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Author Topic: Mesh Build in PhotoScan 1.0 - My Workflow  (Read 9923 times)

David Cockey

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Mesh Build in PhotoScan 1.0 - My Workflow
« on: November 26, 2013, 03:11:29 PM »
PhotoScan 1.0 (pre-release available in http://www.agisoft.ru/forum/index.php?topic=1476.0 ) separates building the mesh from building the dense cloud. Below is a summary of the workflow I'm using in projects involving objects such as boats.

Mesh Creation in PhotoScan 1.0
 
Workflow

1)  Trim significant noise and unwanted parts such as supports from the Dense Point Cloud before creating the mesh. The undo arrow in the icon toolbar at the top can be used to back up during the trimming process. If significant trimming is needed it may be best to create a copy of the chunk, and then trim the copied chunk.

2)  Click on Build Mesh in the Workflow and set the Build Mesh parameters:
Surface type:      Arbitrary
Source data:      Dense cloud
Polygon count:   40000000  (40 million, or a similar very large number)
Advanced:   
Interpolation:   Enabled (default)
Click on okay and build the mesh.

3)  The mesh can be decimated in a separate operation if a smaller mesh is needed than the result from Build Mesh. The Decimate Mesh tool is found under the Tools menu.
    Tools
      > Mesh
         > Decimate Mesh
Specify the number of faces desired and click okay.

4)  Build Texture if needed. A reasonable choice for the settings is:
   Mapping mode:   Generic
   Blending mode:   Mosaic (default)
   Texture size/count:   2048 x 1
   Advanced
      Enable color correction box not checked
 
Notes

Specifying a very large polygon count in Build Mesh results in the smallest amount of memory being used during the mesh generation process, contrary to what may seem obvious. The size of the mesh initially created during Build Mesh depends only on the number of points in the Dense Cloud and the geometry of those points, not on the value specified for Polygon count. The number of faces in the initial mesh is then compared to the specified Polygon count value, and the initial mesh is then decimated if needed so that the number of faces does not exceed the specified Polygon count value. Mesh decimation can use more memory than used for the creation of the initial mesh.

If the desired size of the decimated mesh is not certain, copy the chunk and then decimate the mesh in the copied chunk. If a different size mesh is desired then the original chunk can be copied again and the mesh in the second chunk decimated to the different size.

Enabled is generally the best choice for the mesh interpolation type for objects with strong three-dimensional shape.. Build Texture may not work properly if the mesh was created with Interpolation Disabled. Extrapolation attempts to create a closed mesh without any holes, and the result may not be the desired shape.

Texture should be created if the file is to be exported as a .obj and the mesh needs to have visual texture. Texture can also result more apparent detail and a more pleasing appearance with a relatively coarse mesh. If color correction is enabled for Build Texture the execution time may become much longer, particularly with a large number of photos.

David Cockey
26 November 2013


amaze3d

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Re: Mesh Build in PhotoScan 1.0 - My Workflow
« Reply #1 on: December 02, 2013, 05:08:20 PM »
hi David
  Can I set zero for the polygon count,  the reference PDF says  "0"size means maximum size with no optimize.

Chris