Resolved Shadow caster billboard to camera

Shadow caster code:

Code (CSharp):

1. Tags { "RenderType"="TransparentCutout" "Queue"="AlphaTest" "LightMode" = "ShadowCaster" }
2.     Blend SrcAlpha OneMinusSrcAlpha
3.     AlphaToMask On
4.     Pass
5.     {
6.         CGPROGRAM
7.         #pragma vertex vert
8.         #pragma fragment frag
9.         #pragma multi_compile_instancing
10.      
11.         #include "UnityCG.cginc"
12.  
13.         struct appdata
14.         {
15.             float4 vertex : POSITION;
16.             float2 uv : TEXCOORD0;
17.             UNITY_VERTEX_INPUT_INSTANCE_ID
18.         };
19.  
20.         struct v2f
21.         {
22.             float2 uv : TEXCOORD0;
23.             float4 pos : SV_POSITION;
24.         };
25.  
26.         uniform sampler2D _MainTex;
27.         uniform float4 _MainTex_ST;
28.  
29.         UNITY_INSTANCING_BUFFER_START(Props)
30.         UNITY_DEFINE_INSTANCED_PROP(float4, _Pos)
31.         UNITY_INSTANCING_BUFFER_END(Props)
32.  
33.         v2f vert (appdata v)
34.         {
35.             v2f o;
36.             UNITY_SETUP_INSTANCE_ID(v);
37.  
38. float3 vpos = mul((float3x3)unity_ObjectToWorld, v.vertex.xyz);
39. float4 worldCoord = float4(unity_ObjectToWorld._m03, unity_ObjectToWorld._m13, unity_ObjectToWorld._m23, 1);
40. float4 viewPos = mul(UNITY_MATRIX_V, worldCoord) + float4(vpos, 0);
41. float4 outPos = mul(UNITY_MATRIX_P, viewPos);
42.  
43.             o.pos = outPos;
44.             o.uv = TRANSFORM_TEX(v.uv, _MainTex);
45.             return o;
46.         }
47.  
48.         fixed4 frag (v2f i) : SV_Target
49.         {
50.             fixed4 tex = tex2D(_MainTex, i.uv);
51.             clip(tex.a - 0.1);
52.  
53.             return 0;
54.         }
55.         ENDCG
56.     }

Could someone tell me how to make shadow caster billboard effect rotate towards camera, not the caster itself? It causes visual glitches like this:

 

You need to calculate the orientation in world space using a view matrix that is always for the main camera itself. For example

UNITY_MATRIX_V

is the current view matrix being used for rendering. You’d need to use something like:

Code (csharp):

1. worldCoord.xyz += mul((float3x3)unity_CameraToWorld, vpos);
2. float4 outPos = mul(UNITY_MATRIX_VP, worldCoord);

 

Now I understand that my technique is wrong. The shadow looks properly only if sprite is shaded from behind (no zwrite):

But from the other side:


My question now is: How is it possible to shade billboard grass?
Should I take another approach or just make a little change?

Also if you could guys recommend any good tutorials to learn more complex shaders with problems like this. T

My code:

Code (ShaderLab):

