Compute AABB from boundary representation

This is required for computing the tolerance automatically, as the AABB
is required for that. With the previous approach of computing the AABB
from the mesh, we would have needed the tolerance for the mesh and the
mesh for the AABB, forming a circular dependency.

crates/fj/src/handle_model.rs

@@ -1,8 +1,11 @@
 use std::ops::Deref;
 
-use fj_core::algorithms::{approx::Tolerance, triangulate::Triangulate};
+use fj_core::algorithms::{
+    approx::Tolerance, bounding_volume::BoundingVolume,
+    triangulate::Triangulate,
+};
 use fj_interop::model::Model;
-use fj_math::Aabb;
+use fj_math::{Aabb, Point};
 
 use crate::Args;
 
@@ -20,7 +23,12 @@ pub fn handle_model<M>(
 ) -> Result
 where
     for<'r> (&'r M, Tolerance): Triangulate,
+    M: BoundingVolume<3>,
 {
+    let aabb = model.aabb().unwrap_or(Aabb {
+        min: Point::origin(),
+        max: Point::origin(),
+    });
     let mesh = (model.deref(), tolerance.into()).triangulate();
 
     let args = Args::parse();
@@ -29,7 +37,6 @@ where
         return Ok(());
     }
 
-    let aabb = Aabb::<3>::from_points(mesh.vertices());
     let model = Model { mesh, aabb };
 
     crate::window::display(model, false)?;