OK, here’s the scenario. I have a fairly large flat plane with a particle system of grass covering it. On a regular basis, I will be reusing this grassy plane in different scenes and overlaying it with plants and mulch beds (odd shaped planes slightly above the plane of grass). I need to make it so that the grass (hair) particles do not go through the plant or mulch bed meshes. I am trying to make it work with Collision settings but so far, having no luck. I have seen mentions of Deflector objects and “killing the particles” but can’t figure out how to make those work. I don’t want to have to deal with weight painting the areas where the grass would intersect with these other mesh objects. I just want to make it so the grass does not pass through them. There must be a way of doing this.
My scenes are not going to be animated. They are just for a single rendered frame. Any help would be greatly appreciated.
Thank you for the response. I know about weight painting, but I am looking for a simpler solution. I need to have a secondary plane, slightly above the grassy plane, which blocks the grass from penetrating through. So wherever I move the secondary plane, the grass will not be able to pass through. Like if you were to lay a sheet of plywood on your lawn, the grass is squished underneath. I need 3D plywood power.
You could use dynamic paint. The secondary plane would paint weight onto the grass plane. The weight would determine where grass particles are. Here is an example of dynamic painting of weight https://www.youtube.com/watch?v=J313g2N5hZc .
Paint full weight then invert.
I don’t know much about this to help with details. I’m sure others can.
It turns out that weight painting was just the thing I need.
I did not need to paint the grassy particle surface in advance.
I do not need to have my objects that will be doing the painting intersect with particle surface to do their thing.
What I figured out was that I can use a simple plane (which is perfect because that’s what I wanted to use for my mulch bed) and designate that as the brush and the grassy surface is the canvas. Then I just set the brush to do its weight painting by proximity (or a combination of volume and proximity) to do the painting. And if I hover the mulch bed over the grassy plane about 1/2" up, then it prevents the grass from growing underneath. I just need to remember to re-bake the effect every time I move it, otherwise I’ll have a patch of dead grass for no reason and grass growing through my mulch.
Thanks to everyone for contributing your suggestions.
