How to Repair Line Breaks and Uneven Stroke Width Caused by Deformers in Toon Boom Harmony

Save a separate working version before changing artwork or rig structure. Choose three reference frames: the neutral pose, a moderate bend, and the pose where the defect is most visible. Keep the camera and output resolution consistent while comparing them.

Use the following table as a diagnostic aid. These observations suggest where to investigate; they do not establish the cause by themselves.

What you observe	First investigation	Useful comparison
A continuous outline becomes thicker or thinner during bending	Pencil-line deformation settings	Same pose with thickness preservation enabled and disabled
A small break appears at a tight corner	Curve shape and pencil-line smoothing	Original bend versus a gentler bend
A thin seam appears only in Render view	Cutter, fill boundaries, and anti-aliasing	OpenGL versus Render view
An attached detail stretches unexpectedly	Deformation hierarchy	Detail following a point versus receiving deformation
The defect already exists in the neutral drawing	Original artwork	Undeformed drawing versus posed drawing

Render-only seams deserve particular attention. Toon Boom explains that adjacent artwork cut precisely along matching edges can reveal a thin line through anti-aliasing, even when OpenGL looks correct. Increasing stroke width may conceal that symptom without repairing its source. Why is there a thin line between my layers in the Render view?

The preservation controls discussed here apply to pencil lines. Before adjusting them, establish how the affected outline was created, especially if the drawing was imported, converted, or baked earlier.

If you decide to test brush-to-pencil conversion, duplicate the drawing first. Select the relevant strokes with the Select tool, then choose Drawing > Convert > Brush Strokes to Pencil Lines. Harmony’s manual states that this converts contour strokes into centreline pencil strokes and that the brush stroke thickness will be lost. Conversion therefore requires an artwork comparison and possible cleanup. Converting Brush Strokes to Pencil Lines

Test a small, representative section before converting an entire character. Compare its silhouette, taper, and intersections in both the neutral and bent poses. Keep the original drawing available so that the test remains reversible.

Select the affected drawing layer, open its Layer Properties, and locate Line Thickness > Deformation. Enable Preserve Line Thickness and compare the reference poses. The documented behavior preserves pencil-line thickness during deformation, including preventing pencil textures from stretching or squashing. Element / Drawing Node

Judge continuity and width separately. If the outline now keeps its weight but a gap remains, record the width problem as resolved and continue investigating the gap. Avoid repeatedly thickening the entire drawing to close one local defect.

Use this controlled comparison:

1. Capture the defective pose with the original settings.
2. Enable thickness preservation without moving any controls.
3. Compare the same section at the same viewing scale.
4. Check the neutral pose for unwanted changes.
5. Scrub through the movement before accepting the result.

This comparison answers a specific question: does preserving thickness improve the outline while retaining the intended pose? A repair that looks acceptable on one frame still needs a movement check.

With preservation enabled, test Pencil Lines Smoothing gradually. Its documented range is 0–10. Fit Error, ranging from 1–100, simplifies rendered pencil curves and can help with excessive detail around deformation corners. It has no effect when smoothing is zero. Pencil Lines Quality controls deformed-line rendering quality, but the manual says visible improvements are unlikely except at very high resolutions. Element / Drawing Node

Treat these as separate experiments. First compare the original smoothing value with a small increase. If a corner improves, check whether an intentional point or taper has become too rounded. Keep the lowest tested value that produces an acceptable result.

Only evaluate Fit Error while smoothing is above zero. Change it in small steps and inspect the same corner after each adjustment. A useful comparison includes the defect, a nearby clean curve, and a deliberately sharp feature; improving one should not make the other two unacceptable.

For example, suppose a curved character outline develops a small notch at its strongest bend. A practical test sequence is preservation alone, then modest smoothing, then a Fit Error adjustment if necessary. This is an illustrative troubleshooting sequence, not a universal preset or a measured result.

