Added window imposter shader and material

Assets/measuregeneric/shaders/InteriorImposterShader.shader

@@ -0,0 +1,67 @@
+// Original code from https://gist.github.com/josephbk117/a43f5335cea9b3e12a44f196dc81f30f
+Shader "Custom/InteriorImposterShader"
+{
+    Properties
+    {
+    }
+
+    SubShader
+    {
+        Pass
+        {
+            CGPROGRAM
+            #pragma vertex vert
+            #pragma fragment frag
+            #include "UnityCG.cginc"
+
+            struct appdata
+            {
+                float4 vertex : POSITION;
+                float3 normal : NORMAL;
+            };
+
+            struct v2f 
+            {
+                float3 worldPos : TEXCOORD0;
+                float3 worldNormal : TEXCOORD1;
+                float4 pos : SV_POSITION;
+            };
+
+            v2f vert (appdata v)
+            {
+                v2f o;
+                o.pos = UnityObjectToClipPos(v.vertex);
+                o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
+                o.worldNormal = UnityObjectToWorldNormal(v.normal);
+                return o;
+            }
+
+            // ChatGPT snippet
+            float3 BoxProjectReflectionDir(float3 worldPos, float3 worldRefl)
+            {
+                // Calculate relative position within the box
+                float3 boxMin = unity_SpecCube0_BoxMin.xyz;
+                float3 boxMax = unity_SpecCube0_BoxMax.xyz;
+                float3 boxCenter = 0.5 * (boxMin + boxMax);
+                float3 boxSize = boxMax - boxMin;
+
+                float3 localPos = worldPos - boxCenter;
+                float3 absLocalRefl = abs(worldRefl);
+
+                // Scale the reflection vector based on which side of the box it hits
+                float3 scale = boxSize / absLocalRefl;
+                float scaleMin = min(min(scale.x, scale.y), scale.z);
+                return localPos + worldRefl * scaleMin;
+            }
+
+            fixed4 frag (v2f i) : SV_Target
+            {
+                half3 worldViewDir = normalize(UnityWorldSpaceViewDir(i.worldPos));  // Direction of ray from the camera towards the object surface
+                half4 skyData = UNITY_SAMPLE_TEXCUBE(unity_SpecCube0, BoxProjectReflectionDir(i.worldPos, -worldViewDir));
+                half3 skyColor = DecodeHDR(skyData, unity_SpecCube0_HDR);  // This is done becasue the cubemap is stored HDR
+                return half4(skyColor, 1.0);
+            }
+            ENDCG
+        }
+    }
+}