Matlab去除多余点的快速方法

Question

我在 Matlab 中合并了两个点云对象，比方说 pc1 和 pc2。 pc1 是参考云，即 pc2 中与 pc1 中的点相等或非常接近的所有点都需要在组合云之前移除。

说明：

我知道函数 pcmerge，它几乎可以满足我的要求 - 但我绝对需要删除多余的点并且对这些点进行平均不是一个选项
每个点云大小约为500,000个，我必须比较其中的许多（100个）。这就是为什么速度很重要。
我希望能够在 pc1 的每个点周围定义一个半径来给出 "being redundant" 的标准。但是为了提高速度，可以进行一些简化（参见我的第二种解决方法）。

解决方法：

一个可行但非常慢的解决方案是在 pc2 中的每个点中寻找其最近的邻居：

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

我有一个更快的解决方案（仍然很慢，但比解决方案 1 更快）使用 alpha 形状：我在 pc1 周围定义一个外壳并决定 pc2 的点是否在里面。缺点：只有 "slightly outside" 的点（即靠近 pc1 的点但不在 alpha 形状内）不会被检测为冗余。

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

期待您的想法！如果需要，请随时询问更多信息 - 我是这个平台的新手。谢谢！

Answer 1

您可以使用 ismembertol 和 ByRows 选项来检测冗余点。但是请考虑它使用立方体邻域而不是球形邻域。假设您有两个矩阵 pc1 ,pc2 每个都有 3 列和一个公差 tol:

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

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