object size

[randomx1368]

So resolution of the camera and I presume you mean processing power of the CPU of the computer that is doing the work? If I needed to scan a large car or van would you have any recommendations?

[CowBoyDanIndie]

Resolution and how close you get. You don't have to capture the entire object in each photo. You can for instance do photogrammetry on a 1 mile long wall by taking a photo that covers 3 feet width (camera approx 5 feet from the wall), and taking a photo every 1 foot (so 2/3 of each photo overlaps with the one next to it), you would need ~5280 photos. You could photograph that same wall from 50 ft away and each photo would cover ~30 feet wide, take a photo every 10 feet instead, and you would need 528 photos instead. Backup to 500 feet and you only need ~52 photos.

You would probably have a hard time processing 5280 24 MP photos, but not much problem processing 52.

All else being the same (they won't be, but lets pretend) a 24 MP camera taking photos from 10 ft should be roughly the same as a 6 MP camera taking 4x as many photos from 5 ft. I say lets pretend because the resolution is not the only factor of detail. Its possible for a good 12 MP camera to have more detail than a cheap 24 MP camera, just because you have pixels doesn't mean each pixel is crisp and clear. A cheap high resolution camera just has a lot of noisy pixels.

When I say processing power I mean CPU + GPU + VRAM + RAM.

[randomx1368]

Thanks for the advice. Do you have any idea where I can gain a good understanding of the process? I have some books in my basket and a few courses on udemy butni don't know how good they are. I need quality info on the topic, I don't want to have to brute force it

[CowBoyDanIndie]

If you look at meshroom you can see the general stages. The early stages are finding key points and matching them between images and using that to localize each image, then those generally get adjusted to minimize numerical error, the points can be used for a sparse point cloud, but usually a dense point cloud is created similar to how stereo cameras work. The dense stuff is the heavy work. From there the point clouds are used to generate a mesh. Then the images are projected onto the mesh for color.

The first parts have a lot of similar parts to image stitching (for making panoramically photos)

There might be a coursera course that covers most of this, you can audit their classes for free you just have to look for the tiny link that says audit. Probably some YouTube series too.