Component is the base class for all components within a Viewer.

• Component IDs
• Properties
• Metadata
• Logging
• Destruction

Component IDs

Every Component has an ID that's unique within the parent Viewer. the Viewer generates the IDs automatically by default, however you can also specify them yourself. In the example below, we're creating a viewer comprised of Viewer, Material, Geometry and GameObject components, while letting BIMSURFER generate its own ID for the Geometry:

``
## <a name="componentProps">Properties</a>
Almost every property in a Viewer Component fires a change event when you update it. For example, we can subscribe
 to the Material/diffuse:event event that a
 Material fires when its Material/diffuse:property
 property is updated, like so:
``javascript
 // Bind a change callback to a property
 var handle = material.on("diffuse", function(diffuse) {
    console.log("Material diffuse color has changed to: [" + diffuse[0] + ", " + diffuse[1] + "," + diffuse[2] + "]");
});
// Change the property value, which fires the callback
 material.diffuse = [ 0.0, 0.5, 0.5 ];
// Unsubscribe from the property change event
 material.off(handle);

We can also subscribe to changes in the way components are attached to each other, since components are properties of other components. For example, we can subscribe to the 'GameObject/material:event' event that a GameObject fires when its GameObject/material:property property is set to a different Material:

 // Bind a change callback to the GameObject's Material
 object1.on("material", function(material) {
    console.log("GameObject's Material has changed to: " + material.id);
});
// Now replace that Material with another
 object1.material = new BIMSURFER.Material({
    id: "myOtherMaterial",
    diffuse: [ 0.3, 0.3, 0.6 ]
    //..
});

Metadata

You can set optional metadata on your Components, which can be anything you like. These are intended to help manage your components within your application code or content pipeline. You could use metadata to attach authoring or version information, like this:

 // Viewer with authoring metadata
 var viewer = new BIMSURFER.Viewer({
    id: "myViewer",
    metadata: {
        title: "My awesome 3D viewer",
        author: "@xeolabs",
 date: "February 13 2015"
 }
 });
// Material with descriptive metadata
 var material = new BIMSURFER.Material(viewer, {
    id: "myMaterial",
    diffuse: [1, 0, 0],
    metadata: {
        description: "Bright red color with no textures",
        version: "0.1",
        foo: "bar"
    }
});

As with all properties, you can subscribe and change the metadata like this:

 // Subscribe to changes to the Material's metadata
 material.on("metadata", function(value) {
    console.log("Metadata changed: " + JSON.stringify(value));
});
// Change the Material's metadata, firing our change handler
 material.metadata = {
    description: "Bright red color with no textures",
    version: "0.2",
    foo: "baz"
};

Logging

Components have methods to log ID-prefixed messages to the JavaScript console:

 material.log("Everything is fine, situation normal.");
 material.warn("Wait, whats that red light?");
 material.error("Aw, snap!");

The logged messages will look like this in the console:

 [LOG]   myMaterial: Everything is fine, situation normal.
 [WARN]  myMaterial: Wait, whats that red light..
 [ERROR] myMaterial: Aw, snap!

Destruction

Get notification of destruction directly on the Components:

 material.on("destroyed", function() {
    this.log("Component was destroyed: " + this.id);
});

Or get notification of destruction of any Component within its Viewer, indiscriminately:

 viewer.on("componentDestroyed", function(component) {
    this.log("Component was destroyed: " + component.id);
});

Then destroy a component like this:

 material.destroy();

Other Components that are linked to it will fall back on a default of some sort. For example, any GameObject that were linked to our Material will then automatically link to the Viewer's default Viewer/material:property.