1. Shader "Engine/GrassShader"
2. {
3.     Properties
4.     {
5.         _MainTex ("Texture", 2D) = "white" {}
6.         _Color ("Color", Color) = (0, 1.0, 0, 1)
7.         _Normal("Normal", Vector) = (0.0, 0.0, 0.0, 0.0)
8.         _Pos("Normal", Vector) = (0.0, 0.0, 0.0, 0.0)
9.         _SemiShadow("Semi Shadow", Color) = (0, 0.6, 0, 1)
10.         _SemiShadowThreshold("Semi Shadow Threshold", Float) = 0.4
11.         _Shadow("Shadow", Color) = (0, 0.3, 0, 1)
12.         _ShadowThreshold("Shadow Threshold", Float) = 0.2
13.         _TestTex("TestTex", 2D) = "white" {}
14.     }
15.     SubShader
16.     {
17.         Tags { "RenderType"="TransparentCutout" "Queue"="AlphaTest" "LightMode"="ForwardBase" }
18.         Blend SrcAlpha OneMinusSrcAlpha
19.         AlphaToMask On
20.         Pass
21.         {
22.             CGPROGRAM
23.             #pragma vertex vert
24.             #pragma fragment frag
25.             #pragma multi_compile_instancing
26.             #pragma multi_compile_fwdbase
27.  
28.             #define FORWARD_BASE_PASS
29.  
30.             #include "UnityCG.cginc"
31.             #include "UnityLightingCommon.cginc"
32.             #include "AutoLight.cginc"
33.             #include "Lighting.cginc"
34.  
35.             struct appdata
36.             {
37.                 float4 vertex : POSITION;
38.                 float2 uv : TEXCOORD0;
39.                 UNITY_VERTEX_INPUT_INSTANCE_ID
40.             };
41.  
42.             struct v2f
43.             {
44.                 float2 uv : TEXCOORD0;
45.                 float4 pos : SV_POSITION;
46.                 float3 normal : NORMAL;
47.                 float3 worldPos : TEXCOORD1;
48.                 SHADOW_COORDS(2)
49.             };
50.            
51.             uniform sampler2D _TestTex;
52.             uniform float4 _TestTex_ST;
53.  
54.             uniform sampler2D _MainTex;
55.             uniform float4 _MainTex_ST;
56.             uniform float3 _Color;
57.             uniform float3 _SemiShadow;
58.             uniform float _SemiShadowThreshold;
59.             uniform float3 _Shadow;
60.             uniform float _ShadowThreshold;
61.  
62.             UNITY_INSTANCING_BUFFER_START(Props)
63.             UNITY_DEFINE_INSTANCED_PROP(float4, _Normal)
64.             UNITY_DEFINE_INSTANCED_PROP(float4, _Pos)
65.             UNITY_INSTANCING_BUFFER_END(Props)
66.  
67.             v2f vert (appdata v)
68.             {
69.                 v2f o;
70.                 UNITY_SETUP_INSTANCE_ID(v);
71.  
72.                 float3 vpos = mul((float3x3)unity_ObjectToWorld, v.vertex.xyz);
73.                 float4 worldCoord = float4(unity_ObjectToWorld._m03, unity_ObjectToWorld._m13, unity_ObjectToWorld._m23, 1);
74.                 float4 viewPos = mul(UNITY_MATRIX_V, worldCoord) + float4(vpos, 0);
75.                 float4 outPos = mul(UNITY_MATRIX_P, viewPos);
76.                
77.                 o.worldPos = mul(unity_ObjectToWorld, v.vertex);
78.  
79.                 o.pos = outPos;
80.                 o.normal = normalize(UnityObjectToWorldNormal(UNITY_ACCESS_INSTANCED_PROP(Props, _Normal)));
81.                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
82.                 TRANSFER_SHADOW(o)
83.                 return o;
84.             }
85.  
86.             fixed4 frag (v2f i) : SV_Target
87.             {
88.                 fixed4 tex = tex2D(_MainTex, i.uv);
89.                 clip(tex.a);
90.                
91.                 UNITY_LIGHT_ATTENUATION(atten, i, i.worldPos);
92.  
93.                 float diffuse = dot(i.normal, _WorldSpaceLightPos0.xyz) * atten;
94.                 float3 cel = diffuse < _ShadowThreshold ? _Shadow : (diffuse < _SemiShadowThreshold ? _SemiShadow : _Color);
95.                 fixed4 col = fixed4(cel * _LightColor0, tex.a);
96.  
97.                 #if defined(FORWARD_BASE_PASS)
98.                     col += float4(max(0, ShadeSH9(float4(i.normal, 1))).rgb, 0.0);
99.                 #endif
100.  
101.                 return col;
102.             }
103.             ENDCG
104.         }
105.        
106.         Tags { "RenderType"="TransparentCutout" "Queue"="AlphaTest" "LightMode" = "ShadowCaster" }
107.         Blend SrcAlpha OneMinusSrcAlpha
108.         AlphaToMask On
109.         Pass
110.         {
111.             CGPROGRAM
112.             #pragma vertex vert
113.             #pragma fragment frag
114.             #pragma multi_compile_instancing
115.            
116.             #include "UnityCG.cginc"
117.  
118.             struct appdata
119.             {
120.                 float4 vertex : POSITION;
121.                 float2 uv : TEXCOORD0;
122.                 UNITY_VERTEX_INPUT_INSTANCE_ID
123.             };
124.  
125.             struct v2f
126.             {
127.                 float2 uv : TEXCOORD0;
128.                 float4 pos : SV_POSITION;
129.             };
130.  
131.             uniform sampler2D _MainTex;
132.             uniform float4 _MainTex_ST;
133.  
134.             UNITY_INSTANCING_BUFFER_START(Props)
135.             UNITY_DEFINE_INSTANCED_PROP(float4, _Pos)
136.             UNITY_INSTANCING_BUFFER_END(Props)
137.  
138.             v2f vert (appdata v)
139.             {
140.                 v2f o;
141.                 UNITY_SETUP_INSTANCE_ID(v);
142.  
143.                 float3 vpos = mul((float3x3)unity_ObjectToWorld, v.vertex.xyz);
144.                 float4 worldCoord = float4(unity_ObjectToWorld._m03, unity_ObjectToWorld._m13, unity_ObjectToWorld._m23, 1);
145.                 worldCoord.xyz += mul((float3x3)unity_CameraToWorld, vpos);
146.                 float4 outPos = mul(UNITY_MATRIX_VP, worldCoord);
147.  
148.                 o.pos = outPos;
149.                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
150.                 return o;
151.             }
152.  
153.             fixed4 frag (v2f i) : SV_Target
154.             {
155.                 fixed4 tex = tex2D(_MainTex, i.uv);
156.                 clip(tex.a - 0.1);
157.  
158.                 return 0;
159.             }
160.             ENDCG
161.         }
162.     }
163. }

 

That just looks like you like the look of the grass with shadow casting disabled. Regardless of how you’re rendering the grass, there should be an option to disable the shadow casting, either on the component or the script function being used.

 

Oh, I forgot to disable shadow casting in script, right. Thanks alot!