Category Archives: Uncategorized

Most Popular Posts and Tags

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I have added a permanent page with a summary of the most popular posts on this blog. I also tried to add meaningful tags to all posts. Here are the most important tags:

Content type tags

  • download — a download is available is this post
  • gem — a code snippet or other copy-paste thing is available
  • math — posts that are heavy on math formulae

Topic tags

 

So, where are the stars?

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In my previous rant about dynamic exposure in Elite Dangerous (which honestly applies to any other space game made to date), I made a rough calculation to predict the brightness of stars as they should realistically appear in photos taken in outer space. My prediction was, that,

  • for an illumination of similar strength to that on earth,
  • if the sunlit parts are properly exposed,
  • and with an angular resolution of about 2 arc minutes per pixel,

then the pixel-value of a prominent star should be in the order of 1 to 3 (out of 255, in 8-bit sRGB encoding). Since then I was curious to find some real world validation for that fact, and it seems I have now found it.

ISS_and_Endeavour_EV+0

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\usepackage{cmbright}

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The ‘modern’ looking sans-serif font I use recently in \LaTeX equations on this blog is called ‘Computer Modern Bright‘, and actually is not so modern at all: Designed by Walter Schmidt in 1996, it is still to date the only free sans-serif font available for \LaTeX with full math support. Type-1 versions of this font are available in the cm-super package, but I didn’t need to install anything, because apparently, QuickLaTeX has them already. The only thing to do was adding just one line to the preamble:

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{cmbright}   % computer modern bright

I also turned on the SVG images feature that was added with version 3.8 of QuickLatex, so the equations are no longer pixellated on retina displays or when zooming in! Neat, huh?

Elite Dangerous: Impressions of Deep Space Rendering

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I am a backer of the upcoming Elite Dangerous game and have participated in their premium beta programme from the beginning, positively enjoying what was there at the early time. ‘Premium beta’ sounds like an oxymoron, paying a premium for an unfinished game, but it is nothing more than purchasing the same backer status as that from the Kickstarter campaign.

I came into contact with the original Elite during christmas in 1985. Compared with the progress I made back then in just two days, my recent performance in ED is lousy; I think my combat rating now would be ‘competent‘.

But this will not be a gameplay review, instead I’m going to share thoughts that were inspired while playing ED, mostly about graphics and shading, things like dynamic range, surface materials, phase curves, ‘real’ photometry, and so on; so … after I loaded the game and jumped through hyperspace for the first time (actually the second time), I was greeted by this screen filling disk of hot plasma:

ED001

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X-Plane announces Physically Based Rendering

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I always wondered when X-Plane would jump on the PBR bandwagon. I like X-Plane, I think its the best actively-developed (*) flight simulator out there, but I always felt that shading could be better. For instance, there is this unrealistic ‘Lambert-shaded’ world terrain texture, which becomes too dark at sunset; another is the dreaded ‘constant ambient color’ that plagues the shading of objects.

Now in this post on the X-Plane developer blog, Ben announces that Physically Based Rendering is a future development goal, yay! Then he goes on to say that, while surface shading will be a solved problem™ because of PBR, others like participating media (clouds, atmosphere) would still need magic tricks for the foreseeable future. Continue reading →

Journey into the Zone (Plates)

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I have experimented recently with zone plates, which are the 2-D equivalent of a chirp. Zone plates make for excellent test images to detect deficiencies in image processing algorithms or display and camera calibration. They have interesting properties: Each point on a zone plate corresponds to a unique instantaneous wave vector, and also like a gaussian a zone plate is its own Fourier transform. A quick image search (google, bing) turns up many results, but I found all of them more or less unusable, so I made my own.

Zone Plates Done Right

I made the following two 256×256 zone plates, which I am releasing into the public so they can be used by anyone freely. Continue reading →

Ego mecum conjungi …

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… Twitter!

Twitter_logo_blue

So out of a whim I just embarrassed myself and tried to write in (probably wrong) latin that I joined twitter. You can follow me under: @aries_code.

If you wonder how this came about, this was my train of thought:

  • Twitter has something to do with birds
  • Birds have fancy latin species names
  • The species name for Sparrow is Spasser domesticus
  • This doesn’t sound too fancy …
  • How do you say ‘I joined twitter’ in latin anyway?

But then I discovered that I am onto something: According to one argument, the brand name of Twitter should have been ‘Titiatio‘, had it existed in antiquity. And according to another argument, latin should be an ideal twitter language, because it is both short and expressive.

But I digress. If you are into computer graphics, then you know of Johann Heinrich Lambert, the eponym of our beloved Lambertian refelectance law. The book where he established this law, Photometria, is written entirely in latin—now this is hardcore!

So, now you know what to do if you want to stand out in your next SIGGRAPH paper …

Yes, sRGB is like µ-law encoding

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I vaguely remember someone making a comment in a discussion about sRGB, that ran along the lines of

So then, is sRGB like µ-law encoding?

This comment was not about the color space itself but about the specific pixel formats nowadays branded as ‘sRGB’. In this case, the answer should be yes. And while the technical details are not exactly the same, that analogy with the µ-law very much nails it.

When you think of sRGB pixel formats as nothing but a special encoding, it becomes clear that using such a format does not make you automatically “very picky of color reproduction”. This assumption was used by hardware vendors to rationalize the decision to limit the support of sRGB pixel formats to 8-bit precision, because people “would never want” to have sRGB support for anything less. Not true!Screen Shot 2014-03-06 at 19.02.54I’m going to make a case for this later. But first things first.

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Spellforce 2 Demons of the Past

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Spellforce 2 was released in 2006 and will be 8 years old by april. Nevertheless, the third add-on of the series shipped a month ago. Talk about a long seller!

Of course I’m attached to SF2 because I wrote many parts of its engine back then. This time I was briefly involved to help the developers include my attribute-less normal map algorithm. The original SF2 did not have any normal maps, and therefore none of the original art assets comes with tangent space information. This is an ideal scenario to pimp up the visuals without touching the geometry, simply by making a shader change and adding normal maps. Continue reading →