hologram shader, Pass, colormask, transparent

This shader creates a fresnel style inner rim glow on an object. It uses the dot product between the surface normal and the view direction vector. To give it a transparent/ghostly feel we set the alpha to the rim-glow effect.

In order to actually get it transparent, we add "alpha:fade" to our #pragma and also assign the Transparent Queue tag.

A "problem" that arises is that we can see the internal faces of an object when it has a complex shape -eg the inside of the mouth cavity. This *might* be desirable in a true x-ray shader?
However, if you wanted to have the outer surface occlude the inner parts, then we must add a Pass.

This will take place before the pass that occurs within the CGPROGRAM. We add a Zwrite On within the pass, which enables writing to the depth buffer and set the ColorMask to 0, so we don't write any colour data - only the Z info.

 

 

 Shader "Dave/Hologram"{
    Properties{
        _RimColor("Rim Color", color)=(1,1,1,1)
        _RimPower("Rim Power",Range(0.5,8))=3
    }
    SubShader{
        Tags{"Queue"="Transparent"}

        Pass {
            Zwrite On //enables writing depth
            ColorMask 0 //doesn't write color data to the frame buffer

        }


        CGPROGRAM

        #pragma surface surf Lambert alpha:fade
        struct Input {
            float3 viewDir;
        };

        float4 _RimColor;
        float _RimPower;

        void surf(Input IN, inout SurfaceOutput o) {
            half rim = 1-saturate(dot(normalize(IN.viewDir), o.Normal));
            o.Emission = pow(rim,_RimPower) * _RimColor.rgb*10;
            o.Alpha = pow(rim, _RimPower);
            
        }

        ENDCG
    }



    Fallback "Diffuse"
}