Anatomy of a Visual Effect

See how a still image becomes a moving one!

Occasionally I see stuff posted by folks I’m connected with online that inspires me to experiment on the visual effects front. Here’s a photo taken by author, Den Patrick, of a view across London looking towards BT tower.

If you don’t want to bother with the explanation of how it was done, skip to the bottom of the page to watch the finished movie. Best seen in full-screen with HD on.

It’s a nice shot… the sun has nearly hit the horizon; there are some lovely brooding clouds and the city stretches into the distance with the iconic tower dead-centre. It looked to me as if the sky is threatening snow and because I’d been playing with particles in After Effects recently, I could see this would be the perfect image to try out a few things on. So yeah, I wanted to add some falling snow and I thought it would also look cool if I made it appear the photo was actually moving, as if recorded on a mobile phone or video camera.

Right, a plan. Let’s do it!

But wait. Before I could jump in to the exciting stuff, the original image above needed a small amount of tidying up. If you look at the top section, there’s a sloping area that looks like it might be a window reflection or similar.

Because I knew I wanted the final shot to appear as if the person holding the video camera is standing outside on the balcony, I needed to remove anything that might tell the viewer’s eye and brain otherwise.

I used the good ol’ Clone tool in Photoshop, to do this. Sure, I could have used the newer Context Aware Fill but it hasn’t, to date, yielded very good results for me. And the amount of time it would have taken getting it to work properly was time better spent elsewhere.

Stage Summary: Re-touched the image to clean up any irregularities

Using the same tool/technique, I also removed some steam/smoke from a chimney/vent in the centre section. Again, because that smoke wouldn’t be moving in the final shot/animation, it was better to get rid of it. I wasn’t overly careful with the cloning here because it’s quite a noisy image (to be made noisier by the added falling snow) so I was able to get away with a fair amount of inaccuracy.

Similarly, there are people (GASP, what are they doing there?) on the streets…

However, in this instance, I opted to grade the image instead by intensifying the colours somewhat and increasing the contrast to make it darker and punchier. Not only did this mean those people were less visible (and once the snow was falling, you definitely wouldn’t see them) but it also resulted in suitably moodier image.

At this point we were ready for After Effects. For those who don’t know, After Effects is a compositing and effects tool. It’s like Photoshop, but for movies and animations. For those of you who don’t know what Photoshop is… er, where have you been? 🙂

Stage Summary: Add particles, to resemble falling snow in the foreground.

Once the background image of the city was imported, the next step was to add a layer of particles using a plug-in called Particular (see what they did there?) and modify the parameters to simulate falling snow. Briefly, this was a box emitter set to a large size in XYZ dimensions producing a high number of spherical particles with a nice feathered edge. I used the Physics tab within Particular to control gravity and wind/turbulence, creating small gusts and so on. I matched the colours of the background image and I also added some motion blur. This stage involved a fair bit of going back and forward, creating test renders and then adjusting the settings, in order to obtain as believable a result as possible.

Because the snow particles can be hard to see, the movies on this page are best viewed at full-screen… and preferably with HD on.

Stage Summary: Add particles, to resemble falling snow in the background.

So it was looking good but it could have been better. One of the tricks I used to make it seem like snow was falling ‘in’ the shot, as opposed to merely over the top of it, was to add two layers of particles; one in the foreground and one in the background. For the background snow, this meant masking out the foreground balcony railings. It’s not possible to mask a particle layer however so I had to pre-compose the background snow together with the background image layer first. Pre-composing is like flattening layers in Photoshop; you lose the individual layers’ controls. To that end, I had to ensure everything was set as I wanted it, because once pre-composed I wouldn’t be able to make adjustments to any particle parameters at a later date unless I undid everything.

As you can see, the snow falls behind the balcony railings. It’s a simple but very effective trick that gives the image depth. Also, that background snow adds some much needed moving ‘noise’, helping to disguise the fact it’s a static pic. Interestingly (and, let me be honest, annoyingly), once pre-composed, the snow was falling considerably faster than it was before pre-composing. I’m not sure why… it’s probably a glitch with Particular because it doesn’t seem to affect other pre-compositions using other plug-ins/settings. Whatever, it meant I had to undo the last stage and fiddle some more with the settings, factoring in the speed the falling snow would attain once pre-composed. Some more tests later and I had it sorted.

Stage Summary: Add melted snow droplets on camera lens.

