Thats a great technique I’m stuck on one problem with it though. I don’t want any illumination (or visible color btw) where the light IS hitting the texture. I figured the easy way t odo this would be to set the texture’s diffuse to 0, so that it only self illuminates. Well, it only works reliabily when the total light hitting the surface doesn’t exceed 1. When it goes over 1, you get wierd hot spots which I can’t get rid of.
As an example, I created a plane and give it a default white lambert. The I created a spot light and pointed it down towards the center of the plane. Then I open up the lambert in hypershade, and created the ramp and luminance nodes as you suggested. I tied the outcolor of the ramp into the ambient color of the lambert, and turned the diffuse down to zero.
So it works great, the desired effect is achieved. But here’s the problem. Suppose I go over and change the light’s intensity to say 1.5. All of a sudden I get this wierd hot spot at the center of my ‘dark region’. yuck
This is problematic because It’s really hard to avoid situations in scenes when a surface gets more light than 1. Do you know of a way around this problem so I can still get the desired effect (without the hotspots) with scenes that have a total light value of greater than 1?
Thanks for your thoughts btw, very helpful!