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Author Topic: factors that affect speed of progress  (Read 1446 times)

Aaslestad

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factors that affect speed of progress
« on: September 23, 2021, 11:41:48 PM »
there are a lot of posts about hardware and speed of processing, how to deal with slowness etc.
i wonder if this related topic has been discussed as well: what are the factors that affect the speed of different process that are controllable in settings. for example, if you had something that was going to process a long time for very dense data and you wanted to run through everything before committing a block of time - is it better practice to increase/decrease key point limit, or tie point limit, or is it better to change the accuracy level from medium to high - or something else altogether - maybe using half size photos in a test run??? What are the "dials" that everyone like to use best and how do you use them? I'd love to follow that discussion!

Bzuco

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Re: factors that affect speed of progress
« Reply #1 on: September 26, 2021, 02:05:53 PM »
If you want to make some test run before final one and do not want to wait hours for the result I would advise:

In align photos phase:
-keep accuracy on high because we still want as much precise pointcloud as possible. Medium acc. make sense only if you are sure, that your photos are very good quality and feature rich... otherwise med. acc. could cause errors in camera positions or completelly bad camera position especialy if photos are not perfect.
I would set keypoint limit to 5000 for interior projects(or where all objects on photos are near you) and higher values 10k-20k for exterior projects(where objects are few meters near and also houndreds of meters far from you, e.g. mountains)
With generic preselection enabled, whole alignment phase takes only fraction of total project computation time, so no need to experiment with parameters to save few seconds/minutes...

In build dense cloud phase:
-also here you can keep the quality to your final one value(depth maps will be computed only ones and not twice for test run and for final run).
To speed up test run and see if the result is good and expected it is useful set tweak parameter in preferences dialog: parameter "BuildDenseCloud/max_neighbors" with value 10 or 20. The result will be more noisy or better said with less prefiltered points but computation time will be 2 - 3x quicker and you will still see if the pointlcoud is as expected or with some completelly misaligned parts or doubled parts.
For final run depth maps will be reused from test run and it is enough set the "BuildDenseCloud/max_neighbors" to its default (if I remember 50) or set it even higher...it depends of your projects, how many photos are overlaped and what was your object of interest.

I am only using photogrammetry in garden projects(house, backyard, garden, road) but this debate should be splitted in more parts, because making photogrammetry is slightly different for interiors, exteriors, top down aerial photos with drone, objects on turn table, human body/face scanning, etc.

In every case it is good advise to have enough photos(no more or no less than it is necessary) taken from good positions/angles and with best quality as possible.
I hope you will find something useful in my post.