Spacing Patterns That Make Motion Feel Real in 3D

Spacing Is What the Eye Reads as Acceleration

Timing tells the viewer when something happens; spacing tells them how it moves between frames. If the same action takes 20 frames, you can still make it feel floaty, snappy, heavy, or robotic purely by changing the distance (or angle) traveled each frame. In practice, perceived acceleration/deceleration is mostly a spacing pattern problem: small-to-large spacing reads as speeding up; large-to-small reads as slowing down.

Think in “per-frame steps.” If an object moves 10 units over 10 frames, that does not mean it should move 1 unit per frame. A constant 1-unit step is linear motion (mechanical). Real motion usually has changing step sizes because forces and constraints change the rate of motion.

Common spacing patterns

• Linear spacing: equal distance each frame. Reads as robotic or motor-driven.
• Ease-out (accelerate): small steps that grow. Reads as building speed.
• Ease-in (decelerate): large steps that shrink. Reads as coming to rest.
• Fast-in/fast-out: large steps near the middle, tiny steps near both ends. Reads as smooth, natural transitions.
• Hang time: several very small steps near an apex (often vertical motion). Reads as gravity-dominated arcs.

(1) Visual Spacing Charts for 3D Translation and Rotation

A spacing chart is a quick way to plan and diagnose motion by marking where the object is on each frame (or every other frame). You can do this on paper, in a grease pencil overlay, or by stepping through frames and placing locators/ghosts.

Translation spacing chart (1D example)

Imagine an object moving left to right over 9 intervals (10 frames). Each dot is the object’s position on a frame. Compare patterns:

Linear:   •  •  •  •  •  •  •  •  •  •  (equal gaps)

Ease-out: • •  •   •    •      •        •           •              • (gaps grow)

Ease-in:  •              •           •        •      •    •   •  • • (gaps shrink)

In 3D, you can “draw” this with motion trails/ghosting: the distance between trail markers is your spacing chart. If the trail markers are evenly spaced, the motion is linear; if they bunch up, the object is easing.

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2D/3D path spacing: distance along the arc

When motion follows a curve, spacing is measured along the path, not just in X/Y/Z separately. Two objects can have identical X-curve shapes but different speed if their distance traveled along the curve differs per frame. Use a motion trail that shows frame ticks along the path and judge the gap between ticks.

Rotation spacing chart (angular spacing)

Rotation is spacing too—just measured in degrees per frame. A common mistake is to ease translation but leave rotation linear, which reads as sliding with a “motorized” turn.

Example: rotate 90° over 10 frames.

The ease-in column shows decreasing angular steps: big turns early, tiny turns near the end. That reads as decelerating rotation. You can build the opposite (ease-out) by reversing the step pattern.

Practical diagnostic: “step size” check

• Translation: scrub frame-by-frame and watch how far the object travels each frame in screen space and in world space (motion trail ticks help).
• Rotation: watch the silhouette change per frame; if it changes evenly, rotation is linear. If it changes less near the end, it’s easing-in.
• Mixed motion: if translation eases but rotation doesn’t, the object may feel like it’s “skating while turning.” Match spacing patterns unless you have a reason not to.

(2) Creating Ease-In/Ease-Out Through Spacing (Not Extra Keys)

You can often get better, cleaner motion by shaping spacing with the keys you already have. Adding more keys can hide the real issue (the spacing pattern) and make the curve harder to control.

Step-by-step: ease without adding keys (translation)

1. Set only your start and end keys for the move (e.g., object from A to B over 20 frames).
2. Turn on a motion trail with frame markers (every frame or every 2 frames).
3. Switch to the graph editor and focus on the channel(s) driving the move (often one axis, but sometimes multiple).
4. Shape the curve tangents to control spacing: flattening the tangent near a key reduces per-frame change (smaller spacing); steepening increases per-frame change (larger spacing).
5. Verify with frame stepping: the motion trail ticks should bunch where you want slow movement and spread where you want fast movement.

Step-by-step: ease without adding keys (rotation)

1. Key only the start and end orientation (e.g., 0° to 90° over 12 frames).
2. Check interpolation mode: linear interpolation produces constant angular spacing; spline/auto tangents often introduce easing automatically.
3. Adjust tangents to match intent: if the turn should “snap” then settle, you want larger angular steps early and smaller late (ease-in). If it should “wind up,” do the opposite (ease-out).
4. Scrub by silhouette: the amount of silhouette change per frame is your rotational spacing. Aim for a clear pattern rather than random variation.

When you truly need an extra key

Add a key only when you need a change in intent (a beat, a directional change, a contact, a constraint engaging), not just to “make it smoother.” If the intent is the same and the motion is simply too linear, fix spacing by reshaping the curve and tangents.

(3) Controlling Overshoot and Settle via Spacing Choices

Overshoot and settle are not just “extra frames after the stop.” They are a specific spacing story: the object arrives with remaining energy, passes the target, then returns with diminishing spacing until it rests. If the spacing doesn’t diminish, the settle looks like a vibration or a loop rather than a damped stop.

Overshoot spacing pattern (1D)

Assume the target is at position T. A clean overshoot/settle often looks like this in per-frame spacing:

• Approach: spacing decreases as you near T (ease-in).
• Overshoot: a small extra step past T (not huge unless stylized).
• Return: a slightly larger step back toward T than the overshoot step (because the direction flips, but energy is still present).
• Damping: each subsequent back-and-forth has smaller spacing than the previous.

