Ambient occlusion, when it was introduced in Crysis, was a significantly expensive effect all by itself. These days, high-quality screen-space ambient occlusion is no longer a huge performance drain.

Below you can see the global illumination diffuse occlusion only, compared with the screen space diffuse color added afterwards. Here's a Monarch operative with screen space ambient occlusion applied.

Set your Shadow Quality to Low or Medium Set your SSAO (Screen Space Ambient Occlusion) quality to Low Set your Fog Quality to Low Clutter Quality can go as low as you are happy with. Now that ...