Fix: GPv3: Outline perimeter cap radius too small when points are not coplanar #126687

Lukas Tönne · 2024-08-23T13:59:19+02:00

Lukas Tönne commented

2024-08-23 13:59:19 +02:00

Stroke outlines are used by modifiers, fill tool, exporters, etc. When
the input strokes are not co-planar (different depths from camera view)
the end caps have smaller radii than they should have.

When generating the outline caps the normal vector is created from
the point tangents in 2D (after projection). When points have different
depths (Z positions) the tangents have a non-zero Z component as well
and discarding it leaves them unnormalized, thereby scaling the radius
by an unwanted factor.

Normalizing the vector fixes the issue. Object scale is now also taken
into account.

Stroke outlines are used by modifiers, fill tool, exporters, etc. When the input strokes are not co-planar (different depths from camera view) the end caps have smaller radii than they should have. When generating the outline caps the normal vector is created from the point tangents in 2D (after projection). When points have different depths (Z positions) the tangents have a non-zero Z component as well and discarding it leaves them unnormalized, thereby scaling the radius by an unwanted factor. Normalizing the vector fixes the issue. Object scale is now also taken into account.

Lukas Tönne added 1 commit 2024-08-23 13:59:28 +02:00

Fix outline perimeter cap radii when points are not coplanar. 4833adaf9e

When generating the outline caps the normal vector is created from
the point tangents in 2D (after projection). When points have different
depths (Z positions) the tangents have a non-zero Z component as well
and discarding it leaves them unnormalized, thereby scaling the radius
by an unwanted factor.

Lukas Tönne added this to the Grease Pencil project 2024-08-23 13:59:35 +02:00

Lukas Tönne requested review from Falk David 2024-08-23 13:59:47 +02:00

Lukas Tönne commented

2024-08-23 14:08:43 +02:00

For illustration purposes, here's what the error looks like:

For illustration purposes, here's what the error looks like: ![image](/attachments/98a838ec-6d4a-4460-ae2a-b668973dda72)

image.png

25 KiB

Falk David approved these changes 2024-08-23 14:22:37 +02:00

Falk David left a comment

Makes sense 👍