Messages

1

General / Re: about the photo alignment

« on: July 16, 2016, 05:31:07 PM »

Thinking further from my previous post, I suppose the angle I'm coming from is a little like those for computer graphics rendering systems over the years.

Originally biased renderers were very popular because of very low CPU speeds, so you'd choose settings and the end result would be in line with the initial chosen settings...
...but with time unbiased renderers arrived which were very slow, but the longer you left them running the more accurate the rendering would become, the final render would never arrive, it'd just refine to infinity given time.

I think photogrammetry reconstructions could follow this path in time, simply left to their own devices for as long as desired and the results refine to ever finer details, rather than having arbitrary pre-set limits at the initial camera detection steps etc.


Hmmm

Dave

2

General / Re: about the photo alignment

« on: July 12, 2016, 02:32:45 PM »

Is there any way that Photoscan could juggle these variables iteratively and refine to an 'ideal' result over time?

I've always found it quite counter-intuitive that I have to find this ideal balance of variables myself.


I've increasingly tended to run with no Tie Point limit, and a fairly high Key Point limit.

I then duplicate the chunk, use gradual selection, and then Optimise Cameras, and so on, iteratively.

The only problem is you need to do a 'quick' dense reconstruction to check that there are enough Tie Points left for the dense reconstruction to work on all cameras... since there is no check (that I'm aware of) when Tie Point levels drop too low on a per-camera basis.


Couldn't all this be done automatically somehow? A way to get the very best camera position reconstructions and Tie Points, but without reducing them too much so dense point reconstructions can't work?
And/or warning that dense point reconstructions will not be accurate enough on specific camera image pairs?


As always, I find solutions, it just seems quite manually intensive and slow iterations when I feel that an automatic algorithm could achieve the same given some processing time?


Thanks

Dave

3

General / Re: Scanning surroundings, do I need a target?

« on: June 29, 2016, 02:02:42 PM »

You can buy those small laser range finders to measure between a few different points across your reconstructed scene, and then correct the scene scale/orientation according to those measurements.

You could use anything to act as references.

I don't have the Pro version but do cloud corrections in Cloud Compare.

Setting the orientation to get the scene 'flat' is more difficult, but for your purposes doing it by eye is probably good enough.

4

General / Re: Camera matching and points not seeming to align?

« on: April 23, 2016, 10:09:25 PM »

Hey there,

I didn't use polarising for that specific reconstruction, but it can help depending on the surfaces orientation vs the camera.

At some point I'll write up some best/worst practice approaches for this job, but for now I'm testing different cars/colours and techniques still to find the best ones.

Also I'm remodelling this car which is driving me nuts. The scan is so accurate I'm having to consider the panel offsets and the way each panel edge is formed against the next one.

More detailed reference material just means more things to get right!

5

General / Re: Camera matching and points not seeming to align?

« on: April 08, 2016, 05:33:16 PM »

Well for anyone interested my car results seem pretty robust.

Here is quick few screenshots to show the profile of the car at this point.
The profile here is way off what I've been able to fathom via the usual ortho blueprints, since this part of the car is hidden in blueprints... and the quality of the outline is easily as good as drawing splines over photo matched background images.
So I'll likely work over the model in this way to rebuild the final surface.

I've not worked on a laser scanned car before but these results so far seem quite good for photogrammetry taken in relative haste in non-ideal conditions!

You can even see where the wings sit slightly higher than the bonnet at each side of the car which is reassuring.

Next week I'll hopefully get chance to re-scan the whole car with all the best techniques so far and have a solid low noise full car scan.
I just need to try on some other colours now. I bet a black car or white car are tough!


Thanks

Dave

6

General / Re: Camera matching and points not seeming to align?

« on: April 07, 2016, 11:33:13 PM »

Just more thoughts on this whole alignment thing.

I'd been using a wide area auto focus setting on the Ricoh GR which seemed sensible to make sure most of the elements of the car in view were in sharp focus. I obviously used f-7 or so for a fairly deep DOF.

