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Pauldanc24

Adding Scale Bars after alignment

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Hope this is an appropriate forum. Apologies if it isn’t. I have been looking at the videos on capturing objects on turntables and your workflow is to add the scale bars in a separate set of images. My question is how are these images treated. Are the aligned separately then the two chunks aligned or are all the photos aligned together. If that is the case doesn’t the addition of the scale bars cause confusion in the software?

 

Many thanks in advance 

Paul

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If you shot it properly, all the images should align together in the same chunk.  Also for a turntable project, you likely need to mask background images, and then when you align, apply masks to tie points (in the advanced tab)  You do not need to mask the scale bar images.

You can set the region of the model later in order to remove the scale bars.  There are other ways to remove the scale bars as well - but initially, you want them in the main alignment.

If they don't all align together that may indicate a different problem (such as blurry photos, monochromatic surface with no texture, etc.).  In that case you can align them in separate chunks and try to bring the chunks together.  Just understand that at that point you are working around a problem and a properly shot image set should all align together.

Hope this helps,

Carla

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Hi Paul.

Shooting:  I place the scale bars in a position where I can get both the scale bar and a portion of the object in focus and then shoot sufficient images to accurately capture the scale bar. I repeat this for each orientation of the object, or dispersed throughout a scene.  After removing the scale bar I shoot the object or scene, repeating any angles that had the scale bar.

Processing. All images are aligned together. Add CPs, set scales etc... then disable the images with scale bars to just prior to producing the mesh/dense cloud.  In Reality Capture you can select the scale bar images and disable them from meshing/texturing. In Agisoft, disable the images prior to alignment.

If the scale bars aren't touching the object you can always crop it out later but this saves you a bit of work. By separating the 2 sets of images I find you worry less about where to place the scale bars (wanting them to be less obtrusive) allowing you to focus on placing them where they're needed.  In this scene for example (https://skfb.ly/6JUGE), there were scale bars obscuring part of the sculptures (resting on arms etc) as well as on the ground.

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I think there was an error in the above recommendations - you absolutely need to align the images with the scale bars in order to use them to set scale for your project.  How you placed the scale bars will affect exactly how you work with those images.  The Agisoft software will not be confused by some images that have scale bars and some that don't for the same area of your scene - as long as you have good crisp photos with good overlap between photos and plenty of look angles.

It's a bit difficult to describe in text, but hopefully this makes sense.

Carla 

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