英語翻譯
Once you get a decent low density point cloud,you are ready to move on to denser point cloud and the meshing steps.See ‘Densify your Point Cloud’ section below.
However,if you find it difficult to find an appropriate depth range,and your DSM’s consistently result in a lot of noise and/or gaps etc,you may need to ‘build-up’ an implicit base surface.With a implicit base surface that better matches the true shape,your DSM will usually solve better,due to a smaller required depth range.On a face for example,you might want to mark and reference points on the tip of the nose,around the eyes,and on the cheeks and chin in order to get a closer base/approximate surface.The Help file discusses the implicit surface in more detail.
This image shows a few points marked on the face.Once referenced on other photos,the points 3D positions will be used by PMScanner to build up an ‘internal’ base surface.You won’t be able to see this base surface,but PMScanner will use it as a guide when matching regions on the face.
You can now use a smaller depth range to generate a reasonable initial DSM.
The following shows the 3D points through which PMScanner internally will fit an ‘implicit’ surface:
Notice how the peaks and various elevations of the face have points to help define the base surface.
The following shows the low density point cloud with the points used for a base surface and a depth range of +/- 5cm:
Notice how a depth range of +/-5cm works a lot better with the points marked to define an implicit base surface,as opposed to the example in #2 above where a +/-5cm depth range without the implicit base surface points resulted in a lot of noise.
You now have a reasonable low density point cloud and you are ready to move on to densifying it (see next section).
Densify your Point Cloud
Once your intial set up works well,increase the density of the point cloud (ie decrease the sample rate setting) and set up your meshing steps,then generate the new denser DSM,and run the meshing steps.A well solved DSM looks like this:
If your point cloud has noise points you may want to remove the noise points before meshing.See the ‘Clean up your Point Cloud’ section below.
If the triangulated PointMesh is rippled or wavy,you may need to regenerate your DSM using a higher sample rate (ie less dense point cloud).
Clean up your Point Cloud
Once you have a reasonable point cloud at the density you need,you may have a few outlying noise points.If the DSM solved well and there are very few of these noise points,you may not need to clean up as that will be taken care of in the Meshing Steps (eg filter step,smoothing etc.).