But since I got the camera on a tripod today to do lots of testing today I really noticed how much the focus alters the resultant image recorded. OK it's subtle once the focus gets out beyond 1m, but it's probably enough between some shots which got a tighter focus vs others, to cause issues of misalignment in some photos.

I'm assuming some disconnect between the distortion correction outputs vs the internal corrections for dense cloud generation.


I've now halved my calibration error again by using a fixed focus for this task which is good.

Point clouds now seem more solid and have less surface noise.


I'll do more testing tomorrow to see if this fixes the problem I initally had.

7

General / Re: Camera matching and points not seeming to align?

« on: April 07, 2016, 06:15:14 PM »

Thanks for the thoughts. I knew there was a way to view the points somehow, but it's really hard to see the form of the car still.

Ah feature requested. Fingers crossed. It'd help understand problems like this much faster than going to FBX > Max and undistorting images and so on again and again.



Well I've been having a play and learn a bit about tie points and cropping them out and impacts on dense cloud creation etc.

It still seems quite 'magic' and not so intuitive what is going to happen at each step. It'd be nice if there were more interactivity with what has happened at each step to know you've got a 'solid' result before moving to the next steps.

But hey, it works. It's just these little things you kinda have to learn as you go along.


I've instead continued to focus on just scanning the car to a high accuracy to the point it's clear that the image and model deviate. I'm not sure how else to show the problem but the undistorted images still seem to not align with the model/point cloud.


So far I'm getting this kinda result (check attachment)... but I've already tried some other approaches to improve it in several ways, so once I combine them the results should start to get sharper again.

I'm waiting for the ideal weather but should be able to capture the whole car again in the coming week and really see how good I can get things.
Still not laser scan good, but without proper matching photos to build a spline cage from (till I find out how!), I can just remodel over this kinda data in point cloud form nice and quickly!

Cheers

Dave

8

General / Re: Camera matching and points not seeming to align?

« on: April 06, 2016, 05:27:30 PM »

OK I ran it again and have much better figures now.

16,632 of 59,365
2.4856 overlap
0.129738 error, max 0.395091



But lots of points I generate in 3D at certain features on the car still don't line up very elegantly in the images. Some images seem solid, others don't.
Ie, I place a point in cam1 on the aerial tip, swap to cam 2 and move the point in cam1 orientation to the aerial tip and so on. Some other camera angles the point is on the aerial tip, others it's several centimetres away.


In the dense point cloud, which is obviously unreliable due to the reflective car, I can see ghosted/duplicated features that are offset, quite a lot in some areas (several centimetres).
Clearly some cameras are *not* in the right place but think they are. But there is no clear way to figure that out.


Is there any way to check each cameras alignment in PS?

Ie, 'look through' the camera, but also show the image in the background and the Tie Point cloud overlaid so I can see if there is an obvious error?


Thanks

Dave

9

General / Re: Camera matching and points not seeming to align?

« on: April 06, 2016, 03:52:55 PM »

Here are my chunk details (I'm using non-pro version btw)

Please see attached document.

But basically.

50 cameras around the car.

6,857 of 16,284 points
2.859 overlap
0.474 error (0.996 max)


From what I see here this match should be really great.

I'll re-do everything and post up more details/images later since I'm guessing this workflow should give me perfect alignment from every camera on every point on the car!


Thanks

Dave

10

General / Re: 4K video instead of image files?

« on: April 06, 2016, 11:31:39 AM »

I've used a GoPro and moved it around slowly to minimise rolling shutter issues.

Then I usually export frames from After Effects (after processing where required for whatever reason) and then just use larger or smaller selections and drag into PS.


I've always imagined that a decent video camera (probably CCD to remove rolling shutter issues), and high res (4k would be great if there are CCD cameras with decent sensors in 4k?) would be really nice for photogrammetry work.


But ultimately when stills cameras are smaller, lighter, and give higher res images, and at a cheaper price, you're better off just figuring out the overlaps and intervals for shooting and so on and then just doing your shots just how you need them.


PS results are MUCH better in higher res without the temporal artefacts of video compressions.


