Why are the objects in my hair particle system not sitting on top of the ground?

Question

I made a hair particle system and set the Dupli Group to a group of 3 objects. Each of the 3 objects has:

it's origin set to be touching the XY plane (on layer 2)
it's Scale applied to 1 and it's Rotation applied to 0

enter image description here

I am trying to get each of the objects to sit directly on top of the ground, but instead, they are centered in the plane, half above the plane and half below the plane:

enter image description here

What am I doing wrong? Here is my blend file.

score 14 · Accepted Answer · answered Apr 26 '14 at 20:25

14

This is because hair particles use the global +X axis as "up" for orienting the particle.

If you rotate your objects 90° on the Y axis so that the direction you want to be facing up is instead facing global +X, you get the following result:

enter image description here

It isn't necessary to apply the rotation, since you have Rotation enabled in Particle Settings > Render.

Note that if you don't have Rotation enabled, for some reason the "up" direction becomes global +Y, and you will need to apply rotation for changes to take effect.

answered Apr 26 '14 at 20:25

gandalf3

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Can the axis for the "up" be changed? – arsenbonbon Jul 19 '15 at 12:01
@arsenbonbon AFAIK no, not exactly. You can adjust the rotation and orientation settings, which can work in some cases, but won't be the same as rotating the objects defining the particles. – gandalf3 Jul 19 '15 at 18:42
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Why! Logically it should be +Z axis! – 5argon Sep 17 '16 at 10:13
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@5argon Indeed. I have no idea why this system works how it does (it appears to be quite old, dating back to 2.46), and unfortunately changing it now would break particle systems in existing files. Hopefully the node-based particles planned for 2.8 will fix everything :) – gandalf3 Sep 17 '16 at 20:23

Why are the objects in my hair particle system not sitting on top of the ground?

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