This article was initially published in March 2008 at www.cgfocus.com as a two part series. We're re-publishing it with the kind permission of Timothy Albee. Thank you!
Back, in the early days of 3D, we tried to do everything "In Camera," which meant that what we got out of the 3D "camera's" renders was what we used as final. This made for a lengthy, iterative process of, tweak-render-repeat, especially in the days of wireframe previews and per-frame render-times easily in the hours or days.
In the mid-nineties, a trend developed to render in "Plates" for the different, Foreground, Midground and Background elements, putting them together in a compositor such as Digital Fusion or After Effects. This let us begin to tweak and adjust the individual elements before laying them all together onto a Background Plate. Rendering in Plates, meant that if you wanted that third space-ship from the right to be just a touch brighter, you adjusted its layer, (isolating the effect further with a soft-edged Polygonal Mask if you wanted to,) and got the results in seconds, as opposed to the minutes or hours it would take to re-render every frame of that entire Plate, (or of the entire shot with its cast-of-hundreds).
Using compositing packages to adjust in near-real-time, (on blazingly-fast 150Mhz machines,) instead of waiting hours for a single frame of a five-day-render, meant that more ideas could be tried-out in an afternoon. And the more ideas we could try quickly, the more daring we became with what we tried... and the better our images looked because of the freedom to explore.
Then, a trend developed for having the compositors work with the rendered images in the same manner as the 3D, working with separate passes for things like Specularity, Diffuse, Fill, Reflection, etc. This let us have even more control over the final image, massaging complex, previously prohibitively lengthy effects like "Blooms," Depth-Of-Field, and Motion Blur into being in a matter of moments when it would have taken days to settle on workable settings in the old, In-Camera way of doing things.
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