Is there any way to control how a spotlight fades out?

Hi all. Playing around with the stealth tutorial, i'm trying to add in a spotlight attached to the robot's faces, to show the player where they're looking, and the size of their vision cone.

See this image, and note the long fence in the middle-left of it:

The robot's vision range is 10 units, and so too is the range of the light. That fence is less than 10 units away, and it should, by all accounts, be bathed in a healthy green glow. But it's not lit up at all

My idea works very well for showing the angle of the vision area, but not for showing its distance. The player would be seen if they were infront of that fence just now.

I've tried increasing the distance parameter on the cone, but this has unsatisfactory results, like making it go a bit too far, as well as projecting way over obstacles and lighting up the outer walls of the scene too much

The problem is that the light seems to fade out over its range, so by the time maximum range is reached, it barely has any illumination at all. I guess what i'd like is for some way to control it, like with the curves on 3D audio fading.

Failing that, does anyone have an alternate idea for how i could accomplish what i'm trying to do ?