Actually, this is not a new tutorial; I created this as a part of the Making of Story for my scene Time Under Trees. But I have been requested few times to publish this part in a seperate tutorial so it can get listed in the search engines and include a grass version of the same method. This first part is about how to create grass using Particle Flow Method. (Please click on images to view in higher resolution.)
First, I modeled few different grass strands to scatter around.
Then I created a Particle Flow System.
When you click on the Particle view, you can see the settings of Particle Flow in a new window. Here as the first step, I set the Emit Start and Emit Stop value to 0 as I am not animating but using it for a still image. You can specify the number of particles.I choose my Emitter Object with the Position Object Operator. This is for schoosing the object that we scatter our particles on (emitter).
In the Rotation Operator, it is important to choose Random Horizantal. This setting provides us to limit our rotation on the surface plane, without rotating on the volume.
To choose particle geometry object (our meshes to that will scatter around), we will use Shape Instance Operator. To scatter different objects, you can group them and enable the "Group Objects" settings or you can make a parent dummy object and link the child objects to this. I used a basic primitive box object because my target is to get use of VrayProxy Objects for my particles. I will talk about this in next steps. Now we will distribute the box object.
After distributing the boxes with the particle flow, I baked the particles into a mesh by using Bobo's BakePFlowToObjects script. By making this, all particles become a mesh so they can be replaced. You can find this very useful script in www.scriptspot.com
To replacing the particles with VrayMeshes (proxy objects of little stones),I used another great script ObjectReplacer by Neil Blevins. (www.neilblevins.com) I replaced all dummy boxes with the meshes. These steps aew necessary to retain the proxy characteristic of the scattered objects. Position, Rotation, Scale properties are adjustable.
And now you have your grass as geometry created with Particle FLow.