# How do you use point set devation command - distance between surfaces

I am trying to measure the distance between two seperate surfaces with differnt complex curvatures. I tried using the Point set Devation cmd under the Surface Analysis menu but cant seem to figure out how it works. the help file isnt very useful either. can someone expand on how to use this command to measure the distance between the surfaces over the entire surface.

Hi Gary - one selection will provide points to measure compared to the second object. For two surfaces, one surface will provide a sampling of points from its render mesh vertices and these are measured against the target surface. If the render mesh is too sparse, then you can Mesh the object with custom mesh settings - like a large number of initial grid quads - and measure the deviation of the mesh to the second surface. Mesh vertices will always lie on the surface so it does not matter if you use the render mesh or a mesh object in this case. You can also customize the render mesh.

-Pascal

Pascal thank you for the prompt response. I do have additional questions on this. If I understand correctly I will need to mesh one surface BUT not the 2nd surface to use the command correct? Will the command then use all of the mesh vertices for measurements or just a subset (I want all points)? Also what direction is the measurement made between surfaces ( normal to 1st surface or to a nearest point on the 2nd surface?

Do you have an example of how it works? I’ve tried multiple time and can’t figure what the result is telling me.

My application is design of Archtop guitar/mandolin tops/backs. I want a measurement of “thickness “ between the inner and outer surfaces

Best regards,

Gary Lewandowski

Hi Gary - I would be wary of posting email and phone in this public forum. You can edit your post to remove those.

You do not need to but can mesh the first object - if you do not, the tool will use the vertices from the render mesh.

Here, I am testing the patch surface against the sphere. The patch surface is selected at the prompt to “Select points or objects from which to extract points to test. Press Enter when done ( Visible=No CurveDivisions=20 )”

Notice if I use ShowRenderMesh on the patch surface, the vertices of the mesh are the points being evaluated against the sphere:

@gary3 note the tool does not find distance in a particular direction that the user can set - I don’t know if this matters in your case. The diastance is always to the closest point on the target surface, that is, on the normal of the target surface:

If you want to measure in one particular direction, a script will be needed.

-Pascal