stencil的简单使用

这边给unlit(不发光) shader加上stencil功能

Unlit_Stencil.shader，其中stencil相关的用//-----包起来了

Shader "My/Unlit_Stencil"
{
    Properties
    {
        _MainTex("Texture", 2D) = "white" {}
        _Color("Tint", Color) = (1,1,1,1)

        //----- stencil
        [Enum(UnityEngine.Rendering.CompareFunction)]_StencilComp("Stencil Comparison", Float) = 8 //CompareFunction.Always
        _Stencil("Stencil ID", Float) = 0
        [Enum(UnityEngine.Rendering.StencilOp)]_StencilOp("Stencil Operation", Float) = 0 //StencilOp.Keep
        _StencilReadMask("Stencil Read Mask", Float) = 255
        _StencilWriteMask("Stencil Write Mask", Float) = 255
        //-----
    }
    SubShader
    {
        Tags 
        {
            "RenderType" = "Opaque"
        }
        LOD 100

        Pass
        {
            //----- stencil
            Stencil
            {
                Ref[_Stencil]
                Comp[_StencilComp]
                Pass[_StencilOp]
                ReadMask[_StencilReadMask]
                WriteMask[_StencilWriteMask]
            }
            //-----

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float4 color : COLOR;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                fixed4 color : COLOR;
                float2 uv : TEXCOORD0;
                float4 worldPosition : TEXCOORD1;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            fixed4 _Color;

            v2f vert(appdata v)
            {
                v2f o;
                o.worldPosition = v.vertex;
                o.vertex = UnityObjectToClipPos(v.vertex);

                o.uv = TRANSFORM_TEX(v.uv, _MainTex); //应用贴图的tiling和offset

                o.color = v.color * _Color;
                return o;
            }

            fixed4 frag(v2f i) : SV_Target
            {
                fixed4 c = tex2D(_MainTex, i.uv) * i.color;
                return c;
            }
            ENDCG
        }
    }
}

创建一个Unlit_Stencil.mat, 把材质的shader设置为Unlit_Stencil，就能在材质检查器(Inspector)上修改材质的stencil参数了

简单的例子

效果：stencil相同的区域显示为蓝色

1) 用上面的shader创建材质Stencil_ID1_Always_Replace.mat

这个材质的效果：所在的区域总是将stencil buffer设置为1

2) 场景中的Cube使用该材质

3) 创建材质Stencil_ID1_Equal_Keep.mat, 确保渲染顺序在上面的材质之后

这个材质的效果：检查stencil buffer是否等于1，等于1的绘制像素(蓝色)，否则丢弃像素；

4) 场景中的Capsule使用该材质

5) 运行后就能看到上面的效果

修改共享材质的stencil参数

可以通过MaterialPropertyBlock来修改，这样就不会相互影响

using UnityEngine;
using UnityEngine.Rendering;

public class ChangeRendererStencil : MonoBehaviour
{
    public int m_stencil;
    public CompareFunction m_stencilComp = CompareFunction.Always;
    public StencilOp m_stencilOp = StencilOp.Keep;
    public int m_stencilWriteMask = 255;
    public int m_stencilReadMask = 255;

    private MaterialPropertyBlock m_tempMatProps;

    void Start()
    {
        var renderer = GetComponent<Renderer>();
        if (renderer)
        {
            if (null == m_tempMatProps)
                m_tempMatProps = new MaterialPropertyBlock();

            renderer.GetPropertyBlock(m_tempMatProps);
            m_tempMatProps.SetInt("_Stencil", m_stencil);
            m_tempMatProps.SetInt("_StencilOp", (int)m_stencilOp);
            m_tempMatProps.SetInt("_StencilComp", (int)m_stencilComp);
            m_tempMatProps.SetInt("_StencilReadMask", m_stencilWriteMask);
            m_tempMatProps.SetInt("_StencilWriteMask", m_stencilWriteMask);
            renderer.SetPropertyBlock(m_tempMatProps);
        }
    }

}

参考

UnityShader学习笔记- Stencil Buffer - 飞翔的子明 - 博客园 (cnblogs.com)

Unity3D Shader Stencil模版测试学习 - HONT - 博客园 (cnblogs.com)

MaterialPropertyBlock_阿赵3D的博客-CSDN博客_materiapropertyblock