Plane tool

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isharp
Posts: 8
Joined: Wed Dec 27, 2017 11:37 pm

Plane tool

Post by isharp »

Hello,

I have tried to use a Plane tool in Compass but my cursor and the circle do not correspond. There is about 3 inch distance between them. When I try to put the plane it puts it where the cursor is and not where the circle is. Aren't they suppose to correspond? Also, when I switch off 'auto rotation center' and try to use 'pick rotation center' it does the same thing. I am using MacBook Pro 2017 and CloudCompare version 2.9.1. Please advise.
daniel
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Re: Plane tool

Post by daniel »

Do you have a Retina screen maybe?
Daniel, CloudCompare admin
isharp
Posts: 8
Joined: Wed Dec 27, 2017 11:37 pm

Re: Plane tool

Post by isharp »

Seems like I do indeed... So, can I still make it work on my Mac?
I tried it on windows and it works great.
I aligned the before and after treatment models based only on the posterior teeth and now I need to measure the amount of movement occurred on the front teeth. I can use a linear measurement tool to measure the distance from one model to another of the same tooth. But now I need to find the angulation change as well. I used a 'plane tool' in compass and performed 2 measurements on 2 models. I pretty much eyeballed the center of a tooth in both models. As you can see from the screenshot, one reads 289, the other 285. So,
- is it safe to say that the difference in inclination is 5 deg?
- and what does the first number represent (22 in my case?)
Thank you!
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daniel
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Joined: Wed Oct 13, 2010 7:34 am
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Re: Plane tool

Post by daniel »

The values displayed here are the 'dip' and 'dip direction' values associated to the plane (https://en.wikipedia.org/wiki/Strike_and_dip). They are geological orientations related to the 'default' geological coordinate system where +Z is the vertical orientation, and +Y is the North (or something like that). For your application, just make sure the Z orientation is the vertical one. However in this case you would need to consider both orientations at the same time (i.e. the differences for both the dip and the dip direction). Or of course only one of them if the orientations are meaningful to you.

A more proper way to compute the angle discrepancy between two planes is to compare their normal vectors (you can read it in the plane properties). But to actually get the angle difference, you'll have to do a little bit of maths: angle = inverse cosine(dot product of the normals) = acos(N1 * N2) = acos(N1.x * N2.x + N1.y * N2.y + N1.z * N2.z)
Daniel, CloudCompare admin
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