Add existing to tracked

node_modules/@cesium/engine/Source/Shaders/ViewportQuadFS.glsl

@@ -0,0 +1,16 @@
+
+in vec2 v_textureCoordinates;
+
+void main()
+{
+    czm_materialInput materialInput;
+    
+    materialInput.s = v_textureCoordinates.s;
+    materialInput.st = v_textureCoordinates;
+    materialInput.str = vec3(v_textureCoordinates, 0.0);
+    materialInput.normalEC = vec3(0.0, 0.0, -1.0);
+    
+    czm_material material = czm_getMaterial(materialInput);
+
+    out_FragColor = vec4(material.diffuse + material.emission, material.alpha);
+}