is it possible to make a large cylinder in forge? Such as a grain silo? Whenever I put a building block down there is an option to change the shape. When I change it to a cylinder, it doesnt seem to actually change its shape.
Unfortunately, the shape option only effects fields around objective, dominion, and spawning objects. Your best bet in creating a cylinder is forming one using several blocks or using the silos that are given on the Impact template.
If you are making the map on Impact, Silos are in the Impact structures tab. If its Revine or Erosion, you could use small round ramps in the inclines tab to make something look roughly look like a cylinder.
If you're building it on Erosion, you could use the pipe objects. The basic one can act as an upward cylinder if you flip it that way.
That would be under "Inclines", although those will be filled in the middle, with ramp. If you just want a hollow cylinder your best bet is curved walls (Under Doors and Walls) or the Silo 2, Open from the Impact palette.