# Display the shortest surface to surface distance using python
**URL:** https://discourse.slicer.org/t/display-the-shortest-surface-to-surface-distance-using-python/42500
**Category:** Support
**Tags:** python
**Created:** [April 9, 2025, 12:14pm UTC](https://discourse.slicer.org/t/display-the-shortest-surface-to-surface-distance-using-python/42500 "2025-04-09T12:14:49Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Matteboo](https://discourse.slicer.org/u/Matteboo)
#### Post date: [April 9, 2025, 12:14pm UTC](https://discourse.slicer.org/t/display-the-shortest-surface-to-surface-distance-using-python/42500/1 "2025-04-09T12:14:49Z")
Hello,
I have two segmentations. I want to measure and display the shortest distance between the surfaces (just like the picture below)
I can measure the distance between the two surfaces using `slicer.modules.modeltomodeldistance` but I can’t get the two points that achieve this smallest distance.
Does anyone knows how to get the points achieving the smallest distance given by `slicer.modules.modeltomodeldistance`
---
### Author:  [@chir.set](https://discourse.slicer.org/u/chir.set)
#### Post date: [April 9, 2025, 7:42pm UTC](https://discourse.slicer.org/t/display-the-shortest-surface-to-surface-distance-using-python/42500/2 "2025-04-09T19:42:54Z")
I just discovered this module and AFAIU, the following _should_ solve your problem, at least if your models do not intersect.
If you use `absolute_closest_point`, you can get one point coordinate from the `Absolute` array of the output model (the one(s) with the minimum absolute distance). With this coordinate, the polydata of the `Target Model` can give the second coordinate using `FindPoint()` and `GetPoint()`.
---
### Author:  [@Matteboo](https://discourse.slicer.org/u/Matteboo)
#### Post date: [April 10, 2025, 1:24pm UTC](https://discourse.slicer.org/t/display-the-shortest-surface-to-surface-distance-using-python/42500/3 "2025-04-10T13:24:27Z")
I managed to get this using the following code
```auto
# Step 2: Compute distance from inside to outside
distance_model = findModelToModelDistance(outside_model, inside_model) # Distance from outside to inside
VTKFieldData = distance_model.GetMesh().GetAttributesAsFieldData(0)
created_nodes.append(distance_model)
# Step 3: Extract signed distances and find min
signedVals = []
for i in range(VTKFieldData.GetArray("Signed").GetNumberOfTuples()):
val = VTKFieldData.GetArray("Signed").GetValue(i)
signedVals.append(-val) # Negate to get correct direction
min_index = np.argmin(signedVals)
min_distance = signedVals[min_index]
# Step 4: Get closest point on inside
closest_inside_point = inside_model.GetPolyData().GetPoint(min_index)
# Step 5: Get corresponding closest point on outside
locator = vtk.vtkPointLocator()
locator.SetDataSet(outside_model.GetPolyData())
locator.BuildLocator()
closest_outside_point_id = locator.FindClosestPoint(closest_inside_point)
closest_outside_point = outside_model.GetPolyData().GetPoint(closest_outside_point_id)
def findModelToModelDistance(modelNode1,modelNode2):
vtkOutput = slicer.mrmlScene.AddNewNodeByClass("vtkMRMLModelNode")
vtkOutput.SetName("m2md")
parameters = {}
parameters["vtkFile1"] = modelNode2
parameters["vtkFile2"] = modelNode1
parameters['distanceType'] = "signed_closest_point"
parameters["vtkOutput"] = vtkOutput
cliNode = slicer.cli.runSync(slicer.modules.modeltomodeldistance, None, parameters)
return vtkOutput
```