Transparent shadow caster with fully opaque shadows?

Back in the Unity 4 days - transparent objects could only cast fully opaque shadows. In Unity 5 we got dithered shadows and PCF filtering with soft shadows.

I've got some rooftops I'd like to fade to transparent when my character walks into a building, but I'd like for the shadows to remain fully dark/opaque. In Unity 4 this would've been the default behavior.

The only solution I can find is to duplicate all of the meshrenderers, apply an opaque material, and then tick "Cast Shadows: shadows only".

It seems like a really crappy solution though. Anyone got any ideas? Can we toggle this feature? Do I need some shader voodoo? Or should I seriously keep 2 copies of all my roof objects?

 

Click here to see a gif of this in action!


Success! Got some help on discord.

Just use the alpha slider in the material. Works in Unity 2017.

Thanks porkington

Code (CSharp):

1. Shader "Custom/NewSurfaceShader" {
2.     Properties {
3.         _Color ("Color", Color) = (1,1,1,1)
4.         _MainTex ("Albedo (RGB)", 2D) = "white" {}
5.         _Glossiness ("Smoothness", Range(0,1)) = 0.5
6.         _Metallic ("Metallic", Range(0,1)) = 0.0
7.         _Alpha ("Alpha", Range(0,1)) = 0.0
8.     }
9.     SubShader {
10.         Tags { "RenderType"="Transparent" "Queue"="Transparent" }
11.         LOD 200
12.        
13.         CGPROGRAM
14.         // Physically based Standard lighting model, and enable shadows on all light types
15.         #pragma surface surf Standard fullforwardshadows alpha:fade
16.  
17.         // Use shader model 3.0 target, to get nicer looking lighting
18.         #pragma target 3.0
19.  
20.         sampler2D _MainTex;
21.  
22.         struct Input {
23.             float2 uv_MainTex;
24.         };
25.  
26.         half _Glossiness;
27.         half _Metallic;
28.         fixed4 _Color;
29.         half _Alpha;
30.  
31.         // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
32.         // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
33.         // #pragma instancing_options assumeuniformscaling
34.         UNITY_INSTANCING_CBUFFER_START(Props)
35.             // put more per-instance properties here
36.         UNITY_INSTANCING_CBUFFER_END
37.  
38.         void surf (Input IN, inout SurfaceOutputStandard o) {
39.             // Albedo comes from a texture tinted by color
40.             fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
41.             o.Albedo = c.rgb;
42.             // Metallic and smoothness come from slider variables
43.             o.Metallic = _Metallic;
44.             o.Smoothness = _Glossiness;
45.             o.Alpha = _Alpha;
46.         }
47.         ENDCG
48.     }
49.     FallBack "Diffuse"
50. }
51.  

 

Could you explain on how you did it? Cheers