explainer-motion

Explainer Motion

Energy has a source

Every beat moves energy from one specific point to another. It gathers at a source, travels, and is absorbed where it lands, leaving light that cools. Nothing lights up, flashes, or moves without a cause the viewer can point to. When a beat feels flat or noisy, ask where its energy comes from and where it goes.

Rules

• Quiet at rest. Idle wires and frames are still and matte. Motion and light mean something is happening.
• One focal action. Establish the source, follow the signal, then read the result. Stop background flow during narration. At thumbnail size the active signal should win over the hero object's texture and every frame border.
• Light is local. Light comes from a moving thing and falls off with distance: a packet lights only the border near it. An arrival colors a card from its socket, never with a whole-card wash.
• Receivers do not scale. An arrival is a small ring, a flood of light from the socket, and an ink flash. Geometry moves on entrances (settle-in) and in deliberate physical rigs, not on hits.
• Bloom is for what is alive: packet heads and the hero object. Keep borders, floods, and trails under the bloom threshold, so they read crisp.
• Color means something. Signals are near-white with their tone in the trail and reflections; red is failure; one accent is the thing to follow.
• Physical easing.
  • Packet travel: minimum-jerk quintic (smootherstep), with continuous velocity and acceleration into resting holds. Cubic in-out has an acceleration discontinuity at its middle; don't use it by habit.
  • Camera moves: try critically damped springs for weight and a natural tail. Minimum-jerk glides fit exact timed moves between rests; do not force every camera gesture through a fixed-duration curve if it reads stiff.
  • Draw-on: cubic-bezier(.45, 0, .2, 1), which neither jumps off the port nor parks at the socket.
  • Rigid-panel entrances: small displacement, damped springs; let content follow the body by about 60 ms. Tune amplitude before adding bounce.
  • Flashes: instant attack, convex decay (fast, then a long tail).
  • Struck things ring: a cable twangs on an underdamped spring.
• Reaction follows contact. Include gathering/anticipation when checking causality: a reply must not even prepare before its request arrives. An impact launches decisively; a slow spring from rest makes it look voluntary.
• Pure functions of time. Any frame renders identically in any order. Derive an event's phases from one clock (its age), carry velocity across retargets, never fake an ease with stepped values (it stutters), and render motion blur.
• Continuity. Things transform instead of cutting: the camera flies into the card that opens into its code; the same object carries across beats.
• Physical metaphor. Make the mechanism literal: a killed server shatters, a dropped error falls, a timeout is a ring sweeping closed, data flows along wires.
• Camera. Dolly in to open, drift toward the actor that is speaking, pull focus to the plane that matters, pull back to show consequences, push in on the resolution. Shake only on impact. Follow a message only when its journey is the story; orbit to reveal depth, not to decorate.
• Rhythm. Stagger entrances about 120 ms apart; land impacts on the spoken word, with a quiet sound. To show a fix, rewind visibly (reassemble, reconnect), then replay the same moment resolving differently.

Beats

Constants and formulas for each are in TECHNIQUES.md.

• Send: light gathers at the port (340 ms), a solid dot flies with a trail that cools behind it, and it lands as a small opening ring (720 ms). A reflection rides the dot along nearby borders; an ember glows where it left, and light floods into what it reached.
• Connect: the port resolves softly and the wire draws on cubic-bezier(.45, 0, .2, 1), then holds quietly. Author surge, twang, land, or flow explicitly when a beat calls for an impact or active traffic.
• Settle-in: a rigid panel drifts into place with a small scale correction; its content follows and sharpens. Keep the substrate dark. Exact Stage and source-diagram calibrations are distinguished in TECHNIQUES.md.
• Hit: a flash, pulse, jolt, or shake; instant attack, convex decay. A sphere takes contact on its skin: local indentation, a surface wave, then cooling light. Trigger at the visible silhouette crossing, not at a hidden endpoint or with an unrelated pulse at the center.
• Destroy: brief inward compression → hot release → pressure wave → cooling smoke and falling embers. Let the hot phase be exceptional against a quiet scene. The wave bends existing pixels; smoke occludes instead of glowing. One reversible clock owns all phases. See the volume recipe in TECHNIQUES.md.

Designing a beat

1. For every beat, name the source, the path, and the sink of its energy. Done when no beat lights, flashes, or moves without all three.
2. Block readable poses with competing motion disabled. Take the matching beat from TECHNIQUES.md; match the destination's material and brightness rather than copying source alpha or bounce blindly. Done when the focal action reads at thumbnail size and all retained actors fit every camera composition.
3. Build it as clock-derived, deterministic motion. In Psychopomp, use the StageActor beats (send, send_arriving, connect, connect_contacting, settle_in, hit, twang, land, orb_in, glitch, rewind, swap_status, halo, ring_timer, disconnect), stage::reply_after for a reply's earliest launch, author::stagger for ripples, and psychopomp::math; the psychopomp skill covers the reel workflow.
4. Render short normal-speed studies before the full film (in Psychopomp, plan render <plan> out.mp4 --range a..b in the foreground). Compare against the previous treatment, then inspect contact frames at 40 ms or less. Check body, content, ports, and camera separately. Done when the result reads in motion, every light has a visible source, quiet holds remain quiet, and contact never teleports the receiver or its attached wires. State which playback or frame evidence was actually inspected; endpoint stills cannot prove smooth motion.