Demo 22 - Echolocation

Shader "Custom/Echolocation" {
    Properties {
        _Color ("Color", Color) = (1, 1, 1, 1)
        _Center ("CenterX", vector) = (0, 0, 0)
        _Radius ("Radius", float) = 0
    }
    SubShader {
        Pass {
            Tags { "RenderType"="Opaque" }

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            float4 _Color;
            float3 _Center;
            float _Radius;

            struct v2f {
                float4 pos : SV_POSITION;
                float3 worldPos : TEXCOORD1;
            };

            v2f vert(appdata_base v) {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.worldPos = mul(_Object2World, v.vertex).xyz;
                return o;
            }

            fixed4 frag(v2f i) : COLOR {
                float dist = distance(_Center, i.worldPos);

                float val = 1 - step(dist, _Radius - 0.1) * 0.5;
                val = step(_Radius - 1.5, dist) * step(dist, _Radius) * val;
                return fixed4(val * _Color.r, val * _Color.g,val * _Color.b, 1.0);
            }

            ENDCG
        }
    }
    FallBack "Diffuse"
}