If rendering adjustments do not resolve the defect, test the pose itself. In the working copy, reduce the bend slightly and compare it with the original. If the problem disappears, investigate how that local curve is being shaped before editing the source outline.

For Curve and Envelope deformers, inspect the control points and Bézier handles around the affected area. Harmony distinguishes animation adjustments made with the Transform tool, whose deformation controls display green, from rigging adjustments made with the Rigging tool, whose controls display red. Use the animation workflow when repairing a pose; changing the resting setup is a separate operation. How to Use Deformers

As a practical test, spread the bend over a broader section and compare the silhouette. Move one point or handle at a time so you can identify which adjustment improves the result. Check neighboring frames after each accepted change.

Inspect attached details separately. Toon Boom documents Kinematic Output for applying a deformation point’s position and angle to a drawing without deforming that drawing. It also recommends placing an offset peg above a deformation chain when the offset should not itself be deformed. About Rigging Drawings to Deformations

Use that distinction to decide what each part should do: bend with the surface, or follow a point while retaining its shape. Josh Pinker’s Wacom tutorial also covers Kinematic Output connections and drawing substitutions with different deformers, providing a visual companion for inspecting those rig relationships. Using Deformers in Toon Boom Harmony

When the line appears only in Render view, inspect the compositing setup before making further deformer changes. Toon Boom identifies exact-edge cuts, Auto-Patch arrangements, and certain brush-fill constructions as possible causes. Why is there a thin line between my layers in the Render view?

Match the repair to the construction. For the documented Auto-Patch invert-cut case, Toon Boom recommends using Colour-Art and Line-Art nodes instead, subject to the artwork’s fill boundaries. For brush outlines, it recommends Create Colour Art from Line Art, followed by filling on Colour Art, rather than copying a fill that reaches the brush’s outer edge. For artwork without outlines, it describes an Increase Opacity node to expand artwork enough to hide the seam. These options address different setups. Toon Boom’s render-seam explanation and repairs

After changing the relevant boundary, render the same reference frame again. Then inspect the join throughout the movement. Pay attention to whether the repair introduces an unwanted overlap or changes the visible silhouette.

If one exceptional pose still requires direct artwork cleanup, consider baking a copy of the relevant section. Harmony’s documented command is Animation > Deformation > Convert Deformed Drawing to Drawings. A Transformation Switch must be present, and baking converts pencil lines into brush strokes. How do I bake a deformer?

Preserve the editable rig before doing this. Baking changes the form of the material you will edit, so inspect the resulting drawings before committing to cleanup. Toon Boom also notes that converting baked brush strokes back to pencil lines can require editing and may handle some textures poorly. Baking behavior and conversion limitations

Finish with a short render at the intended delivery resolution. Check the neutral pose, strongest bend, and transitions between them. Review both individual frames and playback: use frame inspection to locate defects and playback to judge their visibility during movement.

Use these acceptance checks:

• The outline remains continuous through the required poses.
• Stroke weight follows the intended drawing style.
• Repaired corners retain their intended shape.
• Attached details move as intended.
• Joins remain clean in rendered output.
• Any converted or baked artwork retains acceptable tapers and textures.

Keep the repair tied to the defect you identified. Thickness preservation addresses changing pencil-line weight; curve adjustments address the pose; fill and cutter changes address render seams. Accept the result when the complete movement preserves the character’s intended outline, and retain the editable version for later pose changes.

• Element / Drawing Node — Harmony 25 Premium Documentation
• Converting Brush Strokes to Pencil Lines — Harmony 24 Premium Documentation
• How to Use Deformers — Harmony 24 Premium Documentation
• About Rigging Drawings to Deformations — Harmony 20 Premium Documentation
• Why is there a thin line between my layers in the Render view? — Toon Boom Help Centre
• How do I bake a deformer? — Toon Boom Help Centre
• Let’s Get Animated with Josh Pinker! Episode 4: Using deformers in Toon Boom Harmony — Wacom