unity-shader-GPU-Instancing

unity-shader-GPU-Instancing

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前篇

• 官方资料
  • GPU instancing - https://docs.unity3d.com/Manual/GPUInstancing.html
• U3D优化批处理-GPU Instancing了解一下 - https://zhuanlan.zhihu.com/p/34499251
• Unity中基于Gpu Instance进行大量物体渲染的实现与分析（一） - https://blog.csdn.net/leonwei/article/details/73274808

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提示

合批优先级

翻译自官网: https://docs.unity3d.com/Manual/GPUInstancing.html

在合批的时候, static batching 优先于 instancing. 如果你把 go 标记成 static batching, unity 会成功的进行合批, 会禁止 instancing, 即使它使用了一个 instancing shader. 如果发生这种情况, inspector 窗口会有个 建议你禁止 static batching 的警告信息. 做法是打开 player settings (edit -> project settings -> player), 打开对应平台的 other settings, 展开 rendering, 取消勾选 static batching.

instancing 优先于 dynamic batching. 如果 unity 可以 instance 一个 mesh, 那么它会禁止 dynamic batching 那个 mesh.

合批的优先级是: static batching > instancing > dynamic batching.

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编写 instancing shader

• shader

  Shader "test/GpuInstancing2"
  {
      Properties
      {
          _MainTex ("Texture", 2D) = "white" {}
          _Color ("Color", Color) = (1, 1, 1, 1)
          _Intensity ("Intensity", float) = 1
      }
      SubShader
      {
          Tags { "RenderType"="Opaque" }
          LOD 100
  
          Pass
          {
              CGPROGRAM
              #pragma vertex vert
              #pragma fragment frag
              // INSTANCE 编译宏
              #pragma multi_compile_instancing
  
              #include "UnityCG.cginc"
  
              struct appdata {
                  float4 vertex : POSITION;
                  float2 uv : TEXCOORD0;
                  UNITY_VERTEX_INPUT_INSTANCE_ID
              };
  
              struct v2f {
                  float2 uv : TEXCOORD0;
                  float4 vertex : SV_POSITION;
                  UNITY_VERTEX_INPUT_INSTANCE_ID // necessary only if you want to access instanced properties in fragment Shader.
              };
  
              sampler2D _MainTex;
              float4 _MainTex_ST;
  
              UNITY_INSTANCING_BUFFER_START(Props) // uniform 变量定义域, Props 参数可以是任意字符串
              UNITY_DEFINE_INSTANCED_PROP(float4, _Color)
              UNITY_DEFINE_INSTANCED_PROP(float, _Intensity)
              UNITY_INSTANCING_BUFFER_END(Props)
  
              v2f vert (appdata v) {
                  v2f o;
                  UNITY_SETUP_INSTANCE_ID(v);
                  UNITY_TRANSFER_INSTANCE_ID(v, o); // necessary only if you want to access instanced properties in the fragment Shader.
                  
                  o.vertex = UnityObjectToClipPos(v.vertex);
                  o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                  return o;
              }
  
              fixed4 frag (v2f i) : SV_Target {
                  UNITY_SETUP_INSTANCE_ID(i); // necessary only if any instanced properties are going to be accessed in the fragment Shader.
  
                  //访问每个 Instance 独有的属性. 这个宏会使用 Instance ID作为索引到 Uniform数组 中去取当前 Instance 对应的数据
                  float4 val = UNITY_ACCESS_INSTANCED_PROP(Props, _Color) * UNITY_ACCESS_INSTANCED_PROP(Props, _Intensity); 
                  fixed4 col = tex2D(_MainTex, i.uv) * val;
                  return col;
              }
              ENDCG
          }
      }
  }

• 效果

  

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测试打断顺序

因为 unity 渲染 不透明物体时, 渲染顺序是由远 ( 参考总结: graphic-前向渲染管线浅析.md 中的 深度测试提前：Early-Z技术)

因为绘制中间的两个物体时, 使用了不同的材质, 所以打断了 gpu instancing.