Apply Scale and Rotation introducing scale differences up to 0.9mm in small scale objects #97244

New Issue

Alexander Dumproff · 2022-04-11T12:38:02+02:00

2022-04-11 12:38:02 +02:00

System Information
Operating system: Windows-10-10.0.19044-SP0 64 Bits
Graphics card: Quadro P2000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 471.11

Blender Version
Broken: version: 3.1.0, branch: master, commit date: 2022-03-08 18:16, hash: c77597cd0e

Short description of error
An object of smaller scale can introduce scale differences of up to 0.9mm when rotation is applied to the model.
Original object:

Applied Object:

Exact steps for others to reproduce the error
Please take a look at the attached file and compare the scale of the two objects.
When the Rotation is applied to the original object you will notice the scale shift slighty.
The example file is reconstructed as the original one I was working on is under NDA and can't be posted to a public bugtracker.

Example file:
Apply_ScaleDiff_example.blend

**System Information** Operating system: Windows-10-10.0.19044-SP0 64 Bits Graphics card: Quadro [P2000](https://archive.blender.org/developer/P2000.txt)/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 471.11 **Blender Version** Broken: version: 3.1.0, branch: master, commit date: 2022-03-08 18:16, hash: `c77597cd0e` **Short description of error** An object of smaller scale can introduce scale differences of up to 0.9mm when rotation is applied to the model. Original object: ![grafik.png](https://archive.blender.org/developer/F12995064/grafik.png) Applied Object: ![grafik.png](https://archive.blender.org/developer/F12995068/grafik.png) **Exact steps for others to reproduce the error** Please take a look at the attached file and compare the scale of the two objects. When the Rotation is applied to the original object you will notice the scale shift slighty. *The example file is reconstructed as the original one I was working on is under NDA and can't be posted to a public bugtracker.* Example file: [Apply_ScaleDiff_example.blend](https://archive.blender.org/developer/F12995031/Apply_ScaleDiff_example.blend)

Alexander Dumproff commented

2022-04-11 12:38:02 +02:00

Added subscriber: @A.Lex_3D

Richard Antalik commented

2022-04-12 18:24:16 +02:00

Added subscriber: @iss

Richard Antalik commented

2022-04-12 18:24:16 +02:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Richard Antalik commented

2022-04-12 18:24:16 +02:00

Can you upload mesh where you need to apply rotation to reproduce this from "good state"?

From what I remember Dimensions property is calculated from mesh. It can happen with small meshes, that precision of vertex positions will result in usually very small difference. Not exactly sure if this is the case here as this mesh isn't that small.

Can you upload mesh where you need to apply rotation to reproduce this from "good state"? From what I remember Dimensions property is calculated from mesh. It can happen with small meshes, that precision of vertex positions will result in usually very small difference. Not exactly sure if this is the case here as this mesh isn't that small.

Richard Antalik commented

2022-04-12 18:30:25 +02:00

Just checked how boundbox looks like and I can see that one is rotated, so I would consider this to be expected behavior unless I am missing something

Just checked how boundbox looks like and I can see that one is rotated, so I would consider this to be expected behavior unless I am missing something ![#97244.png](https://archive.blender.org/developer/F12998452/T97244.png)

Alexander Dumproff commented

2022-04-14 15:18:54 +02:00

If you want to reproduce it, then

duplicate the rotated mesh "Oricinal Sculpt"
expand the N-Panel
watch the Y-Dimension when hitting Apply Rotation and scale.

Object "Original Sculpt" has rotational values and it's dimenstions are [24.5,28.1, 7.49].
As soon as you apply the rotation to the mesh the displayed scale of the mesh changes to [24.5, 27.9, 7.49]

In this example it's merely 0.18 mm and it doesn't seem like the mesh actually changed when overlapping them.
In the file I was working on at work the scale difference was much more noticeable with nearly 1 mm difference in the X-axis.

Nearly 1mm of rounding difference seems quite a lot to me if this was to be a 3D printed piece, for example.

If you want to reproduce it, then * duplicate the rotated mesh "Oricinal Sculpt" * expand the N-Panel * watch the Y-Dimension when hitting Apply Rotation and scale. Object "Original Sculpt" has rotational values and it's dimenstions are [24.5,**28.1**, 7.49]. As soon as you apply the rotation to the mesh the displayed scale of the mesh changes to [24.5, **27.9**, 7.49] In this example it's merely 0.18 mm and it doesn't seem like the mesh actually changed when overlapping them. In the file I was working on at work the scale difference was much more noticeable with nearly 1 mm difference in the X-axis. Nearly 1mm of rounding difference seems quite a lot to me if this was to be a 3D printed piece, for example.

Richard Antalik commented

2022-04-14 18:22:12 +02:00

Changed status from 'Needs User Info' to: 'Archived'

Richard Antalik closed this issue

2022-04-14 18:22:12 +02:00

Richard Antalik commented

2022-04-14 18:22:12 +02:00

Thanks for clarification.

This is correct behavior though. Probably better explanation is when you align boundboxes:

You can see that since you have rotated mesh itself, dimensions of object are in fact different. These dimensions are calculated from boundbox which is defined by object coordinate system not by best fitting the object.

Thanks for clarification. This is correct behavior though. Probably better explanation is when you align boundboxes: ![#97244.png](https://archive.blender.org/developer/F13001660/T97244.png) You can see that since you have rotated mesh itself, dimensions of object are in fact different. These dimensions are calculated from boundbox which is defined by object coordinate system not by best fitting the object.

Alexander Dumproff commented

2022-04-15 19:17:42 +02:00

Ah, I see. Thank you.
So just for clarification: It is expected behaviour that the dimensions can only be trusted 100% as long as there is no odd rotation applied to the object, correct?

Ah, I see. Thank you. So just for clarification: It is expected behaviour that the dimensions can only be trusted 100% as long as there is no odd rotation applied to the object, correct?

Richard Antalik commented

2022-04-15 22:04:33 +02:00

I guess that would depends for what purposes. The value describes box bounding the mesh - if you rotate completely asymetric mesh, the box dimensions will change to fit the mesh. With your example, it's hard to define what rotation would be "odd" as it has no symmetry.

I am not familiar with 3D printing very much, but if you want to array these objects with rectangular pattern and ensure they are not touching, the dimensions provided would provide accurate minimum spacing when you apply rotation. They would also provide accurate necessary printer volume.

I guess that would depends for what purposes. The value describes box bounding the mesh - if you rotate completely asymetric mesh, the box dimensions will change to fit the mesh. With your example, it's hard to define what rotation would be "odd" as it has no symmetry. I am not familiar with 3D printing very much, but if you want to array these objects with rectangular pattern and ensure they are not touching, the dimensions provided would provide accurate minimum spacing when you apply rotation. They would also provide accurate necessary printer volume.

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Apply Scale and Rotation introducing scale differences up to 0.9mm in small scale objects #97244