scaling in viewport doesn't work with snap to nearest vertex. #39161

New Issue

Lukas Tönne · 2014-03-13T16:30:36+01:00

mattali commented

2014-03-13 16:30:36 +01:00

(Migrated from localhost:3001)

System Information
All

Blender Version
Broken: 2.70
Short description of error
Scaling an object relative to 3d cursor and with snap to nearest vertex gives random results.

Exact steps for others to reproduce the error
Open attached file, place mouse cursor on the bottom-left vertex of the active cube, hit S, move cursor to nearest vertex of the bottom cube : it scales properly, now press ctrl to have it exactly touch the vertex, it scales back to a random position.
bug_scale_snap_closest.blend

**System Information** All **Blender Version** Broken: 2.70 **Short description of error** Scaling an object relative to 3d cursor and with snap to nearest vertex gives random results. **Exact steps for others to reproduce the error** Open attached file, place mouse cursor on the bottom-left vertex of the active cube, hit S, move cursor to nearest vertex of the bottom cube : it scales properly, now press ctrl to have it exactly touch the vertex, it scales back to a random position. [bug_scale_snap_closest.blend](https://archive.blender.org/developer/F80967/bug_scale_snap_closest.blend)

mattali commented

2014-03-13 16:30:36 +01:00

(Migrated from localhost:3001)

Changed status to: 'Open'

mattali commented

2014-03-13 16:30:36 +01:00

(Migrated from localhost:3001)

Added subscriber: @mattali

Lukas Tönne commented

2014-03-15 12:00:36 +01:00

Added subscriber: @LukasTonne

Lukas Tönne commented

2014-03-15 12:00:36 +01:00

This behavior is admittedly awkward. Scaling is a very limited operation (1 degree or freedom only), which makes it rather unsuitable for snapping in the way it works with other transform modes. I'm not sure how this could fit better into the snapping system, but it's not a bug or regression.

Afaik the snapping works like roughly this:

Select the element indicated by the mouse (the orange circle)
Select the closest corresponding element of the transformed object (in untransformed state)

Calculate a transform such that the distance (whatever the actual metric is) between snap target and selected element becomes minimal.

The first 2 steps should be independent of the transform mode, but the 3rd can be quite tricky depending on the mode and additional constraints. For scaling there might not be an efficient way to calculate such a transform or it may require an iterative approach. Apart from that you cannot expect the elements to snap together precisely, due to the inherent limitation of (uniform) scaling to 1 degree of freedom.

This behavior is admittedly awkward. Scaling is a very limited operation (1 degree or freedom only), which makes it rather unsuitable for snapping in the way it works with other transform modes. I'm not sure how this could fit better into the snapping system, but it's not a bug or regression. Afaik the snapping works like roughly this: - Select the element indicated by the mouse (the orange circle) - Select the *closest* corresponding element of the transformed object (in untransformed state) # Calculate a transform such that the *distance* (whatever the actual metric is) between snap target and selected element becomes minimal. The first 2 steps should be independent of the transform mode, but the 3rd can be quite tricky depending on the mode and additional constraints. For scaling there might not be an efficient way to calculate such a transform or it may require an iterative approach. Apart from that you cannot expect the elements to snap together precisely, due to the inherent limitation of (uniform) scaling to 1 degree of freedom.

Campbell Barton was assigned by Bastien Montagne

2014-03-15 12:06:22 +01:00

Bastien Montagne commented

2014-03-15 12:06:22 +01:00

Added subscriber: @mont29

Bastien Montagne commented

2014-03-15 12:06:22 +01:00

Assigning to Campbell to get its advice here! :)

mattali commented

2014-03-17 07:19:04 +01:00

(Migrated from localhost:3001)

On the same scene, translating on 1 local axis, here Y, works (G Y Y). So blender finds a way to snap that nearest vertex without it to be presicely snapped (also 1 degree of freedom). If blender succeed in finding the right position for that vertex, it can deduce the scale from the new edge length comparing to the old?

mattali commented

2014-03-17 07:21:25 +01:00

(Migrated from localhost:3001)

Scripting it in Python works (makes a 1 axis translation, save snap location, compute new edge length, divide by old edge length, undo trtanslation and scale with that factor).

mathieu menuet commented

2014-08-18 17:24:40 +02:00

Added subscriber: @bliblubli

mathieu menuet commented

2014-08-18 17:24:40 +02:00

Encountered same bug today, can confirm. When used in "nearest vertex" mode, it is for that nearest vertex a translation constrained on the center-nearest vertex axis. Translating on local axis with snap works (GXX combo with snap active for example). So it is possible to determine a perfect scale factor too, at least in "nearest vertex" (by doing a 1 axis translation with snap of the nearest vertex and using the given new location to determine the appropriate scale). For modes where no factor can be determined, a warning would be better than the current random scale.

mathieu menuet commented

2014-12-16 18:30:46 +01:00

since 2.73 is mostly a bugfix release, would it be possible to fix such old, waiting bugs? Many professionals prefer polishing over new features, please use this quiet release to polish Blender. Would be a lovely Christmas present :)

Georg K commented

2015-04-05 15:06:20 +02:00

Added subscriber: @georgK

blender-admin commented

2015-08-26 12:42:27 +02:00

This issue was referenced by 3dd16946aa

This issue was referenced by 3dd16946aa43e804d028262f7368346c56ba1045

Campbell Barton commented

2015-08-26 12:47:40 +02:00

Changed status from 'Open' to: 'Resolved'

Campbell Barton closed this issue

2015-08-26 12:47:40 +02:00

mathieu menuet commented

2015-08-28 07:23:48 +02:00

thanks for the fix, it works well with "median" as pivot point but with "individual origins" it breaks.
In attached file:
Scale and choose a vertex with "ctrl" pressed, cube seems to disappear.
To compare, press "G" and choose a vertex for snap, the cube's center is moved as a cube (also individual origins could make all selected verts move to that position making a point instead of a cube?) to that vertex.
Scale with "median" as pivot, it works
bug scale individual origins.blend

So maybe to make it consistent, make "individual origins behave like median.

thanks for the fix, it works well with "median" as pivot point but with "individual origins" it breaks. In attached file: Scale and choose a vertex with "ctrl" pressed, cube seems to disappear. To compare, press "G" and choose a vertex for snap, the cube's center is moved as a cube (also individual origins could make all selected verts move to that position making a point instead of a cube?) to that vertex. Scale with "median" as pivot, it works [bug scale individual origins.blend](https://archive.blender.org/developer/F228656/bug_scale_individual_origins.blend) So maybe to make it consistent, make "individual origins behave like median.

Campbell Barton commented

2015-10-16 06:18:31 +02:00

@bliblubli

While we try to keep track of all reports (even updates to closed ones), they do get overlooked sometimes since theres a lot of activity.

Please open new reports if you find further problems, you can always reference other reports if you think they're related.

@bliblubli While we try to keep track of all reports (even updates to closed ones), they do get overlooked sometimes since theres a lot of activity. Please open new reports if you find further problems, you can always reference other reports if you think they're related.

mathieu menuet commented

2015-10-16 08:34:19 +02:00

Ok, as it's stil not resolved by last commit, I made https://developer.blender.org/T46505.

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scaling in viewport doesn't work with snap to nearest vertex. #39161

Calculate a transform such that the distance (whatever the actual metric is) between snap target and selected element becomes minimal.