After searching for any algorithm that could make what I needed, with no success, I decided to develop my own.

The algorithm is very simple, it just takes a rope and a width and creates a set of vertices tha form a TriangleStrip to be rendered on screen.

        /// <summary>
        /// Triangulates a line, returning a list of vertices that form a triangle strip
        /// </summary>
        /// <param name="contour">List of points that form the line</param>
        /// <param name="width">Desired with of the geometry</param>
        /// <returns>list of vertices that form a triangle strip</returns>
        public static List<Vector2> Process(ReadOnlyCollection<Vector2> contour,float width)
        {
            List<Vector2> result = new List<Vector2>();
            Vector2 normal = Vector2.Zero ;
            // Generate vertices for each point in the line
            for (int i = 0; i < contour.Count; i++)
            {
                // First and last are special cases, the normal is calculated right away
                if (i == contour.Count - 1)
                    normal = GameMath.Normal(contour[i] - contour[i - 1]);
                else if (i == 0)
                    normal = GameMath.Normal(contour[1] - contour[0]);
                else
                {
                    // For the rest of points, determine the normal as the middle angle between the direction of the previous and next segments.
                    Vector2 delta1 = contour[i] - contour[i - 1];
                    Vector2 delta2 = contour[i + 1] - contour[i];
                    if ((delta1.Length()!=0)&amp;&amp;(delta2.Length()!=0))
                    {
                        delta1.Normalize();
                        delta2.Normalize();
                        normal = GameMath.Normal(delta1 + delta2);
                    }

                }
                // Add two vertices to the vertex list
                result.Add(contour[i] - normal * width / 2f);
                result.Add(contour[i] + normal * width / 2f);
            }
            return result;

        }
        /// <summary>
        /// Returns one normal of the 2D vector
        /// </summary>
        /// <param name="vector"></param>
        /// <returns></returns>
        public static Vector2 Normal(Vector2 line)
        {
            float x = line.X; float y = line.Y;
            Vector2 normal = new Vector2();
            if (x != 0)
            {
                normal.X = -y / x;
                normal.Y = 1 / (float)Math.Sqrt(normal.X * normal.X + 1);
                normal.Normalize();
            }
            else if (y != 0)
            {
                normal.Y = 0;
                normal.X = (line.Y<0) ? 1 : -1;
            }
            else
            {
                normal.X = 1;
                normal.Y = 0;
            }
            if (x < 0)
            {
                normal *= -1;
            }
            return normal;
        }

That code is well enough to generate a credible line in almost all situations. As for UVs, what I did was assign the even vertices the value (X,0) and odd vertices (X,1), where X is the distance elapsed since the line start.

The reason of this is the way the particle system works: Each particle stores only a seed to generate its random values, and a new Random is generated with that seed each time it needs to be updated (that is, on every frame). So, if we’re showing 50 particles on a frame, we’re calling new Random(seed) 50 times.

With System.Random, there was no possible workaround since it doesn’t have a method available to set the seed without recreating everything. Also, it seems to do some hard work on creation, maybe allocating the N next random numbers, I don’t know.

Anyway, I found a nice replacement called FastRandom:  This class has the same interface that System.Random, so they can be easily interchanged. Also, it has a method to set the seed without having to recreate the class.

Anyway, I found a bug in the provided code, related with the methods Next(int) and Next(int,int) , it seems to store a double with the minimum value of an int and then multiply it by the desired range. It didn’t work for me, so I just replaced it with a modulus. Maybe it’s a little slower, but it works perfectly.

XmlSource project

The first project we’ll create is the one which has the class that stores our xml plain text. I’ve called it XmlSource.It will have two classes in total.

XmlSource

This class is a very simple one. It simply has a string with the xml plain text:

public class XmlSource
{
public XmlSource(string xmlCode)
{
this.xmlCode = xmlCode;
}

private string xmlCode;
public string XmlCode { get { return xmlCode; } }
}

XmlSourceReader

This class extends ContentTypeReader and simply creates an XmlSource instance from its binary representation. In our case, the binary representation wil be a simple string, so the read is straightforward.

public class XmlSourceReader : ContentTypeReader<XmlSource>
{
/// <summary>
/// Loads an imported shader.
/// </summary>
protected override XmlSource Read(ContentReader input, XmlSource existingInstance)
{
string xmlData = input.ReadString();

return new XmlSource(xmlData);
}
}

With this, our first project is finished. This project is platform-independant (The Xbox needs to read the binary data) and will have to be referenced from every project that uses the XmlSource class, including the second project we’re making:

XmlSourceImporter

The second project(I called it XmlDocumentImporter) is a project of type “Content Pipeline Extension Library”. This project is referenced from the Content projects, and converts the source text file to binary data that will be saved in the .xnb files.

This project has 2 files:

XmlSourceImporter.cs

This file converts the XML source file into an XmlSource instance, that will be further converted into binary data

[ContentImporter(".xml", DisplayName = "Xml Source Importer")]
class XmlSourceImporter : ContentImporter<XmlSource>
{
public override XmlSource Import(string filename, ContentImporterContext context)
{
string sourceCode = System.IO.File.ReadAllText(filename);
return new XmlSource(sourceCode);
}
}

XmlSourceWriter.cs

This file converts an XmlSource into binary data, as opposed to XmlSourceReader

[ContentTypeWriter]
class XmlSourceWriter : ContentTypeWriter<XmlSource>
{
protected override void Write(ContentWriter output, XmlSource value)
{
/*StringWriter sw=new StringWriter();
value.Save(sw);
string content = sw.ToString();*/
output.Write(value.XmlCode);
}
public override string GetRuntimeType(TargetPlatform targetPlatform)
{
return typeof(XmlDocument).AssemblyQualifiedName;
}
public override string GetRuntimeReader(TargetPlatform targetPlatform)
{
return typeof(XmlDocumentReader).AssemblyQualifiedName;
}
}

Sample of use

Once both projects set up (remember to add reference to XmlSourceImporter from the Content project), we can add .xml files to the content project. Under “Content importer”, we’ll need to select “Xml Source importer”, instead of the default XNA one.

Once done this, the program sould compile ok. Loading XML from the program now is very easy:

XmlSource xs = Content.Load<XmlSource>(AssetName);
XmlDocument xd = new XmlDocument();
xd.LoadXml(xs.XmlCode);

I know this can be a little confusing, i’ll upload some binaries if someone asks for them.

PS: Here they are: Plain Xml Content Importer