How does one generate accurate isometric grids in Illustrator CC?
I would like to offer an alternate solution. The SSR method used by @CAI is perfectly valid transformation technique that has uses beyond grids. SSR is actually setting a orthographic matrix in place the hard way because theres no way to set it directly (do save the scale sequence as an action it is super useful). While its one of the things you should know, doing a orthographic grid with other construction techniques is also basic shape construction, so good to know.
An Alternate and Simpler Methods Construction
The basic floor isometric grid is simply 2 lines in a 30 and 150 degree (120 degree separation) to the main grid of illustrator. So we can simply do as follows:
Enable line tool and alt click on your canvas.
This opens a dialog:
Type 30 in the angle box
and some nice number in the length box
Move a duplicate whilst holing alt to clone it (or use the move dialog if you want accurate scale)
- Press ctl+d until you have as many copies as you want
- Chose 1:
- Repeats steps with angle of 120
- Rotate 120 with transform each (pivot about lower left corner)
- (Optional) Select all and trim with shape builder (tip: hold shift and alt down to delete square regions)
The benefit of this method is that you can decide other shapes than the diamond pattern too. Though there is no reason you could not cut them out later ro before with SSR either.
Image 1: Quick screen cast of doing it more manually.