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Author Topic: How to improve 3D reconstruction process  (Read 7334 times)

GrinGEO

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How to improve 3D reconstruction process
« on: August 26, 2016, 10:19:05 PM »
Im wondering if you have any idea how we could improve our 3D reconstruction process.

As seen in this example some parts are not clear. what could we do to improve it?

https://skfb.ly/SsHG

Thanks for helping

Shade3

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Re: How to improve 3D reconstruction process
« Reply #1 on: August 28, 2016, 08:45:12 PM »
[delete] sorry wrong advice
i thought something else was the issue while i was looking at your model. not 3d reconstruction.
« Last Edit: August 28, 2016, 08:53:17 PM by Shade3 »

ekbmuts

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Re: How to improve 3D reconstruction process
« Reply #2 on: August 29, 2016, 03:13:31 AM »
GrinGEO,  Sorry - I'd comment but I can't SEE the model close enough to know what the problem is that you're trying to solve.

Can you describe it in a few words?

Jon

GrinGEO

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Re: How to improve 3D reconstruction process
« Reply #3 on: September 04, 2016, 12:16:06 AM »
Im having issues especially on the solar modules on that building... the lines are not very clear

ekbmuts

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Re: How to improve 3D reconstruction process
« Reply #4 on: September 04, 2016, 02:21:38 AM »
I'm assuming you mean that small building on the right.

If so, and those panels are reflective, I think that's the problem.  Because the reflection changes with each shot, Photoscan has nothing to relate to.  In one picture the lines reflect the clouds and in the next (when the camera is in a different position) they reflect trees.  So there are no common points for Photoscan to match.

I've also had trouble with very thin objects not coming out right in the final model.  That could be part of it too.

Jon

renevg

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Re: How to improve 3D reconstruction process
« Reply #5 on: September 04, 2016, 10:54:31 AM »
Looking at the grass I also see blurred parts. That's not reflectionrelated. That brings up a similar question? can we choose a photo for texturing (like in % how much influence a certain photo has on the texture)?

stihl

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Re: How to improve 3D reconstruction process
« Reply #6 on: September 04, 2016, 11:42:53 AM »
Hi Renevg,

You can't do that. With Photogrammetry (and GIS alike) it's very much about the quality of the input data set.
The principal "Rubbish in, rubbish out." applies.
Obtaining a crisp data set should be your first challenge. Post processing can't solve everything unfortunately.

renevg

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Re: How to improve 3D reconstruction process
« Reply #7 on: September 04, 2016, 11:53:52 AM »
Thanks Stihl
I understand. But there is usually a lot of overlapping going on. I thought maybe we can choose the priority for a certain area? (mouseright on the area in mesh and choose photo and give priority for texture)  I know some programs for panoramacreation  have this option

GrinGEO

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Re: How to improve 3D reconstruction process
« Reply #8 on: September 04, 2016, 10:37:11 PM »
Stihl, how can we improve the imput data? Im not shure what we can do on our side... Do you have some really good advice for us?

stihl

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Re: How to improve 3D reconstruction process
« Reply #9 on: September 06, 2016, 12:27:56 AM »
Think about the following things;

-Is my overlap high enough? 80/80% overlap makes a huge difference over lower values. Since you're on location anyway, flying more to reduce your time post processing is an easy gain.

-What do I want to model? If you're only generating a DEM of a terrain, nadir only images will suffice. If you also want to create accurate models of the houses that are on the terrain it might be worth thinking of making an extra oblique flight near the houses to capture all of their geometry and incorporate these images in your alignment.

-How do my images look? Is the quality of the best image consistent over the entire data  set? If not, how so?
I prefer using a fixed zoom lens so that the focal length stays fixed. I also prefer data sets that have a fixed aperture. I've found from many projects that this usually yields the best result.
I'd also advice on using a shutter speed in excess of 1/1200th. Small amounts of blur can be seen in the entire image through engine vibrations. This effect increases when winds pick up which causes additional vibration, the UAV moves more and the engines work more fiercely.

GrinGEO

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Re: How to improve 3D reconstruction process
« Reply #10 on: September 06, 2016, 08:37:04 PM »
ok than let me check to have a higher overlapping. we have 50% front overlap & 60% side overlap. Since the cams are working with intervalometer, the front overlaping should be always more.

But I will try to increase the side overlap to 70%, but it will mean an hughe increasing in flight time...

whats max speed you are flying?

stihl

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Re: How to improve 3D reconstruction process
« Reply #11 on: September 06, 2016, 08:39:34 PM »
Instead of increasing the side overlap which does increas the flight time considerably, try increasing the frontal overlap first.

I assume you're flying with a fixed wing UAV since you're talking about an intervalometer. Can you decrease the interval between images taken? If not, how so?

3D reconstruction of buildings with a fixed wing UAV is a lot more tricky than a multicopter. Why are you using this approach?
« Last Edit: September 09, 2016, 01:40:49 AM by stihl »

stihl

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Re: How to improve 3D reconstruction process
« Reply #12 on: September 06, 2016, 08:43:26 PM »


Results similar to the image above can be achieved with less than 70 images taken with a 20mm lens multicopter.
« Last Edit: September 06, 2016, 08:45:10 PM by stihl »

GrinGEO

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Re: How to improve 3D reconstruction process
« Reply #13 on: September 06, 2016, 09:19:57 PM »
we are using a multicopter. The cams have interval only all 3 seconds, we are talking to developer to increase this. ok maybe if we can have a pic each second, this should really improve the quality a lot. especially becouse the parallax is only done by the moving forward.

on this example, did you have also camera looking forward to have the vertical texture so awesome?
Can you please share a 3D model on sketchfab of this? would be great.

stihl

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Re: How to improve 3D reconstruction process
« Reply #14 on: September 06, 2016, 10:16:24 PM »
I'll see if I have time for that tomorrow - both oblique (45 degree angle) and nadir images (straight down) were obtained. Texture was build with Generic 16384x1 parameters.