AutoDomain

Domain of Definition (DoD) is the rectangular region in which Fusion considers useful image pixels to exist. It is not the same thing as frame dimensions: a 1920x1080 image can have a much smaller active data window around one object.

AutoDomain builds that rectangle automatically by comparing incoming pixels against the background Canvas color. Pixels that differ from the Canvas color define the useful region, and the result becomes metadata/data-window information for downstream processing.

The node does not physically crop the image and does not change resolution. The Viewer can look identical before and after AutoDomain even though downstream tools receive a different DoD and may process fewer pixels.

Blackmagic explicitly describes the DoD as a way to limit image-processing calculations and improve render efficiency. The potential gain is greatest when a small element occupies only part of a large frame, not on ordinary full-frame footage where nearly every pixel contains data.

AutoDomain recalculates the DoD on every frame. A moving CG element, transparent character render, or animated graphic can therefore receive a data window that follows the content without manually animating a fixed rectangle.

Some EXR files already carry optimized data windows. In that case AutoDomain may add little value or duplicate correct upstream metadata, so inspect the source before adding another DoD calculation stage.

Canvas color is fundamental. Fusion documentation describes black as the default Canvas color unless Set Canvas Color changes it. Premultiplied RGBA with transparent black outside the object is therefore a common reliable case; opaque solid-background imagery may require a deliberate Canvas color that matches the actual background.

Left, Bottom, Right and Top are not artistic crop handles and are not post-detection blur margins. The reference describes them as boundaries of the area inside which AutoDomain searches for useful pixels.

Increasing Left excludes more of the left margin from the search, Bottom excludes more from the bottom, while Right and Top define the opposite limits. A bad search rectangle can remove real content before the automatic DoD calculation has a chance to see it.

The captured Inspector screenshot documents one concrete UI state, not a universal production preset. Treat the directional search-bound behavior and the result on your target build as authoritative rather than copying numeric values blindly.

A blue Effect Mask input is physically listed for AutoDomain in the Fusion documentation. It is a separate coverage plane and must not be confused with Canvas color or the alpha inside the image; because AutoDomain is a metadata-oriented utility, verify mask behavior in the target build before relying on it for a critical production boundary.

AutoDomain and SetDomain solve different problems. Use AutoDomain when bounds should be derived from content and can change frame by frame; use SetDomain when an exact fixed or explicitly authored rectangle is required regardless of pixel content.

AutoDomain is not a universal optimization switch. On full-frame sources its DoD may remain the whole image, so the extra node does not meaningfully reduce processing. Target sparse, transparent, or oversized branches first.

Always inspect downstream Blur, Glow, Shadow, Transform and similar tools after changing DoD. Those tools may create pixels beyond the source object, and an over-restricted upstream search region can remove source data before later expansion occurs.

The production check is temporal as well as spatial. Fast motion, motion blur, particles and soft edges can extend beyond the obvious object on individual frames, so over-tight search bounds may appear as popping or clipping during playback.