哈希表的应用-浅析顶点聚簇网格简化算法的实现

public class VertexCluster
{Mesh mesh;public VertexCluster(Mesh mesh){this.mesh = mesh;}public void Clear(){mesh = null;}public void ExecuteSimplification(float unitLength){if (unitLength <= 1){return;}Mesh newMesh = new Mesh();//新建Mesh存放削减后的网格Box3Float box = mesh.GetBox3();//首先获取Mesh的空间范围 XYZ方向的最大最小值存在box中int resx = (int)((box.Max3[0] - box.Min3[0]) / unitLength) + 1;int resy = (int)((box.Max3[1] - box.Min3[1]) / unitLength) + 1;int resz = (int)((box.Max3[2] - box.Min3[2]) / unitLength) + 1;//在新的单位长度下，得出新空间划分出的每一维的长度
HashTable_Double2dArray<int> hash = new HashTable_Double2dArray<int>(resx+1, resy+1, resz+1);//创建hash表，这里使用的是双二维数组哈希表for (int i = 0; i < mesh.Vertices.Count; i++){Point3d p = mesh.Vertices[i];int xindex = (int)((p.X - box.Min3[0]) / unitLength);int yindex = (int)((p.Y - box.Min3[1]) / unitLength);int zindex = (int)((p.Z - box.Min3[2]) / unitLength);//计算点在新单位长度下的坐标int value = 0;bool hasValue = hash.GetHashValue(xindex, yindex, zindex, ref value);if (!hasValue){hash.SetHashValue(xindex, yindex, zindex, newMesh.Vertices.Count);newMesh.AddVertex(new Point3d(xindex, yindex, zindex));}//新单位长度下肯定有原来不同的点映射到相同的位置，//总是添加第一次映射到这个位置的点入Mesh,之后的不再添加
        }for (int i = 0; i < mesh.Faces.Count; i++){Triangle t = mesh.Faces[i];Point3d p0 = mesh.Vertices[t.P0Index];Point3d p1 = mesh.Vertices[t.P1Index];Point3d p2 = mesh.Vertices[t.P2Index];int xindex0 = (int)((p0.X - box.Min3[0]) / unitLength);int yindex0 = (int)((p0.Y - box.Min3[1]) / unitLength);int zindex0 = (int)((p0.Z - box.Min3[2]) / unitLength);int index0 = 0;hash.GetHashValue(xindex0, yindex0, zindex0, ref index0);int xindex1 = (int)((p1.X - box.Min3[0]) / unitLength);int yindex1 = (int)((p1.Y - box.Min3[1]) / unitLength);int zindex1 = (int)((p1.Z - box.Min3[2]) / unitLength);int index1 = 0;hash.GetHashValue(xindex1, yindex1, zindex1, ref index1);int xindex2 = (int)((p2.X - box.Min3[0]) / unitLength);int yindex2 = (int)((p2.Y - box.Min3[1]) / unitLength);int zindex2 = (int)((p2.Z - box.Min3[2]) / unitLength);int index2 = 0;hash.GetHashValue(xindex2, yindex2, zindex2, ref index2);if (!(index0 == index1 || index0 == index2 || index1 == index2)){newMesh.AddFace(new Triangle(index0, index1, index2));}//对于每个三角形，找出其三点对应的新位置，检查是否有两个点重合（退化），//添加不退化的三角形
        }for (int i = 0; i < newMesh.Vertices.Count; i++){Point3d p = newMesh.Vertices[i];p.X = (float)(unitLength * p.X + box.Min3[0]);p.Y = (float)(unitLength * p.Y + box.Min3[1]);p.Z = (float)(unitLength * p.Z + box.Min3[2]);}//将新Mesh的坐标放大到和原来一样的尺度
        mesh.Clear();mesh.Vertices = newMesh.Vertices;mesh.Faces = newMesh.Faces;//替换旧Mesh的数据
    }
}