/// <summary>
/// 2つのVertexを内分するVertexを求める
/// </summary>
/// <param name="v1">1つ目のVertex</param>
/// <param name="v2">2つ目のVertex</param>
/// <param name="isoValue">等値曲面の値</param>
/// <returns>内分されたVertex</returns>
public static Vertex Interpolate(Vertex v1, Vertex v2, float isoValue)
{
if (Math.Abs(isoValue - v1.Value) < 0.00001f) {
return v1;
}
if (Math.Abs(isoValue - v2.Value) < 0.00001f) {
return v2;
}
if (Math.Abs(v1.Value - v2.Value) < 0.00001f) {
return v1;
}
var diff = (isoValue - v1.Value) / (v2.Value - v1.Value);
Vertex v;
v.Point = new Vec3(
v1.Point.X + (v2.Point.X - v1.Point.X) * diff,
v1.Point.Y + (v2.Point.Y - v1.Point.Y) * diff,
v1.Point.Z + (v2.Point.Z - v1.Point.Z) * diff
);
v.Value = (v1.Value + v2.Value) * 0.5f;
v.IsInside = false;
return v;
}
/// <summary>
/// 等値曲面を計算する
/// </summary>
/// <returns>等値曲面を構成する三角形の配列</returns>
public unsafe List<Triangle> CalculateIsosurface()
{
// 等値曲面を構成するポリゴンの動的配列
var triangles = new List<Triangle>();
// ポリゴンを構成する座標の配列
var vertexList = new Vertex[12];
var vertices = (Vertex*)_verticesBuffer.ToPointer();
for (var z = 0; z < _sizeZ - 1; z++) {
for (var y = 0; y < _sizeY - 1; y++) {
for (var x = 0; x < _sizeX - 1; x++) {
var lookup = 0;
var index = x + y * _sizeX + z * _sizeX * _sizeY;
// 等値曲面の内側に存在する頂点を検索する
if (vertices[index + _sizeX + _sizeXY].IsInside) lookup |= 1;
if (vertices[index + 1 + _sizeX + _sizeXY].IsInside) lookup |= 2;
if (vertices[index + 1 + _sizeX].IsInside) lookup |= 4;
if (vertices[index + _sizeX].IsInside) lookup |= 8;
if (vertices[index + _sizeXY].IsInside) lookup |= 16;
if (vertices[index + 1 + _sizeXY].IsInside) lookup |= 32;
if (vertices[index + 1].IsInside) lookup |= 64;
if (vertices[index].IsInside) lookup |= 128;
// 全ての頂点が等値曲面の内側・外側に存在しないときのみ
if ((lookup != 0) && (lookup != 255)) {
if ((EDGE_TABLE[lookup] & 1) != 0)
vertexList[0]= Vertex.Interpolate(vertices[index + _sizeX + _sizeXY],
vertices[index + 1 + _sizeY + _sizeXY], _isoValue);
if ((EDGE_TABLE[lookup] & 2) != 0)
vertexList[1] = Vertex.Interpolate(vertices[index + 1 + _sizeX + _sizeXY],
vertices[index + 1 + _sizeX], _isoValue);
if ((EDGE_TABLE[lookup] & 4) != 0)
vertexList[2] = Vertex.Interpolate(vertices[index + 1 + _sizeX],
vertices[index + _sizeX], _isoValue);
if ((EDGE_TABLE[lookup] & 8) != 0)
vertexList[3] = Vertex.Interpolate(vertices[index + _sizeX],
vertices[index + _sizeX + _sizeXY], _isoValue);
if ((EDGE_TABLE[lookup] & 16) != 0)
vertexList[4] = Vertex.Interpolate(vertices[index + _sizeXY],
vertices[index + 1 + _sizeXY], _isoValue);
if ((EDGE_TABLE[lookup] & 32) != 0)
vertexList[5] = Vertex.Interpolate(vertices[index + 1 + _sizeXY],
vertices[index + 1], _isoValue);
if ((EDGE_TABLE[lookup] & 64) != 0)
vertexList[6] = Vertex.Interpolate(vertices[index + 1],
vertices[index], _isoValue);
if ((EDGE_TABLE[lookup] & 128) != 0)
vertexList[7] = Vertex.Interpolate(vertices[index],
vertices[index + _sizeXY], _isoValue);
if ((EDGE_TABLE[lookup] & 256) != 0)
vertexList[8] = Vertex.Interpolate(vertices[index + _sizeX + _sizeXY],
vertices[index + _sizeXY], _isoValue);
if ((EDGE_TABLE[lookup] & 512) != 0)
vertexList[9] = Vertex.Interpolate(vertices[index + 1 + _sizeX + _sizeXY],
vertices[index + 1 + _sizeXY], _isoValue);
if ((EDGE_TABLE[lookup] & 1024) != 0)
vertexList[10] = Vertex.Interpolate(vertices[index + 1 + _sizeX],
vertices[index + 1], _isoValue);
if ((EDGE_TABLE[lookup] & 2048) != 0)
vertexList[11] = Vertex.Interpolate(vertices[index + _sizeX],
vertices[index], _isoValue);
// 三角形ポリゴンを生成していく
for (var i = 0; i < TRI_TABLE[lookup].Length; i += 3) {
triangles.Add(new Triangle(
vertexList[TRI_TABLE[lookup][i]].Point,
vertexList[TRI_TABLE[lookup][i + 1]].Point,
vertexList[TRI_TABLE[lookup][i + 2]].Point
));
}
}
}
}
}
return triangles;
}
