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The basic approach in light illumination tracking is to put one or more trackers into the scene, then have the average intensity level calculated frame by frame and stored. This process is performed by the Set Illumination from Trackers script.
The calculated illumination data can be stored on a light, so it can illuminate all the objects in a downstream scene; on a mesh, so the mesh's color can directly match the measured color; or on the tracker itself, which is most useful as a way to transfer a number of measured colors to downstream applications.
Trackers can be placed anywhere in the scene, but a flat white wall is a good choice and corresponds to typical white-balancing techniques. If a substantially-colored location is desired, you can have a monochrome light intensity calculated. Since a flat wall provides nothing to track, you can use offset tracking, or alternatively if there is a mesh there, use Drop on Mesh to put a 3D seed point there, and that point can be used to determine the location to be examined. The tracker's size is the area measured (and can be animated).
If you are calculating color for a mesh, you should put the tracker(s) on a relatively flat area of the mesh. SynthEyes can calculate the average interior color of a planar tracker as affected by in-plane masks, so to get fine control over the measured area, you can track a larger planar tracker, then before running the script, add a specific in-plane mask for that area. (Lock the tracker and don't retrack without deleting that mask.)
The selected trackers are averaged to create the illumination track. When the 2D tracker location is examined, the tracker can be used only when it has a valid 2D location. When the 3D location is used, the 3D location can be used throughout the shot (except when it goes offscreen), which might be undesirable if the tracker location is occluded by something else. Accordingly a "3D masked by enable" option allows the tracker's Enable track to control whether or not the tracker's position is examined, even
if the tracker has not been tracked because its 3D location is being used to determine where to analyze the lighting.
Note that while trackers do not have to last for the duration of the shot, there will be consistency issues when trackers appear or disappear. If there aren't any usable trackers on a given frame, no illumination key will be generated on that frame.
The script provides a variety of options to offset and re-scale the data, to remove black levels and to be able to increase the illumination level contrast.
You can control whether illumination keys are generated for the entire shot, the playback range, or a single frame, and can have keys generated on every frame, every other frame, every fifth frame, etc, depending on how rapidly the light levels change.
You can use the graph editor or the color swatch on the 3-D or lighting panels to edit the generated animated illumination level curves, including to change from linear to spline interpolation. Note that there is a separate static color for a light, mesh, or tracker that is shown on swatches elsewhere in SynthEyes, such as the graph editor and hierarchy view.
Once the illumination curve has been created, it can be exported via selected exports, most notably USD or Filmbox (FBX), which are generally the most capable and modern exporters, or Export/Illumination as text to obtain a plain text file.
©2024 Boris FX, Inc. — UNOFFICIAL — Converted from original PDF.