particle system volume grid particles out of volume
Closed, ResolvedPublic

Description

System Information
OS: Ubuntu 16.04.2 LTS
GPU: TITAN X (Pascal)
CPU: Intel(R) Core(TM) i7-6700K

Blender Version
Broken: 2.78 and 2.79
Worked: unknown

Short description of error
Lines of particles appear from -x to x from the mesh with a high-poly (69451 faces) mesh. After decimating the mesh the problem disappears.

Exact steps for others to reproduce the error
1 - Download a high poly STL (e.g. the stanford bunny (69451 faces) )
http://www-static.cc.gatech.edu/data_files/large_models/bunny.ply.gz

2 - Import mesh
3 - Add a particle system and emit from volume grid.
4 - Set emitter start and end to 0, resolution to 15, physics to NO and size to 0.005
5 - Duplicate
6 - Add a decimation modifier and decimate to 0.01 (693 faces) and apply

Related task: https://developer.blender.org/T46481

Javier Felip (xavisomah) renamed this task from particle system volume grid to particle system volume grid particles out of volume.
Javier Felip (xavisomah) updated the task description. (Show Details)
Sergey Sharybin (sergey) triaged this task as Confirmed priority.

The issue here is caused by failed isect_axial_line_segment_tri_v3. This patch will allow to catch that case: P529. What i'm not sure about, is why to use axial here? At least, for volume distribution. Would think something like this will make it: P530. This patch solves this issue.

@Bastien Montagne (mont29), mind having a second pair of eyes here? :)

There are still issues on other grid resolutions, but those are caused by non-manifold nature of the model.

@Sergey Sharybin (sergey) no idea really why that intersection algo was chosen, would bet it was best available in our code at the time. ;)

So if watertight works better, P530 looks totally fine to me.

@Bastien Montagne (mont29), ok, will steal the report back to self, run additional tests and commit fix.

OS: Ubuntu 16.04

Is this truly fixed, or am I overlooking something obvious?
It seems that now no particles appear, unless you press 'invert grid'

I double checked to be sure. The following blend file works "sort of" in 2.79 official - particles appear, but some are outside the "watermelon" shape object.

Made a mistake in original patch which broke quad faces. Fixed in rB95a8e73d400.