How to add shadows to surface shader?

Question

This is a question I've seen around a lot but the shader I'm using seems to resist any solutions I've tried. It's a sort of echolocation shader that behaves like this, made by jinglebiscuits that I modified and would like to add shadows to.

Here's my shader code. Please note I'm a total beginner when it comes to shaders so I don't understand much yet:

 Shader "My/Normal/AlphaPulseShader" {
     Properties {
       _MainTex ("Base (RGB) Trans (A)", 2D) = "blue" {}
       _BumpMap ("Normalmap", 2D) = "bump" {}
       _EmissionMap ("Emission Map", 2D) = "black" {}
       _Color ("Color", Color) = (1, 0, 0, 1)
       _PDistance("PulseDistance", Float) = 0
       _PFadeDistance("FadeDistance", Float) = 10
       _PEdgeSoftness("EdgeSoftness", Float) = 5
       _Origin("PulseOrigin", Vector) = (0, 0, 0, 0)
       
       _RimColor("Rim Color", Color) = (1,1,1,1)
       _RimPower("Rim Power", Range(0.5, 8.0)) = 1.059702
       _RimOn("Rim On", Range(0, 1)) = 0.0
       _EmissionMultiplier("Emission Multiplier",Range(-10,10)) = 1.0
     }
     
     SubShader {
       Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
       LOD 200
 
       ZWrite On
       ZTest LEqual
       Blend SrcAlpha OneMinusSrcAlpha
 
       CGPROGRAM
 
       //LIGHTING
       #include "AutoLight.cginc"
 
       // define finalcolor and vertex programs:
       #pragma surface surf Lambert finalcolor:mycolor vertex:myvert// alpha
       struct Input {
           float2 uv_MainTex;
           float2 uv_BumpMap;
           float2 uv_EmissionMap;
           float3 worldPos;
           float3 viewDir;
           half alpha;
       };
       
       fixed4 _Color;
       sampler2D _MainTex;
       sampler2D _BumpMap;
       sampler2D _EmissionMap;
       half _PDistance;
       half _PFadeDistance;
       half _PEdgeSoftness;
       float4 _Origin;
       
       float4 _RimColor;
       float _RimPower;
       float _RimOn;
       float _EmissionMultiplier;
 
       void myvert (inout appdata_full v, out Input data) {
           UNITY_INITIALIZE_OUTPUT(Input, data);
  
 
       }
       
       void mycolor (Input IN, SurfaceOutput o, inout fixed4 color) {
           // set the vertex color alpha to the value calculated: 
           fixed4 c = tex2D(_MainTex, IN.uv_MainTex) * _Color;
           color.a = c.a;
           half dis;
           half interval;
           half origin;
           dis = sqrt(pow((IN.worldPos.x - _Origin.x),2) + pow((IN.worldPos.y - _Origin.y), 2) + pow((IN.worldPos.z - _Origin.z), 2));
           
           if(dis >= _PDistance)
           {
               color.rgb = color.rgb * (1 - saturate(abs(_PDistance - dis)/_PEdgeSoftness));
           }
           else
           {
               color.rgb = color.rgb * (1 - saturate(abs(_PDistance - dis)/_PFadeDistance));
           }
           
       }
       
       void surf (Input IN, inout SurfaceOutput o) {
           // simply copy the corresponding texture element color:
           fixed4 c = tex2D(_MainTex, IN.uv_MainTex) * _Color;
           o.Albedo = c.rgb;
          // o.Alpha = tex2D(_MainTex,IN.uv_MainTex).a;
           o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_BumpMap));
         //  half rim = 1.0 - saturate(dot(normalize(IN.viewDir), o.Normal));
           if(_RimOn > 0)
          {
               half rim = 1.0 - saturate(dot(normalize(IN.viewDir), o.Normal));
               o.Emission = _RimColor.rgb * pow(rim, _RimPower) + _EmissionMultiplier*tex2D(_EmissionMap,IN.uv_EmissionMap);
           }
       }
       
       ENDCG
     } 
 
    // Fallback "Diffuse"
         Fallback "VertexLit"
 
   }

Anyone have any idea how I could do this?

