Radial Symmetry Sculpting FAILS on Mesh that is BOTH Convex and Concave #121144

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Adam Janz · 2024-04-26T20:43:38+02:00

Adam Janz commented

2024-04-26 20:43:38 +02:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 970/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 536.23

Blender Version
Broken: version: 4.1.1, branch: blender-v4.1-release, commit date: 2024-04-15 15:11, hash: e1743a0317bc
Worked: Unknown

Short description of error
This bug was particularly difficult to diagnose. However, after extensive testing, I can confirm that radial sculpting does NOT work correctly on any mesh that is both convex and concave, and particularly a mesh that is convex in one axis but concave in the other. (See attached image.)

Exact steps for others to reproduce the error

Open the .blend file "Radial_Symmetry_TEST_Final". There are 6 sample meshes in this file, each numbered.
Mesh 4 is active by default. The Draw Sharp tool is active with a Radial value of 32 set in the Z-axis. Attempt to sculpt a fan pattern on the bottom of mesh 4 by dragging from its outer perimeter toward its center. Observe the pattern draws (mostly) correct, except there is a bit of "stepping" on the steepest inner concave part.
Now switch to mesh 5 with Alt+Q. This mesh is identical to mesh 4, but has been made concave in the X-Axis. Attempt to sculpt a fan pattern in the same way, from the outside to the inside. Observe that the full pattern does NOT draw, only a few lines.
Now switch to mesh 6 with Alt+Q and attempt the same radial pattern. This mesh has far less surface normal deviation than ALL the other meshes, yet it also causes the radial sculpt tool to FAIL badly because it is concave in one axis.
Bonus step: Switch to mesh 2 with Alt+Q. Attempt the same radial pattern. Observe that although this mesh is NOT overtly concave in any particular axis, it still causes the tool to partially fail anywhere there is enough concave to convex difference in the surface normal.

Thanks so much for looking into this.

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 970/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 536.23 **Blender Version** Broken: version: 4.1.1, branch: blender-v4.1-release, commit date: 2024-04-15 15:11, hash: `e1743a0317bc` Worked: Unknown **Short description of error** This bug was particularly difficult to diagnose. However, after extensive testing, I can confirm that radial sculpting does **NOT** work correctly on any mesh that is both convex and concave, **and particularly a mesh that is convex in one axis but concave in the other.** (See attached image.) **Exact steps for others to reproduce the error** 1. Open the .blend file "Radial_Symmetry_TEST_Final". There are 6 sample meshes in this file, each numbered. 2. Mesh 4 is active by default. The Draw Sharp tool is active with a Radial value of 32 set in the Z-axis. Attempt to sculpt a fan pattern on the bottom of mesh 4 by dragging from its outer perimeter toward its center. Observe the pattern draws (mostly) correct, except there is a bit of "stepping" on the steepest inner concave part. 3. Now switch to mesh 5 with Alt+Q. This mesh is identical to mesh 4, but has been made concave in the X-Axis. Attempt to sculpt a fan pattern in the same way, from the outside to the inside. Observe that the full pattern does **NOT** draw, only a few lines. 4. Now switch to mesh 6 with Alt+Q and attempt the same radial pattern. This mesh has **far less** surface normal deviation than **ALL** the other meshes, yet it also causes the radial sculpt tool to **FAIL** badly because it is concave in one axis. 5. Bonus step: Switch to mesh 2 with Alt+Q. Attempt the same radial pattern. Observe that although this mesh is **NOT** overtly concave in any particular axis, it still causes the tool to **partially fail** anywhere there is enough concave to convex difference in the surface normal. Thanks so much for looking into this.

Radial Symmetry TEST.png

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Radial Symmetry Sculpt Fails on Concave Axis in Blender.png

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RadialSymmetry_TEST_Final.blend

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Radial Symmetry Sculpt Fails on Concave Axis in Blender.png

Adam Janz added the

labels 2024-04-26 20:43:39 +02:00

Philipp Oeser commented

2024-04-30 09:54:48 +02:00

I assume this has to do with the fact that the effective origins for the dabs/strokes of radial symmetry are distributed on a "flat" plane around the specified axis

That is why you dont get influence in some parts of the mesh.
@AdamJanz : does this make sense?

I assume this has to do with the fact that the effective origins for the dabs/strokes of radial symmetry are distributed on a "flat" plane around the specified axis ![image](/attachments/30368a59-a49c-4d04-abf2-41bdbcc10a34) That is why you dont get influence in some parts of the mesh. @AdamJanz : does this make sense?

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Philipp Oeser added

Status

Needs Information from User

and removed

Status

Needs Triage

labels 2024-04-30 09:55:02 +02:00

Adam Janz commented

2024-04-30 16:31:20 +02:00

@lichtwerk Thanks, Philipp. Yes, that would make sense... so I guess this would be more of a limitation than a bug, then? It's worth noting that switching the brush falloff from "Sphere" to "Projected" almost works on mesh 5 (when in bottom orthographic view), however the effect breaks wherever the surface normal becomes perpendicular to the orthographic view:

But on mesh 6, which has very subtle surface normal changes, the tool breaks especially badly, resulting in a horizontally squashed sculpt:

However, if I have the falloff set to "Projected" and also check the box for "Original Normal" under Advanced Brush Settings, I can get a similar result to Mesh 5. It still flattens a bit at perpendicular areas, and then inverts completely in the concave area, but at least it is a much better result for this type of mesh surface. I'd say this is a decent workaround until the "Projected" mode can be improved to not invert wherever the surface normal changes completely (from concave to convex, or from convex to concave).

@lichtwerk Thanks, Philipp. Yes, that would make sense... so I guess this would be more of a limitation than a bug, then? It's worth noting that switching the brush falloff from "Sphere" to "Projected" **_almost_** works on mesh 5 (when in bottom orthographic view), however the effect breaks wherever the surface normal becomes **perpendicular** to the orthographic view: ![image](/attachments/d5b8075b-5d66-47e6-87ef-36275d02ecdd) But on mesh 6, which has very subtle surface normal changes, the tool breaks especially badly, resulting in a horizontally squashed sculpt: ![image](/attachments/0f7e1ca0-ffa7-41ec-b862-182a2d207b69) However, if I have the falloff set to **"Projected"** and also check the box for **"Original Normal"** under Advanced Brush Settings, I can get a similar result to Mesh 5. It still **flattens** a bit at perpendicular areas, and then **inverts** completely in the concave area, but at least it is a **much better result** for this type of mesh surface. I'd say this is a decent workaround until the "Projected" mode can be improved to not invert wherever the surface normal changes completely (from concave to convex, or from convex to concave). ![image](/attachments/6940e277-63d4-4727-bd3b-0fa8a1a0c457)

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Radial Symmetry Sculpting FAILS on Mesh that is BOTH Convex and Concave #121144