I got a chair without legs, why?

photogrammetry

(Vicolodo) #1

Hello,

i like a lot 3dzephyr but sometimes i get results that discourage me

i use 3dzephyr free and my smartphone huawei p8 max, that has a 12mpix good quality camera

yesterday evening i did a try, taking 50 snapshots of a chair and processing them with 3dzephyr

i selected ‘fast project’ processing, with default settings
and after i retried with ‘deep’ sparse cloud creation and ‘high details’ dense point cloud creation

i thought to get good results because the chair is a static subject, and it was placed in a place with backgroud and ground rich of details to be get as reference points by the program

BUT the results were not good: whole legs, or part of legs were missing , and big holes were present in the final mesh:

https://1drv.ms/f/s!Ahoag6A7lek1jFmomkerVy6bBMu6

This is the set of photos:

https://1drv.ms/f/s!Ahoag6A7lek1jB3ErBNFVP6eel7_

As you can see in the final 3dzephyr screenshots, all the photos were matched, the program did not discard any of them,
but the results are not good.

why?

i wonder if it is mainly a camera problem or an illumination problem or a subjet problem
do you think that with a good canon dslr i could get better results?

thank you!


(Lmendelson) #2

Might be a camera calibration issue. Is the camera 35mm focal length, and if not, did you change that in the settings?


(Vicolodo) #3

perhaps you are right, i used 3dzephyr default camera settings…
i will retry with correct calibration and let you know…
thank you!


(Vicolodo) #4

hello,
i retried with correct calibration (the program downloaded calibration from db),
but the results have not changed too much:

https://1drv.ms/u/s!Ahoag6A7lek1jGTmtoEA0cVOlPNy

legs still missing…
perhaps the problem is that they are too thin?

or could be a bad illumination problem?

(the sun was very down, near the sunset )


(Lmendelson) #5

What does the dense point cloud look like after the adjustment? Maybe just try again with more photos?

I’ve found that thinner details on a scene can be missed in the sfm algorithms, or they are found and just distorted after meshing. A texture can somewhat mask the distorion, but it’s obviously not ideal.


(Nebulousflynn) #6

A couple of suggestions, @vicolodo

  • try masking the chair from the background using the masquerade tool
  • it might be that the material of the chair itself is too plain and does not lend itself to photogrammetry, you could try adding markers / extra detail to the chair before taking photos

Don’t forget you can post to the official 3DFlow forums too: https://www.3dflow.net/forums


(Vicolodo) #7

thank you, with calibration
the point cloud seems better than before
the mesh instead is not good


(Vicolodo) #8

thank you,
i think so…
my friend suggested also that could be a bad illumination problem
today is cloudy, the light is more uniform, surely there are no reflections, i will retry and let you know…