MODEL SPATIAL RESOLUTION FOR CNC

[ioannitiko]

I will need to create the missing part of an ancient architectural member through the CNC (with spatial resolution close to 1 - 1.5 mm). I will create the model of the broken surface through PS. My question is if there is a way to calculate my model spatial resolution in order to be sure that I will be OK  for the CNC. Thank you!

[chrisd]

There are a lot of variables that will all contribute to accuracy ...
Quality of pictures, good focus, low noise
Number of pictures and overlap of pictures
Accurate scaling information

I assume you will rebuild the member in a cad program ... machining from a scan will not give a very even surface. There are some cadcam systems what won't accept meshes.

If you need a faithful reproduction and the member is rough hewn so it does not have any truly flat surfaces, (though they may be smooth), its possible you might need to do some noise reduction as a post operation to using Photoscan. Then use something like Geomagic, TSplines, NPower to produce a nurbs surface if that is needed for the CNC.

[ioannitiko]

What they asked for, is a STL file. I am not familiar with CNC, so I don' t know if they will rebuild that in cad program. My work finishes in providing them the STL file and that's why I want to know how is possible to calculate or to be sure about the resolution of my model. Thank you for your answer.   

[chrisd]

OK, an STL simplifies things to get a file to the CNC.

The resolution and accuracy will depend on several variables I mentioned previously. Unless there is some bright, fairly even lighting already present where the member is, I think you should plan on bringing additional lighting to be able to get the ISO down as low as possible.

If there is bright lighting present but there are areas in shadow, you will still most likely need the additional lights.