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Stylus pressure splike on first dab
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Description

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 980/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 461.40

Blender Version
Broken: version: 2.92.0 Release Candidate, branch: master, commit date: 2021-02-19 18:02, hash: rBb1142858d4ca
Worked: 2.91.2

Short description of error
When using stylus(me wacom CTL-690),the first dab of a stroke has a too high pressure amount regardless of the actual pressure input.
The left stroke of each pair in the following pictures is drawn within Blender 2.92.0 and the right one is 2.91.2:

As what I have tested,sculpting,texture paint,weight paint and grease pencil all get influenced.

Exact steps for others to reproduce the error
OS Conditon: WIN 10 |Blender: 2.92.0 Candidate|Tablet: Wacom CTL-690

  • Using stylus to draw a stroke in sculpt mode , texture paint mode , weight paint mode or grease pencil draw mode .Try having the pressure initially low,then the first dab drawn should get a high pressure amount which is false.

In case,this is the blend file which is used to capture the pictures above:

Event Timeline

Nicholas Rishel (nicholas_rishel) changed the task status from Needs Triage to Confirmed.EditedMon, Feb 22, 4:34 AM
Nicholas Rishel (nicholas_rishel) triaged this task as Low priority.

Note to anyone looking into this issue:

This issue is a result of Win32 mouse input not being synchronized with Wintab pressure. This has been an issue before 2.92, and has reappeared because the heuristics which discourage it from happening no longer work as well because Win32 mouse input was modified to support more accurate mouse movement (smooth lines when drawing).

There is no good long term fix, the issue is how Wintab works and the compromises to support current workflows in Blender.

The fix for this issue is to use Windows Ink (may require restarting Blender).

This issue might needs other stylus or Wacom tablet users.I can't find a way to enable Windows Ink only while keeping my tablet functioning.
"Use Windows Ink" setting in Wacom driver can't fix this problem and possibly my tablet is too old to work correctly without Wacom driver.

Brecht Van Lommel (brecht) raised the priority of this task from Low to High.Mon, Feb 22, 12:14 PM

@Nicholas Rishel (nicholas_rishel) please revert all high frequency mouse input changes as well then.

Correct tablet input is more important than high frequency mouse input.

This issue might needs other stylus or Wacom tablet users.I can't find a way to enable Windows Ink only while keeping my tablet functioning.
"Use Windows Ink" setting in Wacom driver can't fix this problem and possibly my tablet is too old to work correctly without Wacom driver.

Blender offers an option to choose "Windows Ink" under "Input" settings, see if you are able to change it.

kursad k (kursadk) added a comment.EditedMon, Feb 22, 5:13 PM

>>! In T85844#1116544, @Nicholas Rishel (nicholas_rishel) wrote:

Note to anyone looking into this issue:

This issue is a result of Win32 mouse input not being synchronized with Wintab pressure. This has been an issue before 2.92, and has reappeared because the heuristics which discourage it from happening no longer work as well because Win32 mouse input was modified to support more accurate mouse movement (smooth lines when drawing).

There is no good long term fix, the issue is how Wintab works and the compromises to support current workflows in Blender.

The fix for this issue is to use Windows Ink (may require restarting Blender).

I do not think that Windows Ink can handle multiple devices properly , as in using Blender with one device initially (Intuos pro) then turning on another device and keep using the open Blender in another device (Wacom Cintiq). My tests show that Blender cant utilize the pressure when I change to Wacom Cintiq while Windows Ink is the main driver.

Can Windows Ink in Blender handle transient usages between multiple pen devices like this in the same opened session?

This issue might needs other stylus or Wacom tablet users.I can't find a way to enable Windows Ink only while keeping my tablet functioning.
"Use Windows Ink" setting in Wacom driver can't fix this problem and possibly my tablet is too old to work correctly without Wacom driver.

Blender offers an option to choose "Windows Ink" under "Input" settings, see if you are able to change it.

Thank you for the information,had never known there is a setting.I got a solution currently from that and this solves the pressure first-spike and the drawing glitches(T85733) for my Wacom CTL-690.

After changing Blender Tablet API from "Aotomatic" to "Windows Ink" in the preference (restarting Blender might be needed):
If Blender the application is specified in the Wacom driver,make sure the "Use Windows Ink" check box is on in the Mapping tab,according to Wacom Guide this setting will let the tablet get the proper pressure input ( if the setting is not checked,stylus will have no pressure in Blender) :
If Blender is not specified in the Wacom driver,check "Use Windows Ink" setting in the "All Other Applications" Mapping tab.
Issue happens while the Tablet API in Blender is set to Wintab.

All: this build reverts changes to that caused this issue. Please +1 if this fixes things for you or comment if there is still an issue.

All: this build reverts changes to that caused this issue. Please +1 if this fixes things for you or comment if there is still an issue.

Glitches(T85733) are gone for me (Tablet API changed to Wintab/Automatic).
The pressure error is still there when I use Wintab/Automatic Tablet API.

Updated build to test, I don't think it will fix the issue but it would rule out a large section of code as the problem.

Edit: the above build should fix things.

Falk David, I tried the test build provided on the referenced task (T85844) and the problem with the pressure sensitivity was resolved.

Nicholas Rishel, I downloaded the test build provided by your link on task (T85844) at: https://blender.community/c/graphicall/lsbbbc/.
Please be advised, my virus scanner found and deleted two files from that build. Attached is a screen capture of the files that were deleted. I do not know if those are standard Blender files or actually malicious as the scanner suggests. Just be advised.