diff --git a/fusion.py b/fusion.py
index 9cdae72..53651b7 100644
--- a/fusion.py
+++ b/fusion.py
@@ -118,7 +118,7 @@ def __init__(self, vol_bnds, voxel_size, use_gpu=True):
           float depth_diff = depth_value-cam_pt_z;
           if (depth_diff < -trunc_margin)
               return;
-          float dist = fmin(1.0f,depth_diff/trunc_margin);
+          float dist = -fmin(1.0f,depth_diff/trunc_margin);
           float w_old = weight_vol[voxel_idx];
           float obs_weight = other_params[5];
           float w_new = w_old + obs_weight;