HDRenderPipeline: Update UI to only display option for alpha test shadow/prepass with transparent

ScriptableRenderPipeline/HDRenderPipeline/Material/Unlit/Editor/BaseUnlitUI.cs

             m_MaterialEditor.ShaderProperty(alphaCutoffEnable, StylesBaseUnlit.alphaCutoffEnableText);
             if (alphaCutoffEnable.floatValue == 1.0f)
             {
+                EditorGUI.indentLevel++;
-                if (alphaCutoffShadow != null)
+                // With transparent object and few specific materials like Hair, we need more control on the cutoff to apply
+                // This allow to get a better sorting (with prepass), better shadow (better silouhette fidelity) etc...
+                if ((SurfaceType)surfaceType.floatValue == SurfaceType.Transparent)
-                    m_MaterialEditor.ShaderProperty(alphaCutoffShadow, StylesBaseUnlit.alphaCutoffShadowText);
-                }
+                    if (alphaCutoffShadow != null)
+                    {
+                        m_MaterialEditor.ShaderProperty(alphaCutoffShadow, StylesBaseUnlit.alphaCutoffShadowText);
+                    }
-                if (transparentDepthPrepassEnable != null)
-                {
-                    m_MaterialEditor.ShaderProperty(transparentDepthPrepassEnable, StylesBaseUnlit.transparentDepthPrepassEnableText);
-                    if (transparentDepthPrepassEnable.floatValue == 1.0f)
+                    if (transparentDepthPrepassEnable != null)
-                        EditorGUI.indentLevel++;
-                        m_MaterialEditor.ShaderProperty(alphaCutoffPrepass, StylesBaseUnlit.alphaCutoffPrepassText);
-                        EditorGUI.indentLevel--;
+                        m_MaterialEditor.ShaderProperty(transparentDepthPrepassEnable, StylesBaseUnlit.transparentDepthPrepassEnableText);
+                        if (transparentDepthPrepassEnable.floatValue == 1.0f)
+                        {
+                            EditorGUI.indentLevel++;
+                            m_MaterialEditor.ShaderProperty(alphaCutoffPrepass, StylesBaseUnlit.alphaCutoffPrepassText);
+                            EditorGUI.indentLevel--;
+                        }
+                EditorGUI.indentLevel--;
             }
             // This function must finish with double sided option (see LitUI.cs)
             m_MaterialEditor.ShaderProperty(doubleSidedEnable, StylesBaseUnlit.doubleSidedEnableText);