VFX Glossary: Roto, Paint, Keying and Compositing Terms

This glossary covers the vocabulary of 2D VFX work — rotoscoping, paint and cleanup, keying, matchmove and compositing — along with the file formats and production terms that come up when shots move between a production and a vendor. Definitions follow common industry usage; individual facilities sometimes use a term slightly differently, so confirm anything critical in your brief.

A

ACES

The Academy Color Encoding System: an open colour management framework from the Academy of Motion Picture Arts and Sciences. It defines standard colour spaces (such as ACES2065-1 for archiving and ACEScg for CG and compositing work) and transforms between camera, working and display spaces, so footage from different cameras can be handled consistently across facilities.

Alpha channel

A fourth channel stored alongside red, green and blue that records how opaque each pixel is: white (1) is fully opaque, black (0) is fully transparent and grey values are partially transparent. Mattes from rotoscoping and keying are usually delivered in, or converted to, an alpha channel.

B

Beauty work

Cosmetic paint work on performers: removing blemishes, tattoos, stray hairs, sweat or visible make-up lines, and sometimes subtle skin smoothing. It has to track with the face and keep natural skin texture and grain, or the result looks artificial. See beauty cleanup services.

Burn-ins

Text rendered permanently into review media, typically the shot ID, version number, frame number, timecode and date. Burn-ins make review notes unambiguous, but they are added only to review files, never to final deliverables.

C

Camera solve (solve)

The result of 3D camera tracking: a virtual camera whose position, rotation and lens match the real camera for every frame, plus a sparse cloud of 3D points representing the scene. A good solve lets CG and set extensions sit in the plate without sliding. See matchmove.

CG element

Any computer-generated image rendered for a shot — a creature, vehicle, environment, particle effect or digital double — often supplied as separate render passes (diffuse, specular, shadow and so on) for the compositor to combine.

Chroma key

A keying method that builds a matte from a specific hue, usually the green or blue of a screen behind the subject. Modern chroma keyers compare colour channels rather than picking a single colour, which helps preserve hair, motion blur and semi-transparent edges. See chroma keying services.

Clean plate

A version of a shot’s background with the unwanted element removed — a performer, a rig, a wire or a crew member. It can be shot on set as a separate pass, or built in paint by borrowing pixels from other frames, other areas of the frame or projected stills. Clean plates are used to fill areas revealed by removals.

Colour space

A defined set of primaries, white point and transfer function that tells software what an image’s numbers mean. Plates arrive in a camera colour space (for example a log encoding), are often converted to a linear working space for compositing, and are delivered back in an agreed space. Mismatched colour spaces are a common cause of shots that “don’t match” on return.

Compositing

Combining several image elements — the live-action plate, CG renders, mattes, matte paintings and effects — into one final image, matching light, colour, grain, defocus and motion blur so the result reads as a single photographed frame. See compositing services.

Core matte

A solid, conservative matte for the inside of a subject, kept slightly inside the true edge. It is combined with a softer edge matte so the interior is fully opaque while the edge keeps its detail.

D

De-grain and re-grain

Removing film grain or sensor noise from a plate before work (de-grain), then adding matching grain back over the finished result (re-grain). Painting or keying on a de-grained plate gives cleaner results; re-graining makes the repaired area match the rest of the frame.

Deliverables

The agreed outputs for a shot or project: the files themselves (for example EXR mattes, finished comps or clean plates), their format, resolution, bit depth, colour space, naming convention, frame range and delivery method. Agreeing deliverables before work starts prevents re-renders later.

Despill

The process or tool that removes spill — the green or blue colour contamination on a subject from a screen — by suppressing the excess channel and, where needed, replacing it with a colour that suits the new background.

Difference matte

A matte generated by comparing a plate with a clean plate of the same framing: anything that differs between the two (the subject) becomes the foreground. It works best with locked-off cameras and stable lighting, and is usually a starting point rather than a finished matte.

DPX

Digital Picture Exchange: an image-sequence format, one file per frame, long used for scanned film and digital intermediate work. DPX files usually carry 10-bit log-encoded image data and include header fields for timecode and other metadata.

E

Edge matte

A matte that isolates only the soft boundary of a subject — hair, motion-blurred limbs, fabric fringes — so that edge detail can be treated separately from the solid interior. It is typically paired with a core matte.

EXR (OpenEXR)

An open image format developed by Industrial Light & Magic and widely used in VFX. It stores high-dynamic-range data in 16-bit half float or 32-bit float, supports lossless compression and can hold many named channels in one file — for example several mattes, or all of a CG render’s passes.

