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Topics - SP74

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I have a very large 3D modelling project for a mine site survey.  I have broken the project into a large number of sub-chunks, and generated dense clouds.
The dense clouds have been exported, where I have used a Poisson filter to perform a "smart" decimation of the point cloud.  The objective is to significantly reduce the point cloud density then re import the point cloud to Metashape for meshing etc in a reduced time frame.

I have successfully exported, filtered and re imported a dense cloud.  However when I generate a mesh from the Dense Cloud based on an Arbitrary surface type, with a High target face count, I am getting a very low resolution result, with 159K faces when the target was 4.7M faces.  If I generate the mesh using an Height Field surface type, I get the correct face count of 4.7M faces. 

I have attached screen shots of the resulting meshes & the input point cloud.



Feature Requests / Adaptive Tiling/Sub-Chunk based on RAM.
« on: March 23, 2019, 02:32:46 AM »

It would be a great feature for large projects if Metashape could "internally" subdivide a chunk in smaller tiles for sequential processing, based on the available RAM.
This would avoid the user having to guess how many sub-chunks to break a large project down into.



Bug Reports / Merge Chunks - Mesh Merge not working
« on: March 18, 2019, 07:48:13 AM »

Using Metashape Pro Build 7618, I have used the Split into Chucks Python script to split a chuck in 2 x 2 chunks.  I have batched processed a 3D Model for each chunk, using high settings and 10,000,000 faces.  The 3d Models within the chunks are fine.  However when I try to merge the chunks together, ticking the Merge models checkbox, a merged chunk is produced very quickly, but no merged model is produced.

No error is reported in to console, only;

MergeChunks: merge_dense_clouds = off, merge_models = on.
Merging chunks....

I have tried to decimate the models down to 100,000 faces, but it makes no difference.  I have attached a screenshot showing the 4 chucks displayed together and the empty "Merge Chunk"



Bug Reports / Mesh from Depth Maps - False Surface
« on: March 06, 2019, 11:25:55 AM »

Using the latest build of Metashape, I am getting a false dark surface as per the attached image, when processing a mesh using depth maps as the datasource.  As my project is urgent I reverted to Photoscan 1.4.4, no issues were found. 

The mesh is a small region from a much larger project (~14300 photos).  I extracted a low resolution dense cloud over the entire project area and no issues we detected in the area of this mesh.  The project aligned well, with ppk camera locations and plenty of GCPs/Check points.



General / 4DMapper Upload Broken?
« on: February 22, 2019, 07:16:09 AM »

I have generated an number of 3D Tiled models with Metashape (1.5.0 build 7492), and have attempted to upload them to 4DMapper.  The upload appear to be successful, and the relevant project and 3D Tiles layer was created and no errors were reported.  However the model does not load, there is just a black globe.    I have provided a link to the dataset.

I also tried to upload a model from Metashape that I had previously uploaded using Photoscan and I got the same failure to load.  It looks like something has changed/broken with Metashapes 4DMapper upload.



General / Cesium 3D Tiles - Poor Overview Geometry & Texture Resolution
« on: October 18, 2018, 07:14:47 AM »

I have produced a number of Tiled 3D Models and output them in both Photoscan tiled format, and Cesium 3D Tiles.  The Cesium 3D tiled models have poor geometry and low texture resolution when viewed at a zoomed out overview zoom level.  It is only once zoomed in that the geometry and texture resolution are acceptable.  The models vary in size from a few hundred input photos to a few thousand.  All display the same issues.  I have also loaded the models into 4DMapper, and the again when zoomed out poor results are obtained.

The models have been output using a mix of Photoscan 1.4.4 & Metashape.  The only noticeable difference is that a back (un rendered) side of the mesh is now transparent, so the model disappears when viewed from the back.  I am viewing the Cesium models using the cesium viewer (via html/apache web server).  I have tried numerous optimizations for the Cesium viewer, with little changes.

I have attached side by side comparisons of the 3D models, with the Photoscan model on the left and Cesium model on the right.




We fly the vast majority of our projects with survey grade GPS using PPK method.  Whilst ee may have our GCPs and airborne photocentre coordinates in the same datum/map projection, they have been derived off different origins.  For example, a mine-site survey may have the airborne photocentres derived from a CORS network. Meanwhile the mine surveyors have tied their GCPs into a existing geodetic network, potentially derived many years ago using optical survey methods.  In remote areas, there may be decimetre level differences between these datums, most notably in elevation.

To combat this some additional parameters in the block adjustment are introduced to allow the translation (and/or rotation & scale) of the airborne data to fit the GCPs.  Block adjustment applications such as PATB & ORIMA allow solution of such parameters, and it  doing so may increase the solution accuracy for Photoscan.

At the moment the GCPs are used as check points to determine the magnitude of any systematic translations, which are then manually applied using excel to the airborne photocentre coordinates.

Best regards,

Stu Paisley.

Hi All,

I have noticed that for large dense point clouds;

a) The project is very slow to save if the point cloud has been modified using the Select Points by Color tool, followed by the Assign Class tool
b) The project saves at normal speeds if the point cloud edited manually, say using the Free-Form Selection tool followed by the Assign Class tool
c) The Select Points by Color tool does not complete if it is used a second time.  The user must save the project, restart photoscan & reload project for successful operation.

This has been observed at least since version 1.3.5

Machine spec

Photoscan Pro Version 1.4.2 Build 6204 (64 Bit)
AMD Ryzen Threadripper 1950X
Windows 10 Pro x64
2x NVIDIA GeoForce GTX 1080 Ti

General / Adding a new geoid model
« on: December 03, 2015, 08:52:47 AM »

Would it be possible to provide a tutorial on how to add a geoid model.  I have converted the geoid model for Australia (AUSGEOID09) to Geotiff, but it is not clear in Photoscan Pro how to add this as a vertical reference system.



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