There are some limitations when using grid builder which is outlined in the following article. Most of what is built can be expanded however, see ‘Expanding’.
Although this system is set up to run smoothly on most devices, increasing cell counts to high numbers especially on a single cell or chequered mode will certainly impact performance depending on hardware.
On single cell and chequered I have tested up to 90,000 cells before a slowdown on my midrange machine.
On simple mode, I have tested up to 250,000 cells, with absolutely no slow down at runtime. For this kind of application such as painting or anything using high cell counts, I would turn off gizmos so working in the editor is useable.
Currently, the Grid Selector only checks once for the cell size of the first grid it finds. So it sets its own size based on that. If you decide to have different cell sizes for different grids, then it would not match up. You could however do this check for cell size when entering each different grid. In the Grid Selector class, this should be fairly easy, I have left it to check once purely for performance as in most games the size of the grid/grids will be the same.
There is no limit to how many different grids you can place, and where. The grid selector will work on all of them. Some below on the ground, some on mountains, and some in between, all good.
The grid is limited to running on the XZ axis with Y being up. You could if you are comfortable with coding dive into the classes to change the XYZ values around with whatever you choose.
Simple mode is designed for exactly that, simple grids. High cell counts are fine, however, this does not have the auto cell block feature.
The design aspect of this system is totally in your hands. I have supplied a few prefabs and Materials/Textures to get started but the look of it is totally up to you.
This package can be used with any renderer. It is created in the legacy renderer so all materials are standard. However, a simple material conversion to URP or HDRP is all it takes. See the Unity Documentation for how to do that.
This system could certainly be expanded on if desired, creating perhaps a check for cells next to one another so you could place objects larger than one cell large.
Creating the option to rotate objects could easily be implemented.
Allowing for currently placed objects to be moved.
And many more features that current games of many genres already have.
Grid builder 2 features all of this and more including an option to save the objects on the grid, and many more design features.