Hair, Gravity, Vertex groups

Hello all,

I am trying to have create hair that moves as the object that is emitting it moves. So, I’ve create a box, create a vertex group, have applied a hair particle mod and can see the hair but it is not reacting the way I would like. I would like to apply a softbody mod and have the hair sort of trail behind as the box moves, but it is not quite working.




hair3.blend (170 KB)

I think I found your solution:



Thanks a59303,
the last link was the exact google search string I’ve been using. It will take a bit of tweaking to get it right, but I think the my big mistake was selecting the object and not the particle system.




The hair is sort of reacting the way I’d like it to, but the vertex groups are not being used in the solve. I have the group selected under Vertex group and I am using the density mod, but I still have hairs being sent by faces outside of the group.
I’ve take a look at this in Vertex Paint mode and the weighting look ok, but I am obviously missing something.

Thanks in Advance.



hair7.blend (179 KB)

Aside from the hair particle distribution issue (which is part of the particle system setup specs), you need to set your Soft Body simulation up differently for your hair particles. Currently you have Soft Body set up for both the emitter mesh and the hair particle system – usually only the hair is made Soft Body (unless a character has a kind of squishy head :wink: )

Soft Body (SB) for a hair system is different in some ways than for a mesh object. The Goal for SB hair is the entire hair particle system – its arrangement (combing, etc.) before baking the sim is the Goal “shape.” The keypoints for each particle strand (which can be edited in Particle Mode) are sort of like control points on a curve, and can be given a weight in Particle Mode. That weight is used by the SB sim to determine how much the strands match the Goal shape and how much they act like a soft body when the sim is baked. A weight of 1.0 means that part of the strand will completely match the Goal shape. A zero weight means that part is completely free to act as a soft body.

All the SB values that can be set determine how the strands react to forces like Gravity and acceleration when an object moves. In the Goal section, they affect how much the Goal shape is preserved in certain ways. You can even scale the painted weight using Goal Min and Max. Best way to figure how all these various specs actually work is by plugging in different values and seeing the results. Only change one at a time though, since the effects interact a lot.

Suggestion: Edit your hair in Particles Mode to give it a specific shape, then paint the keypoints with some weight values. Apply the SB to only the hair system, and plug in some starting values (like Gravity = 9.8 rather than 0), then bake the sim and check the results. Free the bake and change a value in the sim specs and bake it again to see the difference it makes. Change the Goal section values to see how much of the shape can be kept, or how much it can be over-ridden by the SB sim. After some playing around with the values you’ll get a better idea of how to control the hair reactions.

And then, you can start to learn about Collision…


thanks a lot. I can’t tell you how helpful your post has been. I’ve tried editing in particle mode and gave up thinking it was something that I should try and tackle after I figured the vertex group thing out. For the vertex groups, it was only that I did not have enough resolution in the mesh to isolate the area I was interested in.
Unfortunately, I’ve worked some time in other packages so it seems clear that I am projecting a procedure here.
Again this is a neon light pointing in the right direction. Thanks again.