Bloom

Bloom

A treatment of the user's own footage over a short range. Outside it the clip plays as shot; inside, the highlights swell into a soft glow, a red-orange halation bleeds around them, and thin blue streaks stretch sideways through every hot light, held for the phrase, then everything settles back. It is one Tella Motion overlay laid over the clip that plays the clip's footage again with the effects on it; the clip's sound is untouched. It suits night streets, neon, headlights, screens, stage lights and backlit hair: a romantic, dreamy or cinematic lift on one moment.

Builds on tella-motion-design (timing, checking) and pairs with tella-camera-moves (a slow push-in under the swell). Not for retro looks (retro-footage-looks) or cut stingers (glitch-transitions).

Ask once

Work these out yourself and never ask: the clip and its source (list_clips, list_sources), the stressed word or beat (get_transcript word timings; over music get_music_beats), whether the footage has highlights (look at a frame at the planned peak with get_clip_frame), the canvas size and the clip's layout.

Then one ask_form, every field prefilled, so the user can just submit:

If the frame at the peak has no real highlights (flat daylight, a lit talking head against a wall), say so in the form's intro: the bloom will mostly fog the shot, and lights in frame help. Don't ask for other media: the footage is the user's clip. If the range is a screen recording or a graphic, say bloom needs camera footage and stop, or offer a night clip from Tella's vintage catalogue (list_library scope vintage) as b-roll under it.

Skipped or dismissed form: build with the prefilled values. One bloom per range, at most a few per video; it is an accent.

Timing

Times are on the overlay's clock (word time − overlay start). Start the overlay 0.9 s before the ramp begins, or at the clip's start.

• Swell and settle (the example, 5 s): 0 until 0.9 s, ramp in to the peak by 1.6 s (easeInOutSine), hold to 3.8 s, ramp out to 0 by 4.5 s, overlay ends at 5.0 s. With a word: the peak lands on the word's start, the hold lasts the phrase, the ramp out starts at the phrase's end. Ramps stay 0.7 s.
• In Swell and settle, every keyed track starts with a hold key of 0 at 0 s (easing applies from a key to the next, so the value stays 0 until the ramp's own easeInOutSine key of 0 at 0.9 s), and the replay matches the clip at the overlay's edges.
• Steady: full strength for the whole range. Inside a clip: a key of 0 at 0 s with easeInOutSine easing, full strength at 0.3 s, held, then full strength with easeInOutSine at 0.3 s before the end and 0 at the end. Never a hold key of 0 first, or the effect snaps on at 0.3 s. On a cut (the overlay starts or ends with the clip): put a full-strength key there instead of the 0 key and its ramp.

The look (from the example, 1920×1080)

Three media nodes playing the same source, full frame, painted in this order. All three envelopes share the key times above.

• footage (normal blend): curves "cool" (red 0.5→0.46, 1→0.97; blue 0→0.03, 0.5→0.55), curves "pink_tint" (red 0→0.04, 0.25→0.30; green 0.25→0.23; blue 0→0.03, 0.25→0.28), then glow radius 120, threshold 0.45, softness 0.5, intensity keyed 0 → 2.2.
• streaks (blend screen): erode radiusX 0, radiusY 12 → fx.levels inputBlack 0.78 → blur radiusX 30, radiusY 1 (decal) → the streak shader (references/streak-shader.md): threshold 0, reach 800, tint Blue 0.4, 0.65, 1, 1; amount keyed 0 → 1.8.
• halation (blend screen): fx.levels inputBlack 0.6 → blur 24 × 24 (decal) → fx.tint black to 0,0,0, white to 1, 0.235, 0.078 (#FF3C14), amount 1 → fx.exposure 1.2; node opacity keyed 0 → 1 with easeInOutCubic ramps.

Form mapping:

• Strength scales the three peaks linearly (100% = 2.2 / 1.8 / 1). Above about 120% the frame fogs; on bright daylight footage raise the glow threshold to 0.6 instead of the strength.
• Streak colour: Blue 0.4, 0.65, 1, 1; Warm 1, 0.62, 0.3, 1; White 1, 1, 1, 1. Streaks off: leave out the streaks node.
• Halation off: leave out the halation node.
• The two curves are a static cool/pink grade. Keep them when the overlay covers whole clips (it starts and ends on cuts, as in the example). On a range inside a clip, leave them out, or the grade switches on at the overlay's edge.

Building it

1. add_overlay of a new Tella Motion document on the clip: point 0,0, dimensions the video size, depth: "front", transition: "hard_cut", no animation. Canvas duration = the overlay's. Name it "Bloom: <word>". If the clip's layout is padded, switch it to fullscreen first: the replay is full frame.
2. addMedia the clip's source three times as footage, streaks, halation (that paint order). One node.patch each: fit: "cover" (addMedia lands with contain), audio {assetId: "media.<sourceId>", mute: true} so the sound isn't doubled, and sourceIn = range start in source time, in ticks (1 s = 254016000000; add the clip's trim). streaks and halation also get common.blendMode: "screen".
3. addEffect the stacks above in order (index sets order; on a new document run one addEffect of each built-in shader kind before any raw insert). The streak shader is kind: "shader" with the source passed as written and every uniform given a value.
4. setKeyframes on the glow intensity, the shader's amount and halation opacity. Take each field: path from inspect_motion_node_properties: on a media node the index is the effect's storage index, not its place in the stack.

A range that crosses a cut: an overlay belongs to one clip and can't span clips, so split the range at each clip boundary and build one document and overlay per clip, each with its own source and sourceIn and its keys on that clip's own clock. The envelope carries over the cut: the side before the cut ends at the value the curve has at the cut, and the side after starts there (a full-strength key on each side for Steady; in Swell and settle, put the peak's hold across the cut where possible).

Several ranges: build one, check it, then duplicate_motion_document (a document plays in one place only) and change the keys and sourceIn. Sound is optional: a soft riser from list_library sound effects at 0.3–0.5 under the swell, only if asked.

Checking it

• get_filmstrip of the clip at the overlay start, the ramp start, the peak, the ramp-out end and the overlay end: identical to the clip before and after, the peak on the word, nothing popping at the edges.
• One frame at the peak at 1920 wide: streaks thin and smooth (beads mean the blur before the shader is too small; flat grey bars mean the levels cut is too low), halation a red rim on the lights, not a red wash; faces still readable.
• A 5 fps get_video_preview across the range: the swell moves without a step.
• Report the range, peak strength, streak colour and what the peak lands on.

Gotchas

• glow can't be a backdrop, and a backdrop shape with a non-normal blend drops its backdrop: that's why the footage is replayed instead of filtered from above.
• A shader that changes source needs removeEffect, addEffect again, then re-keying. A broken SkSL asset poisons the document's renders: rebuild in a fresh one.
• SkSL loops must be for (int i = 0; i < N; i++) with N ≤ 128; the streak shader uses 121 taps.
• Deleting the clip leaves its document marked as playing; duplicate_motion_document it to reuse it.

Variations

• Halo only: streaks and halation off, glow peak 1.3, radius 80, threshold 0.55 (subtler, for faces).
• Warm streaks with the halation off, for sunset or candle light.