CG: 4+ color gradient

Question

I am trying to write a shader that takes multiple colors and applies them to a B&W texture. Now, 3 colors works just fine, but i will need 6 in order for this to function. If somebody could please explain how adding more colors would work or refer me to some documentation that would be appreciated!

What i have so far is the following (tex = B&W texture, _Middle = 0.5):

fixed4 c = lerp(_ColorA, _ColorB, tex.y / _Middle) * step(tex.y, _Middle);
c += lerp(_ColorB, _ColorC, (tex.y - _Middle) / (1 - _Middle)) * step(_Middle, tex.y);

Source: http://answers.unity3d.com/questions/1108472/3-color-linear-gradient-shader.html

Answer 1

The following code creates a 4 color gradient texture and applies it to the shader. The code needs to be attached to the object that has the shader on it.

private Texture2D _tex; //Texture that will go into the shader
private Renderer _rend; //Renderer of the object


private void Awake () {
    _rend = this.GetComponent<Renderer> ();

    //create new texture, width == amount of colors
    _tex = new Texture2D (4, 1);  

    //Set each pixel to specified color (StarGradient is function below)
    _tex.SetPixels32 (StarGradient (
        new Color32 (255, 186, 0, 1), 
        new Color32 (224, 100, 45, 1), 
        new Color32 (118, 73, 41, 1), 
        new Color32 (60, 73, 55, 1))
    );
    _tex.filterMode = FilterMode.Trilinear;
    _tex.wrapMode = TextureWrapMode.Clamp;
    _tex.Apply ();

    //Pass _tex to the material
    _rend.material.SetTexture ("_RampTex", _tex);
}

//Returns a Color32 array of specified colors
private Color32[] StarGradient(Color32 a, Color32 b, Color32 c, Color32 d) {
    Color32[] _colors = new Color32[4];
    _colors [0] = a;
    _colors [1] = b;
    _colors [2] = c;
    _colors [3] = d;
    return _colors;
}

Answer 2

if any one still need it.

 Shader "Custom/Gradient_4Color" {
     Properties {
         [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
         _ColorTop ("Top Color", Color) = (1,1,1,1)
         _ColorMidTop ("MidTop Color", Color) = (1,1,1,1)
         _ColorMidBot ("MidBot Color", Color) = (1,1,1,1)
         _ColorBot ("Bot Color", Color) = (1,1,1,1)
         _MiddleBot ("MiddleBot", Range(0.001, 0.999)) = 0.33
          _MiddleTop ("MiddleTop", Range(0.001, 0.999)) = 0.66
     }

     SubShader {
         Tags {"Queue"="Background"  "IgnoreProjector"="True"}
         LOD 100

         ZWrite On

         Pass {
         CGPROGRAM
         #pragma vertex vert  
         #pragma fragment frag
         #include "UnityCG.cginc"

         fixed4 _ColorTop;
         fixed4 _ColorMidTop;
         fixed4 _ColorMidBot;
         fixed4 _ColorBot;

          float  _MiddleBot;
          float  _MiddleTop;

         struct v2f {
             float4 pos : SV_POSITION;
             float4 texcoord : TEXCOORD0;
         };

         v2f vert (appdata_full v) {
             v2f o;
             o.pos = UnityObjectToClipPos (v.vertex);
             o.texcoord = v.texcoord;
             return o;
         }

         fixed4 frag (v2f i) : COLOR {

             fixed4 c = lerp(_ColorBot, _ColorMidBot, i.texcoord.y / _MiddleBot) * step(i.texcoord.y, _MiddleBot);
             c += lerp(_ColorMidBot, _ColorMidTop, (i.texcoord.y - _MiddleBot) /(_MiddleTop - _MiddleBot) ) * step(_MiddleBot,i.texcoord.y) * step(i.texcoord.y,_MiddleTop);
             c += lerp(_ColorMidTop, _ColorTop, (i.texcoord.y - _MiddleTop) / (1 - _MiddleTop)) * step(_MiddleTop, i.texcoord.y);
             c.a = 1;

             return c;
         }
         ENDCG
         }
     }
 }