This is an interesting question. How about a combined RailClone and Forest Pack approach where you create the base mesh with RailClone and then scatter grass on only the areas between the pavers using material IDs. To do this you would use the following approach:
1 - Create a RailClone style with the pavers and spacers.
2 - Assign an Material ID of 1 to the pavers and an ID
to the spacers
3 - In the Display rollout, turn off Use Instancing Engine
and set the Display Mode
. You can now use this RailClone object as a surface in Forest Pack.
4 - Create a Forest Pack object and assign the RC object as a Surface
5 - Choose a Detail grass preset, or use your own. It need to small enough and the distribution dense enough to get into the gaps.
6 - In the Areas Rollout
, set the Surface Material ID
to match the ID on the spacer geometry.
You should now have grass only between the paving stones. If your paving stones are high poly, you may wish to create two RailClone objects. One as a surface for FP and a more detailed version for the render.
Alternatively you could create the whole thing with RailClone. If there isn't a lot of clipping this approach could be much more efficient. To do this you'd just create RailClone segment's that incorporate the grass:
Add these segments to the default input of an A2S array and adjust the padding until they overlap correctly to account for the overhanging blades of grass.
You could also add them to a Forest Object if you like and use the Full Distribution map, adjusting the Density to create the correct size for the grid.
All three of these approaches are demonstrated in the attached files. I hope that helps, please let me know if you have any further questions.