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Install the Recharm video effects skill: download https://recharm-growth-staging.s3.us-east-2.amazonaws.com/website/downloads/recharm-video-effects.zip and unzip it into ~/.claude/skillsAsk for the effect
Add water caustics to input.mp4 Second the light fades in: 0.5 How many times the pattern repeats across the frame width: 2.2
Several videos, several effects, one ask
Put your clips in the folder, mention them with @, and ask for everything at once. Claude runs one tested script after another on each clip, then joins them.
Add water caustics to @clip1.mp4, put a sale badge on @clip2.mp4, give @clip3.mp4 a VHS look, then join all three with crossfades.
Settings you can change
Ask Claude to change any of these, or edit them at the top of the script.
| Setting | Default | What it does |
|---|---|---|
START | 0.5 | Second the light fades in. |
TILES | 2.2 | How many times the pattern repeats across the frame width. Higher gives smaller cells. |
SPEED | 0.6 | How fast the ripples move. |
COLOR | (170, 235, 255) | Color of the light. |
STRENGTH | 0.75 | Brightness of the light lines, 0 to 1. |
SHARPNESS | 14 | Higher gives thinner, crisper lines. |
Without the skill
Don’t want to install the skill? Paste this prompt into Claude Code and Claude writes the script itself.
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Add a water caustics light overlay to input.mp4: a moving net of thin, bright pale aqua (170, 235, 255) lines, like sunlight through rippling pool water, covering the whole frame. Build the pattern with numpy (for example by bending a grid with a few layers of moving sine waves and brightening where they bunch up, then raising the result to a high power so the lines stay thin), with about 2.2 cells repeating across the frame width and round cells, drifting and rippling slowly. Add it on top of each frame (additive light, 75% strength at the brightest lines) so the brightest lines reach near white, while the dark gaps between them leave the footage untouched. Nothing before 0.5 seconds; it fades in from 0.5 to 1.1 seconds, then stays until the end. Use Python with numpy and ffmpeg (this effect has no text; any text would be drawn with Pillow, not ffmpeg's drawtext filter). Keep the size, frame rate and audio, and save it as output.mp4.Run it without Claude
This is the exact script we tested. Save it as water-caustics.py and run:
python3 water-caustics.py input.mp4 output.mp4Show the script
#!/usr/bin/env python3
"""Water caustics: a rippling net of pale aqua light, like sun through a pool, shimmers across the whole frame.
Usage: python3 water-caustics.py input.mp4 output.mp4
Needs ffmpeg, numpy and Pillow (pip install numpy pillow).
"""
import json
import subprocess
import sys
import numpy as np
from PIL import Image
START = 0.5 # second the light fades in
FADE = 0.6 # seconds the fade-in takes
TILES = 2.2 # how many times the pattern repeats across the frame width (higher = smaller cells)
SPEED = 0.6 # how fast the ripples move
COLOR = (170, 235, 255) # light color: pale aqua
STRENGTH = 0.75 # brightness of the light lines, 0-1
SHARPNESS = 14 # higher = thinner, crisper lines of light
DETAIL = 2 # pattern is worked out at 1/DETAIL size, then smoothly scaled up
def caustics(t):
"""The light pattern at time t, 0-1 per pixel, at full frame size (h, w, 1).
Five layers of swirling sine waves bend the grid; light piles up where they cross, which draws the net.
"""
p = grid * 2 * np.pi * TILES - 250
i = p.copy()
c = np.ones(p.shape[1:])
for n in range(5):
tn = t * SPEED * (1 - 3.5 / (n + 1))
i = p + np.stack([np.cos(tn - i[0]) + np.sin(tn + i[1]), np.sin(tn - i[1]) + np.cos(tn + i[0])])
c += 1 / np.hypot(p[0] / (np.sin(i[0] + tn) / 0.005), p[1] / (np.cos(i[1] + tn) / 0.005))
light = np.abs(1.17 - (c / 5) ** 1.4) ** SHARPNESS
small = Image.fromarray((np.clip(light, 0, 1) * 255).astype(np.uint8))
return (np.asarray(small.resize((w, h), Image.BICUBIC), np.float32) / 255)[..., None]
def add_light(frame, t):
amount = np.clip((t - START) / FADE, 0, 1)
if amount == 0:
return frame
light = caustics(t) * np.array(COLOR) * STRENGTH * amount
return (frame + light).round().clip(0, 255).astype(np.uint8)
def probe(path):
info = json.loads(subprocess.check_output(["ffprobe", "-v", "error", "-select_streams", "v:0", "-show_entries",
"stream=width,height,r_frame_rate", "-of", "json", path]))
s = info["streams"][0]
num, den = s["r_frame_rate"].split("/")
return s["width"], s["height"], s["r_frame_rate"], float(num) / float(den)
src, out = sys.argv[1:3]
w, h, rate, fps = probe(src)
ys, xs = np.mgrid[0:h:DETAIL, 0:w:DETAIL]
grid = np.stack([xs / w, ys / w]) # same scale on both axes, so cells stay round
reader = subprocess.Popen(["ffmpeg", "-v", "error", "-i", src, "-f", "rawvideo", "-pix_fmt", "rgb24", "-"],
stdout=subprocess.PIPE)
writer = subprocess.Popen(["ffmpeg", "-y", "-v", "error", "-f", "rawvideo", "-pix_fmt", "rgb24", "-s", f"{w}x{h}",
"-r", rate, "-i", "-", "-i", src, "-map", "0:v", "-map", "1:a?",
"-c:v", "libx264", "-crf", "18", "-pix_fmt", "yuv420p", "-c:a", "copy", "-shortest", out],
stdin=subprocess.PIPE)
i = 0
while True:
raw = reader.stdout.read(w * h * 3)
if len(raw) < w * h * 3:
break
frame = np.frombuffer(raw, np.uint8).reshape(h, w, 3)
writer.stdin.write(add_light(frame, i / fps).tobytes())
i += 1
writer.stdin.close()
if reader.wait() or writer.wait():
sys.exit("ffmpeg failed")
