Photogrammetry

I had mostly positive results with both Meshroom and 3DF Zephyr, both produce reasonable consistent results of detailed rough objects, and seem to struggle with similar issues.

I've had mixed results with flat surfaces. I can only think that perhaps sometimes floors/ceilings are too regular reducing the amount of points for the software to use for tracking.

Only 3 usable images from 19 captured

6 usable images from 16

In both of the above cases I also failed experimenting with removing some of the unusable and useable images to see if it was possible to manipulate a better result

Removing the 3 usable images from the set, didn't make the others usable

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Below are some points from the Documentation for the Meshroom software on "Capturing Basics", with my added notes

Your scene/object should be well lit.

I think the dark shadows from only one light source left less detail for tracking points.

Avoid shadows, reflections, and transparent objects.

I tested a few reflective object with poor results. The software finds edges particularly difficult to maintain, as well as struggling to find tracking points on the regular surfaces. Not worth attempting.

Take the photos in diffuse or indirect lighting, such as on an overcast day (outdoor) or using multiple light sources (indoor).

I had good results with indoor lighting, although the colour of the lighting has to be kept in mind for the textured mesh. Light bleed from the sun for external captures can also taint the textured mesh.

Original Image | Meshroom | 3DF Zephyr

Light bleed from the sun causing texture issues

Don´t use the flash setting on the camera.

I actually had pretty reasonable results with flash in terms of producing a good model - the textures aren't "true to life" and have less detail however.

Do not change the focal length/zoom while shooting. Use a fixed focal length lens if possible.

Meshroom and Zephyr both did a good job of using the meta data of the images used to cross reference lens properties. I don't think that this is a major issue.

Try to take pictures from all angles.

This is difficult to do indoors without casting unwanted shadows, a rotating rig would potentially be easier for indoor captures.

The object of interest should always fill most of the image.

I experimented with taking photos with different aspect ratios to remove unwanted areas of the scene with positive results.

1:1 Aspect Ratio

Do not take multiple images from the same spot.

I found that "same angle" is probably better advice, and is probably targeted at something that you're orbiting when taking photos. The larger rock faces had no issues of photos from the same position, but with a different target location.

All 38 images used despite taking multiple from the same spot but with different targets

The more images you have, the better. You can always filter out repetitive or poor quality images to reduce processing time.

I've had some issues where lots of pictures have been discarded, so a secondary pass is definitely worth it for scans difficult to visit again.

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Strategy

• Avoid harsh shadows/reflective surfaces.

• Overcast conditions are ideal with low shots towards the sun avoided if possible to avoid light bleed.

• Do a second pass in case some photos are bad quality or unusable.

• Keep camera settings consistent if possible to maintain texture lighting.

• For more regular surfaces closeup shots may be required.

• Also use close-ups for added detail.

• Maintain photo overlap, only move or rotate the subject a little each time.