Add FillMode::MajorWireframe for more significant ellipsoid wireframes. (#7044)

### What

* Add `FillMode::MajorWireframe`. For ellipsoids, this causes them to be
drawn as three axis-aligned ellipses. It has no other effects. This
implements the main part of #6962.
* The previous `FillMode::Wireframe` has also been been renamed to
`DenseWireframe` to reflect its relative role.
* Updated `hexasphere` to 14.1.0 and removed the bug workaround code.

I'm not sure if adding another `FillMode` is the best way to expose this
rendering functionality, but it works out tidily enough for now.

This does not modify any examples, but if we applied `MajorWireframe` to
the `ellipsoid3d_batch` snippet, we'd get:

![Screenshot 2024-08-02 at 14 23
09](https://github.com/user-attachments/assets/e25a3244-d0b8-4e49-a4bf-388c6d7e9d33)

### 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)
* [ ] I have tested the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7044?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/7044?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/7044)
- [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`.

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

Author: kpreid

Cargo.lock

@@ -2505,9 +2505,9 @@ checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
 [[package]]
 name = "hexasphere"
-version = "14.0.0"
+version = "14.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6c64d70ed6295005e2bc5a6f624300cfd6d49908da76b3654c4cbdb1d4222705"
+checksum = "344d5bf5d6b6da1020fcfd4014d44e0cc695356c603db9c774b30bd6d385ad2b"
 dependencies = [
  "constgebra",
  "glam",

Cargo.toml

@@ -171,7 +171,7 @@ glam = "0.28"
 glob = "0.3"
 gltf = "1.1"
 half = "2.3.1"
-hexasphere = "14.0.0"
+hexasphere = "14.1.0"
 image = { version = "0.25", default-features = false }
 indent = "0.1"
 indexmap = "2.1" # Version chosen to align with other dependencies

crates/store/re_types/definitions/rerun/components/fill_mode.fbs

@@ -7,13 +7,31 @@ enum FillMode: ubyte(
     /// Invalid value. Won't show up in generated types.
     Invalid = 0,
 
-    /// Lines are drawn around the edges of the shape.
+    // Design note: This entire enum is an temporary mechanism which should be replaced by
+    // allowing entities to simultaneously have fill and stroke colors.
+    // Doing that is blocked on tagged components:
+    // <https://github.com/rerun-io/rerun/issues/6889>.
+    // Once those colors exist, visualizers should be updated to simply render whichever combination
+    // of these features have non-(0, 0, 0, 0) colors set.
+
+    /// Lines are drawn around the parts of the shape which directly correspond to the logged data.
+    ///
+    /// Examples of what this means:
     ///
-    /// The interior (2D) or surface (3D) are not drawn.
-    Wireframe (default),
+    /// * An [archetypes.Ellipsoids3D] will draw three axis-aligned ellipses that are cross-sections
+    ///   of each ellipsoid, each of which displays two out of three of the sizes of the ellipsoid.
+    /// * For [archetypes.Boxes3D], it is the edges of the box, identical to `DenseWireframe`.
+    MajorWireframe (default),
 
-    /// The interior (2D) or surface (3D) is filled with a single color.
+    /// Many lines are drawn to represent the surface of the shape in a see-through fashion.
     ///
-    /// Lines are not drawn.
+    /// Examples of what this means:
+    ///
+    /// * An [archetypes.Ellipsoids3D] will draw a wireframe triangle mesh that approximates each
+    ///   ellipsoid.
+    /// * For [archetypes.Boxes3D], it is the edges of the box, identical to `MajorWireframe`.
+    DenseWireframe,
+
+    /// The surface of the shape is filled in with a solid color. No lines are drawn.
     Solid,
 }

crates/store/re_types/src/components/fill_mode.rs

@@ -4,8 +4,8 @@
 
 use std::sync::Arc;
 
-use ahash::HashSet;
 use glam::{uvec3, vec3, Vec3, Vec3A};
+use hexasphere::BaseShape;
 use itertools::Itertools as _;
 use smallvec::smallvec;
 
@@ -28,15 +28,25 @@ pub enum ProcMeshKey {
     ///
     /// The resulting mesh may be scaled to represent spheres and ellipsoids
     /// of other sizes.
-    Sphere { subdivisions: usize },
+    Sphere {
+        /// Number of triangle subdivisions to perform to create a finer, rounder mesh.
+        subdivisions: usize,
+
+        /// If true, then when a wireframe mesh is generated, it includes only
+        /// the 3 axis-aligned “equatorial” circles, and not the full triangle mesh.
+        axes_only: bool,
+    },
 }
 
 impl ProcMeshKey {
     /// Returns the bounding box which can be computed from the mathematical shape,
     /// without regard for its exact approximation as a mesh.
     pub fn simple_bounding_box(&self) -> re_math::BoundingBox {
         match self {
-            Self::Sphere { subdivisions: _ } => {
+            Self::Sphere {
+                subdivisions: _,
+                axes_only: _,
+            } => {
                 // sphere’s radius is 1, so its size is 2
                 re_math::BoundingBox::from_center_size(Vec3::splat(0.0), Vec3::splat(2.0))
             }
@@ -166,21 +176,19 @@ fn generate_wireframe(key: &ProcMeshKey, render_ctx: &RenderContext) -> Wirefram
                 line_strips,
             }
         }
-        ProcMeshKey::Sphere { subdivisions } => {
+        ProcMeshKey::Sphere {
+            subdivisions,
+            axes_only,
+        } => {
             let subdiv: hexasphere::Subdivided<(), OctahedronBase> =
                 hexasphere::Subdivided::new(subdivisions, |_| ());
 
             let sphere_points = subdiv.raw_points();
 
