在Matlab中快速去除冗余点的方法

Question

我在Matlab中合并了两个pointCloud对象，比如pc1和pc2。pc1是参考云，即，在组合云之前，需要移除来自pc2的与来自pc1的点相等或非常接近的所有点。

澄清：

• 我知道函数pcmerge，它几乎在做我想要的事情，但我肯定需要删除多余的点，并且平均这些点不是的选项

• 每个点云的大小大约是500000，我必须比较其中的许多(100(个。这就是为什么速度很重要。

• 我更希望能够定义pc1的每个点周围的半径，以给出"冗余"的标准。但在速度方面，一些简化是可以的(参见我的第二种解决方案(。

解决方案方法：

• 一个有效但非常慢的解决方案是在pc2中查找其最近邻居的每个点：

  function [ pc ] = pcaddcloud( pc1, pc2, res )
  limits = overlapRange(pc2, pc1);
  pc1idx = findPointsInROI(pc2, limits);
  pc2Overlap = select(pc2, pc1idx);
  idx = findPointsInROI(pc1, limits);
  pc1Overlap = select(pc1, idx);
  endi = pc2Overlap.Count;
  pc2Overlap = pc2Overlap.Location;
  for i=1:endi
  [idx, ~] = findNeighborsInRadius(pc1Overlap, pc2Overlap(i,:), res);
  % keep only indices of redundant points to delete them later
  if isempty(idx)
  pc1idx(i) = 0;
  end
  end
  pc1idx(pc1idx==0) = [];
  pc2 = pc2.Location;
  pc2(pc1idx,:) = [];
  pc = pointCloud([pc1.Location; pc2]);
  end
  % Compute the bounding box of overlapped region (from pcmerge)
  function rangeLimits = overlapRange(pcA, pcB)
  xlimA = pcA.XLimits;
  ylimA = pcA.YLimits;
  zlimA = pcA.ZLimits;
  xlimB = pcB.XLimits;
  ylimB = pcB.YLimits;
  zlimB = pcB.ZLimits;
  if (xlimA(1) > xlimB(2) || xlimA(2) < xlimB(1) || ...
  ylimA(1) > ylimB(2) || ylimA(2) < ylimB(1) || ...
  zlimA(1) > zlimB(2) || zlimA(2) < zlimB(1))
  % No overlap
  rangeLimits = [];
  else
  rangeLimits = [ min(xlimA(1),xlimB(1)), max(xlimA(2),xlimB(2)); ...
  min(ylimA(1),ylimB(1)), max(ylimA(2),ylimB(2)); ...
  min(zlimA(1),zlimB(1)), max(zlimA(2),zlimB(2))];
  end
  end
  

• 我有一个处理alpha形状的更快的解决方案(仍然很慢，但比解决方案1更快(：我在pc1周围定义一个外壳，并决定pc2的点是否在里面。缺点：仅"稍微在外面"的点(即靠近pc1的点，但不在alpha形状内部(不会被检测为多余。

  function [ pc ] = pcaddcloud( pc1, pc2 )
  limits = overlapRange(pc2, pc1);
  pc2 = pc2.Location;
  pc1 = pc1.Location;
  %seems to be faster than findPointsInROI:
  pc2Overlap = pc2(pc2(:,1)>=limits(1,1)&pc2(:,1)<=limits(1,2) ...
  &pc2(:,2)>=limits(2,1)&pc2(:,2)<=limits(2,2)...
  &pc2(:,3)>=limits(3,1)&pc2(:,3)<=limits(3,2),:);
  pc2idx = find(pc2(:,1)>=limits(1,1)&pc2(:,1)<=limits(1,2) ...
  &pc2(:,2)>=limits(2,1)&pc2(:,2)<=limits(2,2)...
  &pc2(:,3)>=limits(3,1)&pc2(:,3)<=limits(3,2));
  pc1Overlap = pc1(pc1(:,1)>=limits(1,1)&pc1(:,1)<=limits(1,2) ...
  &pc1(:,2)>=limits(2,1)&pc1(:,2)<=limits(2,2)...
  &pc1(:,3)>=limits(3,1)&pc1(:,3)<=limits(3,2),:);
  shape = alphaShape(double(pc1Overlap));
  in = inShape(shape, double(pc2Overlap));
  pc2idx(~in) = [];
  pc2(pc2idx,:) = [];
  pc = pointCloud([pc1; pc2]);
  end
  % Compute the bounding box of overlapped region (from pcmerge)
  function rangeLimits = overlapRange(pcA, pcB)
  xlimA = pcA.XLimits;
  ylimA = pcA.YLimits;
  zlimA = pcA.ZLimits;
  xlimB = pcB.XLimits;
  ylimB = pcB.YLimits;
  zlimB = pcB.ZLimits;
  if (xlimA(1) > xlimB(2) || xlimA(2) < xlimB(1) || ...
  ylimA(1) > ylimB(2) || ylimA(2) < ylimB(1) || ...
  zlimA(1) > zlimB(2) || zlimA(2) < zlimB(1))
  % No overlap
  rangeLimits = [];
  else
  rangeLimits = [ min(xlimA(1),xlimB(1)), max(xlimA(2),xlimB(2)); ...
  min(ylimA(1),ylimB(1)), max(ylimA(2),ylimB(2)); ...
  min(zlimA(1),zlimB(1)), max(zlimA(2),zlimB(2))];
  end
  end
  

我很期待你的想法！如果需要，请毫不犹豫地询问更多信息——我是这个平台的新手。非常感谢。

Answer 1

您可以使用ismembertol和ByRows选项来检测冗余点。但考虑一下，它使用的不是球面邻域，而是三次邻域。假设您有两个矩阵pc1，pc2，每个矩阵有3列和一个容差tol:

idx = ismembertol(pc2, pc1, tol,'ByRows', true, 'DataScale' , 1);
result = [pc1; pc2(~idx,:)];