iOS shader with no texture, just vertex colouring and main colour

Questions & Answers
1

Hi,
I’m using a vertex coloured sky plane model from Blender to create a sky gradient.

I’ve painted near black at the bottom vertices and near white at the top, and I am controlling the sky colour itself via Playmaker/script.

So I require a mobile shader which can read the vertex colours from my Blender mesh, and it also needs a colour. The only shader I can seem to find that does this is a shader called “Simple Texture” (still has a texture slot), and I’m not sure how fast/slow this is.

It does look extremely simple:

Shader "Simple Texture" {
   Properties {
      _Color ("Main Color", Color) = (1, 1, 1, 1)
      _MainTex ("Base (RGB)", 2D) = "white"
   }
   SubShader {
      Pass {
         SetTexture [_MainTex] {
            constantColor [_Color]
            Combine texture * constant
         }
      }
   }
}

Since it fills the whole screen a lot of the time, I’d like to be sure! I have absolutely no idea with shaders I’m afraid! Does iOS play nice without a texture being used, and if that slot is unused, does it affect performance at all?

If you could confirm for me that this is a suitable shader, or know of something better, I’d love to hear it.

Thanks,
Jay

2

this shader as simple as possible. uses only vertex color and main color.

Shader "Unity Answers/Mobile with Vertex Color"
{
	Properties
	{
		_Color ("Main Color", Color) = (1, 1, 1, 1)
	}
	SubShader
	{
		Tags { "Queue"="Background" "RenderType"="Background" }
		Cull Off
		ZWrite Off
		Fog { Mode Off }
	Pass
	{
		CGPROGRAM
		#pragma vertex vert
		#pragma fragment frag
		fixed4 _Color;
		struct appdata
		{
			float4 vertex : POSITION;
			float4 color : COLOR;
		};
		struct v2f
		{
			float4 pos : SV_POSITION;
			fixed4 color : COLOR;
		};
		v2f vert (appdata v)
		{
			v2f o;
			o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
			o.color = v.color;
			return o;
		}
		half4 frag(v2f i) : COLOR
		{
			return i.color * _Color;
		}
		ENDCG
		}
	}
}