|Compositing a Realistic 3D Background
Submitted by: Ian Hubert
This is not a modeling tutorial. It is a compositing tutorial.
I'll tell a BIT about modeling, but not much. Cause that's not what this tut is
about. However, I will tell you a BIT about the modeling.
This background was made for an online miniseries, called, "Spacemen Belong in the Future, Probably", in which our only goal is to make
them good, but make them fast. This means that, whenever possible, I take
shortcuts. The biggest (and most blatant) is that I reuse pieces. In the below
image, I spent a few days modeling a hangar for a ship. This was the most time
intensive process. Even THEN I cheated, reusing pipes and beams. In fact, I
don't think there's a single piece in that room I didn't use at least 4 times,
excluding the overall room body itself.
Once finishing the Hangar, I duplicated it 7 times, giving me a
total of eight hangars. It's supposed to look like a "hole", of sorts, with the
walls being made up of hangars, however, I didn't have to make the ENTIRE hole,
since the point of view is from one of the hangars anyways, so you'd only see
the other hangars on the opposite wall. Meaning, besides what you see in the
image, there really isn't much there.
BUT! Even THEN I wouldn't have enough computer "umph" to render
out (or just have exist on the computer at once) 16 separate hangars. MEANING,
that I'd have to cheat again. I turned off everything but the in bay lights, and
rendered that out. It ended up looking like this:
Cute. Now, the top of the image is supposed to be open, and
you'll see the sky, but the cavern is supposed to look like it has some depth,
so I needed another two levels of hangars. To do this, I just moved all 8 of the
bays down, so that they'd line up with the bottom of where they previously used
to be. I rendered that out, and, using the "screen" option in photoshop,
combined them into one image.
So this is what those two images look like when put together,
made just of just the interior lights. You'll notice I went through the trouble
of changing small things in each bay, such as the amount the door is open, or
the angle or ships inside. I didn't go all out, cause that would have taken too
long. Heck yeah.
Now, this is all fine and good, but the scene is supposed to
take place during the day, meaning that just having interior lights isn't gonna
cut it. We need to see everything ELSE, too. To do this, I rendered out an
ambient occlusion layer, that is, an image in which the light is coming from all
directions, simulating ambient light (such as the sky, and light from the sky
reflecting off the ground). I made it so that the light from above is brighter
than below, cause hey, sky is generally brighter than ground. Because dirt
Though that would be cool.
Then I moved all 8 bays down again, and rendered THAT out, then
put them together, getting the below image.
NOW you can kinda see how this is supposed to look. And I dig
it. To put this image together with the interior lights, I just lined up the
"interior lights" layer with the ambient occlusion layer, and used the "screen"
option to add the brightness of the interior lights to the ambient occlusion
layer. The result is seen below.
The rest of the process is very similar to this, with adding
lights, then screening them on. Next we needed a sun. To create the appropriate
shadow, I created an object that would simulate the rest of the nonexistent
hangar cavern. Then I set up an area light (A nifty thing from which light is
emitted from a certain area, instead of an infinitely small point. For, as we
know, the sun is not infinitely small, and that's why your shadow appears more
blurry the further from the ground it is.
So this is the result (at, like, 1/8 scale or something).
Just the sun layer. I had to also render out the same thing after moving the
hangars down, but I'm not gonna show you that. cause it's boring.
AHH! Now THAT is lookin' nice! It has a good contrast to it. I
like it. I had to tweak around the brightness and contrast of the "sun" layer,
but it was well worth it.
Now THIS is where it gets fun. Have you ever seen how when
someone is holding a white piece of paper on a sunny day, the sun can reflect
off the paper and make their face really bright? Then when they move the paper
away it gets dark? Or how when a ray of light can shine onto a brightly colored
blanket or piece of paper, it can make a whole wall that color?
An awesome thing. Which we should duplicate. With all the
sunlight hitting the floor of the hangar bays, you'd think that SOME of it would
be reflected back up to the ceiling. To show this, I just set up a light beneath
the hangars, turned off shadows (cause otherwise it couldn't shine through he
floors, and shadows aren't that important for this anyway), and rendered it out.
Ahh! As you can see, the light is just illuminating the ceiling.
I erased by hand everything that should have been hit by the "reflected floor
light", such as light shining onto the ceilings of hangars in which no light is
hitting the floor. When added....
Oh! Now THAT is looking very much more realistic. Compare it to
the image above. Yeah. It looks good.
A few years back I took a bunch of digital pictures of a local
cement factory. This Hangar cavern thing is supposed to be in the middle of a
factory, so I decided I could easily use those image. It took some rotating and
resizing to make it look right (I had to flip the image to match sun angles),
but it worked.
Here's the finished "above ground" stuff, with a few more pieces
from the factory stuck in there. I made the ones furthest in the background
brighter, with less saturation, so it would look like they were blending in with
the background due to kinda a hazy air.
Now, here's something new that I've never done before: little
lights. I'll include lights in my scene when I render them, but as far as just
slapping lights onto an already made image... I've never done that.
To do it, I found an image I took of a local strip mall. I
increased the contrast, decreased the saturation, and was pleased. It ended up
just showing the brightest parts of the image (signs, bulletin boards, neon
sights, little lights). Using the clone tool, I copied, piece by piece, those
lights over to a new layer in the background.
This is what that layer looks like just on its own. Very nice.
Lots of little lights.
And THIS is what it looks like composited with everything else.
Ahh. I love it. Gives everything a feeling of realism, and random detail. I dig
And here's that same image with a little gradient wash on it.
Obviously, in the final movie, the image will use the correction for the scene,
but as a standalone image, I like it. I've always loved yellow blue color
So yeah! Hope this was at least a little help, even if just
with the basics.