Host wide polyline quads on their 3D plane instead of billboarding in screen space

src/scene/pipeline/gpu_tests.rs

@@ -662,6 +662,25 @@ fn test_tilted_3d_donut_and_thick_arc_gpu_rendering() {
     assert_eq!(circles[0].instance_count, 2);
     pipeline.gpu_circles = std::sync::Arc::new(circles);
 
+    // Wide straight polyline segment on the 3D plane
+    let mut straight_wide = WireModel::default();
+    straight_wide.name = "wide_straight".into();
+    straight_wide.points = vec![[0.0, 0.0, 0.0], [50.0, 50.0, 0.0]];
+    straight_wide.world_width = 10.0;
+    straight_wide.color = [0.9, 0.2, 0.3, 1.0];
+
+    let wide_wires = vec![straight_wide];
+    let gpu_wires = wire_gpu::WireGpu::from_run(
+        &device,
+        &queue,
+        &wide_wires,
+        &depth_map,
+        false,
+        pipeline.wire_const_bgl.as_ref(),
+    );
+    assert!(!gpu_wires.is_empty());
+    pipeline.gpu_wires = std::sync::Arc::new(gpu_wires);
+
     pipeline.ensure_depth_texture(&device, iced::Size::new(512, 512));
     let texture = device.create_texture(&wgpu::TextureDescriptor {
         label: Some("tilted_donut_target"),

src/scene/pipeline/wire_gpu.rs

@@ -532,7 +532,35 @@ fn finite3(p: [f32; 3]) -> bool {
 
 fn marker_metadata(wire: &WireModel) -> ([f32; 4], [f32; 4], [f32; 4]) {
     let Some(marker) = wire.point_marker else {
-        return ([0.0; 4], [0.0; 4], [0.0; 4]);
+        for tg in &wire.tangent_geoms {
+            match tg {
+                crate::scene::model::wire_model::TangentGeom::Arc { axis_x, axis_y, .. }
+                | crate::scene::model::wire_model::TangentGeom::PlanarCircle { axis_x, axis_y, .. } => {
+                    let ax = glam::DVec3::from_array(*axis_x);
+                    let ay = glam::DVec3::from_array(*axis_y);
+                    let n = ax.cross(ay).normalize_or(glam::DVec3::Z);
+                    return ([0.0; 4], [0.0; 4], [n.x as f32, n.y as f32, n.z as f32, 0.0]);
+                }
+                crate::scene::model::wire_model::TangentGeom::PlanarEllipse { normal, .. } => {
+                    let n = glam::DVec3::from_array(*normal).normalize_or(glam::DVec3::Z);
+                    return ([0.0; 4], [0.0; 4], [n.x as f32, n.y as f32, n.z as f32, 0.0]);
+                }
+                _ => {}
+            }
+        }
+        if wire.points.len() >= 3 {
+            let p0 = glam::Vec3::from_array(wire.points[0]);
+            for i in 1..wire.points.len() - 1 {
+                let v1 = glam::Vec3::from_array(wire.points[i]) - p0;
+                let v2 = glam::Vec3::from_array(wire.points[i + 1]) - p0;
+                let cross = v1.cross(v2);
+                if cross.length_squared() > 1e-6 {
+                    let n = cross.normalize();
+                    return ([0.0; 4], [0.0; 4], [n.x, n.y, n.z, 0.0]);
+                }
+            }
+        }
+        return ([0.0; 4], [0.0; 4], [0.0, 0.0, 1.0, 0.0]);
     };
     let origin = marker.origin;
     let (hx, lx) = WireModel::split_ds(origin.x);