如何使用open3d提取底层体素？

Question

我想要提取底层的体素。例如，从鲤鱼身上提取出部分。有人知道怎么做吗？

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我就是这样找到最低的体素的。

#Get voxels center coordinate
def get_voxel_center_coordinate(voxel_grid):
    voxels = voxel_grid.get_voxels()
    voxel_center = []
    
    for voxel in voxels:
        voxel_center.append(voxel_grid.get_voxel_center_coordinate(voxel.grid_index))
    
    return voxel_center

#Find lowest voxels index
def find_lowest_voxel_index(voxel_grid):
    voxels = voxel_grid.get_voxels()
    voxel_center = get_voxel_center_coordinate(voxel_grid)
    
    for i in range(0, len(voxel_center)):
        if i == 0:
            min_z = voxel_center[i, 2]
        else:
            if min_z > voxel_center[i, 2]:
                min_z = voxel_center[i, 2]
    ind = 0
    lowest_voxel_index = []
    
    for center in voxel_center:
        if center[2] == min_z:
            print(center[2])
            lowest_voxel_index.append(voxels[ind].grid_index)
            ind += 1
    
    return lowest_voxel_index

Answer 1

你的解决方案几乎是正确的。我将指出一些您应该更改的内容，然后给出验证解决方案的方法。

解决方案

在给定的解决方案中应该更改的内容：

1. 您不能通过voxel_center[i, 2]访问z轴，因为voxel_center是一个列表，而不是numpy数组。相反，您应该访问它们，因为voxel_center[i][2].
2. You应该在每个循环中增加ind，而不仅仅是在条件为真时。或者，您可以使用enumerate来彻底克服这种情况.

因此，正确的实施如下：

#Get voxels center coordinate
def get_voxel_center_coordinate(voxel_grid):
    voxels = voxel_grid.get_voxels()
    voxel_center = []
    
    for voxel in voxels:
        voxel_center.append(voxel_grid.get_voxel_center_coordinate(voxel.grid_index))
    
    return voxel_center

#Find lowest voxels index
def find_lowest_voxel_index(voxel_grid):
    voxels = voxel_grid.get_voxels()
    voxel_center = get_voxel_center_coordinate(voxel_grid)
    
    for i in range(0, len(voxel_center)):
        if i == 0:
            min_z = voxel_center[i][2]
        else:
            if min_z > voxel_center[i][2]:
                min_z = voxel_center[i][2]
    ind = 0
    lowest_voxel_index = []
    
    for center in voxel_center:
        if center[2] == min_z:
            print(center[2])
            lowest_voxel_index.append(voxels[ind].grid_index)
        ind += 1
    
    return lowest_voxel_index

验证

要验证解决方案，您可能需要可视化结果。但是，VoxelGrid没有允许用户改变特定体素颜色的任何方法。因此，您可以考虑创建额外的网格来可视化过滤后的体素。由于VoxelGrid提供了get_voxel_bounding_points，所以可以使用这些点来创建AxisAlignedBoundingBox。

lowest_index = find_lowest_voxel_index(voxel_grid)  # this uses your solution after modifications

bounding_box = []
for i in lowest_index:
    bb = o3d.geometry.AxisAlignedBoundingBox.create_from_points(voxel_grid.get_voxel_bounding_points(i))
    bb.color = np.array([1,0,1])  # feel free to choose any other color
    bounding_box.append(bb)


axes = o3d.geometry.TriangleMesh.create_coordinate_frame(origin=np.array([100,100,100]), size=100)  # in order to be sure of the direction

o3d.visualization.draw_geometries([voxel_grid, *bounding_box, axes])

这是如何运行这段代码上的墨迹网格。请注意，我添加了坐标框来确定方向。蓝色箭头指向+z。z值最低的体素有紫色的边。

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