/// <summary>
/// Builds a new truncated cone buffer.
/// The cone is aligned to the x axis.
/// </summary>
/// <param name="description">The description used to build the cone</param>
/// <param name="tesselation">The tesselation, must be greater than 2</param>
public VertexPosition[] Build(TruncatedConeDescription description, int tesselation = 32)
{
var sections = description.Sections;
if (sections.Length < 2)
{
throw new ArgumentException("sections must contain more than 1 element.");
}
if (tesselation < 3)
{
throw new ArgumentException("tesselation must be greater than 2.");
}
// build tesselation angles
var tessInverse = (float)1 / tesselation;
var tesselationAngles = new Vector2[tesselation];
for (var i = 0; i < tesselationAngles.Length; i++)
{
var quat = Quaternion.RotationAxis(Vector3.BackwardRH, tessInverse * i * MathUtil.TwoPi);
var transformed = Vector3.Transform(Vector3.Up, quat);
tesselationAngles[i] = new Vector2(transformed.X, transformed.Y);//discard x value
}
var vertCount = (sections.Length - 1) * tesselation * 6;
var buffer = new VertexPosition[vertCount];
// the first time this gets used it increments to 0
int bufferIndex = -1;
var prevSection = sections[0];
for (var i = 1; i < description.Sections.Length; i++)
{
var section = description.Sections[i];
// start at the last item
var prevAngle = tesselationAngles.Last();
for (var j = 0; j < tesselation; j++)
{
var angle = tesselationAngles[j];
buffer[++bufferIndex] = GetVertex(prevSection, angle);
buffer[++bufferIndex] = GetVertex(section, angle);
buffer[++bufferIndex] = GetVertex(prevSection, prevAngle);
buffer[++bufferIndex] = GetVertex(section, angle);
buffer[++bufferIndex] = GetVertex(section, prevAngle);
buffer[++bufferIndex] = GetVertex(prevSection, prevAngle);
prevAngle = tesselationAngles[j];
}
prevSection = sections[i];
}
Debug.Assert(bufferIndex + 1 == buffer.Length);
return(buffer);
}
void LoadContent(IEditorGame game)
{
var arrowDesc = new TruncatedConeDescription(
new ConeSection(0, 0),
new ConeSection(.03f, 0),
new ConeSection(.03f, 2f / 3),
new ConeSection(.10f, 2f / 3),
new ConeSection(0, 1f));
var arrowMesh = new TruncatedConeBuilder().Build(arrowDesc);
var arrowBuffer = Buffer.Vertex.New(game.GraphicsDevice, arrowMesh);
var effect = new FullColorEffect(game.LoadContent <Effect>("FullColor"));
_effect = effect;
_arrowMesh = new Mesh <VertexPosition>(arrowBuffer, effect.Effect);
}
