# Accuracy measurement between two STL model T1 - immediate after surgery T2 one year after surgery

**URL:** <https://discourse.slicer.org/t/accuracy-measurement-between-two-stl-model-t1-immediate-after-surgery-t2-one-year-after-surgery/26880>\
**Category:** Support\
**Created:** [December 22, 2022, 6:30am UTC](https://discourse.slicer.org/t/accuracy-measurement-between-two-stl-model-t1-immediate-after-surgery-t2-one-year-after-surgery/26880 "2022-12-22T06:30:24Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![wael\_telha](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/wael_telha/32/16914_2.png) [@wael\_telha](https://discourse.slicer.org/u/wael_telha)\
**Post date:** [December 22, 2022, 6:30am UTC](https://discourse.slicer.org/t/accuracy-measurement-between-two-stl-model-t1-immediate-after-surgery-t2-one-year-after-surgery/26880/1 "2022-12-22T06:30:25Z")

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Dear 3D- Slicer Community I am conducting a research regarding the accuracy between two STL model following orthognathic surgery to check the accuracy between model immediate surgery and one following surgery. the steps I used  
1- VOXEL BASE REGISTERATION FOR BOTH CT  
2- PRODUCTION OF TWO STL MODEL T1, T2  
3. CHOOSING A PICK’N POINT ON THE T2

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/a/4/a423479b23a6d30ff51c27ae3e7823748fe05360.jpeg)

IN PICK’N POINT I HAVE CHOSEN NON-CORROSPONDING MESHES !!

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/a/1/a1805858d7c29dbbe0ef35492fb9096f840315fd.jpeg)

IN MODEL TO MODEL DISTANCE WHAT SHALL I USED - SIGNED DISTANCE OR ABSLOUTE DISTANCE

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/b/2/b22e5fead956b679d3cf56bbff309d563bf03c9d.jpeg)

IN MESH STATISTICS I NEED TO KNOW THE TRANSVERSE , SAGITTAL AND VERTICAL DISTANCE THAT’S WHY I USED POINT TO POINT X,Y,Z

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/b/5/b5df3c093fb6769c85c8d226664b5b51c0ed1868.jpeg)

I NEED YOU HELP CONFIRMING THE STEPS USED ABOVE

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [December 22, 2022, 7:05pm UTC](https://discourse.slicer.org/t/accuracy-measurement-between-two-stl-model-t1-immediate-after-surgery-t2-one-year-after-surgery/26880/2 "2022-12-22T19:05:35Z")

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Model to model distance module cannot provide you accurate displacement vectors, as it can only establish point-to-point correspondence based on closest distance, independently for each point.

Instead, you can use the the transform computed in the registration step to get displacement of each mesh point.