F

Feathering

Softening the edge of a roto shape so it fades from opaque to transparent over a set distance. Spline tools allow feather to vary along the shape, so a sharp shoulder and a blurred hand can be handled in the same matte.

Frame range

The first and last frame numbers of a shot as delivered, usually including handles. Quoting, scheduling and delivery all depend on agreed frame ranges, so they belong in every brief.

Frame rate

The number of frames per second at which footage is captured or played back — commonly 23.976, 24, 25, 29.97 or higher for slow motion. Work is done frame by frame at the plate’s native rate, and review files must use the same rate so notes line up.

G

Garbage matte

A rough, loose shape drawn to exclude areas that a key or comp should ignore, such as lighting stands, the edge of the screen or crew outside the subject area. It doesn’t need to follow the subject closely; it simply keeps unwanted pixels out of the result.

Grain

The fine random texture in film images, and the equivalent sensor noise in digital footage. Grain differs by channel and by brightness level, and any added or repainted area must carry matching grain or it will look flat against the rest of the plate.

H

Handles

Extra frames delivered before and after the cut length of a shot, often 8 to 12 frames at each end, so the editor can adjust the cut without the shot running out of finished frames. Handles count towards the work, so they should be stated in the brief.

HDRI and lighting reference

Reference captured on set to help match CG lighting to the plate. An HDRI is a high-dynamic-range panoramic image of the set, made by merging bracketed exposures, which can light CG elements directly. Lighting reference also includes grey and chrome balls and colour charts shot in the same light as the action.

Holdout matte

A matte used to cut a hole in an element so that something in front of it stays visible — for example, holding out a CG creature where an actor’s arm passes in front. Roto of foreground objects is often delivered specifically as holdouts.

K

Keying

Generating a matte procedurally from image properties — colour, brightness or difference — rather than drawing it by hand. Keys are usually combined with roto for areas the keyer can’t separate cleanly. See chroma key, luma key and keying services.

L

Lens distortion (ST map, undistort)

The bending of straight lines caused by a real lens, such as barrel or pincushion distortion. Matchmove artists measure it, often from a lens grid, and produce an undistort/redistort setup or an ST map — an image whose red and green channels store remapping coordinates — so CG can be rendered without distortion and then distorted to match the plate.

Log and linear

Two ways of encoding image values. Log encoding compresses a wide brightness range into the available code values and is how most cameras record. Linear encoding stores values proportional to light, which is what compositing maths expects, so plates are usually converted from log to linear for work and back again, or to the agreed delivery space, on output.

Luma key

A key built from brightness rather than colour, isolating areas that are brighter or darker than a threshold. Useful for skies, smoke, fire and bright windows, and as a helper inside larger keys.

LUT

A look-up table: a file that maps input colour values to output values. LUTs are used to view log footage correctly, to apply a show look in review, or to convert between colour spaces. A viewing LUT changes how an image is displayed, not the pixel values that are delivered.

M

Marker removal

Painting out tracking markers placed on set, on green screens, walls, props or performers’ faces and bodies. Markers that cross the subject or move with skin need tracked patches and careful grain matching. See marker removal services.

Matchmove

Recreating the movement of the real camera, and sometimes of objects in the scene, in 3D software so CG elements can be placed into live action with the correct perspective and motion. See camera solve and matchmove services.

Matte

A greyscale image that defines which parts of a frame are kept, removed or partially transparent. Mattes come from roto, keying, CG renders or combinations of these, and are delivered either as an alpha channel or as separate image files.

Matte painting

A painted or photo-built image of an environment — a skyline, landscape or building — used to extend or replace parts of a shot. Modern digital matte paintings are often projected onto simple 3D geometry so they hold up under camera movement.

Motion blur

The smear captured when a subject or camera moves while the shutter is open. Roto shapes and CG elements must reproduce the plate’s motion blur, in direction and length, or edges look cut out. Matching it is one of the main quality checks in rotoscoping.

P

Paint and prep

Frame-by-frame image repair that removes unwanted elements or prepares plates for later work: wire and rig removal, marker removal, object and logo removal, and beauty work. “Prep” often refers to preparing a clean plate before compositing. See paint and cleanup services.

Parallax

The way objects at different distances appear to move at different speeds when the camera moves. Parallax is what gives a camera solve its depth information, and it is also what makes cleanup on moving shots harder: a single flat patch can’t follow surfaces at several depths.

