Add support for scene units in the map view (#8015)

### What

- Fixes #7872 
- Limitation: #8013

Add support for scene units (aka meter)  in the map view.


https://github.com/user-attachments/assets/012c86d7-70cd-4144-9e54-414570ca286e


### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/8015?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/8015?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!
* [x] If have noted any breaking changes to the log API in
`CHANGELOG.md` and the migration guide

- [PR Build Summary](https://build.rerun.io/pr/8015)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

To run all checks from `main`, comment on the PR with `@rerun-bot
full-check`.

crates/store/re_types/definitions/rerun/archetypes/geo_line_strings.fbs

@@ -25,6 +25,9 @@ table GeoLineStrings (
   // --- Recommended ---
 
   /// Optional radii for the line strings.
+  ///
+  /// *Note*: scene units radiii are interpreted as meters. Currently, the display scale only considers the latitude of
+  /// the first vertex of each line string (see [this issue](https://github.com/rerun-io/rerun/issues/8013)).
   radii: [rerun.components.Radius] ("attr.rerun.component_recommended", nullable, order: 2000);
 
   /// Optional colors for the line strings.

crates/store/re_types/definitions/rerun/archetypes/geo_points.fbs

@@ -21,6 +21,8 @@ table GeoPoints (
   // --- Recommended ---
 
   /// Optional radii for the points, effectively turning them into circles.
+  ///
+  /// *Note*: scene units radiii are interpreted as meters.
   radii: [rerun.components.Radius] ("attr.rerun.component_recommended", nullable, order: 2000);
 
   /// Optional colors for the points.

crates/viewer/re_space_view_map/src/visualizers/geo_line_strings.rs

@@ -15,8 +15,7 @@ use re_viewer_context::{
 #[derive(Debug, Default)]
 struct GeoLineStringsBatch {
     lines: Vec<Vec<walkers::Position>>,
-    //TODO(#7872): to be converted to scene vs. ui
-    radii: Vec<f32>,
+    radii: Vec<Radius>,
     colors: Vec<re_renderer::Color32>,
     instance_id: Vec<PickingLayerInstanceId>,
 }
@@ -93,7 +92,7 @@ impl VisualizerSystem for GeoLineStringsVisualizer {
                             .map(|pos| walkers::Position::from_lat_lon(pos.x(), pos.y()))
                             .collect(),
                     );
-                    batch_data.radii.push(radius.0.abs());
+                    batch_data.radii.push(*radius);
                     batch_data.colors.push(color.0.into());
                     batch_data
                         .instance_id
@@ -159,7 +158,15 @@ impl GeoLineStringsVisualizer {
                         let ui_position = projector.project(*pos);
                         glam::vec2(ui_position.x, ui_position.y)
                     }))
-                    .radius(re_renderer::Size(*radius))
+                    //TODO(#8013): we use the first vertex's latitude because `re_renderer` doesn't support per-vertex radii
+                    .radius(super::radius_to_size(
+                        *radius,
+                        projector,
+                        strip
+                            .first()
+                            .copied()
+                            .unwrap_or(walkers::Position::from_lat_lon(0.0, 0.0)),
+                    ))
                     .color(*color)
                     .picking_instance_id(*instance)
                     .outline_mask_ids(

crates/viewer/re_space_view_map/src/visualizers/geo_points.rs

@@ -15,8 +15,7 @@ use re_viewer_context::{
 #[derive(Debug, Default)]
 pub struct GeoPointBatch {
     pub positions: Vec<walkers::Position>,
-    //TODO(#7872): to be converted to scene vs. ui
-    pub radii: Vec<f32>,
+    pub radii: Vec<Radius>,
     pub colors: Vec<re_renderer::Color32>,
     pub instance_id: Vec<PickingLayerInstanceId>,
 }
@@ -90,7 +89,7 @@ impl VisualizerSystem for GeoPointsVisualizer {
                         position.latitude(),
                         position.longitude(),
                     ));
-                    batch_data.radii.push(radius.0.abs());
+                    batch_data.radii.push(*radius);
                     batch_data.colors.push(color.0.into());
                     batch_data
                         .instance_id
@@ -138,20 +137,16 @@ impl GeoPointsVisualizer {
         );
 
         for (entity_path, batch) in &self.batches {
-            let positions = batch
+            let (positions, radii): (Vec<_>, Vec<_>) = batch
                 .positions
                 .iter()
-                .map(|pos| {
+                .zip(&batch.radii)
+                .map(|(pos, radius)| {
+                    let size = super::radius_to_size(*radius, projector, *pos);
                     let ui_position = projector.project(*pos);
-                    glam::vec3(ui_position.x, ui_position.y, 0.0)
+                    (glam::vec3(ui_position.x, ui_position.y, 0.0), size)
                 })
-                .collect::<Vec<_>>();
-
-            let radii = batch
-                .radii
-                .iter()
-                .map(|radius| re_renderer::Size(*radius))
-                .collect::<Vec<_>>();
+                .unzip();
 
             let outline = highlight.entity_outline_mask(entity_path.hash());
 
@@ -190,7 +185,7 @@ impl TypedComponentFallbackProvider<Color> for GeoPointsVisualizer {
 
 impl TypedComponentFallbackProvider<Radius> for GeoPointsVisualizer {
     fn fallback_for(&self, _ctx: &QueryContext<'_>) -> Radius {
-        Radius::from(5.0)
+        Radius::new_ui_points(5.0)
     }
 }
 

crates/viewer/re_space_view_map/src/visualizers/mod.rs

@@ -92,6 +92,23 @@ pub fn update_span(span: &mut Option<GeoSpan>, other: Option<GeoSpan>) {
     }
 }
 
+/// Convert a [`re_types::components::Radius`] to a [`re_renderer::Size`], considering scene units
+/// as meters.
+#[inline]
+pub fn radius_to_size(
+    radius: re_types::components::Radius,
+    projector: &walkers::Projector,
+    position: walkers::Position,
+) -> re_renderer::Size {
+    re_renderer::Size(
+        radius
+            .scene_units()
+            .map(|radius_meter| projector.scale_pixel_per_meter(position) * radius_meter)
+            .or(radius.ui_points())
+            .unwrap_or_default(),
+    )
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;