Shader inverting light direction

I`ve been following this tutorial

, but the result turned out not as It had been excepted: the lighting on geometry with the shader applied looked inverted.
http://snag.gy/PIqia.jpg
I found the cause pretty quickly though I cannot figure out why it behaves that way, here take a look(pay attention to lines 37-40):

Code (CSharp):

1.  
2. Shader "1_Lambdert" {
3.     Properties {
4.         _Color ("Color", Color) = (1.0,1.0,1.0,1.0)
5.     }
6.     SubShader {
7.         Pass {
8.             Tags { "LightMode" = "ForwardBase"}
9.             CGPROGRAM
10.             #pragma vertex vert
11.             #pragma fragment frag
12.        
13.             //user defined variables
14.             uniform float4 _Color;
15.        
16.             //unity defined variables
17.             uniform float4 _LightColor0;
18.        
19.             //base input structs
20.             struct vertexInput{
21.                 float4 vertex : POSITION;
22.                 float3 normal : NORMAL;
23.             };      
24.             struct vertexOutput{
25.                 float4 pos : SV_POSITION;
26.                 float4 col : COLOR;
27.             };
28.        
29.             //vertex functions
30.             vertexOutput vert(vertexInput v){
31.                 vertexOutput o;
32.            
33.                 float3 normalDirection = normalize( mul( float4(v.normal,0.0), _World2Object ).xyz );
34.                 float lightDirection;
35.                 float atten = 1.0;
36.            
37.                 lightDirection = normalize( _WorldSpaceLightPos0.xyz );          
38.                 float3 diffuseReflection = max( 0.0, dot(normalDirection, lightDirection));          
39.                 //replacing to upper lines with these fixes the error      
40.                 //float3 diffuseReflection = max( 0.0, dot(normalDirection, normalize( _WorldSpaceLightPos0.xyz )));
41.            
42.            
43.                 o.col = float4(diffuseReflection, 1.0);
44.                 o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
45.                 return o;
46.             }
47.        
48.             //fragment function
49.             float4 frag(vertexOutput i) : COLOR
50.             {
51.                 return i.col;
52.             }
53.        
54.             ENDCG
55.         }
56.     }
57. }
58.  

Does anyone has any ideas what`s wrong with that assignment?

 

You're assigning a vector of 3 floats to just a single float, but you then use it as a vector again. So instead of the .xyz components being used, the components .xxx form the vector, because a float can only store one number. Unity unfortunately does not throw a warning when this happens, so you'll have to watch out for this yourself.

So, "float lightDirection" should be "float3 lightDirection" instead.

 

Thank you, that was obvious, should have figured out myself