So I was digging though the BSG CGI archives and ran across some early renders that used a process called radiosity. In most cases, renders like this are only used for tests and are never seen by the general public but I’ve always thought they looked pretty nifty so I thought I’d share a few. After all, it’s Christmas and I can’t think of anything Galactica fans would like more than never-before-seen pictures of the Galactica! Click ahead for more images and an explanation of what this wacky radio-city-thingamajig is all about…
In the wild and wooly world of 3D animation, radiosity is essentially bounce lighting; in the real world, it’s a simple fact of life – light naturally bounces off whatever surface it hits and scatters to its neighbors (walk into your bathroom and shine a flashlight against the wall. Light doesn’t just stick to that one wall, it bounces all over the place and lights up the room – that’s radiosity). In 3D animation, however, there is no such natural luxury – if you build a CGI bathroom and shine a light against the virtual wall, it willstick to only that surface… unless you click the radiosity button! Then you can bounce your light all over the place, as shown in these simple examples of before and after turning on the radiosity feature:
The render on the left shows a normal spotlight aimed at a corner of the room. It hits the top of the box and a few walls, but since radiosity is off, that’s where the life of the light ends. On the right, we see what happens when radiosity is turned on – light reflects off the walls and the box and now surfaces that were not in the direct path of the spotlight have also been lit up! Note the corner of the room, where the two lit walls bounce light onto each other, causing the crease between the walls to get so much light it’s now overexposed – just as it would be in real life.
So, naturally, now you’re wondering why anyone would ever bother to turn off radiosity – it looks so much more realistic! Yes, it does, but that sort of realism comes at a cost. That simple render on the left only took two seconds for the computer to draw. But the one on the right took almost thirty seconds. Calculating all that bounce light takes time! Now, thirty seconds may not seem like a lot of time to create a frame of your favorite TV show, and if it were only thirty seconds we were talking about here, sure, every frame of Battlestar Galactica would be rendered that way. But the scene up above is only 12 polygons (two six-sided cubes). The model of the Galactica is nearly two million. One frame of that ship with all the bells and whistles of radiosity would take many, many hours per frame (it has been used, but it’s generally on a case-by-case basis, depending on how noticeable the artist thinks the effect would be).
BG TO THE RESCUE
However, there is another aspect of radiosity that is used more frequently, and that is called backdrop radiosity. This is a form of radiosity that forgoes all that directional bouncing in favor of a method that simply fires light evenly from an omnidirectional source (generally a backdrop color or image, hence the name backdrop radiosity). Basically, what it means is if you simply make a blue backdrop for your scene and turn it on, it will cast a very smooth, even light on your object. This ends up looking very much like sunlight on a cloudy day, where you have no distinct, hard shadows and no obvious light direction. So, what use is that? Well, one thing it’s useful for is mimicking the soft lighting in a photo studio, typically used for “product shots” where you want something lit very evenly and very tastefully, with no harsh shadows to get in the way of what you’re trying to sell. Car commercials like to use this, but it’s also very handy when you want to get a good look at your 3D model with real-world lighting from all sides. Kind of like this:
This is a test render of the unfinished “Flattop” model (one of the ships of the Rag Tag Fleet) from 2003, created during production of the original BSG miniseries. The backdrop radiosity (in this case, a backdrop of all-white) lights the model very smoothly and evenly, but still shades nooks and corners realistically (note how the top part of the engine under the main hull is darker, since the light coming from above can’t reach it). It almost looks like a real, unpainted plastic model! This is why model makers love doing these backdrop radiosity renders – it’s an easy way to show off every last detail of your hard work and make your model look very realistic (it’s also a great way to look at your work-in-progress to spot geometry errors or just figure out what to do next). Here’s another shot of some close-up detail on the Flattop model:
Traditionally, these images are rarely seen outside of the visual effects studios because, really, who wants to see a boring old test render? Well, if you’re a big nerd like me who loves to see all the details on your favorite spaceship, renderings like the one below really make your pulse race:
Notice how you can clearly see every last bit of detail in the model? That’s partly due to the fact that that the standard “realistic” lighting isn’t used here, which traditionally casts large portions of the ship in shadow. Another big difference is that you are seeing the model here -for the first time- with no texture maps. This is the geometry-only, folks. Essentially, the “paint job” that adds color, decals, burn marks and finer detail has yet to be added.
As you can see, even without final textures, the Galactica (built by VFX veteran Lee Stringer) is a very detailed model. Very often, fine details are “faked” by simply drawing them on with the texture maps, but modeled (or “built-in”) detail work always looks better. Since the Galactica was clearly one of the most important models in the series, the time was taken to hardwire a fine level of detail into the model itself (uber fans of the original BSG may notice some of the fine details are exactly duplicated from the original 1978 Galactica miniature). Here are a few close-up shots, with the flightpod out and retracted:
These images (which you can click to make bigger) would help not only the model makers see how their work was progressing, but are often shown to producers and studio heads to get final approval of the basic design before the painstaking work of adding the final paint job is finished. Also, to let you in on a little secret, most often these renders are done so the model maker can bask in the glory of how awesome his work looks fully rendered :-) [Don’t deny it, Lee!]
On the left, we see the launch tube as pure geometry and with backdrop radiosity providing the only illumination. On the right, we’ve added a few texture maps and some of the launch tube lighting:
The Gemini Freighter:
And, last but not least, here is an early radiosity render of everyone’s favorite mechanical bad-guy:
Ok, class, that about wraps it up for this behind-the-scenes look at the world of 3D visual effects. Since this is the first time anyone has seen these radiosity renders, I’m very curious what people think of them, so please leave comments with your opinions! Are they ho-hum boring or are you bouncing off the walls, ready to see more? Heh heh, bouncing off walls, radiosity, get it?
Oh, and remember, Battlestar Galactica returns to Sci-Fi channel on January 16th at 10pm, so be sure to tune in. Like I even have to tell you.