working with particles to make grass in the wind

[talkingskunk]

I built a grass object, inserted into a plane object with particles under (Render as object), and populated the grass, added Wind and Turbulence force field objects.

Now, the grass does move, but the roots are not staying stationary to the ground. They’re kind of dancing around. Any way to fix this?

[spikeyxxx]

@talkingskunk

You need to give the Grassblades a Particle Instance Modifier with the following settings:

Mind how the Grassblade is modeled along the Y-axis and its Origin is at the sme place as the Ground.

[spikeyxxx]

@tanya53 no, I use the Particle Instance Modifier in order to be able to make the grassblades react to the Forcefield. If you try rendering the Hair Particles as Object (grassblade), they will go straight from root to tip of the hairs, but will not bend.

[tanya]

@spikeyxxx thanks you helped me out

[talkingskunk]

How do you fix this when you add the Particle Instance modifier?

[tanya]

hi,  I was glad you asked this question, I changed how I was doing something now.  I watched this video https://www.youtube.com/watch?v=JPzYJp5Mfvs (only 6 min) and it helped a lot.  I am still using wind and turbulence, so ignored the last half of video.  You need to reposition you grass piece,  in edit mode.  The origin of my grass and the origin of the mesh with the particles is in the same place.  You can change the way they point in edit mode. or in the particle instance change the coordinate space axis.  The offset in the air change the grass strand in edit mode or adjust the length of the hair.   Hope this helped some, good luck.

[spikeyxxx]

@talkingskunk you need to tick the Create Along Paths in the Particle Instance Modifier.

You might want to watch this demo by Daniel Bysted: https://www.youtube.com/watch?v=oqjKMd9CYI4

Watch the whole BlenderToday episode or start from 15.00 minutes, where he explains the Particle Instance Modifier.

[talkingskunk]

Thank you Tanya, and Spikey. I checked both videos out.

I was able to get to this point, but still not sure how to make the grass react to wind.

[spikeyxxx]

Hi @talkingskunk don’t use Keep Shape, because that ‘keeps the shape’ of the grass and prevents it from bending.

[tanya]

I am using wind and turbulence,  animating their movement and strength.   I also had to change the stiffness in the particle setting,  in the effector collection area to a value near zero .  It takes awhile to get it like you want, so don’t get frustrated, you’ll get it.  

I also don’t have keep shape checked in the particle instance.

[spikeyxxx]

@tanya53 and @talkingskunk you can also, instead of the stiffness, add a Forcefield > Force below the ground to get a nice “bending gradient”:

[tanya]

@spikeyxxx thanks for the force idea, that is easier to use then the wind and turbulence.  

[spikeyxxx]

@tanya53 you’d still need at least a turbulence with that, but the grass will appear be stiffer, less influenced by the wind or turbulence, at the roots

[tanya]

@spikeyxxx finally done with animating the grass, I’m a lot happier with it after all your help.  The only issue I still have is the hair particle still renders, I can turn off the plane with the hairs, but not the actual hair.  Do you know how to do that or should I just use a transparent material for it?  thanks again

[spikeyxxx]

#tanya53 I don’t think you can turn the hair off, but you can, as you mentioned give it a transparent material, or, in the Hair Shape panel of the Particle System, set the Diameter Root to 0 (the Tip should already be 0).

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