Point clouds: lighting, 2D visual style, real-time density

Points carry their world normal: POINTCLOUDLIGHTING lights them in the
shaded visual styles (1 lit from both sides, 2 with back faces dark),
from the view (POINTCLOUDLIGHTSOURCE 0) or the default lights (1).
The 2D wireframe style draws no cloud points: a found cloud shows its
extents and "Point clouds are not displayed in 2D visual style.",
or nothing with POINTCLOUD2DVSDISPLAY 1. While the view moves only
POINTCLOUDRTDENSITY per cent of the points are drawn; the points are
stored in an order where every leading part samples the whole cloud.
The colour map dialog lists its schemes by name.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/scene/mod.rs

@@ -8429,6 +8429,50 @@ impl Scene {
         arc
     }
 
+    /// Wireframe 2D draws no cloud points: each shown cloud whose file is
+    /// found draws its extents box and a message instead, unless
+    /// POINTCLOUD2DVSDISPLAY is 1.
+    // ponytail: model-space clouds only, rebuilt per frame; cache by epoch if
+    // drawings with many clouds make it show.
+    pub(super) fn point_cloud_2d_wires(&self) -> Vec<WireModel> {
+        use crate::scene::model::point_cloud::{resolve_source, setting, setting_value};
+        if !crate::scene::model::point_cloud::any_definition(&self.document)
+            || setting("POINTCLOUD2DVSDISPLAY").is_some_and(|s| setting_value(&self.document, s) == 1)
+        {
+            return Vec::new();
+        }
+        let mut wires = Vec::new();
+        for entity in self.document.entities() {
+            let EntityType::Extended(extended) = entity else {
+                continue;
+            };
+            let codec::entities::ExtendedEntityData::PointCloudEx(data) = &extended.data else {
+                continue;
+            };
+            let common = entity.common();
+            if common.invisible
+                || self.entity_temporarily_hidden(common.handle)
+                || self.document.layers.get(&common.layer).is_some_and(|layer| layer.is_off() || layer.is_frozen())
+                || resolve_source(&self.document, data).is_none()
+            {
+                continue;
+            }
+            let color = if matches!(common.color, codec::types::Color::ByLayer) {
+                self.document.layers.get(&common.layer).map(|layer| layer.color.clone()).unwrap_or(common.color.clone())
+            } else {
+                common.color.clone()
+            };
+            let (r, g, b) = color.rgb().unwrap_or((255, 255, 255));
+            wires.push(WireModel::solid_f64(
+                common.handle.value().to_string(),
+                crate::entities::extended::point_cloud_2d_style_lines(data),
+                [f32::from(r) / 255.0, f32::from(g) / 255.0, f32::from(b) / 255.0, 1.0],
+                false,
+            ));
+        }
+        wires
+    }
+
     /// Image / OLE models for a content viewport, with its frozen layers removed.
     pub(super) fn images_for_viewport(
         &self,