Planar tracking

Tracking a flat surface — a wall, screen, sign or tabletop — as a plane rather than as individual points. It handles perspective changes and partial occlusion well, which makes it a common choice for screen replacements and paint patches.

Plate

The original photographed footage for a shot, as supplied for VFX work. A shot can have several plates: the main action plate, a clean plate, element plates such as smoke or water, and reference passes.

Premultiplied and straight alpha

Two ways of storing colour alongside an alpha channel. In premultiplied (associated) alpha, the colour values have already been multiplied by the alpha; in straight (unassociated) alpha, they have not. Handling one as the other produces dark or bright fringes around edges, so the convention should be agreed with every delivery.

ProRes

A family of Apple video codecs widely used for editorial and review media. In VFX it is usually a convenient format for review files and editorial turnovers, while finished work is delivered as image sequences such as EXR or DPX.

Q

QC

Quality control: the checks made before a shot is delivered. For roto and paint, QC typically covers edge chatter, holes in mattes, motion-blur match, grain match, frame range, naming, colour space and file integrity. Internal QC happens before client review, not instead of it.

R

Reference

Any material that shows the intended result or real-world behaviour: stills from the edit, look references, previous approved shots, photos of the set or props, or notes from the supervisor. Good reference shortens the review cycle.

Rig removal

Painting out equipment used to support or move performers and props — harnesses, arms, stands, rods, cranes or green-suited puppeteers — and rebuilding the background behind them. See wire and rig removal services.

Rotomation

Matching a 3D model of a performer or object to the plate, frame by frame, so that its movement follows the live action. It is used when CG must interact with a body precisely, for example costume additions, digital make-up or contact shadows.

Rotoscoping (roto)

Drawing and animating shapes around a subject, frame by frame, to create a matte that separates it from its background. Roto is used when a subject can’t be keyed, and alongside keys for hair, edges and problem areas. See what rotoscoping is and rotoscoping services.

S

Set extension

Adding to a physical set digitally — extra floors on a building, a crowd-filled stadium, a full street where only a corner was built — using matte paintings, CG environments or both, tracked to the plate.

Shot ID

The unique code that identifies a shot across editorial, VFX and delivery, usually combining sequence and shot numbers (for example a sequence code followed by a four-digit shot number). Every file, note and invoice line should carry it.

Slate

Information identifying a take. On set it is the clapperboard filmed at the start of a take; in post-production it is often a title frame added at the head of review media, showing the shot ID, version, artist, date and frame range.

Spill and spill suppression

Spill is coloured light reflected from a green or blue screen on to the subject, most visible on hair, skin and shiny surfaces. Spill suppression is the set of techniques that remove that colour cast while keeping natural skin tones. See despill.

Spline (shape)

A curve defined by control points, used in roto to outline a subject. Artists build a subject from several simple shapes rather than one complex one — separate shapes for the head, torso and each limb — so each can be animated and feathered independently.

Survey data

Measurements taken on set — distances, object sizes, the positions of tracking markers, sometimes a LiDAR scan — that give matchmove artists real-world scale and help a camera solve converge accurately.

T

Temp vs final

A temp is a quick version made for editorial or preview purposes — enough to judge timing or story — while a final is the finished, approved shot for delivery. Briefs should say which is expected, because the effort and the checks involved are very different.

Timecode

A time-based label for each frame, in hours, minutes, seconds and frames, recorded by the camera or assigned in editorial. VFX vendors use it alongside frame numbers to make sure work lines up with the cut.

Track (2D track)

Following a feature in the image, such as a corner, marker or high-contrast point, across frames to record its position, and sometimes rotation and scale, in screen space. 2D tracks drive paint patches, roto shapes and stabilisation.

Tracking marker

A small, high-contrast mark placed on set — often a cross or dot on a green screen or wall — to give the tracker reliable features to follow. Markers help matchmove but must later be removed in paint, so their size and number are a trade-off. See marker removal.

Turnover

The package editorial sends to the VFX team when shots are handed over: plates, reference movies of the cut, frame ranges with handles, shot IDs, notes and any on-set data. A complete turnover is the starting point for accurate scoping.

V

Version

A numbered iteration of a shot, such as v001, v002, v003. Each round of notes produces a new version, and the version number on files and burn-ins makes it clear which iteration feedback refers to and which one was approved.

W

Wire removal

Painting out wires used for stunts, flying rigs or suspended props, and restoring the background behind them. Thin wires over simple backgrounds are fast; wires crossing hair, smoke or moving detail take far longer. See wire and rig removal services and paint and cleanup explained.