Skeleton Constraints and Export Practices for Stick-Figure Explainer Animations

Unconstrained generation may produce an image quickly, but it rarely creates a stable reusable asset. Models often place narration, styling, timing, and drawing logic on the same page. Head-to-body proportions then change between shots, arm lengths lack a shared reference, and the character appears to have “a different skeleton” whenever the scene changes. As soon as you need to adjust a pose, duration, or resolution, the entire page may need to be rebuilt.

For a solo team producing landscape explainer videos, the expensive part is not generating the first frame. It is the repeated rework: consuming context again, debugging timing again, and reconstructing the same visual rules for every revision.

A more reliable approach is to establish an animation production specification first, then use the generation process to fill in the shot content. The specification does not replace creativity. It fixes the elements that should not vary randomly: the protagonist’s body proportions, joint ranges of motion, canvas aspect ratio, frame rate, shot duration, and export method. The content layer describes what each shot communicates and what the character does. The rendering layer turns that description into a consistent stick figure.

Define a Visual Contract First

For a typical landscape computer explainer, define a contract such as the following and preserve it across every finished video:

• Use a 16:9 canvas. Record the logical resolution and output resolution separately so that scaling does not make joint widths appear inconsistent.
• Make a sample approximately 15 seconds long and divide it into three shots. Each shot should include entrance, hold, and exit phases rather than compressing all information into a single moment.
• Design the timeline at 60 frames per second. Even if the final container uses a lower frame rate, interpolation should still follow one consistent timing rhythm.
• Keep only the character, necessary titles, and explanatory cards. Do not add decoration unrelated to the narrative.
• Store narration, the shot list, and drawing code in separate files. Do not hard-code an entire voice-over script inside a drawing function.

Write this contract as a short document and load it before each generation. When the topic changes, only the shot list needs to be replaced; the character’s mathematical reference system remains unchanged.

Define the Skeleton with Proportions, Not Pixels

Stick figures usually break down because the head, torso, and limbs are defined with unrelated absolute coordinates. Choose a body-length unit instead and express every component as a proportion. For example, define the head radius, shoulder width, torso length, upper arm, forearm, thigh, and shin as fixed fractions of total body height. Derive elements such as glasses and line width from the head radius as well.

A position change should modify only the root node. A pose change should modify only the joint angles.

Joints should not be described with vague instructions such as “bend it slightly.” Give each joint an angle range and a default pose. The shoulders, elbows, hips, and knees should have defined flexion limits, and elbows and knees must not bend backward beyond those limits.

You can prepare preset poses such as:

• Pointing
• Thinking
• Walking

Each shot then selects a pose name and specifies a transition duration. Use ease-in and ease-out interpolation instead of linear interpolation, which can make joint movement feel mechanical and abrupt.

A single protagonist should use one skeleton definition throughout the project. If you need to express different emotions, first adjust line rhythm, pause duration, and camera composition rather than changing the head-to-body ratio. This allows multiple short videos to share the same character while still using different scripts and topics.

Separate the Page into Four Layers

A single-page presentation can work well as a preview container, but its internal responsibilities should remain separated:

1. Specification layer: Stores body length, joint limits, colors, safe margins, and shot durations.
2. Shot layer: Stores each shot’s narration, pose name, prop cards, and start and end times. Use milliseconds or frame numbers, but do not include drawing details.
3. Rendering layer: Calculates the skeleton points for the current frame and draws them with lines and circles. It is responsible for antialiasing, line width, and canvas scaling.
4. Export layer: Drives the preview at a fixed duration, captures frames, and packages them into a common video file. If the process fails, preserve logs instead of repeatedly retrying downloads of large components.

The rendering layer should expose only a small set of functions, such as loading a skeleton, setting a pose, sampling by time, and drawing a frame. The shot layer should not directly manipulate the low-level drawing context. This separation makes proportion problems easier to inspect in the skeleton data and narrative problems easier to inspect in the shot list.

The following product-independent structure illustrates the proportional relationships. The values are examples and can be adjusted for the visual style of the finished video:

skeleton
  unit: bodyHeight
  headRadius: 0.12
  torso: 0.28
  upperArm: 0.18
  forearm: 0.16
  thigh: 0.22
  shin: 0.20
limits
  elbow: 5° ~ 160°
  knee: 5° ~ 170°
timeline
  fps: 60
  shots: 3
  durationMs: 15000

During sampling, first calculate normalized time, then interpolate between the preceding and following key poses. Clamp each angle to its allowed range afterward. Calculate point coordinates by accumulating positions from the root node through the torso and limbs. Do not manually write a separate set of screen coordinates for every frame.

Drive a 15-Second Sample with a Shot List

Consider the challenge of taking a one-person business global with short-form video. The three shots can divide the narrative without placing business-specific logic inside the renderer:

• Choosing a topic: The character hesitates in front of several topic cards, emphasizing the cost of making a decision.
• Production: The character moves back and forth between filming and editing, emphasizing the burden of switching roles alone.
• Publishing: The character looks toward multiple distribution nodes, emphasizing inconsistent formats, subtitles, and pacing.

Each shot can last approximately five seconds:

• The first 0.5 seconds are used for entrance.
• The middle 3.5 seconds hold a readable pose.
• The final second transitions to the next shot.

Keep the number of cards within the range that viewers can scan quickly. Do not let text overlap the character. Leave sufficient margins inside the landscape safe area so that the hands are not cut off during recording.

This table-based input is shorter and easier to reuse than a prompt such as “freely create an animation.” The model or developer only needs to change the narration and pose names. The skeleton, line width, and timing functions remain unchanged. Context is therefore focused on what differs between videos instead of repeatedly explaining how to draw a circle and a line.

Make Export Repeatable and Time-Bounded

After the preview is approved, sample the animation offline using the same timeline. The export script should prioritize rendering capabilities already available on the local machine. Set an explicit timeout and output path, and avoid temporarily downloading a large runtime environment.

A practical export sequence is:

1. Open the preview.
2. Wait until the first frame is ready.
3. Capture frames or sample at a fixed interval.
4. Package the result as a common video file.
5. Verify the duration and resolution.
6. If the process fails, output the final frame and the reason for failure.

At minimum, validate four items:

• Whether the final duration is close to the specification.
• Whether the head-to-body ratio remains consistent across all three shots.
• Whether the elbows and knees stay within their limits.
• Whether all text remains complete and readable inside the 16:9 safe area.

You can extract the first, middle, and final frames for still-image comparison instead of relying only on watching the video once.

If the file must be smaller, reduce the resolution or bitrate first. Do not shorten or simplify the skeleton data and hope the result remains stable. Logs only need to record generation time, final duration, and file size. A single measurement should not be presented as a universal performance guarantee.

How to Verify That the Specification Works

Generate two versions for comparison:

1. One version that does not load the skeleton specification.
2. One version that must use the same skeleton and shot list.

A properly constrained version should satisfy the following conditions:

• The same pose produces the same limb lengths in different shots.
• Changing only the narration does not change the character’s geometry.
• Changing one joint angle does not cause other body parts to drift.
• The export script does not alter the visual content of the animation.

If the entire page still contains tightly coupled logic, the problem is that the file responsibilities are not properly separated—not that the prompt needs to be longer.

Once the specification, rendering, and export processes are formalized, a stick-figure explainer changes from “drawing a random image every time” into “having the same actor perform different scripts.” Future additions such as walking cycles, multi-character staging, or subtitle tracks then require new poses or tracks, not a complete rebuild of the validated proportional system.