Where do those shorter strands of hair come from which seem to ignore their parent particles?


I use a particle system to simulate fur (for an animation). To mimic the structure of the fur I combed it back.

Unfortunately, the ‘Simple Children’ option spawns some shorter strands of hair which I can’t explain as all of the hair particles are much longer and pointing backwards.
Those strands of hair pretty much seem to ignore their parent particles.

What am I doing wrong?

Top-down view:

Side view:

Close up view (pointing topwards):

Render results:

Image of my particle settings:

I use blender 2.93.5 on linux.

Some of my attempts that turned out false:

  • First I thought it is caused by the emitters ‘Subdivision Surface’ modifier, but the ‘Use Modifier Stack’ option is checked and the problem also occurs when I apply the modifier.
  • Then I thought it is caused by the kink, but the undesired hair is also spawned when there is no kink at all (the hair is less prominent though).
  • Obviously I also tried to comb the hair in a different manner, but this barely affected the shorter hair.

In case anyone is wondering why I don’t use the ‘Interpolated Children’ option: The result seemed very unpredictable with ‘Hair Dynamics’ activated as well (at least for this kind of animation).

I posted this question on blender stackexchange, too. (link to the question)

Best regards :vulcan_salute:

Hello! Could it be due to an excessive radius on the children? Simple interpolation tends to separate the roots from the surface as the radius goes bigger, as it works as a simple offset of the parent particle, completely ignoring the surface for the root attachment. If you post a scene maybe I can take a look at why it does not work with interpolated children.

Hey @Strangerman !

The ‘Root’ parameter has definitely an effect on the shorter hair. (It still spawns, but is a bit less noticeable.)

The reason I didn’t use the ‘Interpolated Children’ option is the weird hair behavior, like in the following example:

Simple Children:

Interpolated Children:

‘Simple Children’ seemed to give me more control over the result, even though I still don’t understand why some of the hair particle from the ‘Particle Edit View’ are ignored in the result.

Best regards and thanks for your answer :vulcan_salute:

Yes, I see, it does look weird even with the radius at low values. Are you using any modifier after the particle system? If so, the particles will not take it into account. Particle system should always be the last modifier after any mesh deformation modifier in order for the particles to behave as expected. If that’s not your case and your particle system is the last modifier in the stack, have you tried to apply the transforms? Particles are finicky with non applied transforms.
Let me know if it helped.

Hey @Strangerman

Afaik both of your advices have been implemented.

Modifier stack:

Transform properties:

Also, when I apply the ‘Subdivision Surface’ modifier there is no visible change.

Best regards :vulcan_salute:

Hello again! Then I’m afraid I’m clueless for the simple children issue. On the other hand and after taking a closer look to your screen capture, I think you need more guides in the area where the hair gets crazy for the interpolated one, as it needs to have parent particles all over the surface where the children are supposed to grow, or mask the growth area with a vertex group or a mask texture to avoid children on said area.
I couldn’t perform any tests yet, but I will today, I’ll let you know my results.