Human skull: Cannot create dense point cloud

[CarlosVenator]

Hello.

I'm very new to 3D and this is the first time I try to scan an object. I've tried several times in different ways to create the dense point cloud but it wasn't possible. One time I tried and I waited 27 hours, so last time I've converted the images to JPEG and reduced the size of the photos to approximately 1400x900 pixels. I've taken photos from 5 different angles. The first steps seem to work fine, even the sparse point cloud looks good and without gaps, until I create the dense point cloud: The photos appear on the inside of the 3D model and as you can see in the photos, it has many incomplete areas.

I'd really appreciate any help. Thank you in advance.

[Alexey Pasumansky]

Hello CarlosVenator,

Can you please send the project saved in PSZ format with only alignment results (no need of the dense cloud) to support@agisoft.com? If you have the project with the alignment that is based on the source images and not on the lossy compressed low resolution JPGs, it would be better.

In case too many tie points have been removed from the sparse cloud, Metashape wouldn't be able to use all the overlapping image pairs for the depth maps and dense cloud generation, as the number of common tie points for some image pairs would be below the threshold.

[CarlosVenator]

Thank you for your help. I will try to align the photos again but this time using the source format as you suggested. However, when I aligned the images in JPEG format and reduced to 25% (1400x900 pixels) it took many hours to complete.

By the way, is it normal to have to wait 27 hours for the dense point cloud to create from those reduced JPEG photos? Since this process is so computationally expensive, I couldn't use my computer for anything else for more than a day, even though my computer is rather potent.

I'll write again when I've sent the project saved in PSZ format with alignment.

Regards.

[Alexey Pasumansky]

Hello CarlosVenator,

27 hours is too long for 140 image project. However, you have not specified the hardware used and processing parameters.

Before starting the processing I can also recommend to enable writing the log to file in the General Preferences tab, re-start the application and run the processing.
If you have a discrete GPU, then please make sure that it is enabled in the GPU Preferences tab.

Instead of downscaling the images you can just vary Accuracy and Quality settings in the Align Photos and Build Dense Cloud dialogs respectively.

[CarlosVenator]

Sorry, I forgot to add that when it took 27 hours, I had imported 413 photos, so it weren't 140 photos. In a later attempt, once aligned I reduced the number of images from 413 to 140 to make it less costly. In all my attempts at building the Dense Cloud I haven't used a superior quality than "medium".

The computer is a Lenovo Yoga 720 i7 (8th generation) 16 GB RAM.

I'm now trying to create the dense cloud with all 413 source images. The dialogue now says 5 hours, but the time estimation keeps increasing. I have also sent the project saved in PSZ to support@agisoft.com.

Regards.

[Alexey Pasumansky]

Hello CarlosVenator,

The laptop configuration doesn't seem to be very powerful. If there's no discrete GPU, long processing time is expected.
To reduce the time required for the reconstruction, you can try to use Lowest quality for the dense cloud. Also it might be reasonable to disable every second or even every third camera in the project after having all 413 images aligned, and basing on the enabled cameras generate the dense cloud.

[Alexey Pasumansky]

Hello CarlosVenator,

I have generated the full scale images from the thumbnails and generated rough dense cloud and mesh from them (see screenshot below).

The processing of all the four hundred images, however, on High quality took quite long on a medium desktop with single GPU (about 3 hours for depth maps and about 7 hours for dense cloud), but I think that the processing time can be reduced by disabling some images or by using a dense cloud neighbors tweak that will result in faster dense cloud filtering for such dataset.

[CarlosVenator]

Hello Alexey,

Thank you for creating the model, I really appreciate all your help.

So, the 27 hour-long process is due to the lack of a discrete GPU - I'll take that into account the day I end up buying my next computer.

In any case, I have also just finished creating the dense cloud and mesh. I've added a screenshot of it. I have another question about the results. I'm not sure if I can ask it here or if I have to start a new topic. The skull has several holes, but as you can see in the circle, in its right eye socket it has an extra hole that is not present in the real skull. I have tried several ways of closing it: building the mesh with "interpolation enabled" and with "extrapolation", as well as with the "close holes" tool, trying with various percentages. None were able to close that hole. I have also tried by creating the mesh with different amounts of faces. Are there other ways of closing it?

Thanks again.

[Mak11]

Do you need the Dense cloud for your project or not? If not then I would suggest this you generate the mesh by using the new depth-maps based method which should would probably "automatically" close the whole (and also be faster than the Dense cloud based worlkflow.
In either cases you can use Meshlab (which is free) to close the holes in your meshes (or any other modeling software like 3Dciat/zbrush/max/maya/modo etc).

Mak

[CarlosVenator]

I would suggest this you generate the mesh by using the new depth-maps based method
Mak

Hello Mak, thanks for your reply.

I definitely want to try out that method. I'm completely new to Metashape, do I have to create a depth map previously? And where can I find the depth-maps based method it in the program?

Regards.

[Mak11]

Carlos,

Just select Depth maps as the source data instead of Dense Cloud (and check re-use depth-maps if available.)

Mak