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[Unity]ZTestやBlend等をシェーダー外から設定する

サンプルとして単純なSprite用のシェーダーっぽいの

Shader "Custom/Sprite" {
    Properties {
        // TIPS: モバイル環境でScaleとOffsetは使えないのでNoScaleOffsetで封印する
        [NoScaleOffset] _MainTex ("Base (RGB), Alpha (A)", 2D) = "white" {}

        [Enum(UnityEngine.Rendering.CullMode)]
        _Cull("Cull", Float) = 0                // Off

        [Enum(UnityEngine.Rendering.CompareFunction)]
        _ZTest("ZTest", Float) = 4              // LEqual

        [Enum(Off, 0, On, 1)]
        _ZWrite("ZWrite", Float) = 0            // Off

        [Enum(UnityEngine.Rendering.BlendMode)]
        _SrcFactor("Src Factor", Float) = 5     // SrcAlpha

        [Enum(UnityEngine.Rendering.BlendMode)]
        _DstFactor("Dst Factor", Float) = 10    // OneMinusSrcAlpha
    }

    SubShader {
        Tags {
            "Queue" = "Transparent"
            "IgnoreProjector" = "True"
            "RenderType" = "Transparent"
            "PreviewType" = "Plane"
        }

        Cull [_Cull]
        ZTest [_ZTest]
        ZWrite [_ZWrite]
        Blend [_SrcFactor][_DstFactor]

        Pass {
            CGPROGRAM
            #include "UnityCG.cginc"

            #pragma vertex vert
            #pragma fragment frag

            struct appdata_t {
                float4 vertex : POSITION;
                half2 texcoord : TEXCOORD0;
                fixed4 color : COLOR;
            };

            struct v2f {
                float4 pos : SV_POSITION;
                half2 uv : TEXCOORD0;
                fixed4 color : COLOR;
            };

            sampler2D _MainTex;

            v2f vert(appdata_t v) {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.uv = v.texcoord;
                o.color = v.color;
                return o;
            }

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

これでシェーダーファイルを増やさずにInspector上からMaterialでの設定ができる
メリットとしてはShaderVariantが減るのでシェーダーコンパイル時のスパイクが減らせる
あとコピペシェーダー作る必要がないのでコピペ漏れみたいなミスが減る
デメリットはマテリアルの生成難度が上がるので、
エンジニアでない人が「加算にしたいんだけどどうしたら・・・」となってしまいがち
(プリセット設定が選択出来ればいいのだけれど・・・MaterialPropertyDrawerは拡張できるのだろうか・・・)
キャプチャ.PNG

スクリプトからも変更できる・・・が、MaterialPropertyBlockでは値を変えても変化がなかった
renderer.materialを呼び出すとMaterialが複製される・・・
sharedMaterialを使うとなると参照しているRenderer全てに影響が出る・・・
動的に変更することが有用な場面は非常に限定的かなと

// Materialを直接変更すると変わる
Material mat = new Material(Shader.Find("Custom/Sprite"));
mat.SetFloat("_Cull", (float)UnityEngine.Rendering.CullMode.Off);
mat.SetFloat("_ZTest", (float)UnityEngine.Rendering.CompareFunction.Always);
mat.SetFloat("_ZWrite", 0f);
mat.SetFloat("_SrcFactor", (float)UnityEngine.Rendering.BlendMode.SrcAlpha);
mat.SetFloat("_DstFactor", (float)UnityEngine.Rendering.BlendMode.OneMinusSrcAlpha);

// MaterialPropertyBlockでは無効(SpriteRendererはそもそも無理)
MaterialPropertyBlock mpb = new MaterialPropertyBlock();
mpb.SetFloat("_Cull", (float)UnityEngine.Rendering.CullMode.Off);
mpb.SetFloat("_ZTest", (float)UnityEngine.Rendering.CompareFunction.Always);
mpb.SetFloat("_ZWrite", 0f);
mpb.SetFloat("_SrcFactor", (float)UnityEngine.Rendering.BlendMode.One);
mpb.SetFloat("_DstFactor", (float)UnityEngine.Rendering.BlendMode.One);
MeshRenderer render = this.GetComponent<MeshRenderer>();
renderer.SetPropertyBlock(mpb);

【公式リファレンス】
https://docs.unity3d.com/jp/current/Manual/SL-Properties.html
https://docs.unity3d.com/jp/current/ScriptReference/MaterialPropertyDrawer.html

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17
Help us understand the problem. What are the problem?