Request to customize origin and size in octree.convert_from_point_cloud()

[dunbar12138]

Checklist

• I have searched for similar issues.
• For Python issues, I have tested with the latest development wheel.
• I have checked the release documentation and the latest documentation (for main branch).

Proposed new feature or change

Hi, I found that octree.convert_from_point_cloud() will adaptively adjust the origin and size of the octree based on the input pointcloud even if they are set when the octree was initialized.

Is it possible for this function to take two extra optional arguments origin and size so that they can be fixed?

References

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Additional information

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[timohl]

From a coding perspective, it would be possible and not very hard to add.
But I cannot decide if that is wanted (gotta wait for some maintainer to decide).

Alternatively, you could use the constructor:
o3d.geometry.Octree.__init__(self, max_depth, origin, size)
Followed by looping over every point in the point cloud and insert it using:
o3d.geometry.Octree.insert_point(self, point, f_init, f_update, fi_init, fi_update)
The documentation for insert_point is not very helpful, but the following classes have static methods, which should be used to get the callbacks:
o3d.geometry.OctreePointColorLeafNode
o3d.geometry.OctreeInternalPointNode

octree.convert_from_point_cloud() does basically the same, looping over all points and inserting them:

Open3D/cpp/open3d/geometry/Octree.cpp

Lines 544 to 575 in f02e7d2

	void Octree::ConvertFromPointCloud(const geometry::PointCloud& point_cloud,
	double size_expand) {
	if (size_expand > 1 || size_expand < 0) {
	utility::LogError("size_expand shall be between 0 and 1");
	}
	// Set bounds
	Clear();
	Eigen::Array3d min_bound = point_cloud.GetMinBound();
	Eigen::Array3d max_bound = point_cloud.GetMaxBound();
	Eigen::Array3d center = (min_bound + max_bound) / 2;
	Eigen::Array3d half_sizes = center - min_bound;
	double max_half_size = half_sizes.maxCoeff();
	origin_ = min_bound.min(center - max_half_size);
	if (max_half_size == 0) {
	size_ = size_expand;
	} else {
	size_ = max_half_size * 2 * (1 + size_expand);
	}
	// Insert points
	const bool has_colors = point_cloud.HasColors();
	for (size_t idx = 0; idx < point_cloud.points_.size(); idx++) {
	const Eigen::Vector3d& color =
	has_colors ? point_cloud.colors_[idx] : Eigen::Vector3d::Zero();
	InsertPoint(point_cloud.points_[idx],
	OctreePointColorLeafNode::GetInitFunction(),
	OctreePointColorLeafNode::GetUpdateFunction(idx, color),
	OctreeInternalPointNode::GetInitFunction(),
	OctreeInternalPointNode::GetUpdateFunction(idx));
	}
	}