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Author Topic: Poor mesh with good dense cloud  (Read 2982 times)

seamone

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Poor mesh with good dense cloud
« on: December 19, 2017, 06:29:11 PM »
Dear all.
I'm making a 3D model of a stuffed shark and I'm struggling to obtain a complete and correct mesh. The dense cloud is generally very good and reproduces very well the animal, but in some areas the derived mesh is holed. In particular the tail is great in the dense cloud but it is later not correctly reconstructed in the mesh. What I noticed is that the dense cloud class shows pixels with not exactly the same colors (they are mainly gray and some of them are black) and I noticed that the black ones are not used for the mesh and let the holes. I did not use dense cloud classification.
What are those black pixels in the dense cloud?
Why the mesh does not use them?
Thank you in advance.
Best regards
Simone

n@sk

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Re: Poor mesh with good dense cloud
« Reply #1 on: December 21, 2017, 07:17:23 AM »
One of the  images you used would help so that we could tell what this is supposed to look like but the dense cloud doesn't really look that good.
It seems to be quite noisy.

seamone

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Re: Poor mesh with good dense cloud
« Reply #2 on: December 28, 2017, 11:51:03 PM »
One of the  images you used would help so that we could tell what this is supposed to look like but the dense cloud doesn't really look that good.
It seems to be quite noisy.

Thank you n@sk! and sorry for my late!
Find attached one of the images of the tail...
Thank you in advance

James

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Re: Poor mesh with good dense cloud
« Reply #3 on: January 03, 2018, 04:18:47 PM »
In your attachments 'DenseCloud_Classes.JPG' and 'DenseCloud_RGB.JPG' the light colour points are on the top surface of the tail, and the dark points are on the underside, facing the opposite direction - away from you.

If you looked at it from below you would then see that the dark points become lighter, and the light points become dark as you view them from the other side. The dark colour indicates the orientation of the surface that the point corresponds to.

Your attachment illustrates that you do not have many points on the upper surface of the tail, and photoscan can not create a good watertight mesh of an object with only one side available in the dense cloud so it only meshes the parts with data from both sides, as shown in your attachment 'Mesh.JPG'.

So you need to check your images of the upper side of the tail to check overlap with each other and adjacent parts of the object to see why this part is not being reconstructed in the dense cloud. Likely causes are that it is out of focus in some/all images, insufficient images, or it moved during the scan.

n@sk

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Re: Poor mesh with good dense cloud
« Reply #4 on: January 07, 2018, 12:22:14 AM »
Adding to what James points out.

It appears that the matching was based on points detected on the shark alone which means that the camera position and orientation may not be precise which in turn may cause problems with  the dense matching.
I would suggest retaking the images with a greater depth of field so that the floor is in focus as well.

seamone

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Re: Poor mesh with good dense cloud
« Reply #5 on: January 07, 2018, 11:35:11 PM »
In your attachments 'DenseCloud_Classes.JPG' and 'DenseCloud_RGB.JPG' the light colour points are on the top surface of the tail, and the dark points are on the underside, facing the opposite direction - away from you.

If you looked at it from below you would then see that the dark points become lighter, and the light points become dark as you view them from the other side. The dark colour indicates the orientation of the surface that the point corresponds to.

Your attachment illustrates that you do not have many points on the upper surface of the tail, and photoscan can not create a good watertight mesh of an object with only one side available in the dense cloud so it only meshes the parts with data from both sides, as shown in your attachment 'Mesh.JPG'.

So you need to check your images of the upper side of the tail to check overlap with each other and adjacent parts of the object to see why this part is not being reconstructed in the dense cloud. Likely causes are that it is out of focus in some/all images, insufficient images, or it moved during the scan.

You're right!!!
That is why the different colors!!!
Thank you!!!
I have to try to obtain more data on the opposite side (upperside) of the tail in order to obtain a "closed" mesh.
Thank you very much for your great support!


seamone

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Re: Poor mesh with good dense cloud
« Reply #6 on: January 07, 2018, 11:36:38 PM »
Adding to what James points out.

It appears that the matching was based on points detected on the shark alone which means that the camera position and orientation may not be precise which in turn may cause problems with  the dense matching.
I would suggest retaking the images with a greater depth of field so that the floor is in focus as well.

You're right...
Unfortunately I will have no chance to make further photos but I will try to improve the usage of the ones I have.
Thank you very much for your kind support.