Untested: implement gltf convex decomposition optimisation function

formats/gltf.lisp

@@ -215,7 +215,7 @@
          (mesh (make-instance (if skin 'skinned-mesh 'static-mesh)
                               :name name :vertex-form (gltf:mode primitive)
                               :vertex-attributes attributes)))
-    (when (gltf:material primitive)
+    (when (and model (gltf:material primitive))
       (setf (material mesh)
             (find-material (or (gltf:name (gltf:material primitive))
                                (gltf:idx (gltf:material primitive)))
@@ -473,3 +473,34 @@
                    (enter (load-environment-light (gltf:light node)) scene))
                  (recurse (gltf:nodes node) scene)))
       model)))
+
+(defun add-convex-shape (base-node vertices faces)
+  (let* ((primitive (gltf:make-mesh-primitive base-node vertices faces '(:position)))
+         (mesh (gltf:make-indexed 'gltf:mesh base-node :primitives (vector primitive)))
+         (shape (gltf:make-indexed 'gltf:convex-shape base-node :mesh mesh :kind "convex"))
+         (collider (make-instance 'gltf:collider :collision-filter (gltf:collision-filter (gltf:collider base-node))
+                                                 :physics-material (gltf:physics-material (gltf:collider base-node))
+                                                 :shape shape
+                                                 :gltf (gltf:gltf base-node)))
+         (child (gltf:make-indexed 'gltf:node base-node :collider collider)))
+    (vector-push-extend child (gltf:children base-node))))
+
+(defun precompile (file &rest args &key (output file) &allow-other-keys)
+  (let ((decomposition-args (remf* args :output)))
+    (gltf:with-gltf (gltf file)
+      (let ((work-done-p NIL))
+        (loop for node across (gltf:nodes gltf)
+              do (when (and (gltf:collider node)
+                            (typep (gltf:shape (gltf:collider node)) 'gltf:trimesh-shape))
+                   (let* ((shape (gltf:shape (gltf:collider node)))
+                          (primitives (gltf:primitives (gltf:mesh shape)))
+                          (mesh (load-mesh (aref primitives 0) NIL "" NIL))
+                          (verts (reordered-vertex-data mesh '(location))))
+                     (loop for hull across (apply #'org.shirakumo.fraf.convex-covering:decompose verts (faces mesh) decomposition-args)
+                           do (add-convex-shape node
+                                                (org.shirakumo.fraf.convex-covering:vertices hull)
+                                                (org.shirakumo.fraf.convex-covering:faces hull)))
+                     (setf (gltf:collider node) NIL)
+                     (setf work-done-p T))))
+        (when work-done-p
+          (gltf:serialize gltf output))))))