Brush Falloff normalized on many brushes #116747

New Issue

Julien Kaspar · 2024-01-03T15:21:34+01:00

Julien Kaspar commented

2024-01-03 15:21:34 +01:00

System Information
Operating system: Linux-6.6.7-gentoo-x86_64-AMD_Ryzen_Threadripper_1950X_16-Core_Processor-with-glibc2.37 64 Bits, X11 UI
Graphics card: AMD Radeon RX 7900 XT (radeonsi, navi31, LLVM 16.0.6, DRM 3.54, 6.6.7-gentoo) AMD 4.6 (Core Profile) Mesa 23.3.1

Blender Version
Broken: version: 4.1.0 Alpha, branch: main, commit date: 2024-01-03 00:09, hash: 29b1658124b8
Worked: (newest version of Blender that worked as expected)

Short description of error
When reducing the value of the highest point in the falloff curve of the brush settings, some brushes will reduce the maximum Strength as a result.
(Grab, Snake Hook, Clay Strips, Layer, Paint)

But there are many brushes seem to instead normalize the curve back to a 0-1 range, making it impossible to fine tweak the brush strength.
(Draw, Draw Sharp, Inflate, Blob, Pinch)

I didn't test all sculpt mode brushes for this yet.

Exact steps for others to reproduce the error

In sculpt mode, use the Draw brush
Set the Strength to 1
Set the Falloff Curve to "Custom" and use the Linear preset
Test the brush with different vertical values for the highest point in the falloff curve

**System Information** Operating system: Linux-6.6.7-gentoo-x86_64-AMD_Ryzen_Threadripper_1950X_16-Core_Processor-with-glibc2.37 64 Bits, X11 UI Graphics card: AMD Radeon RX 7900 XT (radeonsi, navi31, LLVM 16.0.6, DRM 3.54, 6.6.7-gentoo) AMD 4.6 (Core Profile) Mesa 23.3.1 **Blender Version** Broken: version: 4.1.0 Alpha, branch: main, commit date: 2024-01-03 00:09, hash: `29b1658124b8` Worked: (newest version of Blender that worked as expected) **Short description of error** When reducing the value of the highest point in the falloff curve of the brush settings, some brushes will reduce the maximum Strength as a result. (Grab, Snake Hook, Clay Strips, Layer, Paint) But there are many brushes seem to instead normalize the curve back to a 0-1 range, making it impossible to fine tweak the brush strength. (Draw, Draw Sharp, Inflate, Blob, Pinch) ![image](/attachments/2fe48974-1321-4633-8ed2-8caf99955b77) I didn't test all sculpt mode brushes for this yet. **Exact steps for others to reproduce the error** - In sculpt mode, use the Draw brush - Set the Strength to 1 - Set the Falloff Curve to "Custom" and use the Linear preset - Test the brush with different vertical values for the highest point in the falloff curve

image.png

17 KiB

Julien Kaspar added the

labels 2024-01-03 15:21:35 +01:00

Richard Antalik added

Module

Sculpt, Paint & Texture

and removed

labels 2024-01-03 21:19:49 +01:00

Sean Kim commented

2024-01-25 22:28:44 +01:00

Starting to take a look at this.

Sean Kim commented

2024-01-30 00:06:39 +01:00

I may have to let someone else more experienced with this area of the code take over; I've hit a wall with my investigation into the issue and can't seem to find any particular leads. I've checked the sculpt_brush_types.cc file and don't see any major differences between brushes that see this issue and ones that don't.

Ultimately, every brush from sculpt_brush_types.cc ends up calling SCULPT_brush_strength_factor in sculpt.cc which evaluates the curve with BKE_brush_curve_strength inside colortools.cc.

To add onto Julien's comments of the bug, the only values that seem to apply when modifying the curve are either 1 or 0. If the falloff curve is at a non-0 value on the leftmost point it applies the full strength, only if it's at y=0 does it seem to be factored into the brush stroke.

I may have to let someone else more experienced with this area of the code take over; I've hit a wall with my investigation into the issue and can't seem to find any particular leads. I've checked the `sculpt_brush_types.cc` file and don't see any major differences between brushes that see this issue and ones that don't. Ultimately, every brush from `sculpt_brush_types.cc` ends up calling `SCULPT_brush_strength_factor` in `sculpt.cc` which evaluates the curve with `BKE_brush_curve_strength` inside `colortools.cc`. To add onto Julien's comments of the bug, the only values that seem to apply when modifying the curve are either 1 or 0. If the falloff curve is at a non-0 value on the leftmost point it applies the full strength, only if it's at y=0 does it seem to be factored into the brush stroke.

Sean Kim commented

2024-01-30 00:18:16 +01:00

If it helps in further debugging, I can also repro this behavior on the current 3.6 LTS release (3.6.8, f6ae60f3ee)

If it helps in further debugging, I can also repro this behavior on the current 3.6 LTS release (3.6.8, f6ae60f3eeda)

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Brush Falloff normalized on many brushes #116747