Here is a shader which aims to give the effect of black crystal. Assign a grayscale image (dark with occasional highlight) to the main texture slot and adjust brightness.
Shader ignores original mapping coordinates of mesh and performs a type of spherical mapping (with help from: [Cg] Environment Maps - Ogre Forums)
I am using this shader for the windows of a ship!
Shader "Custom/Black Crystal" {
Properties {
_MainTex ("Main Texture", 2D) = "black" {}
_Brightness ("Brightness", Range(0, 1)) = 1
}
SubShader {
Tags { "Queue"="Geometry" }
Lighting Off
Pass {
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
struct appdata {
half4 vertex : POSITION;
half3 normal : NORMAL;
};
struct v2f {
half4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
};
sampler2D _MainTex;
half _Brightness;
half4 _MainTex_ST;
v2f vert(appdata v) {
v2f o;
o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
half3 normalViewSpace = mul((float3x3)UNITY_MATRIX_MVP, v.normal);
o.uv = normalViewSpace - o.pos.xy / 10;
return o;
}
half4 frag(v2f i) : COLOR {
half4 outColor = tex2D(_MainTex, half2(0.5, -0.5) * i.uv.xy * half2(0.75, 0.75));
return outColor * _Brightness;
}
ENDCG
}
}
}