I have been using some blades of grass that are meshes and add that as an object to the particle system. When I increase the number enough to cover my ground plane I run out of horse power on my computer. How would I instance the grass mesh with this approach?
Thanks!
The first question would have to be whether it is necessary to use the mesh for all the grass? Even using the hair particles, there is no way to have fields of rolling grass unless you have a massive computer system to handle it.
So I have the following comments:
Resolution - How detailed will the grass be in the final render? If the blades will only be a few pixels wide, you will not see any benefits fron using a mesh. If you need to see the grass in detail, only use the mesh for the blades closest to the camera, with hair particles for those further away.
Field of view - only put grass within the cameras line of sight. Remove anything that is not visible as Blender will try to render everything, not just what you will see. This should reduce the amount of processing.
Without seeing what you are trying to do, it is difficult to give a proper analysis, but remember to keep it simple, and use whatever tools are available to reduce the load on the CPU/GPU.
Use hair children. These are interpolated so you can get a massive number of them with little performance hit. You can have separate child counts for the viewport and at render time in case viewport update is causing problems. With children you should be able to have well over a million instances without much performance hit at all.
Also, don’t use a mesh of a single blade or render as hair strands. Model a clump (or several clumps) and instance that. Not only do you get more blades for each particle simulated, but it’s actually more realistic anyway because that is how grass grows. Each root ball sprouts multiple blades. This is especially true for wild grass which can grow into big clumps instead of being mowed short.
Hair children are great, but if you have a close up of grass, you need a mesh to give the fine detail for those blades close to you (grass is thicker in the central spine and has an interesting shape). Individual blades or clumps make no difference since it is the vertex count that is important. Clumps will help if you have a problem with the display, but does not make any difference to the render, as far as I know.
Also if you set the hair in cycles to triangle>ribbon you save a lot on rendering and it should be accurate.
You can have hair children be a mesh too. As for the vertex count, not sure I follow? The meshes are instanced, the total vertex count of the whole field is pretty much meaningless.