Gate
A film projector's gate, for Resolume
What it does
An FFGL effect for Resolume Arena and Avenue. A projector pulls the film down one frame at a time with a claw, holds it in the gate, and lets the lamp through only while a shutter blade is out of the way; the print going through it is a physical strip with grit, dust and splices on it and dyes that fade. Gate models that machine, and the look falls out of it.
The clip is held at the projector's rate (16, 18, 24 or 25 frames a second) and changes only at pull-downs, which happen in the dark. The light the blades pass (one, two or three blades, each open for 45 to 315 degrees of its cycle) is integrated over each frame your display shows, so a 24 fps projector on a 60 Hz display beats at 12 Hz, by an amount the shutter alone decides, and a display frame that spans a pull-down shows both frames in the proportions of light each got.
Each frame lands in the gate a little off, correlated with the last because the same perforations carried it, and a shrunk print weaves more. Grit in the gate cuts scratches that stay put on screen while the picture weaves under them, dark on the base side and green, yellow or clear on the emulsion side; dust rides the print for a frame or a few; a hair trembles at the aperture's edge; splices jump and flash; Cue Dots fires the reel-change marks; and Age fades the cyan dye first and the magenta last, so an old print goes pink and its blacks go red.
Lamp picks a carbon arc, xenon or tungsten colour, Framing slides the frame line into view, Vignette sets the lens's cos to the fourth falloff, and Mix fades back to the clip. The projection paints the whole frame, so the output is opaque at full mix whatever the clip's alpha.
- The clip held at the projector's rate, 16, 18, 24 or 25 fps, changing only at pull-downs
- One, two or three shutter blades at 45 to 315 degrees, integrated over each display frame: flicker at the beat of the two rates
- Frames spanning a pull-down blend both frames in the shutter's proportions
- Correlated gate weave, more of it on a shrunk print, and Framing onto the frame line
- Scratches fixed in the gate, dust on the print, a hair, splices and reel-change cue dots
- Dyes that fade at their own rates, cyan first, so an old print goes magenta
- Carbon arc, xenon and tungsten lamps, and the lens's cos to the fourth falloff
- Universal macOS bundle and a Windows x64 DLL
Where it stands
v0.1.0, and honestly early. The projector is measured, not asserted, by an offline harness that drives the real plugin class headlessly and reads every property back out of the picture it renders: a flat grey's brightness at 60 Hz has, bin for bin to 2e-8, the spectrum the shutter's Fourier series predicts; the picture changes only at pull-downs, 24 times a second at 24 fps, and every pull-down happens in exactly the dark; a scratch holds its x to 2e-5 px while the picture weaves and moves under it; a thousand frames' weave has the stated deviation and correlation, more and less of each on a shrunk print; each dye keeps its stated density to 1e-7 and a grey goes magenta; and a resize leaves the print and the previous frame untouched. Eight deliberately broken models each fail their check, and all 15 controls change the picture. The default shutter is 3 blades at 270 degrees, not the classic 2 at 180: at a 60 Hz output the classic shutter pulses the whole frame at 12 Hz by about 25 to 29 percent, inside the band broadcast flash guidelines restrict; the default keeps it to 7 to 9 percent. The checks verify the stated model, not a projector: the weave, the dirt rates and the fading rates are chosen numbers, the lamps are black bodies, the double image at a pull-down is always on, and there is no Stock control, only Age. It has not yet been loaded into Resolume on macOS. On Windows it has: a build of this source loads, registers and renders in Resolume Arena 7.27.1 on software rendering (win-lab, no GPU), with every parameter as declared and the fleet gate's 9 checks passed; the gate's still carrier reads nine controls as moving the picture and six (FPS, Shutter Angle, Scratches, Dust, Hair, Splices) as inconclusive, because the projection itself never stands still. The macOS build is Developer ID-signed and notarised. There is a user guide and a browser demo; no presets and no OpenFX port. Check it in your own rig before trusting it in a show.
Watch it running
Nothing loads from YouTube until you press play.Watch it there instead