Add config resource for transform gizmo

studio/src/interaction/gizmos/mod.rs

@@ -10,8 +10,36 @@ pub(super) struct StudioGizmosPlugin;
 
 impl Plugin for StudioGizmosPlugin {
     fn build(&self, app: &mut App) {
-        app.add_systems(PreUpdate, (model::update_spawns, view::configure))
+        app.insert_resource(StudioGizmoConfig::default())
+            .add_systems(PreUpdate, (model::update_spawns, view::configure))
             .add_systems(Update, model::update)
             .add_systems(PostUpdate, view::draw);
     }
 }
+
+#[derive(Resource, Clone, Copy)]
+pub struct StudioGizmoConfig {
+    /// Measured (roughly) as a fraction of the viewport height
+    pub base_size: f32,
+    /// Measured in device-independent "pixel" units
+    pub line_thickness: f32,
+}
+
+impl Default for StudioGizmoConfig {
+    fn default() -> Self {
+        Self {
+            base_size: 0.125,
+            line_thickness: 4.,
+        }
+    }
+}
+
+impl StudioGizmoConfig {
+    fn base_size_world_units(&self, gizmo_origin: Vec3, camera_origin: Vec3) -> f32 {
+        let dist = Vec3::distance(gizmo_origin, camera_origin);
+        // The magic numbers here are because I first decided that dist/20
+        // looked pretty good, then measured it as ~1/8 of the viewport height,
+        // and then factored that measurement in as a configurable parameter.
+        self.base_size * 8. * (dist / 20.)
+    }
+}

studio/src/interaction/gizmos/model.rs

@@ -1,7 +1,7 @@
 use bevy::prelude::*;
 use bitflags::bitflags;
 
-use super::{InteractionMode, Selected, TransformSpace, TransformType};
+use super::{InteractionMode, Selected, StudioGizmoConfig, TransformSpace, TransformType};
 
 pub(super) fn update_spawns(
     mut cmd: Commands,
@@ -24,6 +24,7 @@ pub(super) fn update(
     mut q_gizmo: Query<(&mut Gizmo, &GlobalTransform)>,
     q_camera_xform: Query<&Transform, With<Camera>>,
     mode: Res<InteractionMode>,
+    config: Res<StudioGizmoConfig>,
 ) {
     let Ok((mut gizmo, world_xform)) = q_gizmo.get_single_mut() else {
         return;
@@ -41,7 +42,7 @@ pub(super) fn update(
     };
 
     for el in gizmo.0.iter_mut() {
-        el.update(mode.transform, &xform, &basis, cam_xform);
+        el.update(mode.transform, &xform, &basis, cam_xform, &config);
     }
 }
 
@@ -63,9 +64,9 @@ impl GizmoElement {
         xform: &Transform,
         basis: &Transform,
         cam_xform: &Transform,
+        config: &StudioGizmoConfig,
     ) {
-        let dist = Vec3::distance(cam_xform.translation, xform.translation);
-        let base_size = dist / 20.;
+        let base_size = config.base_size_world_units(xform.translation, cam_xform.translation);
 
         match self.control {
             Control::Translation(axes) => match axes {