<h2>Reference objects</h2>
<p>When scanning something, including a simple reference geometry, such as a cube, is best. This can then be used to scale the final model to the correct size and as a reference for if the item has the correct angles. Besides cubes, coins (esp. matte ones) make handy markers and scale references.</p>
<p>If your scan contains color values, a simple photo scale angle could suffice. That item would be taken directly from photography. There it is sometimes required to contain size information and a pointer to the angle the photo was made at. This is made by using a square or angle with scale markings and distortions of the item can be solved later till the angle appears properly and to the right scale.</p>

CC BY-SA 4.0
2024-02-03T08:33:53.237Z
Do you know if there is a way to do this automatically? Like select the object and tell the size. I can think of 3D scanning something first. Then make a photo of the object with a reference, use overlay to position but it likely won't be too accurate. What if you want milimeter precision? It's hard to do manually with a reference object.
Bob Ortiz
CC BY-SA 4.0
2024-02-03T09:11:26.170Z
@BobOrtiz I don'T think Kiri has it, but some scan engines with turntable from about 2020 used a reference item they scanned first before scanning an actual item on the turntable, using the known reference as scale
Trish
CC BY-SA 4.0
2024-02-03T13:05:42.120Z
I have a RevoPoint Inspire with a turntable and 'magic pad' too, I suppose they use those markers as reference too. But so far I absolutely hate using it.
Bob Ortiz
CC BY-SA 4.0
2024-02-02T09:07:55.773Z
2024-02-02T09:07:55.773Z
Trish
<p>I noticed when scanning objects using photogrammetry or the AI-based Neural Radiance Field (NeRF) in apps such as Kiri Engine that the original size is not retained in the object.</p>
<p>How can I actually retain the original size, or set the proper sizes when or after scanning objects like that? So that, when 3D printed it is the same size as the original?</p>

<cad><scanning><artificial-intelligence>
How to set or retain original object size in photogrammetry scans with apps such as Kiri Engine?
Bob Ortiz
# How to set or retain original object size in photogrammetry scans with apps such as Kiri Engine?

(Asked by: username_0 on 2024-01-22)

I noticed when scanning objects using photogrammetry or the AI-based Neural Radiance Field (NeRF) in apps such as Kiri Engine that the original size is not retained in the object.

How can I actually retain the original size, or set the proper sizes when or after scanning objects like that? So that, when 3D printed it is the same size as the original?

**Tags:** cad, scanning, artificial-intelligence

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## 1 answers

### Answer by username_1 on 2024-02-02. Score: 2 | Accepted answer

## Reference objects

When scanning something, including a simple reference geometry, such as a cube, is best. This can then be used to scale the final model to the correct size and as a reference for if the item has the correct angles. Besides cubes, coins (esp. matte ones) make handy markers and scale references.

If your scan contains color values, a simple photo scale angle could suffice. That item would be taken directly from photography. There it is sometimes required to contain size information and a pointer to the angle the photo was made at. This is made by using a square or angle with scale markings and distortions of the item can be solved later till the angle appears properly and to the right scale.

> **Comments:**
> **username_0**: Do you know if there is a way to do this automatically? Like select the object and tell the size. I can think of 3D scanning something first. Then make a photo of the object with a reference, use overlay to position but it likely won't be too accurate. What if you want milimeter precision? It's hard to do manually with a reference object.  
> **username_1**: @BobOrtiz I don'T think Kiri has it, but some scan engines with turntable from about 2020 used a reference item they scanned first before scanning an actual item on the turntable, using the known reference as scale  
> **username_0**: I have a RevoPoint Inspire with a turntable and 'magic pad' too, I suppose they use those markers as reference too. But so far I absolutely hate using it.  

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