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Subdivide a hair segment causes the high light to appear at the wrong place
Closed, ResolvedPublicBUG

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 418.81

Blender Version
Broken: version: 2.80 (sub 50), branch: master, commit date: 2019-03-18 20:40, hash: rBce09b93955de
Worked:
Subdivide the entire hair does not cause the problem, the highlight appear at the correct place.

Short description of error
In Particle edit mode, subdivide a segment of the hair will cause the selection highlight appear at the wrong part.

Exact steps for others to reproduce the error
With the default cube, add a hair system, reduce the number to 1, switch to particle edit mode, select 2 connecting vertices, then subdivide.
Now if you select an individual vertex, the highlight appear at the wrong place

Event Timeline

Lance Phan (ssendam) updated the task description. (Show Details)
Sebastian Parborg (zeddb) lowered the priority of this task from 90 to 50.

@Sergey Sharybin (sergey) as always, feel free to reassign if this is not for you.

@Sebastian Parborg (zeddb), not sure i am properly understanding the issue here (could be multiple ones). Mind testing the patch?

@Sergey Sharybin (sergey) the issue is that the highlight on the line seem to be centered around the wrong center point.
(However, your patch fixed a refresh issue, the hair geometry now updates after the subdiv command. So be sure to include it too)

Correctly centered before subdivide:

Shifted highlight after subdivide:

Test file:

This highlight offset issue also seems to happen in 2.79 btw.

Lance Phan (ssendam) added a comment.EditedMar 20 2019, 2:25 AM

This highlight offset issue also seems to happen in 2.79 btw.

In Blender 2.79, the wrong highlight is a different issue, it is because of the low path steps, regardless of subdivide or not. Increase the path steps will solve the issue. This also happens in 2.8.
If you set the hair segments to 7 and path steps to 2, you can see it very clearly in both 2.79 and 2.8.

The subdivide issue is different, increasing the path steps doesn't help

@Clément Foucault (fclem) , as far as i know the highlight is handled by the drawing code, which i am not familiar with. The annoying part is that the highlight is somewhat decoupled from control points, but think it should be possible to have it behave similar to 2.79.
Mind having a look?

P.S. I've committed my fix for the refresh issue.

Looks like the drawing code expects that the points are uniformly spaced along the hair strand.

Clément Foucault (fclem) triaged this task as Low priority.
Clément Foucault (fclem) changed the subtype of this task from "Report" to "Bug".