Clearing entities with transforms leaves an identity transform behind

[stonier]

Describe the bug

Everything seems to be working as documented, i.e.

• Clear - empties all components of an entity
• Spaces & Transforms - unless otherwise specified, every path is trivially connected to it's parent by the identity transform

However, it's the combination of the two when a non-identity transform is logged to an entity. It gets first cleared, and then reactivated as the identity keyframe which is subsequently visualized at the origin.

This can cause spurious transforms to appear in the 3D view, it can also cause rerun to excessively zoom out if entities are all far from the origin to compensate for the one re-registered at the world origin.

To Reproduce

1. Log a transform under an entity name, e.g. recording_stream.log("/bob", &transform);
   (transform must not be the identity)
2. Clear the entity, e.g. recording_stream.log("\bob", &rerun::Clear::recursive());
3. View the replay - the original transform keyframe is replaced by an identity transform keyframe at the origin

Expected behavior

The transform is not restored (and thus not re-visualized).

Desktop (please complete the following information):

• OS: Ubuntu 24.04

Rerun version
0.18.2

[stonier]

A reproduceable program:

use rerun as rr;

fn generate_transform(x: f32) -> rr::Transform3D {
    rr::Transform3D::from_translation_rotation(
        rr::Vec3D::new(x, 0.0, 0.0),
        rr::Quaternion::IDENTITY,
    )
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let (stream, storage) = rr::RecordingStreamBuilder::new("Clear").memory()?;
    let t_3 = generate_transform(3.0);
    let t_5 = generate_transform(5.0);
    let t_6 = generate_transform(6.0);
    stream.set_time_seconds("sim_time", 0.0);
    stream.log("/foo", &t_3)?;
    stream.log("/bar", &t_5)?;
    stream.set_time_seconds("sim_time", 1.0);
    stream.log("/foo", &t_3)?;
    stream.log("/bar", &t_6)?;
    stream.set_time_seconds("sim_time", 2.0);
    stream.log("/foo", &t_3)?;
    stream.log("/bar", &rerun::Clear::flat())?; // <-- sends the visual 3d axes back to the origin
    rr::native_viewer::show(storage.take())?;
    Ok(())
}

[Nikita240]

Here is a workaround for now:

use rerun as rr;

fn generate_transform(x: f32) -> rr::Transform3D {
    rr::Transform3D::from_translation_rotation(
        rr::Vec3D::new(x, 0.0, 0.0),
        rr::Quaternion::IDENTITY,
    )
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let (stream, storage) = rr::RecordingStreamBuilder::new("Clear").memory()?;
    let t_3 = generate_transform(3.0);
    let t_5 = generate_transform(5.0);
    let t_6 = generate_transform(6.0);
    stream.set_time_seconds("sim_time", 0.0);
    stream.log("/foo", &t_3)?;
    stream.log("/bar", &t_5)?;
    stream.set_time_seconds("sim_time", 1.0);
    stream.log("/foo", &t_3)?;
    stream.log("/bar", &t_6)?;
    stream.set_time_seconds("sim_time", 2.0);
    stream.log("/foo", &t_3)?;
    stream.log("/bar", &rerun::Clear::flat())?; // <-- sends the visual 3d axes back to the origin
    stream.log("/bar", &rr::Transform3D::clear().with_axis_length(0.0))?; // <-- workaround
    rr::native_viewer::show(storage.take())?;
    Ok(())
}

[stonier]

Aye, started with that workaround, but going two steps further...

Step 1: Use that zero'd axis length to make them vanish (easy)

but ... if entities are far from the origin, rerun zooms out excessively to try and fit in a transform that has been sent to the origin

Step 2: Reset the transform with the last transform (more of a pain)

but ... none of this handles transforms that have been cleared for sub-entities when using recursive

Step 3: Reset the transforms of all subentities with their last transforms (can be too difficult to be worth chasing)