Relativistic Universe, and fourth dimension...

[Guest]

Don't know if anyone was aware, but there was a course at last year's SIGGRAPH concerning visualising special relativistic geometry.

The course notes are online at http://cave.cs.nps.navy.mil/Courses/cd1 ... avc15.html

Very cool stuff, particularly the saturn flyby.

Andrew.

[Guest]

Great FAQ entry! It's always nice to see a new one appear...

Glad you liked it! It took some effort to write it.

By the way, I'm not actually an astronomer, just a programmer who used to be a grad student in particle physics.

Well, and I'm still a grad student (in astronomy)...

Don't know if anyone was aware, but there was a course at last year's SIGGRAPH concerning visualising special relativistic geometry.

Thanks for the reference, Andrew, I found it very interesting! Especially the included papers, which I've had difficulties to find (the online resources of the Cambridge Philosophical Society, e.g., extend only back to 1997). I didn't know this topic had been discussed in such detail. Excuse my ignorance, but I don't know what this SIGGRAPH is. I assume it is an annual conference of some sort? I had some problems with the web site.

Saturn looks cool indeed, but it seems the radiative effects were not included, only aberration? I would have expected some strong colour/intensity gradients at these velocities, like in the next set of colour plates.

This course focuses a lot on visualising relativistic effects by ray tracing. That works great for complicated scenes with extended geometrical objects, but I don't think that's the way to go in interstellar space where we have point like stars. Then it makes more sense to transform the incoming light directly. I also doubt ray tracing techniques are able to render scenes in real time (with, say, at least 25 fps), though I have to read the t-buffer article more carefully first.

Sometimes it's good to be ignorant. Had I known of this material, I would never had cared about introducing relativistic effects in a real time space simulator, I would've only had seen the difficulties.

I also found the article about visualising gravitational physics interesting, though it also focused on ray tracing. I have some ideas on how to do it directly (i.e. without ray tracing) if one limits oneself to (the astronomically important) Schwarzchild metrics and point sources (and an observer outside the photon sphere, although I'm not sure it's essential). Unfortunately, I don't have the time to work out the details for the moment.

Is any of the relativistic visualisation software/algorithms/methods described in the course material available as a commercial/free application? Is any of these capable of simulating relativistic effects in real time? A quick search on the internet didn't find them (but other interesting links, like Antony Searle's backlight).

/Alexis

[Vicware]

You know, I believe Celestia is meant to be viewable as if the user
was in a bubble visiting the galaxy. All this relativistic stuff is very
interesting, but I don't believe that's what Chris means the software
to be. I think.

Vic

[alexis]

To travel realistically, even in a bubble, you need to consider special relativity. But I know what you mean, you mean that Cris's only interested in simulating the universe in the limit of infinite light speed (i.e., the 'classical' picture). So be it, there are so many other interesting things to devote his (and our) attention to. But wouldn't it be cool to model a black hole accurately? There is another thread that discusses black holes with some enthusiasm. I think it's a cool idea anyhow, and I will give it a shot later this year when I find the time.

/Alexis

[Andrew]

Alexis,
Sorry, I should have provided a link. SIGGRAPH is an annual computer graphics conference, you can find info at http://www.siggraph.org.

I provided the link only because it was along the lines of the topic of discussion, as for actually implementing it? Well I'd have to take a closer look at the material myself, my interest is in computer graphics, I'm strictly a layman when it comes to relativity.

Ray tracing in real time? there's been some work done in this area, again theres some info at the siggraph site, http://cave.cs.nps.navy.mil/Courses/cd1 ... avc13.html
Also, a search of the acm digital library at http://portal.acm.org/dl.cfm?coll=porta ... EN=4153342 might turn something up. You'll need a subscription though, perhaps your university/college may have one.

Andrew.