I found the reason for why sometimes all Latex in my posts got clobbered. The culprit was an outdated plugin, which—as a side effect—deleted backslashes from posts. So I deinstalled the sinner and also repaired all math that I found was broken. If you still find broken math, drop me a line.
This post is the first in a series to follow-up on my 2012 GPU Pro 3 article about atmospheric scattering [11]. What I showed there was a full single-scattering solution for a planetary atmosphere running in a pixel shader, dynamic and in real time, without pre-computation or simplifying assumptions. The key to this achievement was a novel and efficient way to evaluate the Chapman function [2], hence the title. In the time since then I have improved on the algorithm and extended it to include aspects of multiple scattering. The latter causes horizontal diffusion (twilight situations) and vertical diffusion (deep atmospheres), and neither can be ignored for a general atmosphere renderer in a space game, for example.
I have written a Shadertoy that reflects the current state of affairs. It’s a mini flight simulator that also features clouds, and other rendering goodies. A WebGL2 capable browser is needed to run it. Under Windows, the ANGLE/Direct3D translator may take a long time to compile it (up to a minute is nothing unusual, but it runs fast afterwards). When successfully compiled it should look like this:
Continue reading
I just waded though a lot of recent comment spam and approved the legit ones along the way. So if you posted something recently it may now appear.
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:
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,
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.
The ‘modern’ looking sans-serif font I use recently in 
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 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?
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:
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
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.
I made the following two 256×256 zone plates, which I am releasing into the public so they can be used by anyone freely.
Cosine zone plate
Sine zone plate
This page is my personal collection of highlights from GDC 2014. I was not able to attend in person, so I had to rely on Twitter to get updated. The immersion was not perfect, but some of the thrill was definitely carried over. So here it goes (in release order): Continue reading