/// <summary>
/// Triangulate this csg and pack the triangulated data into buffers
/// appropriate for use with gltf.
/// </summary>
internal static GraphicsBuffers Tessellate(this Csg.Solid csg)
{
var buffers = new GraphicsBuffers();
ushort iCursor = 0;
(Vector3 U, Vector3 V)basis;
const float SEARCH_RADIUS = 0.001f;
// Setup the octree to fit around the csg.
// This requires one expensive initialization.
var verts = csg.Polygons.SelectMany(p => p.Vertices).Select(v => v.Pos.ToElementsVector()).ToArray();
var bounds = new BBox3(verts);
var center = bounds.Center();
var origin = new Point((float)center.X, (float)center.Y, (float)center.Z);
var size = (float)bounds.Max.DistanceTo(bounds.Min);
var octree = new PointOctree <(Vector3 position, Vector3 normal, ushort index)>(size, origin, SEARCH_RADIUS);
foreach (var p in csg.Polygons)
{
var vertexIndices = new ushort[p.Vertices.Count];
var a = p.Vertices[0].Pos.ToElementsVector();
var b = p.Vertices[1].Pos.ToElementsVector();
var c = p.Vertices[2].Pos.ToElementsVector();
basis = ComputeBasisAndNormalForTriangle(a, b, c, out Vector3 normal);
// Anything with 3 vertices is a triangle. Manually
// tesselate triangles. For everything else, use
// the tessellator.
if (p.Vertices.Count > 2 && p.Vertices.Count <= 3)
{
for (var i = 0; i < p.Vertices.Count; i++)
{
var v = p.Vertices[i];
var op = new Point((float)v.Pos.X, (float)v.Pos.Y, (float)v.Pos.Z);
var ep = v.Pos.ToElementsVector();
if (TryGetExistingVertex(op, ep, octree, normal, SEARCH_RADIUS, out ushort vertexIndex))
{
vertexIndices[i] = vertexIndex;
continue;
}
vertexIndices[i] = iCursor;
iCursor++;
var uu = basis.U.Dot(ep);
var vv = basis.V.Dot(ep);
buffers.AddVertex(ep, normal, new UV(uu, vv));
octree.Add((ep, normal, vertexIndices[i]), op);
internal static GraphicsBuffers ToGraphicsBuffers(this IList <Vector3> vertices, bool lineLoop)
{
var gb = new GraphicsBuffers();
for (var i = 0; i < vertices.Count; i++)
{
var v = vertices[i];
gb.AddVertex(v, default(Vector3), default(UV), null);
var write = lineLoop ? (i < vertices.Count - 1) : (i % 2 == 0 && i < vertices.Count - 1);
if (write)
{
gb.AddIndex((ushort)i);
gb.AddIndex((ushort)(i + 1));
}
}
return(gb);
}
/// <summary>
/// Get all buffers required for rendering.
/// </summary>
public GraphicsBuffers GetBuffers()
{
var buffers = new GraphicsBuffers();
for (var i = 0; i < this.Vertices.Count; i++)
{
var v = this.Vertices[i];
buffers.AddVertex(v.Position, v.Normal, v.UV, v.Color);
}
for (var i = 0; i < this.Triangles.Count; i++)
{
var t = this.Triangles[i];
buffers.AddIndex((ushort)t.Vertices[0].Index);
buffers.AddIndex((ushort)t.Vertices[1].Index);
buffers.AddIndex((ushort)t.Vertices[2].Index);
}
return(buffers);
}