With both foreground and background snow layers in place and behaving as they should, it was time for some additional touches, in order to up the ante and make the shot seem even more genuine. I thought it would be nice to see a few water droplets (melted snow) hitting the ‘lens’ of the camera so for this I turned to an effect called Mr. Mercury (I’m not making this up) which allows for liquid blobs to be created on an image layer, thus simulating rain etc. I’d previously duplicated the background image a couple of times for the purpose and added the Mr. Mercury effect to each one.

One layer of droplets sprinkles the lens for the duration of the movie, while the other (larger droplets) hit in a more random fashion. With some fast blur added (to simulate being out of focus), they look really great.

For the uninitiated, all effects, transforms, timing and so on are denoted on a timeline with keyframes. This allows for the full control of each layer, whether it be particles or an image… or just about anything. For example, I position the larger droplets where I want and then at a certain point in the movie when I want them to appear, I ‘keyframe’ the parameters for appearance and size and duration and a whole host of other settings. I do this for all layers within the entire composition.

Stage Summary: Add motion to resemble hand-held cam effect.

With the snow and water droplets in place, it was really looking rather cool. In fact, I could have left it there, as a kind of arty animated GIF-style thing. But I wanted to see how far I could push this so the next step was to think about adding some camera motion.

Before I could proceed, I needed to render out all the relevant layers (background image and snow). I could have pre-composed instead of rendering but I didn’t want to suffer the speed change issue with the remaining Particular layer of foreground snow… and it wasn’t necessary in any case. I also left the water/snow droplets as separate layers because they were supposed to be on the camera lens, so would move with it.

As explained above, I could have manually inserted keyframes, adjusting the position of the background image/movie to simulate a hand-held cam. Experience told me however, this would have required a lot of tweaking to get it to feel just right. Instead I opted to use the Motion Tracker within After Effects. I shot a separate piece of footage on my phone of our conservatory door and then imported it into the After Effects composition. I created a tracking point in the footage (the window frames on the door make good reference points) and let Motion Tracker do all the hard work.

Once Motion Tracker had analysed the footage, it created a bunch of keyframes that I could then copy over to the rendered background movie of the city and snow and – hey presto! – have it match the movement. The result is very natural because, well, it is natural.

Stage Summary: Add exposure/focus and mist/haze.

Nearly there! At this point I had the rendered city and snow movie, which looked like a piece of hand-held footage… and the water droplets which looked as if they were hitting the camera lens. For some final visual touches, I added an exposure and focus adjustment at the beginning, using Levels and Blur respectively. This gives it the feel of a camera being switched on and pointed at the scene. Also, bearing in mind lots of snow falling in the distance would appear like a haze or mist, slightly obfuscating objects further out, I used a fractal noise layer with reduced opacity to suggest this.

Stage Summary: Add sound effects.

To really sell the shot though, I was going to need some sound effects.

Although I use PCs for graphic/animation and compositing work, for audio I use Logic Studio on a Mac. Logic is a music production suite which allows for the recording, editing and mixing of music and sounds. To be honest, if Logic were available on a PC (it used to be!) I’d probably not use a Mac at all. I’ve used Macs since way before most people had even heard of them (they were the only machines to run Photoshop and Quark back in the mid-90s) so, please, no comments about platform of choice. In my opinion, they both suck…


Using a low resolution version of the entire movie as a guide (hi-res wasn’t needed for this bit of the process), I added background city noise (Logic has some wonderful built-in effects/ambient noise loops) and some wind. I then recorded some random clicks and creaks, simulating a camera casing being handled (this was me using my mouse) and some extra gusts of wind (me blowing gently over my mobile phone mouthpiece). When all of these sounds were mixed appropriately, it sounded as if someone was standing outside on the balcony holding their video camera.

And that’s it, from a still image to a final composition with visual/sound effects! It’s very short… blink and you’ll miss it, but I wanted to keep the final file size down to a manageable level for uploading. It’s not perfect… for added realism I’d ordinarily want to see some parallax, that is, the balcony railings would move at a different speed to the objects in the distance. There are also some light splashes/artefacts that should move with the lens, not the background. And, of course, the snow hasn’t settled… but y’know, it’s only just started to fall and it’s that wet stuff that never does! Despite this, it’s a good demonstration, I think, of what can be achieved.

Finished Movie

I’ve only briefly provided an insight into the processes above… please feel free to ask questions if you want anything explained in more detail!

Thanks for reading.

One Comment

  1. Bennycrime December 3, 2012 Reply

    Excellent breakdown, you could have totally added that smoke back in with particular too, and made it green, and a squadron of badgers. 😉 GODZILLLLLLLA

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