public static void AddArcVerts(List <Vertex3DColor> verts, Vector3 pos1, Vector3 pos2, float radius, Vector4 color)
{
// Project points onto sphere of given radius
pos1.Normalize();
pos2.Normalize();
// Determine arc degree:
double dot = Vector3.Dot(pos1, pos2);
if (dot != 1)
{
double theta = Math.Acos(dot);
pos2 *= radius;
pos2 *= radius;
double SineTheta = Math.Sin(theta);
// Slerp = Sine(theta-angle)*pos1/Sine(theta) + Sine(angle)*pos2/Sine(theta)
// angle: 0 -> theta
// iterate along arc, generating points each 0.2 degrees
for (double angle = 0.0f; angle <= theta; angle += Math.PI / 1800.0f)
{
Vector3 pAngle = (float)(Math.Sin(theta - angle) / SineTheta) * pos1 + (float)(Math.Sin(angle) / SineTheta) * pos2;
Vertex3DColor vertex = new Vertex3DColor(pAngle, color);
verts.Add(vertex);
}
}
}
static public IComplexGeometry CreateIcosphere(int subDivisions)
{
Vertex3DColor[] verts = new Vertex3DColor[12];
Vector4 color = new Vector4(0.2f, 0.2f, 1.0f, 1.0f);
Vector4 color2 = new Vector4(1.0f, 0.2f, 1.0f, 1.0f);
Vector4 color3 = new Vector4(0.2f, 1.0f, 1.0f, 1.0f);
const float t = 1.61803398875f; // approximation of golden ratio
verts[0] = new Vertex3DColor(Vector3.Normalize(new Vector3(-1, t, 0)), color2); // Subdivision generates Sierpinski triangle at pole
verts[1] = new Vertex3DColor(Vector3.Normalize(new Vector3(1, t, 0)), color);
verts[2] = new Vertex3DColor(Vector3.Normalize(new Vector3(-1, -t, 0)), color);
verts[3] = new Vertex3DColor(Vector3.Normalize(new Vector3(1, -t, 0)), color3); // Subdivision generates Sierpinski triangle at other pole
verts[4] = new Vertex3DColor(Vector3.Normalize(new Vector3(0, -1, t)), color);
verts[5] = new Vertex3DColor(Vector3.Normalize(new Vector3(0, 1, t)), color);
verts[6] = new Vertex3DColor(Vector3.Normalize(new Vector3(0, -1, -t)), color);
verts[7] = new Vertex3DColor(Vector3.Normalize(new Vector3(0, 1, -t)), color);
verts[8] = new Vertex3DColor(Vector3.Normalize(new Vector3(t, 0, -1)), color);
verts[9] = new Vertex3DColor(Vector3.Normalize(new Vector3(t, 0, 1)), color);
verts[10] = new Vertex3DColor(Vector3.Normalize(new Vector3(-t, 0, -1)), color);
verts[11] = new Vertex3DColor(Vector3.Normalize(new Vector3(-t, 0, 1)), color);
var mesh = new Mesh <Vertex3DColor>(verts);
var indices = new List <uint>();
AddIndices(ref indices, 0, 1, 7);
AddIndices(ref indices, 0, 5, 1);
AddIndices(ref indices, 0, 11, 5);
AddIndices(ref indices, 0, 10, 11);
AddIndices(ref indices, 0, 7, 10);
AddIndices(ref indices, 1, 5, 9);
AddIndices(ref indices, 5, 4, 9);
AddIndices(ref indices, 5, 11, 4);
AddIndices(ref indices, 11, 2, 4);
AddIndices(ref indices, 11, 10, 2);
AddIndices(ref indices, 10, 6, 2);
AddIndices(ref indices, 10, 7, 6);
AddIndices(ref indices, 7, 8, 6);
AddIndices(ref indices, 7, 1, 8);
AddIndices(ref indices, 1, 9, 8);
AddIndices(ref indices, 3, 4, 2);
AddIndices(ref indices, 3, 2, 6);
AddIndices(ref indices, 3, 6, 8);
AddIndices(ref indices, 3, 8, 9);
AddIndices(ref indices, 3, 9, 4);
var geometry = new ComplexGeometry <Vertex3DColor>(mesh, indices.ToArray());
int vertCount = geometry.SubDivide(subDivisions);
return(geometry);
}
