/// <summary>
/// Creates a new <see cref="Mesh"/> representing a textured sphere with spherical mapping.
/// </summary>
/// <param name="device">The <see cref="Device"/> to create the mesh in</param>
/// <param name="radius">The radius of the sphere.</param>
/// <param name="slices">The number of vertical slices to divide the sphere into.</param>
/// <param name="stacks">The number of horizontal stacks to divide the sphere into.</param>
/// <remarks>The sphere is formed like the one created by <see cref="Mesh.CreateSphere"/>.</remarks>
public static Mesh Sphere(Device device, float radius, int slices, int stacks)
{
#region Sanity checks
if (device == null)
{
throw new ArgumentNullException(nameof(device));
}
if (slices <= 0)
{
throw new ArgumentOutOfRangeException(nameof(slices));
}
if (stacks <= 0)
{
throw new ArgumentOutOfRangeException(nameof(stacks));
}
#endregion
int numVertexes = (slices + 1) * (stacks + 1);
int numFaces = slices * stacks * 2;
int indexCount = numFaces * 3;
var mesh = new Mesh(device, numFaces, numVertexes, MeshFlags.Managed, PositionNormalTextured.Format);
#region Build sphere vertexes
var vertexes = new PositionNormalTextured[mesh.VertexCount];
int vertIndex = 0;
for (int slice = 0; slice <= slices; slice++)
{
float alphaY = (float)slice / slices * (float)Math.PI * 2.0f; // Angle around Y-axis
for (int stack = 0; stack <= stacks; stack++)
{
if (slice == slices)
{
vertexes[vertIndex] = vertexes[stack];
}
else
{
var pnt = new PositionNormalTextured();
float alphaZ = ((stack - stacks * 0.5f) / stacks) * (float)Math.PI * 1.0f; // Angle around Z-axis
pnt.X = (float)(Math.Cos(alphaY) * radius) * (float)Math.Cos(alphaZ);
pnt.Z = (float)(Math.Sin(alphaY) * radius) * (float)Math.Cos(alphaZ);
pnt.Y = (float)(Math.Sin(alphaZ) * radius);
pnt.Nx = pnt.X / radius;
pnt.Ny = pnt.Y / radius;
pnt.Nz = pnt.Z / radius;
pnt.Tv = 0.5f - (float)(Math.Asin(pnt.Y / radius) / Math.PI);
vertexes.SetValue(pnt, vertIndex);
}
vertexes[vertIndex++].Tu = (float)slice / slices;
}
}
#endregion
BufferHelper.WriteVertexBuffer(mesh, vertexes);
#region Build index buffer
var indexes = new short[indexCount];
int i = 0;
for (short x = 0; x < slices; x++)
{
var leftVertex = (short)((stacks + 1) * x);
var rightVertex = (short)(leftVertex + stacks + 1);
for (int y = 0; y < stacks; y++)
{
indexes[i++] = rightVertex;
indexes[i++] = leftVertex;
indexes[i++] = (short)(leftVertex + 1);
indexes[i++] = rightVertex;
indexes[i++] = (short)(leftVertex + 1);
indexes[i++] = (short)(rightVertex + 1);
leftVertex++;
rightVertex++;
}
}
#endregion
BufferHelper.WriteIndexBuffer(mesh, indexes);
return(mesh);
}
