the same point as the Earth shadow (black-filled circle) on the ring display, and there is a full moon. Again, a lunar eclipse does not always occur when there is a full moon, but again if the full moon happens near a nodal point (red line), then a lunar eclipse is possible.

When an eclipse of some sort happens, or even almost happens, the dial inside the ring shows a simulation of what will appear in the sky (with better graphics than on Geneva, since we aren’t constrained here by the mechanical model). For example, if we tap the Set button and then the phase button to advance to December (20th or) 21st, we see

Lunar eclipse simulation

The moon is shown eclipsed, and the Earth shadow is very faintly shown as a gray outline. If we move forward or backward in time, we can see the eclipse progress. Here we’ve moved backward an hour, to show the partial eclipse at that time:

As I said earlier, we removed the leap-year indicator. We moved the year itself next to the date (as shown in the top picture), and have a simple “Leap” indicator that turns on when there is a leap year, but the complex 1/2/3/4/100/400 display is gone. We were somewhat ambivalent about it from the start anyway, and at least one observer agreed.

Anyway, here’s wishing for clear skies for everyone. But if you can’t see the eclipse outdoors, you’ll be able to see it inside on Emerald Observatory. 🙂

You’ll need version 1.3 of Emerald Observatory to see it. It was approved for the store last night and should show up in the next 24 hours.

Retina support and app size

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The new iPhone 4 support that Bill just posted about required a whole new set of artwork, which is why it took so long for us to get this support out. Most simple apps simply use built-in widgets and graphic routines to render their displays, and those apps got Retina support simply by recompiling. (Our own apps Emerald Time and Emerald Timestamp fall into that category, and we supported the Retina display in those apps when the iPhone 4 came out). But the displays you see in Emerald Chronometer are rendered using a “parts list” of display objects that is generated with a custom external tool.

For example, here’s a parts list (this is really an OpenGL texture atlas, for the technically inclined) from Geneva’s front side, at the old resolution:
Old display 'parts list' or texture atlas

That image, and many more like it, are included with every copy of the app we ship.

The only way to get higher resolution imagery with this scheme is to provide a higher resolution image of parts; because the Retina display has 4x the pixels of the older displays, that means these artwork images need to be about 4 times the size of the old ones, which turns out to be a pretty large number (40 MB of images). Here’s just a portion of the same artwork image at the higher resolution for comparison:

We sympathize with those of you with older phones and slower connections who have to download all of the bytes of the new app with no appreciable benefit. For what it’s worth, we considered a couple of different options before settling on this one:

1) Creating a separate app with the high-resolution artwork in it, and leaving the existing app as is. This would have removed any impact on owners of 3GS and earlier devices. But we didn’t think this was fair to our existing iPhone 4 customers, since they would have to pay full price for the new app for a relatively minor feature upgrade, and we didn’t see any other app developers do this.

2) Making an in-app purchase option for $1 to get the higher resolution artwork. At first this seemed like a good idea (especially since it would bring in a small amount of revenue for our not inconsiderable effort generating the new artwork), and we spent a little time developing some store infrastructure to support it. But this would mean that users would have to download the additional 35 megabytes or so of Retina-specific imagery while running the app. This maybe wouldn’t be so bad, but the artwork typically changes in minor ways every time we release a new version, so it would mean that going forward as more and more people had iPhone4-class devices, we’d all be forced to do this extra step every time a new version was released.

We finally decided that the right long-term architecture was to just support the Retina display as part of the normal app. Anyway we hope those of you with Retina displays like it.

iPhone 4 support

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We’re about to release a new version of Emerald Chronometer with high-resolution graphics for the Retina display.  iPhone 3 users won’t see much difference but iPhone 4 users will finally get the full benefit of their new screens.  It makes a huge difference, especially on all our small text:

Tricks with Miami

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There are a couple of tricks with Emerald Chronometer’s Miami front-side watch face that might not be obvious, so I thought I’d throw them out here:

Moon Phase

The first is that you can tell the approximate phase of the moon with this display, by noting the relationship between Moon rise/set and Sun rise/set. From day to day, moonrise (and moonset) are later by about an hour, and thus the inner violet moon ring (see below) rotates (clockwise!) around the face of the watch. When the Moon ring is completely aligned with the gray “Sun is up section”, it means they are rising and setting at the same time and thus the moon is new:

If the Sun and Moon indicators are opposite each other, it means the moon is full:

And you can judge approximately any other phase by noting how far around the Moon ring has rotated from complete alignment with the Sun. For example, in the following image, the Moon has passed full and is approximately at “third quarter”:

Position of planets in the sky

This one is a bit more hand-wavy and subjective. But it does work, at least in mid-latitudes in the northern hemisphere. If you rotate the watch face so that a particular planet’s ring is centered at the top, with its rise on the left and its set on the right, and face south, then the 24-hour hand will point approximately at the position along the ecliptic in the sky that the given planet can be found. This works because in this configuration the rise point on the watch face corresponds to left, meaning east when facing south, and the set point corresponds to right, meaning west. In the southern hemisphere mid-latitudes you would have to mirror the result around South. Here’s an example, where we want to see where Saturn is approximately; the 24-hour hand points to its approximate position along the visible portion of the ecliptic:

Of course it’s a lot easier to flip the watch around and use the other side to get the answer precisely 🙂 :

OK, first feedback question:  What’s your favorite watch in Emerald Chronometer?  Submit your answer via the comments (click on the Comments link to the upper right of this post; you’ll have to register the first time you comment but it’s free).

My personal favorite tends to change depending on what I’m working on.  For a while my favorite was Miami, because, odd as it is, the front side can tell you a lot of stuff about what’s going on in the sky (it might be worth a separate posting at some point; you can use it to find planets in the sky and even quickly estimate the phase of the moon).  But Geneva, because of its zillion complications, will probably always be the one I keep coming back to.

– Steve