OPEN GATE CROP — Documentation

01 — Annotated UI Overview Hover a callout number to highlight it. Image size: 601x1366

Open Gate Crop is a dockable panel that builds a camera around two film-back states — a full Open Gate (the whole sensor / plate) and a cropped Show region inside it — and lets you toggle the camera between them with one click. Because the focal length is held constant, shrinking the film back is a real sensor crop: the field of view narrows and Show becomes a true punch-in of the open-gate plate, exactly like a windowed sensor mode on a cinema camera. The whole state is stored on the camera so the toggle survives save, reload and relaunch.

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1
Sensor / Crop Diagram
A live top-down chart of the two film backs: the open gate as the outer rectangle and the show crop inset inside it, positioned by the film offset. The currently-active state is drawn bright (the other dimmed), and the readouts report each state's size in mm and pixels — OPEN 28.0×19.2mm 4608×3164 over SHOW 28.0×11.7mm 4608×1928 [2.39:1] here — with a ▶ OPEN / ▶ SHOW flag showing which one the camera is on.
2
Camera Dropdown
Lists every Open-Gate camera in the scene — those carrying the tool's state attribute. Selecting one seeds the whole UI from its stored Open / Show setup, so you can re-open the tool later and keep working.
3
Refresh
Re-scans the scene for tool cameras — handy after opening a file, importing or renaming.
4
Create Open-Gate Camera
Builds a fresh camera from the current UI values, attaches an open-gate image plane, writes the state, and looks through it in the active viewport. This is the usual starting point.
5
Adopt Selected
Attaches Open-Gate state to a camera you already have (the selected one) instead of creating a new one — useful for cameras that came in from tracking or a layout publish.
6
Open-Gate Sensor Preset
Grouped list of real open-gate bodies — ARRI Alexa 35 / LF / 65, RED, Sony Venice 2, Blackmagic, Super 35, 65mm/IMAX, Full Frame, APS-C — plus Custom…. Each preset fills the width, height, native open-gate resolution and squeeze in one shot.
7
Open Width (mm)
Full sensor width in millimetres → horizontalFilmAperture (written as inches, mm ÷ 25.4). This is the plate the crop lives inside.
8
Open Height (mm)
Full sensor height → verticalFilmAperture. Width × height define the open-gate aspect.
9
Squeeze
Anamorphic squeeze ratio → lensSqueezeRatio. 1.0 is spherical; the crop inherits the same squeeze and the diagram desqueezes horizontally to match.
10
Open Res W
The camera's native open-gate pixel width. Used as the basis for deriving the cropped Show resolution (see #21).
11
Open Res H
Native open-gate pixel height. When the camera is on Open Gate and Drive render resolution is on, this is pushed to the scene render settings.
12
Focal Length
Lens focal length in mm → focalLength. It is shared by both states and held constant across the toggle — which is exactly why shrinking the film back reads as a sensor crop rather than a zoom.
13
Aspect Presets
One-click delivery aspects — 2.39 · 2.40 · 2.35 · 2.00 · 1.85 · 16:9 · 3:2 · 4:3 · 1:1 · 2.76 · 9:16. Picking one insets the largest centred rectangle of that aspect inside the open gate and fills the crop fields below. Editing the crop by hand clears the chip back to custom.
14
Crop W (mm)
Width of the cropped sensor in millimetres. Set by an aspect chip or typed directly for an exact windowed mode → Show horizontalFilmAperture.
15
Crop H (mm)
Height of the cropped sensor → Show verticalFilmAperture. Width ÷ height is the Show aspect.
16
Scale %
An extra punch-in on top of the chosen aspect — 100% uses the largest fit, lower values tighten the crop further inside the open gate for a centre-extract zoom.
17
Show Res W
Cropped delivery pixel width. With Auto on it is derived from the crop and open resolution; otherwise type it.
18
Show Res H
Cropped delivery pixel height, kept on the crop's exact aspect (rounded to even numbers so codecs are happy).
19
Offset H (mm)
Slides the crop horizontally within the open gate → Show horizontalFilmOffset. Leave at 0 for a centred crop.
20
Offset V (mm)
Slides the crop vertically → Show verticalFilmOffset — e.g. a positive value for a top-weighted 2.39 extract.
21
Auto show-res
When ticked, the Show resolution is computed from the crop size relative to the open gate (resW = openResW × cropW / openW), so the cropped delivery always matches the sensor area. Untick to type bespoke pixel dimensions.
22
Open Plate File
Optional image / footage frame for the open-gate plate. Browse with …. Left blank, the image plane shows a flat placeholder tint so you can still see the sensor area.
23
Show Plate File
Optional separate plate for the Show state (e.g. a graded or re-framed version). If left blank, Show falls back to the Open plate so the crop is a punch-in of the same image.
24
Resolution Gate
Toggles the resolution gate (displayResolution) so the active state's render framing is drawn in the viewport.
25
Film Gate
Toggles the film gate (displayFilmGate) — the physical sensor outline. Either gate switches on the surrounding mask automatically.
26
Mask Opacity
How dark the area outside the gate is drawn (displayGateMaskOpacity) — 0 invisible, 1 solid black surround.
27
Drive Render Resolution
When on, toggling also pushes the active state's pixels to defaultResolution so the resolution gate frames the crop exactly. Note this is the global render resolution — turn it off if you'd rather leave render settings untouched.
28
Show Crop Guide
While the camera is on Open Gate, draws a dotted rectangle (a template, unselectable curve parented to the camera) showing exactly where the Show crop will land — a framing preview before you toggle.
29
Toggle Open / Show
The headline control. Flips the camera's film back, offset and (optionally) render resolution between the Open Gate and Show states in a single undo chunk, and refreshes the viewport. One camera, two looks.
30
State Readout
Confirms the target camera and which state it is currently showing (e.g. → camera2 · showing OPEN), tinted cyan for Open and amber for Show.
31
Status Readout
Confirms the last action (e.g. ✓ adopted cameraShape2) in green, or an error in red.

