# Blog Archive

Viewing page 1 from archive of November 2013

# @classproperty

## Is this an amazing, or terrible idea?

Lets define a classproperty in Python such that it works as a property on both a class, and an instance:

class classproperty(object):

def __init__(self, func):
self.func = func

def __get__(self, obj, cls):
return self.func(cls, obj)


It can be used thusly:

class Example(object):

@classproperty
def prop(cls, obj):
return obj or cls

x = Example()
assert x.prop is x
assert Example.prop is Example


Is this a good idea, or a bad idea?

(Hint: I don't know.)

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After a concerted effort, I broke my longest streak on @GitHub. Finally, I can slack off again. http://twitter.com/mikeboers/status/402187403072270336/photo/1

@mikeboers on . Visit on Twitter.

@mikeboers on . Visit on Twitter.

# Linear RAW Conversions

## The first step when using photos in your computer graphics.

Real world photography is a fantastic and easy source of data in computer graphics and visual effects, be it for textures, backgrounds, or light maps. There is one complication that is very easy to overlook, and tricky to get right: linearity.

In real world light transport (and the simulated version of it in our various renderers) the math of light operates in a linear manner. That is, light source A with intensity 1 and light source B with intensity 1 will combine to intensity 2 (in whatever units those numbers are).

However, image capture and display devices do not work in a linear space. This is mostly historical, and maintained for backward compatibility for the content that has been produced in the past, but we must still deal with it to this day. In order to be immediately useful for 99% of cases, non-RAW image formats (as produced by your camera or the RAW converter) have the inverse curve already baked into the image so that they appear similar to the real world when viewed on a display.

It is this curve that must not be applied in order for our photography to be representative of the world (as far as the math is concerned).

I won't get into what "gamma" means, or scene-referred vs. display-referred imagery, so for an in-depth look at linear workflows see Sony Pictures Imageworks' 2012 SIGGRAPH course nodes (PDF) and this FXGuide article.

So how do we get linear output from our DSLR?

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Recently, someone broke into Adobe's network, stealing source code and part of their password database. It later turned out to affect at least 38 million people.

I always try to investigate to see if I am personally impacted by these leaks. Usually, that means submitting a carefully hashed password to some online service built to inform you if you were part of the leak. This time, however, the entire file was readily, and easily availible (by which I mean my Twitter feed included a link to it, several times).

So... why not take a peek?

\$ grep mikeboers cred


While not surprising, I am still dissapointed to be included.

Digging just a little bit deeper, there are some very troubling things in this file.

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My office (see: local coffee shop) is standing room only today. Must find another facilitator of productivity.

@mikeboers on . Visit on Twitter.

After a day long refactor, everything is back to working the same. Time for those previously impossible features!

@mikeboers on . Visit on Twitter.

# Yet Another Reason I Hate Time

While the Y2K bug turned out to be a bust, the concept behind it is pretty solid.

I have always had a lingering concern for 3:14:07 am on January 19th, 2038 UTC, as that is the last second representable in signed Unix time, and time in systems that still use that representation will wrap around to January 1, 1970. (See the year 2038 problem.)

At the time, 70 years in the future seemed infinitely far away.

There is no chance this will still be running in 70 years.
— Likely said by someone on the POSIX committee.

Unfortunately, that type of thinking just cost a very expensive space probe. 8 years into the Deep Impact mission that was designed for a single event, its clock rolled over, the probe couldn't figure out where the sun was and so couldn't point its solar panels at it, and lost power.

"Basically, it was a Y2K problem, where some software didn't roll over the calendar date correctly," said A'Hearn. The spacecraft's fault-protection software (ironically enough) would have misread any date after August 11, 2013, he said, triggering an endless series of computer reboots aboard Deep Impact.
"NASA Declares End to Deep Impact Comet Mission", National Geographic

As always, anthropomorphized space probes pull at the heart strings:

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