FXWARS! Tribute: Race To The Future

Alright, it's been about 5 years since I've participated in a FXWARS! challenge, and I just had to be a part of this one. I'm doing the Race to the Future/Clock Tower in "Back To The Future". My home town square is strikingly similar to the Hill Valley Clock Tower and Square, so I figured I'd use that for background plates to place my CG DeLorean.

This weekend I went out and shot some background plates to run a test to see if I could use our courthouse "clock tower" as a stand in. After the effects test was done, I decided to go ahead and make a little teaser out of it. You can view it below. Please view in HD. Thanks.

VFX Tip #3 - Compositing Fog or Mist

Compositing fog elements seems like a pretty straightforward thing to do in After Effects. Shoot or render your fog element against black, and then Add or Screen it on top of your footage, right? Wrong. This method is incorrect. Let's go over why.

The Add transfer mode should only be used when compositing light passes, or something that is made up of light, such as fire, lasers, or lens flares. However, fog, as we know, is not made up of light, but rather tiny particles of moisture suspended in the air. They may reflect, refract, and diffuse light, but they do not emit it. Therefore, we must not composite fog elements with Add or Screen because it is an incorrect representation of real life. This holds true of smoke elements as well.

On a simple compositing level, fog elements should occlude their background plate, not Add to it. The following is a technique I use for compositing fog elements into background plates using After Effects. This method can apply to other compositing programs as well, so if you use Shake, Combustion, Nuke, Fusion, or other such program, please continue to read on.

First, let's look at our original background plate...

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As you can see, this image provides a good reference for a starting point to add more fog. Notice how the fog completely obsures the top of the bridge tower. The fog is not see through as an Add operation would be. Now, let's take a look at our fog element...

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I purchased this fog element from http://www.detfilmshd.com/, which is a great resource for low cost elements that composite nicely into VFX shots. I highly recommend them. If you do not have a filmed element of fog, Fractal Noise or Turbulent Noise can be used as a decent substitute.

Now, we can't just put this element over the background plate using Add, because we get this result...

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That doesn't look very natural when we compare it with our original plate. It's blowing out the bridge details and the sky, because it seems to be adding light. This is not what we are going for. Remember, we want occlusion, not addition.

A better alternative, is to create a new soild layer, and use the color eyedropper tool to select an appropriate gray color to use for our fog. I generally try to use a color near the horizon.

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Now all we have to do, is use the fog footage's luminance as a mask on the new gray solid we just created. To do this, simply layer the fog element footage over the solid, and set the solid's track matte to "Luma Matte." That's all their is to it. Your composite will now look much more natural.

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Finally, we can add one more last touch to this composite. Select your background plate layer (in this case, the bridge) and add a Compound Blur. This will look strange at first, so we need to make a couple of adjustments. Set to Blur layer in the Compound Blur controls menu to be the fog footage element. This will use the fog element's luminance as a mask for blurring the background plate. This simulates the way fog in the real world diffracts light behind it. The blur by default, though, will be 20, which is too high for fog, so set it to be around 0.5-1.0.

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A little extra work than using transfer modes to be sure, but it will greatly help the realism of your shots. And here is our finished composite...

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Essential Reading For Every Visual Effects Artist

I have been meaning to write a new VFX tip for weeks now, but I haven't gotten around to it yet. Life's been busy...or I've been lazy, I don't know which. Perhaps a little of both, skewing toward lazy.

However, while this is not a VFX tip or tutorial of my own, I hope it is helpful nonetheless. I learned CG by spending hours at the local Barnes and Noble reading books on graphics and visual effects. Today, there is a wealth of knowledge and reference out there regarding these subjects. Here is a list of three books, that are at the top of my list of essential reading for visual effects artists.

1. Adobe After Effects CS3 Professional Studio Techniques by Mark Christiansen

This is my favorite book of all time. Never before I have seen so much information about visual effects crammed into one book. None of the material is wasteful, and it includes great tips on compositing, along with explainations on why photographed elements look the way they do. While this book is specifically for Adobe After Effects, the information can be used across almost any compositing package, as it also includes general theory along with detailed examples of how to perform the effects in After Effects. Pick this book up.

2.Digital Lighting and Rendering (2nd Edition) by Jeremy Birn

I know I said number one was my favorite book of all time, but I think this book has to be tied. It's fantastic, but in a different way. While AE Studio Techniques covers a wide array of compositing techniques, this book covers 3D lighting, texturing, and compositing. The first edition of this book almost single handedly taught me how to light CG shots. When I was a visual effects noob way back in 2000-2001, I spent many weekends at my local Barnes & Noble reading that book. The second edition is the latest one, and it covers everything from old school techniques, to the newest of lighting and compositing. This is the best book on CG lighting that has ever been written, period.

3. The DV Rebel's Guide: An All-Digital Approach to Making Killer Action Movies on the Cheap by Stu Maschwitz

I included this book in the list because not only is it clever, informative, and well written, it's just plain fun. This book excited me the first time I thumbed through it. Stu explains ways to get big budget looks on a not so big budget. He covers almost all aspects of filmmaking from your first script idea all the way to the finished product. There is a chapter on effects, which even covers miniatures, along with digital effects. The information in this book is fantastic. Pick it up, and be on your way to shooting a low budget action flick.

VFX Tip #2 - Lightwrap: Less is More

Light wrapping is a useful technique for making a blue/greenscreen subject or CG object really set in the background it is being composited into. It creates the illusion of the light from the background plate appear to bleed over the foreground, which helps the element blend naturally with its background.

However, this technique should be used subtly. A common mistake I see often in composites is using too much lightwrap. If you just leave the lightwrap effects at 100% opacity, most of the time, it will be too much. In fact, I try not to go above about 50% opacity. Look at the example below to see what I mean.

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Clearly, the default 100% is far too much lightwrap, which looks unnatural, and gives away the composite. However, on the right, the lightwrap is only at 25% and feels far more natural.

VFX Tip #1 - Hunk Of Burning Love

No, I'm not the hunk of burning love. However, you may love me after this easy tip. In addition, you'll most certainly love the power of blending fire elements using 1.0 gamma.

This is the first of what I hope to be a continued series of visual effects tips. Sometimes they will be quick tips, and sometimes a bit more involved.

For my first tip, I thought I would share the benefits of compositing using a gamma blending of 1.0 in Adobe After Effects. Without going into a detailed explanation, blending with a gamma of 1.0 allows a more natural looking blend of light inside of a composite. This is especially true of elements shot against black such as fire or explosions.

In After Effects, you can enable 1.0 gamma blending by going to File>Project Settings and put a check mark next to "Blend Colors Using 1.0 Gamma." Below is an image example. All settings are identical, except for the gamma blending change. Both fire elements are composited using the "Add" transfer mode.

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Notice how the fire on the left is quite blown out, and has lost much of it's orange color, which was in the original plate. After enabling blending, you can see on the right that it sets in the in the image much nicer, and looks far more natural. Well, as natural as burning stone can look, anyway. There is also a noticeable difference in the cast lighting that I faked on the ground under the fire.

Also keep in mind, that this can also be useful for energy effects, such as sparks, lightning, lasers, or even lightsaber blades.

I hope this little tip was helpful. Stay tuned for more.