Positions relative to T (example):  -8, -5, -3, -2, -1, +1, -0.5, +0.2, -0.1, 0

Notice how the “distance from T” shrinks over time. That shrinking distance is the settle.

Overshoot in rotation

Rotational overshoot is often more readable than translational overshoot because silhouette changes are obvious. The same spacing logic applies: degrees-per-frame should diminish as the rotation settles. If the rotation overshoots by 10° and then returns by 10° repeatedly, it reads like a spring with no damping (or a looped noise), not a physical settle.

Practical controls you can apply immediately

• Reduce overshoot size before adding more oscillations: if it feels “wobbly,” the first overshoot is usually too large or too fast (spacing too big right after the stop).
• Make the first return slightly faster than the overshoot: a tiny overshoot step followed by a slightly larger corrective step often reads as a believable correction.
• Damp by spacing, not by random keys: ensure each oscillation has smaller spacing than the last. You can do this with just a few keys by scaling tangents and spacing between breakdowns.
• Watch for axis fights: if X settles but Y doesn’t (or rotation settles but translation doesn’t), the object can feel like it’s made of different materials. Match damping patterns across related channels.

(4) Practical Drills: Same Timing, Different Spacing

These drills force you to separate timing from spacing. You will keep the same frame counts for each action and change only the spacing pattern. The goal is to learn how strongly spacing alone changes the perceived physics.

Drill A: Pendulum with identical timing, different spacing

You will animate a simple pendulum (a ball on a rod or a single object rotating around a pivot). Keep the swing duration identical in both versions.

Setup

• Create a pivot at the top and a pendulum object.
• Animate rotation around one axis (e.g., Z).
• Decide a fixed timing: for example, left extreme at frame 1, right extreme at frame 25, back to left at frame 49.

Version 1: Incorrect (linear angular spacing)

1. Key the left extreme at frame 1.
2. Key the right extreme at frame 25.
3. Key the left extreme again at frame 49.
4. Set rotation interpolation to linear (or force straight-line tangents).
5. Frame-step and observe: the pendulum moves fastest at the ends and slowest at the center, which is the opposite of a gravity swing.

Version 2: More believable (fast through center, slow at extremes)

1. Keep the same keys at frames 1, 25, 49 (do not change timing).
2. In the graph editor, shape the rotation curve so that the slope is steepest at the middle of the swing and flattest at the extremes.
3. Use motion trail ticks (or frame stepping) to confirm spacing: near the extremes, angular change per frame should be small; near the center, it should be large.
4. Check symmetry: the spacing pattern from left-to-center should mirror center-to-right unless you intentionally add energy loss.

Critique checklist (pendulum)

• At the extremes, do you see “hang time” (small angular steps)?
• At the center, is the motion clearly faster (larger angular steps)?
• Does it feel like gravity is pulling it through, rather than a motor rotating it evenly?

Drill B: Bouncing ball with identical timing, different spacing

You will animate a ball bouncing vertically (and optionally moving forward). Keep the same timing for contacts and apexes in both versions; change only spacing.

Setup

• Ball starts at an apex, falls to the ground, bounces to a smaller apex, and repeats.
• Lock timing: for example, Apex1 at frame 1, Contact1 at frame 13, Apex2 at frame 21, Contact2 at frame 29, Apex3 at frame 35.

Version 1: Even spacing (floaty/incorrect gravity)

1. Key the Y positions at the apex and contact frames listed above.
2. Force linear interpolation on Y (or make the curve a straight line between keys).
3. Frame-step: you’ll see equal vertical spacing on the way down and up, which reads like constant speed (no gravity).

Version 2: Gravity spacing (accelerate down, decelerate up)

1. Keep the same keys at the same frames (do not change timing).
2. Shape the Y curve so that on the fall the per-frame spacing increases toward contact (accelerating).
3. On the rise, make per-frame spacing decrease toward the apex (decelerating).
4. Near the apex, allow a small cluster of frames with very small spacing (subtle hang time), especially on higher bounces.
5. If you add forward motion, decide whether it is constant (even X spacing) or affected by impact (slight spacing change at contact). Keep it intentional.

Critique checklist (bouncing ball)

• On the fall, do the gaps between frames get larger as the ball approaches the ground?
• On the rise, do the gaps shrink as it approaches the apex?
• At contact, does the direction change feel crisp without a “sticky” pause (unless intended)?
• Across bounces, does the spacing reflect energy loss (smaller peak heights and typically reduced vertical spacing overall)?

Frame-by-frame spacing checks (a repeatable method)

Use this method to critique both drills objectively.

1. Turn on onion-skin/ghosting or motion trails with markers every frame.
2. Step through frames (do not scrub) and observe the distance between successive positions.
3. Mark problem zones: places where spacing suddenly changes without a reason (a kink in speed), or where spacing contradicts the intended force (e.g., pendulum fastest at extremes).
4. Fix by reshaping tangents first. Only add a breakdown key if you need a specific change in behavior (like a sharper impact or a constrained moment).
5. Re-check the pattern: you are looking for a clear, consistent spacing story—accelerate, decelerate, overshoot, damp—rather than accidental jitter.

What to write down after each pass

• Where is the motion fastest? (Identify by largest spacing.)
• Where is it slowest? (Identify by smallest spacing.)
• Does that match the physics/intent? If not, you have a spacing problem, not a timing problem.
• Which channels disagree? (Translation vs rotation, or X vs Y vs Z.) Decide whether they should match or intentionally contrast.