Cowboy prototyping

studio/src/interaction/gizmos.rs

@@ -0,0 +1,72 @@
+use bevy::{prelude::*, window::PrimaryWindow};
+
+use super::{InteractionMode, InteractionTransform, Selected, TransformSpace};
+
+pub(super) fn draw(
+    q_selection: Query<&GlobalTransform, With<Selected>>,
+    q_camera_xform: Query<&Transform, With<Camera>>,
+    q_window: Query<&Window, With<PrimaryWindow>>,
+    interaction_mode: Res<InteractionMode>,
+    mut gizmos: Gizmos,
+    mut config: ResMut<GizmoConfig>,
+) {
+    if !q_selection.is_empty() {
+        // TODO: Use an app state or something so we only have to set this up once
+        let scale_factor = q_window.single().scale_factor() as f32;
+        config.line_width = 4. * scale_factor;
+        config.line_perspective = false;
+        config.depth_bias = -1.;
+
+        let InteractionMode { transform, space } = *interaction_mode;
+        let camera_xform = q_camera_xform.single();
+
+        // TODO: We only want to render one gizmo -- this is just for testing
+        for world_xform in q_selection.iter() {
+            let xform = world_xform.compute_transform();
+            // Note: Scaling the gizmo size by this isn't perfect due to
+            // distortion from the perspective projection. It bugged me at
+            // first, but even Blender exhibits this type of gizmo distortion if
+            // you dial the camera's focal length way down, so I'm gonna call it
+            // good enough.
+            let dist = Vec3::distance(camera_xform.translation, xform.translation);
+
+            if transform.contains(InteractionTransform::TRANSLATE) {
+                draw_translate_gizmo(&xform, &mut gizmos, space, dist / 14.);
+            }
+            if transform.contains(InteractionTransform::ROTATE) {
+                draw_rotate_gizmo(&xform, &mut gizmos, space, dist / 20.);
+            }
+        }
+    }
+}
+
+#[inline]
+fn draw_translate_gizmo(xform: &Transform, gizmos: &mut Gizmos, space: TransformSpace, size: f32) {
+    let origin = xform.translation;
+    let basis = match space {
+        TransformSpace::Local => xform,
+        TransformSpace::World => &Transform::IDENTITY,
+    };
+
+    let mut draw_axis = |direction: Vec3, color: Color| {
+        let end = origin + direction * size;
+        gizmos.line(origin, end, color);
+    };
+
+    draw_axis(basis.local_x(), Color::RED);
+    draw_axis(basis.local_y(), Color::GREEN);
+    draw_axis(basis.local_z(), Color::BLUE);
+}
+
+#[inline]
+fn draw_rotate_gizmo(xform: &Transform, gizmos: &mut Gizmos, space: TransformSpace, radius: f32) {
+    let origin = xform.translation;
+    let basis = match space {
+        TransformSpace::Local => xform,
+        TransformSpace::World => &Transform::IDENTITY,
+    };
+
+    gizmos.circle(origin, basis.local_x(), radius, Color::RED);
+    gizmos.circle(origin, basis.local_y(), radius, Color::GREEN);
+    gizmos.circle(origin, basis.local_z(), radius, Color::BLUE);
+}