Simple Unlit/Frag Shader Problem

Hi, i have a simple shader-coding question.

I dont understand why i dont get the desired Color and just a grey tone when i pass the RGBA values in seperated manner. ->

fixed4 mainColor = _MainColor;
fixed4 col = (mainColor.r, mainColor.g, mainColor.b, mainColor.a);

If i would return only mainColor is would get my desired Color but if i return col i just get grey.
Whats the problem?

Code (HLSL):

1. Shader "Unlit/test"
2. {
3.     Properties
4.     {
5.         _MainColor("MainColor", Color) = (1,1,1,1)
6.         _MainTex ("Texture", 2D) = "white" {}
7.     }
8.     SubShader
9.     {
10.         Tags { "RenderType"="Opaque" }
11.         LOD 100
12.  
13.         Pass
14.         {
15.             CGPROGRAM
16.             #pragma vertex vert
17.             #pragma fragment frag
18.             // make fog work
19.             #pragma multi_compile_fog
20.  
21.             #include "UnityCG.cginc"
22.  
23.             struct appdata
24.             {
25.                 float4 vertex : POSITION;
26.                 float2 uv : TEXCOORD0;
27.             };
28.  
29.             struct v2f
30.             {
31.                 float2 uv : TEXCOORD0;
32.                 UNITY_FOG_COORDS(1)
33.                 float4 vertex : SV_POSITION;
34.             };
35.  
36.             float4 _MainColor;
37.             sampler2D _MainTex;
38.             float4 _MainTex_ST;
39.  
40.             v2f vert (appdata v)
41.             {
42.                 v2f o;
43.                 o.vertex = UnityObjectToClipPos(v.vertex);
44.                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
45.                 UNITY_TRANSFER_FOG(o,o.vertex);
46.                 return o;
47.             }
48.  
49.             fixed4 frag (v2f i) : SV_Target
50.             {
51.                 fixed4 mainColor = _MainColor;
52.                 // sample the texture
53.                 fixed4 texColor = tex2D(_MainTex, i.uv);
54.  
55.                 fixed4 col = (mainColor.r,mainColor.g,mainColor.b,mainColor.a);
56.  
57.                 // apply fog
58.                 UNITY_APPLY_FOG(i.fogCoord, col);
59.                 return col;
60.             }
61.             ENDCG
62.         }
63.     }
64. }
65.  

 

Hi Chris,

Your syntax is just slightly wrong. Use:

Code (HLSL):

1. float4(mainColor.r,mainColor.g,mainColor.b,mainColor.a);

and you can use also this kind of variable declaration, similar to setting values to an array:

Code (HLSL):

1. fixed4 col = { mainColor.r,mainColor.g,mainColor.b,mainColor.a };

I suggest you open the Microsoft HLSL reference. It's a dry but good source for exact information. Helps a lot when you run into this kind of things especially when starting with shaders.

 

ah thank you ! so simple xD

 

Yeah but not so simple when you don't get an error . Happens to me a lot from time to time with different things when trying to write shaders/HLSL.

P.S. also notice that you're mixing two data types there, fixed and float.

 

yeb thats the thing, i thought it was accepted.
im just starting out with this... thx

 

This is orthogonal to what the OP asked, but avoid using custom names for things unless you have a specific reason. For example using _MainColor instead of the more standard _Color might cause problems, since there are things in Unity that rely on things being named a certain way.

 

Or, you know, just

fixed4 col = mainColor;

Specifically

material.color = myColor;

expects the shader to be using

_Color

, as it's just an alias for

material.SetColor("_Color", myColor);

. Really, just don't ever use

material.color

and it won't be a problem.

The other place it's expected is with fallback shadowcaster passes and replacement shaders. This is really only an issue with an alpha tested shader, where it's expecting the alpha of the

_MainTex

is multiplied by

_Color.a

before doing the

clip()

. If you're not using alpha testing, or not using a fallback for the shadowcaster and not using the _CameraDepthNormalsTexture, this can also be safely ignored.

 

Also lightmapping expects certain things to be named in certain ways, although if you are writing completely custom Lightmapped shaders, you might as well write a Meta pass too.

 

thanks everybody... i just wanted to understand why it didnt work when i seperate the RGBA and make a new float. all good now

 

@bgolus I thought there might be something going to happen with those values after that specific issue was resolved by the author, so I tried to suggest a fix it with minimal changes. But of course you're absolutely correct.