Cheers

Dave

11

General / Re: Camera matching and points not seeming to align?

« on: April 05, 2016, 05:52:02 PM »

I'll have another bash at it.

I've never been too sure about the whole optimisation process in PS.

I wish there were a bit more automation in this regard since PS must know internally if things are better or worse than before... there is no way to really tell as a user if what you've just done has made things better or worse, or just not changed them... or even if certain cameras will now skip when doing dense reconstruction due to the Tie Point being lost during optimisation!


I'll post up pics and samples of my issues when I see them again. I'm certain they shouldn't be a problem so I want to get to the bottom of it!


Thanks

Dave

12

General / Camera matching and points not seeming to align?

« on: April 05, 2016, 04:36:34 PM »

Hi all,

I quite like modelling cars in 3D.

I've taken photos of my car on a Ricoh GR and let Photoscan do it's work to get camera alignments really nice.


I then undistort and export images too for use in the background.

I export the model (patchy but usable for quick reference) to 3DS Max via FBX or 3DS format.



But for some reason points I place don't seem to line up so great.

Things towards the centre of the images usually line up ok over several images, but elements towards the edges of the shot seem to drift out by a few centimetres. Ie, a part near the centre of the car looks ok in several shots but as the camera distance increases from that point it can drift.

Is this normal?

Surely for Photoscan to work correctly these points should be perfectly aligned?

Is there any way to check inside Photoscan how accurate a camera position is? I usually use gradual selection and make sure reprojection error tie points over 0.25 or 0.5 or so are deleted (if this helps?)

Am I better shooting the checkerboard to get a lens profile to use from Lens, since currently I've just used the automatic Photoscan camera calibration detection.


Any help would be much appreciated since this workflow 'should' work, but I can't figure out why it's not.


Many thanks

Dave

13

General / Re: Clarification on feature, GPS in standard Photoscan?

« on: July 19, 2015, 10:08:45 PM »

Thanks for the clarification!

I appreciate many users will make a lot of money from the DEM/DSM etc that they can produce with these features, so the pricing has to be high.



But for my requirements I just wanted to make sure that over many hundreds of images that there wasn't significant drift that was impossible to correct for. Ie, a strip of cameras may be 50m out over 10km.


I suppose I can just export many smaller chunks, where the total error over a smaller chunk is within an acceptable tolerance, and then align each chunk against reference maps chunk by chunk.
It's not ideal but it's a work around to make sure start/end points are correct I suppose.



It's a shame there isn't a Photoscan version at about £500 that has some better features to manage big data sets, drift, scaling etc, but doesn't impact the features in the pro version for people doing industrial/cartographic level work.



Thanks!

Dave

14

Feature Requests / Re: Add markers in standard version...

« on: July 19, 2015, 04:23:22 PM »

I'd like to see the standard version improved a bit more with some useful features.

Generally it's really great software for the money, and it's by far the best I've found.

But sometimes when you're struggling to get a reconstruction to work, or want to realign/scale your point cloud it's frustrating to have to spend a lot of time doing manual tasks or using other software to do it.


I'm sure we could have 'lite' versions of some features that don't make the standard version too powerful for high end professional use, but do make life easier for standard users.



Ie, just being able to say camera X is orientated flat (bubble level) and pointing in X+ direction (roughly North) for example, so your point cloud is rotated correctly, would save me a LOT of time, but it wouldn't undermine the much more robust geo-referencing alignment and scaling tools in the professional version.

15

General / Re: Aligning chunks...again

« on: July 19, 2015, 04:12:00 PM »

Sometimes I get this, and on the ones (often blocks) that don't align, I select a few in the menu on the left and right click and then choose align and then after processing against the existing aligned imagery, they align ok.

This at least works for me half the time. The other half of the time if they don't all align at the start then they never will.


It'd be nice for a 'helper' kind of feature, perhaps overlay the image in the viewport background with some transparency, and then rotate the view so you can guide the software to the rough correct location of the camera for the given image.


Cheers

Dave