Changing the Dimension value after rotation apply in a plane generates unexpected results #75596

New Issue

Pasang Bomjan · 2020-04-10T21:57:41+02:00

Pasang Bomjan commented

2020-04-10 21:57:41 +02:00

System Information
Operating system:
Graphics card:

Blender Version
Broken: (example: 2.80, edbf15d3c0, master, 2018-11-28, as found on the splash screen)

Short description of error
Reopening #75562 here again. I'm sure this is a bug.

Exact steps for others to reproduce the error

Add a plane and rotate it 90 degrees in X and apply the rotation
Slide the y-dimension value. A plane perfectly flat in such axis shouldn't scale like that.

Also notice how the y-scale value goes crazy when doing step 2, and the value snaps to zero even if the operation is cancelled.

**System Information** Operating system: Graphics card: **Blender Version** Broken: (example: 2.80, edbf15d3c044, master, 2018-11-28, as found on the splash screen) **Short description of error** Reopening #75562 here again. I'm sure this is a bug. **Exact steps for others to reproduce the error** 1. Add a plane and rotate it 90 degrees in X and apply the rotation 2. Slide the y-dimension value. A plane perfectly flat in such axis shouldn't scale like that. Also notice how the y-scale value goes crazy when doing step 2, and the value snaps to zero even if the operation is cancelled.

Pasang Bomjan commented

2020-04-10 21:57:41 +02:00

Added subscriber: @Pasang

Evan Wilson commented

2020-04-11 08:37:07 +02:00

Added subscribers: @brecht, @EAW

Evan Wilson commented

2020-04-11 08:37:07 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Evan Wilson commented

2020-04-11 08:37:07 +02:00

I can confirm. The two top vertices have a Y location of -0, while the two bottom ones have a Y location of 0. This is a floating point math issue, for which there is no general efficient solution.

You can fix this simple example by going into edit mode, selecting all, and scaling the Y axis to 0. This eliminates the negative zeros. I realize that your simple (well made and annotated 👍 ) test file and video in the other report is just an example, and this work around might not work in more complex scenarios.

Given @brecht's comment that I linked above, I can't say for certain if this is considered a bug or a known issue.

I can confirm. The two top vertices have a Y location of -0, while the two bottom ones have a Y location of 0. This is a [floating point](https:*en.wikipedia.org/wiki/Signed_zero) math issue, [for which there is no general efficient solution.](https:*developer.blender.org/D4795#109815) You can fix this simple example by going into edit mode, selecting all, and scaling the Y axis to 0. This eliminates the negative zeros. I realize that your simple (well made and annotated 👍 ) test file and video in the other report is just an example, and this work around might not work in more complex scenarios. Given @brecht's comment that I linked above, I can't say for certain if this is considered a bug or a known issue.

Pasang Bomjan commented

2020-04-11 11:35:40 +02:00

@EAW, Ok, and any idea why it snaps to zero even when cancelled?