Shader的自定义特性使用

使用自定义特性关键字，可以动态对Shader某一部分代码进行开关操作

shader(定义了KEYWORD1特性)：

定义：#pragma shader_feature KEYWORD1

判断：#ifdef KEYWORD1

Shader "Custom/NewSurfaceShader" {
    Properties {
        _Color ("Color", Color) = (,,,)
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
        _Glossiness ("Smoothness", Range(,)) = 0.5
        _Metallic ("Metallic", Range(,)) = 0.0
    }
    SubShader {
        Tags { "RenderType"="Opaque" }
        LOD 

        CGPROGRAM
        // Physically based Standard lighting model, and enable shadows on all light types
        #pragma surface surf Standard fullforwardshadows

        // Use shader model 3.0 target, to get nicer looking lighting
        #pragma target 3.0

        #pragma shader_feature KEYWORD1

        sampler2D _MainTex;

        struct Input {
            float2 uv_MainTex;
        };

        half _Glossiness;
        half _Metallic;
        fixed4 _Color;

        void surf (Input IN, inout SurfaceOutputStandard o) {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
#ifdef KEYWORD1
            o.Albedo = float3(,,);
#else
            o.Albedo = float3(,,);
#endif
            // Metallic and smoothness come from slider variables
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}

脚本：

using UnityEngine;
using System.Collections;

public class ShaderKeywordTest : MonoBehaviour
{
    public Material mat;

    void OnEnable()
    {
        mat.EnableKeyword("KEYWORD1");
    }

    void OnDisable()
    {
        mat.DisableKeyword("KEYWORD1");
    }
}

测试效果如下：