diff --git a/plugin/sdf/sdflib.cc b/plugin/sdf/sdflib.cc
index 392119ae..a1405eb7 100644
--- a/plugin/sdf/sdflib.cc
+++ b/plugin/sdf/sdflib.cc
@@ -31,6 +31,34 @@ inline unsigned int* MakeNonConstUnsigned(const int* ptr) {
   return reinterpret_cast<unsigned int*>(const_cast<int*>(ptr));
 }
 
+mjtNum boxProjection(glm::vec3& point, const sdflib::BoundingBox& box) {
+  glm::vec3 r = point - box.getCenter();
+  glm::vec3 q = glm::abs(r) - 0.5f * box.getSize();
+  mjtNum dist_sqr = 0;
+  mjtNum eps = 1e-6;
+
+  // skip the projection if inside
+  if (q.x <= 0 && q.y <= 0 && q.z <= 0) {
+    return glm::max(q.x, glm::max(q.y, q.z));
+  }
+
+  // in-place projection inside the box if outside
+  if ( q.x >= 0 ) {
+    dist_sqr += q.x * q.x;
+    point.x -= r.x > 0 ? (q.x+eps) : -(q.x+eps);
+  }
+  if ( q.y >= 0 ) {
+    dist_sqr += q.y * q.y;
+    point.y -= r.y > 0 ? (q.y+eps) : -(q.y+eps);
+  }
+  if ( q.z >= 0 ) {
+    dist_sqr += q.z * q.z;
+    point.z -= r.z > 0 ? (q.z+eps) : -(q.z+eps);
+  }
+
+  return mju_sqrt(dist_sqr);
+}
+
 }  // namespace
 
 // factory function
@@ -89,7 +117,8 @@ void SdfLib::Visualize(const mjModel* m, mjData* d, const mjvOption* opt,
 // sdf
 mjtNum SdfLib::Distance(const mjtNum p[3]) const {
   glm::vec3 point(p[0], p[1], p[2]);
-  return sdf_func_.getDistance(point);
+  mjtNum boxDist = boxProjection(point, sdf_func_.getGridBoundingBox());
+  return sdf_func_.getDistance(point) + (boxDist <= 0 ? 0 : boxDist);
 }
 
 // gradient of sdf