Answer 1

Simple answer: you can't. Transparent objects cannot receive shadows in Unity, that's just how things are. There used to be ways of faking it/getting around this, but they had issues of their own and no longer work. From the looks of it, your shader doesn't have to rely on transparency, so you could simply change the colour of the areas that aren't visible rather than having them transparent.

Here is the shader with support for shadows (and cleaned up a bit);

 Shader "My/Normal/AlphaPulseShader" {
     Properties{
         _MainTex ("Base (RGB) Trans (A)", 2D) = "blue" {}
         _BumpMap ("Normalmap", 2D) = "bump" {}
         _EmissionMap ("Emission Map", 2D) = "black" {}
         _Color ("Color", Color) = (1,0,0,1)
         _PDistance ("PulseDistance", Float) = 0
         _PFadeDistance ("FadeDistance", Float) = 10
         _PEdgeSoftness ("EdgeSoftness", Float) = 5
         _Origin ("PulseOrigin", Vector) = (0, 0, 0, 0)
 
         _RimColor ("Rim Color", Color) = (1,1,1,1)
         _RimPower ("Rim Power", Range(0.5, 8.0)) = 1.059702
         [Toggle(USE_RIM)]_RimOn ("Rim On", Int) = 0.0
         _EmissionMultiplier ("Emission Multiplier", Range(-10,10)) = 1.0
     }
 
     SubShader{
         Tags{ "RenderType"="Opaque" }
         LOD 200
 
         CGPROGRAM
         //LIGHTING
         #include "AutoLight.cginc"
         // define finalcolor and vertex programs:
         #pragma surface surf Lambert finalcolor:mycolor// alpha
 
         #pragma shader_feature USE_RIM
 
         struct Input {
             float2 uv_MainTex;
             float2 uv_BumpMap;
             float2 uv_EmissionMap;
             float3 worldPos;
             float3 viewDir;
             half alpha;
         };
 
         fixed4 _Color;
         sampler2D _MainTex;
         sampler2D _BumpMap;
         sampler2D _EmissionMap;
         half _PDistance;
         half _PFadeDistance;
         half _PEdgeSoftness;
         float4 _Origin;
 
         float4 _RimColor;
         float _RimPower;
         float _RimOn;
         float _EmissionMultiplier;
 
         void mycolor (Input IN, SurfaceOutput o, inout fixed4 color) {
             // set the vertex color alpha to the value calculated: 
             fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
             color.a = c.a;
             half dis;
             half interval;
             half origin;
             dis = sqrt (pow ((IN.worldPos.x - _Origin.x),2) + pow ((IN.worldPos.y - _Origin.y), 2) + pow ((IN.worldPos.z - _Origin.z), 2));
 
             if (dis >= _PDistance)
             {
                 color.rgb = color.rgb * (1 - saturate (abs (_PDistance - dis) / _PEdgeSoftness));
             }
             else
             {
                 color.rgb = color.rgb * (1 - saturate (abs (_PDistance - dis) / _PFadeDistance));
             }
 
         }
 
         void surf (Input IN, inout SurfaceOutput o) {
             // simply copy the corresponding texture element color:
             fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
             o.Albedo = c.rgb;
             // o.Alpha = tex2D(_MainTex,IN.uv_MainTex).a;
             o.Normal = UnpackNormal (tex2D (_BumpMap, IN.uv_BumpMap));
             //  half rim = 1.0 - saturate(dot(normalize(IN.viewDir), o.Normal));
             #ifdef USE_RIM
                 half rim = 1.0 - saturate (dot (normalize (IN.viewDir), o.Normal));
                 o.Emission = _RimColor.rgb * pow (rim, _RimPower) + _EmissionMultiplier * tex2D (_EmissionMap, IN.uv_EmissionMap);
             #endif
         }
         ENDCG
     }
     // Fallback "Diffuse"
     Fallback "VertexLit"
 }

How to add shadows to surface shader?

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