-            // TODO(kpreid): There is a bug in `hexasphere` where it fails to return lines which
-            // reach the original corners of the shape. This will be fixed as part of
-            // <https://github.com/OptimisticPeach/hexasphere/issues/19>,
-            // which is merged but not yet published on crates.io.
-            // When hexasphere 15.0 or 14.0.1 is available, update, then keep the first branch
-            // of this `if` only.
-            let line_strips: Vec<Vec<Vec3>> = if false {
-                subdiv
-                    .get_all_line_indices(1, |v| v.push(0))
+            let line_strips: Vec<Vec<Vec3>> = if axes_only {
+                let mut buffer: Vec<u32> = Vec::new();
+                subdiv.get_major_edges_line_indices(&mut buffer, 1, |v| v.push(0));
+                buffer
                     .split(|&i| i == 0)
                     .map(|strip| -> Vec<Vec3> {
                         strip
@@ -190,24 +198,14 @@ fn generate_wireframe(key: &ProcMeshKey, render_ctx: &RenderContext) -> Wirefram
                     })
                     .collect()
             } else {
-                // Gather edges from the triangles, deduplicating.
-                let lines: HashSet<(u32, u32)> = subdiv
-                    .get_all_indices()
-                    .chunks(3)
-                    .flat_map(|triangle| {
-                        let [i1, i2, i3] = <[u32; 3]>::try_from(triangle).unwrap();
-                        [(i1, i2), (i2, i3), (i3, i1)]
-                    })
-                    .map(|(i1, i2)| if i1 > i2 { (i2, i1) } else { (i1, i2) })
-                    .collect();
-
-                lines
-                    .into_iter()
-                    .map(|(i1, i2)| {
-                        vec![
-                            sphere_points[i1 as usize].into(),
-                            sphere_points[i2 as usize].into(),
-                        ]
+                subdiv
+                    .get_all_line_indices(1, |v| v.push(0))
+                    .split(|&i| i == 0)
+                    .map(|strip| -> Vec<Vec3> {
+                        strip
+                            .iter()
+                            .map(|&i| sphere_points[i as usize - 1].into())
+                            .collect()
                     })
                     .collect()
             };
@@ -296,7 +294,10 @@ fn generate_solid(
                 vertex_texcoords: vec![glam::Vec2::ZERO; num_vertices],
             }
         }
-        ProcMeshKey::Sphere { subdivisions } => {
+        ProcMeshKey::Sphere {
+            subdivisions,
+            axes_only: _, // no effect on solid mesh
+        } => {
             let subdiv: hexasphere::Subdivided<(), OctahedronBase> =
                 hexasphere::Subdivided::new(subdivisions, |_| ());
 
@@ -374,7 +375,7 @@ fn materials_for_uncolored_mesh(
 #[derive(Clone, Copy, Debug, Default)]
 struct OctahedronBase;
 
-impl hexasphere::BaseShape for OctahedronBase {
+impl BaseShape for OctahedronBase {
     fn initial_points(&self) -> Vec<Vec3A> {
         vec![
             Vec3A::NEG_X,

crates/viewer/re_space_view_spatial/src/proc_mesh.rs

@@ -111,7 +111,7 @@ impl Boxes3DVisualizer {
                 );
 
                 match data.fill_mode {
-                    FillMode::Wireframe => {
+                    FillMode::DenseWireframe | FillMode::MajorWireframe => {
                         let box3d = line_batch
                             .add_box_outline_from_transform(world_from_instance)
                             .color(color)
@@ -283,7 +283,7 @@ impl VisualizerSystem for Boxes3DVisualizer {
                     .unwrap_or_default();
 
                 match fill_mode {
-                    FillMode::Wireframe => {
+                    FillMode::DenseWireframe | FillMode::MajorWireframe => {
                         // Each box consists of 12 independent lines with 2 vertices each.
                         line_builder.reserve_strips(num_boxes * 12)?;
                         line_builder.reserve_vertices(num_boxes * 12 * 2)?;

crates/viewer/re_space_view_spatial/src/visualizers/boxes3d.rs

@@ -107,8 +107,18 @@ impl Ellipsoids3DVisualizer {
 
                 // TODO(kpreid): subdivisions should be configurable, and possibly dynamic based on
                 // either world size or screen size (depending on application).
-                let subdivisions = 2;
-                let proc_mesh_key = proc_mesh::ProcMeshKey::Sphere { subdivisions };
+                let subdivisions = match data.fill_mode {
+                    FillMode::DenseWireframe => 2, // Don't make it too crowded - let the user see inside the mesh.
+                    FillMode::Solid => 6,          // Smooth, but not too CPU/GPU intensive
+                    FillMode::MajorWireframe => 12, // Three smooth ellipses
+                };
+                let proc_mesh_key = proc_mesh::ProcMeshKey::Sphere {
+                    subdivisions,
+                    axes_only: match data.fill_mode {
+                        FillMode::MajorWireframe => true,
+                        FillMode::DenseWireframe | FillMode::Solid => false,
+                    },
+                };
 
                 // No need to take half_size times 2 since the mesh we're using is already scaled accordingly.
                 let world_from_instance =
@@ -120,7 +130,7 @@ impl Ellipsoids3DVisualizer {
                 );
 
                 match data.fill_mode {
-                    FillMode::Wireframe => {
+                    FillMode::MajorWireframe | FillMode::DenseWireframe => {
                         let Some(wireframe_mesh) =
                             ctx.viewer_ctx
                                 .cache