init

Assets/ExternalViewportShader.shader

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+Shader "Custom/ExternalViewportShader"
+{
+    Properties
+    {
+        //_MainTex ("External Texture", 2D) = "white" {}
+    }
+    SubShader
+    {
+        Tags { "RenderType"="Opaque" "Queue"="Geometry" }
+        LOD 100
+
+        Pass
+        {
+            // GLSLPROGRAM block is required for raw GLSL in Unity
+            GLSLPROGRAM
+
+            // 1. Enable the EGL Image External extension for Android
+            //#extension GL_OES_EGL_image_external_essl3 : require
+
+            // Unity 6 predefines VERTEX and FRAGMENT during separate compilation passes
+            #ifdef VERTEX
+            
+            // Unity 6 uses built-in matrices but they must be declared or used via Unity-specific naming
+            // In raw GLSL, we use the standard attribute/varying naming convention
+            varying vec2 v_texcoord;
+
+            void main()
+            {
+                // gl_ModelViewProjectionMatrix is still available in Unity's GLSL compatibility layer
+                gl_Position = gl_Vertex;
+                v_texcoord = gl_MultiTexCoord0.xy;
+            }
+            #endif
+
+            #ifdef FRAGMENT
+            
+            // 2. Use samplerExternalOES for AHardwareBuffer data
+            //uniform samplerExternalOES _MainTex;
+            varying vec2 v_texcoord;
+
+            void main()
+            {
+                // 3. For Unity 6, use textureExternal for maximum compatibility 
+                // on GLES3 devices to ensure the compiler handles the conversion properly.
+                // texture2D(s, coord) also works, but textureExternal is the modern Unity GLSL recommendation.
+                gl_FragColor = vec4(1, 0, 0, 1);//texture2D(_MainTex, v_texcoord);
+            }
+            #endif
+
+            ENDGLSL
+        }
+    }
+    Fallback "Unlit/Texture"
+}