Accessing shader properties in cg

Unity Engine
1

Hi guys:
I’m trying to learn how to write my own shader using cg. But I can not access the shader properties in my cg program. I’m doing what the following page told me, but it did not work.

And here is my code:
Shader “CGTest_PureColor” {
Properties {
_Color (“Main Color”, Color) = (0.5,0.5,0.5,1)
}
SubShader {
Pass{
CGPROGRAM
#pragma fragment frag
#include “UnityCG.cginc”

uniform float4 _Color;
float4 frag() : COLOR
{
float4 c = _Color;
return _Color;
}
ENDCG
}
}
}

It’s very simple, I only want to color all the primitive to _Color. But whatever the “Main Color” is in inspector, it always be black.

2

I have to correct something here. The function frag() is actually look like this:
float4 frag() : COLOR
{
float4 c = _Color;
return c;
}

Then I change the float4 to half4, it still does not work.
But if I use solid color, like this:
half4 frag() : COLOR
{
half4 c = half4(1, 0, 0, 1);
return c;
}
It does work. The primitive becomes red.

Why is this? Can anyone give me an explanation? Thx.

3

That is weird. It looks like you need an input structure for it to work, even if it’s just position. This works as you’d expect:

Shader "CGTest_PureColor" {
	Properties {
		_Color ("Main Color", Color) = (0.5,0.5,0.5,1)
	}
	SubShader {
		Pass {
			CGPROGRAM
			#pragma fragment frag
			#include "UnityCG.cginc"
			struct v2f {
				float4 pos : POSITION;
			};
			
			uniform float4 _Color;
			
			float4 frag(v2f v) : COLOR {
				return _Color;
			}
			ENDCG
		}
	} 
}
4

Thanks. It does work.