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Author Topic: Point colors in Point View Mode, what does it mean?  (Read 15358 times)

bisenberger

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Point colors in Point View Mode, what does it mean?
« on: May 18, 2013, 09:52:06 PM »
When View Points is selected to show the points used for alignment overlayed on the image the points are in two different colors, blue and grey. What is the difference?
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Alexey Pasumansky

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Re: View Points point color
« Reply #1 on: May 31, 2013, 12:52:17 PM »
Hello bisenberger,

Blue points mark used matches (also they correspond to the points of the sparse point cloud) and white points - unused.
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Alexey Pasumansky,
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bisenberger

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Re: View Points point color
« Reply #2 on: May 31, 2013, 05:34:31 PM »
Thanks for the info Alexey.
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jtuhtan

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Re: View Points point color
« Reply #3 on: January 08, 2014, 11:55:16 AM »
Hi,

It may also be worth noting that the blue points displayed in PhotoScan are not always the same points as those exported in the *.out file. I noticed this when comparing the PhotoScan point-image overlays against a manual overlay of the exported sparse cloud point locations onto the same images.

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Marcel

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Point colors in Point View Mode, what does it mean?
« Reply #4 on: July 02, 2014, 07:56:53 AM »
When I show the extracted points on the camera (by clicking the camera and then clicking the "Point View Mode" icon), I see blue points and grey colored points. What is the meaning of the color?

There seem to be more grey points at the edges of the scan (it's a flat object), so I was thinking it might be points with a low number of images. But when I use Gradual Selection to select images with 3 cameras or less, none of the grey points are selected (see second attachment).

Alexey Pasumansky

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Re: Point colors in Point View Mode, what does it mean?
« Reply #5 on: July 02, 2014, 09:45:01 AM »
Hello marcel,

I've merged two topics, so you can see that grey points are unused matches. Since in the sparse cloud only used (blue) points are present, gradual selection will not effect on unused (grey) matching points.
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Marcel

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Re: Point colors in Point View Mode, what does it mean?
« Reply #6 on: July 02, 2014, 11:05:52 AM »
Thanks for clearing that up Alexey!

I was already wondering because the grey points seemed to be in featureless areas.

Bruno Andrieu

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What means the colour of the points in the photo panel ?
« Reply #7 on: November 02, 2014, 01:24:44 AM »
Hi when looking on a photo in the photo panel we can see the point from used to build the sparse point cloud.

In grey I think it is all the candidate points in the initial image (?)
in blue it looks as the tie points (?)

They are also points in red and I do not know what they are ?

can you help ?

Alexey Pasumansky

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Re: Point colors in Point View Mode, what does it mean?
« Reply #8 on: November 02, 2014, 06:53:04 AM »
Hello Bruno,

Red points are tie points selected in the model view.
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Alexey Pasumansky,
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Mycobiont

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Re: Point colors in Point View Mode, what does it mean?
« Reply #9 on: October 30, 2015, 01:32:53 AM »
Hi!  I'm working on a rather complex topography project and have noticed some odd things about the points overlaid on photos.  In the attached image, I would expect the whole image to have lots of unused points, with a couple blocks of blue points where points are used in conjunction with other images.  Instead, I have a big gap in the middle with very few points, a block of blue on one side as expected, and a block of gray points on the other side where I would expect more blue. 

Is there something more to the gray points than just unused points?

[using version 1.1.6 pro]

Thanks!

Alexey Pasumansky

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Re: Point colors in Point View Mode, what does it mean?
« Reply #10 on: October 30, 2015, 04:32:01 PM »
Hello Mycobiont,

The blank space in the middle of the photo is likely indicating to the lack of overlap between photos. I can assume that the alignment broke on this photo, as the subset from the right has no overlap with the subset to the left. But it's only a guess, as there's no other information regarding the alignment results.
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Alexey Pasumansky,
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Mycobiont

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Re: Point colors in Point View Mode, what does it mean?
« Reply #11 on: November 03, 2015, 09:29:15 PM »
Thanks Alexey!  But either I'm still missing something obvious, or my project has some sort of corrupion, or maybe I've even run into a bug...

I have a large, complex project with hundreds of photos taken obliquely to create a topo model of a site.  I ran the initial alignment with Key and Tie point limits set to 0 (unlimited).  The alignment was reporting many tens of thousands of points per photo, sometimes even over 100,000.  The initial model aligned less than half the images and many were aligned improperly, needing further adjustments (I'm adding markers).

While working on these unaligned, or poorly aligned, images, I've noticed that some *non*-aligned show no grey points, some show grey points, particularly in areas where I might expect alignment with another image, and I've even seen one or two *non*-aligned images with blue dots.  Images do have high-precision camera coordinates... maybe this is how a non-aligned image can show dots?

I've also found images that are aligned (though not reporting any projections) that show no grey or blue dots.

So I'm thinking that grey dots are key points in areas expected to overlap with other photos?  How is the photo orientation managed in these cases?

What do blue dots in a non-aligned image mean?

Why do many images that are aligned not show any dots?  These images appear to be correctly placed according to the look-through at the model, and they have very good overlap with other aligned images.  However they are also not reporting any projections in the reference panel... but then I also have aligned images without projections that do show grey dots...?

Thanks!
-Eric

Mycobiont

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Re: Point colors in Point View Mode, what does it mean?
« Reply #12 on: November 11, 2015, 02:22:50 AM »
Maybe I can simplify my question...

Why do I have some images in my project that show gray points, even sometimes a few blue points, even though they will not align, while others that are not aligned show no points at all, even when I force alignment with markers?

Thanks!

Wishgranter

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Re: Point colors in Point View Mode, what does it mean?
« Reply #13 on: November 11, 2015, 10:48:13 AM »
Hi Mycobiont

what sort of  Oblique setup you used ? a fixed 3+ cams  rig or just captured with ublique positions ?

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Alexey Pasumansky

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Re: Point colors in Point View Mode, what does it mean?
« Reply #14 on: November 11, 2015, 08:32:05 PM »
Hello Mycobiont,

Unlimited number of key points is not always a good choice as it can result in big number of low confident features that will be used for the image matching. In the most cases I don't see any reason to go above 80 000 - 100 000 for common digital images.

Blue and grey points, as I've already mentioned, are matching points. So if there are no points on any image, it means that PhotoScan was unable to find any matches of this image with the rest of the images from the set.

You can use markers as valid matches between photos to help the alignment, but adding them will not result in any new automatically found matching points, as they appear during Align Photos stage (during Matching Photos step in particular), whereas Align Selected cameras operation just uses already exsising matching points for camera position/orientation estimation.

Blue dots may be present on NA (not aligned) images, because matching points may have more than two projections. It just means that the same point appears on at least two photos from the aligned sub-set and was actually used.

Maybe you can provide the project file to us, so that we could take a closer look at it? You can send it to support@agisoft.com.
Best regards,
Alexey Pasumansky,
Agisoft LLC