[DF教程] Creating Sci-Fi Arsenals with Digital Fusion 3.1

Creating Sci-Fi Arsenals with Digital Fusion 3.1
By Greg Morgan

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For a sci-fi project I was working on recently, I needed a way to create weapon blasts. I was given a rough idea of what the effect was supposed to look like -- a gaseous ball of plasma.

In the past, in movies like Star Wars, weapon blasts were hand rotoscoped frame by frame. On Star Trek: The Next Generation, they used a Quantel Paintbox for the phasers. Since this was a effects test for a project with a limited budget, spending several hundred thousand dollars for a Quantel Paintbox was out of the question. Initially I considered rendering an animation of the bolt in Newtek's Lightwave 3D or Illusion from Impulse Inc.and then compositing that element into the shot. However I wanted each bolt to be a little unique, and the idea of rendering a seperate element for each bolt was going to take to long. Ideally, I'd should be able to finish my composite and do the weapon effects in one application without having to switch back and forth.

About that time I saw the latest version of Digital Fusion by eyeon Software (www.eyeonline.com) demoed at Siggraph 2001 here in LA.

Digital Fusion is a fully integrated, non-linear compositing and special effects post-production system for the finishing, designing and effects creation used in feature films, HDTV, broadcast video, web-based and multimedia projects and more. Digital Fusion 3.1 expertly combines an incredible toolset with benchmark speed, bringing expensive high-end capabilities to the cost-effective desktop. DF has been used by Frantic Films in the opening sequence of the movie Swordfish, and by Digital Dominion for the movie Driven. It has also been used used in television by Digital Muse on such shows as Star Trek: Deep Space Nine and Star Trek: Voyager.
DF 3.1 is eyeon's 8th major release, marking a feature set of sophisticated tools and mature interface. Including an extremely robust particle system. This particle system is capable of simulating smoke, fire, water, etc. It has all of the behavior controls you'd expect in a particle system built into a 3D Application. But best of all, it's integrated directly into the main Fusion flow workspace. So I can tweak settings and instantly see how it looks in my final composite.

DF 3.1 also has a built in expression system, that while powerful is also easy for a non-programmer to use.

It should be noted that Digital Fusion is currently available only on Windows systems.

The test footage we shot was on NTSC SVHS, which of course means the footage was 29.97FPS with fields. However the project was going to be edited at 24FPS and the client wanted the final footage delivered as 24FPS. Fortunately, with DF I was able to down convert the footage in the same flow as the weapon tests. Again, the more I can stay in the same application, the happier I am.

Bring up the preferences screen (FILE -> PREFERENCES), select FRAME FORMAT.

On the drop down for "Default Format" Choose NTSC (D1).Click Copy, and give the new format a name like NTSC (D1) 24FPS. Change frame rate to 24FPS. Remove the check from "Has Fields?" Click Save

Something to keep in mind when setting the frame format is that the setting is global, it becomes the frame format setting for all flows you currently have loaded. Currently, there is no way in DF to have one flow in memory set for 24fps and another at 29.97. Hopefully this will be changed in a future release as its one of my only pet peeves with Digital Fusion

Add a loader to load the file sequence you are working with. Make sure it doesn't process fields by setting the process mode to "Full Frame"

Next I want to turn these interlaced frames into progressive frames. If I had set the Process Mode in my loader to NTSC fields it would have interpolated the frames automatically. In this case I wanted more control over how the frames were processed. Instead of blending the fields together, I wanted to get rid of the first field entirely.

To do that, add a Fields tool. Go to the tools menu, click Miscellaneous and then select fields. Change the Operation to Strip Field 1

As you can see, the fields tool stripped field 1 and left only field two in the image. The resulting image is half the height of the original.

The next step is to reduce the frames per second to 24FPS. In Adobe After Effects I would create a seperate composition with the footage in it and attach a Posterize Time filter set to 24 to lock the frame rate to 24FPS. Digital Fusion doesn't come with a filter that's an exact match for the Posterize Time plugin, but with expressions we can make it's Time Stretcher Plugin work just like Posterize Time. Time Stretcher works the same way as time remapping does in Adobe After Effects

Click on the tools menu, choose Miscellaneous then Time Stretcher.

This should add a Time Stretcher tool to your flow. Remove check from Inerpolate between frames.

The Source Frame value designates which frame in the original sequence to begin sampling from. To change the frame rate of the video we need to be able to figure out what frame in the original footage maps to the current frame in the flow.

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