Non-Trivial Custom ContentProcessor - Part 1

This is part one on my series on writing a non-trivial custom content processor for XNA Game Studio 3.1. If you want you can read the introduction of this series for useful background information on why I went about writing a content processor.

Besides the tutorial and samples I mentioned in the introduction MSDN also has a very nice tutorial on how to create a complete content processor.

A complete content pipeline extension project consists of the following parts:

• A content importer
• A content processor(s)
• A content data class(es)
• A content writer
• A content reader

Each piece is a distinct step in the process of importing and loading content in your project.

The content importer is a very simple object. All it has to do is open the basic content (image, model, game data etc.) and parse it enough that it's usable by the content processor. Since I originally chose to use XML my importer only needs to open the file as an XML document. If you're using XML you might want to test the document against a DTD to save in sanity checking code in the processor.

Here's the importer:

using System;
using System.Xml;
using System.Collections.Generic;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Content.Pipeline;
using Microsoft.Xna.Framework.Content.Pipeline.Graphics;

// Entity group type specs/annotations are in XML format
using TImport = System.Xml.XmlDocument;

namespace EntityGroupProcessor
{
    /// 

    /// Basic entity group type importer. Entity group types are always in XML. All this does
    /// is load the file.
    /// 
    [ContentImporter(".ent", DisplayName = "Entity Group Importer", DefaultProcessor = "EntityGroupTypeProcessor")]
    public class EntityGroupTypeImporter : ContentImporter
    {
        public override TImport Import(string filename, ContentImporterContext context)
        {
            XmlDocument document = new XmlDocument();
            document.Load(filename);

            return document;
        }
    }
}

Notice the line

[ContentImporter(".ent", DisplayName = "Entity Group Importer", DefaultProcessor = "EntityGroupTypeProcessor")]

The first part ".ent" specifies the extension of the file that this importer processes. This allows Visual Studio to automatically use this importer when content with the extension of ".ent" is added to the project. The second part specifies the name of the importer as it appears in Visual Studio. The third, and most important part, names the class used to process the output (in this case an XmlDocument instance) in the next step.

The bulk of the code, at least in my case, ends up in the content processor and the content data classes. Stay tuned for Part 2 where I get into the basics of the ContentProcessor and content data classes.