Apply shadow property to OL-Cesium and add short documentation about properties

Author: pedroslvieira

PROPERTIES.md

@@ -0,0 +1,37 @@
+# OLCEsium Properties 
+
+## olcs_extruded_height 
+Value: number
+The distance in meters between the polygon's extruded face and the ellipsoid surface.
+Check buildings example for usage in context.
+
+## olcs_shadows
+Value: boolean
+Enables shadow casting in 3D. Can be either applied to the entire feature set or by feature individually. 
+In order for it to work, [shadowMap](https://cesium.com/learn/cesiumjs/ref-doc/Scene.html?classFilter=scene#shadowMap) needs to be enabled in the Cesium scene. To use the sun as light source, enable [enableLighting](https://cesium.com/learn/cesiumjs/ref-doc/Globe.html#enableLighting) on the Globe.
+Check buildings example for usage in context.
+
+## olcs_model
+Value: object({cesiumOptions: options})
+Is used to define the 3D model representation of an OpenLayers vector feature in the Cesium scene. This property allows you to customize how the feature is visualized and positioned in the 3D world.
+
+To use the olcs_model property, set it as a property on your OpenLayers vector feature. It should be an object that specifies the properties of the 3D model. The olcs_model object can have the following key-value pairs:
+
+- url: The URL of the 3D model's data source (required).
+- scale: A numeric value representing the scale of the model (optional).
+- minimumPixelSize: The minimum pixel size at which the model will be visible (optional).
+- heightReference: Specifies how the model's height is interpreted in the scene (optional).
+
+Check vectors example for usage in context.
+
+## olcs_skip
+Value: boolean
+Allows you to exclude specific layers from being rendered in the Cesium 3D view. This can be useful when you want to control which layers are displayed in the 2D map view and which are displayed in the 3D Cesium view.
+
+## olcs_minimumLevel
+Value: number
+Allows you to set a minimum zoom level for rendering 3D tiles in the Cesium view. This property helps to control the level of detail displayed in the 3D view based on the current zoom level.
+Check mvt example for usage in context.
+
+
+

README.md

@@ -96,6 +96,8 @@ Going further
 
 See the [examples](https://openlayers.org/ol-cesium/examples/).
 
+Use properties to control specific aspects of OL-Cesium integration, see the [PROPERTIES.MD](https://github.com/openlayers/ol-cesium/blob/master/PROPERTIES.md).
+
 If you are new to Cesium, you should also check the [Cesium tutorials](https://cesiumjs.org/tutorials).
 
 

examples/buildings.js

@@ -45,11 +45,22 @@ const map = new olMap({
     zoom: 2,
   }),
 });
+// Enable the property 'olcs_shadows' for the entire set of features 
+// Alternatively, you can enable 'olcs_shadows' for each feature individually   
 vector.set('olcs_shadows', true);
 
+
 const ol3d = new OLCesium({map, target: 'map3d'});
 ol3d.setEnabled(true);
 
+// Be aware that enabling the following properties can impact performance
+// Enable shadow map to allow Cesium to cast scene's shadows
+const scene = ol3d.getCesiumScene();
+scene.shadowMap.enabled = true;
+// Enable lighting the globe with the sun as a light source to have dynamic lighting conditions according to the position of the sun
+scene.globe.enableLighting = true;
+
+
 const vectorSource = vector.getSource();
 vectorSource.once('featuresloadend', () => {
   if (vectorSource.getState() === 'ready') {