Shadow artifacts on vertex animation shader

Question

I'm trying to write a simple vertex-animation-surface shader. The animation works fine and I managed to add animated shadows by using pragma: addshadow. However, the shader still produces strange artifacts: alt text I can get rid of them by changing the shader's render queue to "Transparent" but that also disables shadow-receiving. Any ideas?

Here's my code:

 Shader "Custom/AnimateTest" {
     Properties {
         _Color ("Color", Color) = (1,1,1,1)
         _MainTex ("Albedo (RGB)", 2D) = "white" {}
         _Glossiness ("Smoothness", Range(0,1)) = 0.5
         _Metallic ("Metallic", Range(0,1)) = 0.0
     }
     SubShader {
         Tags { "RenderType"="Opaque" "DisableBatching" = "True" }
         LOD 200
 
         CGPROGRAM
         // Physically based Standard lighting model, and enable shadows on all light types
         #pragma surface surf Standard vertex:myvert addshadow 
 
         // Use shader model 3.0 target, to get nicer looking lighting
         #pragma target 3.0
 
         sampler2D _MainTex;
 
         struct Input {
             float2 uv_MainTex;
         };
 
         half _Glossiness;
         half _Metallic;
         fixed4 _Color;
 
 
 
         void myvert(inout appdata_full v) {
             v.vertex = v.vertex + ((sin(_Time.x * 50.0) + 1.0) * 0.5) * 0.50;
         }
 
         void surf (Input IN, inout SurfaceOutputStandard o) {
             // Albedo comes from a texture tinted by color
             fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
             o.Albedo = c.rgb;
             // Metallic and smoothness come from slider variables
             o.Metallic = _Metallic;
             o.Smoothness = _Glossiness;
             o.Alpha = c.a;
         }
         ENDCG
     }
     FallBack "Diffuse"
 }

Thanks in advance! :)

Answer 1

Best Answer

Answer by Friedemann_A · Jul 19, 2018 at 07:43 PM

The great @bgolus helped me figure it out on the forums, posting the solution here in case somebody needs it in the future:

The v.vertex is a float4 value, the xyz values of which are the position, but you do not want to modify the w component unless you know exactly what you're doing. For the main forward passes modifying the w component doesn't do anything as the shaders forceably override it to a value of 1.0 (the value it defaults to), but the shadow caster pass used for the camera depth and shadows maps do not, and the side effect of modifying the w component is it scales the object in projection space, which moves it away from the camera on PC and desktop due to the use of a reversed depth buffer. The solution is to only modify the xyz components.

The correct line of code in the vertex shader would be:

 v.vertex.xyz = v.vertex.xyz + (sin(_Time.y * 2.5) - 1.0) * 0.25;

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Shadow artifacts on vertex animation shader

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