I'm trying to create some metal people using a skin-only effect shader, but I'm running into an issue. The effect is disappearing when their eyes aren't in frame, and also when I'm standing more than a few metres from them (sometimes).

http://www.etherealsoftware.com.au/ultima/auto-steel.jpg

http://www.etherealsoftware.com.au/ultima/auto-nosteel.jpg

The first image shows what it is meant to look like, the second is when the camera is moved down slightly (the skin is usually that greyish colour without the shader).

Just hoping someone has an idea why this happens, or an idea of what might be causing it. I've already spent hours fixing one Skin shader issue (females not getting the shader), so it'd be a shame to be defeated now.