There are a few options. I usually get the World Normal and extract the B channel and use that as a mask. That way only upwards facing polys get affected strongly which tends to help. You could also try masking by things like shading model.
There are a few options. I usually get the World Normal and extract the B channel and use that as a mask. That way only upwards facing polys get affected strongly which tends to help. You could also try masking by things like shading model.