Hacky support for transparency in semantic segmentation

com.unity.perception/Runtime/GroundTruth/RenderPasses/CrossPipelinePasses/SemanticSegmentationCrossPipelinePass.cs

 
             if (shaderVariantCollection != null)
             {
-                shaderVariantCollection.Add(
-                    new ShaderVariantCollection.ShaderVariant(m_ClassLabelingShader, PassType.ScriptableRenderPipeline));
+                // shaderVariantCollection.Add(
+                //     new ShaderVariantCollection.ShaderVariant(m_ClassLabelingShader, PassType.N));
             }
 
             m_OverrideMaterial = new Material(m_ClassLabelingShader);
 
             // Set the labeling ID so that it can be accessed in ClassSemanticSegmentationPass.shader
             mpb.SetVector(k_LabelingId, found ? entry.color : Color.black);
+
+            if (renderer != null && renderer.material != null && renderer.material.HasProperty("_MainTex"))
+            {
+                var maintex = renderer.material.GetTexture("_MainTex");
+                if (maintex != null)
+                    mpb.SetTexture("_MainTex", renderer.material.GetTexture("_MainTex"));
+            }
         }
 
         public override void ClearMaterialProperties(MaterialPropertyBlock mpb, Renderer renderer, Labeling labeling, uint instanceId)

com.unity.perception/Runtime/GroundTruth/Resources/SemanticSegmentation.shader

     Properties
     {
         [PerObjectData] LabelingId("Labeling Id", Vector) = (0,0,0,1)
+        _MainTex ("Main Texture", 2D) = "white" { }
-    HLSLINCLUDE
-
-    #pragma target 4.5
-    #pragma only_renderers d3d11 ps4 xboxone vulkan metal switch
-
-    //enable GPU instancing support
-    #pragma multi_compile_instancing
-
-    ENDHLSL
-
-        Tags { "RenderType"="Opaque" }
+        Tags { "Queue"="Transparent" "RenderType"="Transparent" }
+        
+        ZWrite on
+        Blend SrcAlpha OneMinusSrcAlpha
-            Tags { "LightMode" = "SRP" }
-
-            Blend Off
-            ZWrite On
-            ZTest LEqual
-
-            Cull Back
+            //Tags { "LightMode" = "SRP" }
 
             CGPROGRAM
 
             #include "UnityCG.cginc"
 
             float4 LabelingId;
+            sampler2D _MainTex;
+            float4 _MainTex_ST;
+                float2 uv : TEXCOORD0;
+                float2 uv : TEXCOORD0;
             };
 
             vertexToFragment semanticSegmentationVertexStage (in_vert vertWorldSpace)
+                vertScreenSpace.uv = TRANSFORM_TEX(vertWorldSpace.uv, _MainTex);
+                // sample the texture
+                fixed4 col = tex2D(_MainTex, vertScreenSpace.uv);
+                if (col.a == 0)
+                    return fixed4(0, 0, 0, 0);
+
                 return LabelingId;
             }