control zoom in non-blocking visualizer

[MrGoort]

Hi all,

I have several point clouds of the same environment and each of them have more or less height. Instead of loading everything at the same time, I am loading each cloud at a time, and register it against the previous loaded one and then show the result in a non-blocking visualizer. When I am trying to move the camera to place it in the center of each new point cloud and in a top-view (like birds eye view), I have problems setting the view to keep at the same height, meaning, if the new point cloud has more height than the previous one, the camera zoom shouldn't move. Right now I am trying to do it like this:

Eigen::Vector3d minBound = cloud->GetMinBound();
Eigen::Vector3d maxBound = cloud->GetMaxBound();
open3d::visualization::ViewParameters viewParams;
viewParams.boundingbox_min_ = minBound;
viewParams.boundingbox_max_ = maxBound;
viewParams.lookat_ = (minBound + maxBound) / 2;
viewParams.field_of_view_ = 60.0;
viewParams.zoom_ = 0.7;
viewParams.up_ << 0.0, 1.0, 0.0;
viewParams.front_ << 0.0, 0.0, 1.0;
visualiser.GetViewControl().ConvertFromViewParameters(viewParams);

while the view is moving to keep it to the center of the x,y coords of the new cloud, the zoom keeps changing all the time.
Is there any way of keeping the same Z position in the viewer? Keeping a global variable for it or recomputing it every time, doesn't matter.
I cannot find anything indicating or explaining how to do it.

Thanks for the help

[pablospe]

Perhaps you can modify the code to avoid the max/min in the code (check code in issue #1427):
https://github.com/intel-isl/Open3D/blob/fab6441b763b4964ef898cbb3fae8d10ef98442f/src/Visualization/Visualizer/ViewControl.cpp#L191

Note: I guess it is also related to this issue: #497

[MrGoort]

Hey thanks for the help!.
I don't know if this is the same problem as those linked issues as Z moves around and the zoom works, but it doesn't keep it at the same value.
Anyway, I would like to avoid modifying the source code of the library, unless it is strictly necessary.
Maybe one of the authors have an idea of how to efficiently control the camera and zoom in the viewer.

[pablospe]

Maybe just trying (in the line mentioned above):
zoom_ = ideal_zoom;
?

[germanros1987]

Hi! In the Open3D team, we take your question very seriously. In order to provide better assistance to our users, we are implementing new policies. Now general questions should be asked in our forum: https://forum.open3d.org

Github issues will remain in use for bug reports and feature requests.

We are looking forward to answering your question in our forum!

Best regards.

[germanros1987]

This should be now possible in the new visualization module. Please, see examples here: https://github.com/intel-isl/Open3D/tree/master/examples/python/gui