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Hair particle selection broken in Point selection mode in specific blend file.
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Description

System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 419.35

Blender Version
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e
Worked: (optional)

Short description of error
Selection of hair particles in "Point" selection mode has stopped working in my blend file. Most selection hotkeys and operations under the "Select" menu as well as box select no longer do anything. Some selection operations like Lasso select and Ctrl + Numpad "+" still work, but you cannot comb the hair event when it is selected. "Tip" selection mode works normally. Restarting Blender and reloading the project does not fix the issue.

Exact steps for others to reproduce the error


I don't know of steps to reproduce on new blend files, but using the above blend file where the bug has occurred:

  1. Select the Body mesh and enter Particle Edit mode.
  2. Enable "Point" selection mode.
  3. Attempt to select or deselect any hair particle(s) using box select, L to select a strand, A and Alt+A. You will not be able to select or deselect anything with these methods.
  4. Attempt to select any hair particle(s) using lasso select. This will allow you to select hair particles, but you cannot comb them.
  5. Enable "Tip" selection mode.
  6. Confirm that all selection methods and combing works normally in this mode

Event Timeline

Kevin (Crazymonkay) renamed this task from Some hair particle selection methods no longer work in Point selection mode in specific blend files. to Hair particle selection broken in Point selection mode in specific blend file..Sep 26 2019, 2:11 AM
Kevin (Crazymonkay) updated the task description. (Show Details)
Philipp Oeser (lichtwerk) lowered the priority of this task from 90 to 80.Sep 26 2019, 10:01 AM

Can confirm in this particular file...
All seems to be fine if I append the body into a fresh file... checking...

Appending the collection is also fine.
Something in the scene is preventing the selection, you can also make a fresh new scene in your file and select the body, then Object > Make Links > Objects to Scene > Scene.001.
Everything is fine in Scene.001 then.

However, if you do this in a copied scene [that has been created with Copy Settings] then problems arise...
Still checking...

more findings:

For some reason the PTCacheEditKeys are flagged PEK_HIDE.
This also explains why lasso select partially works (because lasso loops with LOOP_KEYS, whereas e.g. box select loops with LOOP_VISIBLE_KEYS).
In this regard lasso select is actually wrong imho, shouldnt let you select those... also explains why combing is not working then (this wont work on hidden...)

Still need to wrap my head around the PEK_HIDE, but we are getting there :)

Philipp Oeser (lichtwerk) lowered the priority of this task from 80 to 50.

Ha! found the culprit:
There is a setting (particle_edit.use_fade_time) that usually is only for Emitter particles, and that makes particles be flagged PEK_HIDEunder certain circumstances.
For some reason this is turned ON in your scene.
This leads to a couple of issues (that need fixing -- see below), but to get you up and running quickly here is the woraround for now:
call bpy.context.scene.tool_settings.particle_edit.use_fade_time = False in your file and you are good to go...

OK, now to fixing:

  • this bug was also present in 2.79 (you could turn this ON for hair as well and couldnt select anymore)
  • this should be ignored for hair alltogether in PE_hide_keys_time (or other code should not respect that flag when editing hair)
  • this needs to be checked if working well with drawing with non-hair (but there are T62893, T64843 to solve first)

Working on fixes...

Thank you for the very quick response and fix! All is working now :)