diff --git a/models/renderer.py b/models/renderer.py
index a509029..cae704b 100644
--- a/models/renderer.py
+++ b/models/renderer.py
@@ -319,13 +319,17 @@ def render(self, rays_o, rays_d, near, far, perturb_overwrite=-1, background_rgb
             with torch.no_grad():
                 pts = rays_o[:, None, :] + rays_d[:, None, :] * z_vals[..., :, None]
                 sdf = self.sdf_network.sdf(pts.reshape(-1, 3)).reshape(batch_size, self.n_samples)
-
+                
                 for i in range(self.up_sample_steps):
+                    _n_importance = self.n_importance // self.up_sample_steps
+                    # add padding to the last step when it is not divisible
+                    if ((i+1) == self.up_sample_steps):
+                        _n_importance += (self.n_importance - (self.n_importance // self.up_sample_steps) * self.up_sample_steps)
                     new_z_vals = self.up_sample(rays_o,
                                                 rays_d,
                                                 z_vals,
                                                 sdf,
-                                                self.n_importance // self.up_sample_steps,
+                                                _n_importance,
                                                 64 * 2**i)
                     z_vals, sdf = self.cat_z_vals(rays_o,
                                                   rays_d,