02 — How the Crop Works Same lens, smaller sensor = a real crop

A camera in Maya is a film-back size plus a focal length. Hold the focal length still and shrink the film back, and the frustum narrows — so the active sensor area gets smaller and the image is cropped tighter. That is exactly what a windowed / cropped sensor mode does on a real camera, and it is the whole trick behind the toggle.

Millimetres in, inches out

Humans talk in millimetres; Maya stores film back in inches. Each state is held in mm and divided by 25.4 on write. Per toggle the tool sets:

horizontalFilmAperture ← (state) W mm / 25.4
verticalFilmAperture    ← (state) H mm / 25.4
horizontalFilmOffset    ← (Show) offset H / 25.4   (0 on Open)
verticalFilmOffset      ← (Show) offset V / 25.4   (0 on Open)
lensSqueezeRatio       ← squeeze (shared)
defaultResolution.w/h ← (state) show / open pixels   (optional)

Deriving the cropped film back

Choosing an aspect insets the largest centred rectangle of that aspect inside the open gate:

if aspect ≥ openW/openH:
cropW = openW; cropH = openW / aspect
else:
cropH = openH; cropW = openH × aspect

Scale % then shrinks both for a punch-in, and the show resolution scales with the sensor area so pixels and millimetres always agree.

State lives on the camera

Both states — sizes, resolutions, offsets, plate paths and which one is active — are serialised to JSON on a string attribute (ogcData) on the camera shape. Nothing is kept in machine-local prefs, so the setup travels with the scene: save, reopen, relaunch the tool, and the toggle still flips between the same two looks. The image plane is anchored to the open frustum so toggling crops into the plate rather than re-fitting it.

03 — Open Gate & Crop Reference What ships in the dropdowns

🎥 Digital Cinema (Open Gate)

ARRI Alexa 35 4.6K · Alexa LF 4.5K · Alexa 65 6.5K · RED V-Raptor 8K VV · RED Komodo 6K · Sony Venice 2 8.6K · Blackmagic URSA 12K — each with its native open-gate pixel count.

🎞 Film / Stills

Super 35 (4-perf) · 35mm Academy · Anamorphic 35 (2×) · 65mm / IMAX · Full Frame · APS-C. The photochemical and large formats to crop down from.

▣ Custom

Type any width, height and resolution for a bespoke sensor — and dial the crop numerically for an exact windowed or surround mode.

Delivery Aspects

The Show panel offers the aspects a show actually delivers to, as one-click chips — and the slider-free numeric fields cover anything in between:

2.39 · 2.40 · 2.35 · 2.76   scope / anamorphic
2.00 · 1.85   wide / flat
16:9 · 3:2   broadcast / stills
4:3 · 1:1   academy / square
9:16   vertical / social

04 — Plate, Gate & Crop Guide See the crop against the full sensor

The Open-Gate Plate

The image plane is sized to the open frustum (fit = To Size, derived from the focal length and open aperture at a fixed depth) and anchored there. That is what makes the toggle convincing: when you switch to Show, the frustum narrows and the plate is cropped into rather than rescaled to fill the new gate. Browse a real plate per state, or leave it blank for a flat placeholder tint that still shows the sensor area.

Open gate camera with the show crop region shown in a Maya viewport — An Open-Gate camera in a Maya viewport — the outer frame is the full open-gate plate; the brighter inner rectangle is the Show crop region. Toggling re-frames the camera between the two.

The Dotted Crop Guide

While the camera sits on Open Gate, ticking Show dotted crop guide parents a dashed, dimmed, unselectable rectangle to the camera at the exact Show crop — including any film offset. It is a live preview of where the punch-in will land before you commit to the toggle, and it rebuilds itself whenever you change the open gate, crop or offset.

Good to Know

Building the guide and toggling both run inside an undo chunk, and your selection is saved and restored so the new curve never hijacks what you had selected. The guide is a real scene curve parented to the target camera, so — like any layout aid — it is technically visible from other cameras too. Toggle the checkbox off to remove it.

05 — Workflow From open gate to a one-click crop

1
Launch
Run the script in Maya's Script Editor, then call run(). The panel opens floating — drag it to a dock edge and it behaves like the Attribute Editor.
2
Set the open gate
Pick an open-gate sensor body (or Custom… and type the millimetres + native resolution) and dial the focal length. This is the full plate everything crops from.
3
Create the camera
Press Create Open-Gate Camera (or select a tracked / published camera and Adopt selected). An open-gate image plane is attached and the viewport looks through it.
4
Define the show crop
Click a delivery aspect chip (e.g. 2.39:1), or type exact crop millimetres / show pixels. Add a Scale % punch-in and an Offset if the extract isn't centred.
5
Load plates & gates
Optionally browse a plate for Open and/or Show, switch on the resolution / film gate, set the mask opacity, and turn on the crop guide to preview the punch-in.
6
Toggle
Hit ⇄ TOGGLE OPEN ⟷ SHOW to flip the camera between the full sensor and the cropped framing. The state is stored on the camera, so it survives save, reload and relaunch.

Run It

exec(open('C:/path/to/OpenGateCropTool/OpenGateCropTool.py').read())
run()