Data Preview of group containing only group instances is empty. #49423

New Issue

Duarte Farrajota Ramos · 2016-09-22T06:18:02+02:00

2016-09-22 06:18:02 +02:00

System Information
Windows 7 64bits Nvidia Gtx580 + Gtx980ti

Blender Version
Broken: 2.78rc2 and at least since 2.77
Worked: Unknown, probably unsupported or a limitation of the system since the beginning

Short description of error
Batch-Generate data previews for a group containing only other group instances gives empty preview

Exact steps for others to reproduce the error

On a default startup file select the default cube
Assign it to a group (henceforth called GroupA)
Now add a new group instance of GroupA
Select the previously created group instance of GroupA (Empty Object type)
Now add it to a new group (henceforth calle GroupB)
Save the file and close it
Go to File > Data Previews > Batch Generate Data Previews
Select the previously saved file
You can select the Groups option only
When done browse to Append/Link from that file, and change the file browser to Thumbnails mode

You will notice that the data preview for GroupB is empty instead of displaying the cube

If you add any other mesh object directly to GroupB and retry to generate the data previews, both the new mesh and the geometry instanced through the dupligroup will correctly appear in the preview.

This may well be a limitation of the current system, and not a bug per-se.

**System Information** Windows 7 64bits Nvidia Gtx580 + Gtx980ti **Blender Version** Broken: 2.78rc2 and at least since 2.77 Worked: Unknown, probably unsupported or a limitation of the system since the beginning **Short description of error** Batch-Generate data previews for a group containing only other group instances gives empty preview **Exact steps for others to reproduce the error** - On a default startup file select the default cube - Assign it to a group (henceforth called **GroupA**) - Now add a new group instance of **GroupA** - Select the previously created group instance of GroupA (Empty Object type) - Now add it to a new group (henceforth calle **GroupB**) - Save the file and close it - Go to *File > Data Previews > Batch Generate Data Previews* - Select the previously saved file - You can select the *Groups* option only - When done browse to Append/Link from that file, and change the file browser to Thumbnails mode You will notice that the data preview for **GroupB** is empty instead of displaying the cube If you add any other mesh object directly to **GroupB** and retry to generate the data previews, both the new mesh and the geometry instanced through the dupligroup will correctly appear in the preview. This may well be a limitation of the current system, and not a bug per-se.

Duarte Farrajota Ramos commented

2016-09-22 06:18:02 +02:00

Changed status to: 'Open'

Duarte Farrajota Ramos commented

2016-09-22 06:18:02 +02:00

Added subscriber: @DuarteRamos

Bastien Montagne commented

2016-09-22 16:36:37 +02:00

Added subscriber: @mont29

Bastien Montagne commented

2016-09-22 16:36:37 +02:00

Please follow our submission template and guidelines and make a complete, valid bug report, with required info, precise description of the issue, precise steps to reproduce it, small and simple .blend and/or other files to do so if needed, etc.

Please follow our submission template and guidelines and make a complete, valid bug report, with required info, precise description of the issue, precise steps to reproduce it, **small and simple** .blend and/or other files to do so if needed, etc.

Duarte Farrajota Ramos commented

2016-09-22 20:06:42 +02:00

Certainly, here is a demo file.
Browse GroupDatablock_Preview.blend for link/append, set the file browser for thumbnail display, go into GroupDatablock_Preview.blend>Groups category.

Now inspect the available group thumbnails, if you notice Group A has a correct datablock preview. (It contains only that table-like mesh)
Group B contains only an instance of Group A alone (empty object with dupligroup of Group A) and displays an empty preview <- Incorrect Preview
Group C also contains an instance of Group A (empty object with dupligroup of Group A) but with an additional Susane Mesh object, and already displays a correct datablock preview.

From my purely speculative point of view it looks like whatever script is in charge of creating the datablock previews fails to correctly frame an object if that object is an empty. Maybe it can't calculate it's extents of the linked geometry?

Certainly, here is a demo file. Browse [GroupDatablock_Preview.blend](https://archive.blender.org/developer/F366323/GroupDatablock_Preview.blend) for link/append, set the file browser for thumbnail display, go into *GroupDatablock_Preview.blend>Groups* category. Now inspect the available group thumbnails, if you notice **Group A** has a correct datablock preview. (It contains only that table-like mesh) **Group B** contains only an instance of **Group A** alone (empty object with dupligroup of Group A) and displays an empty preview <- Incorrect Preview **Group C** also contains an instance of **Group A** (empty object with dupligroup of Group A) but with an additional Susane Mesh object, and already displays a correct datablock preview. From my purely speculative point of view it looks like whatever script is in charge of creating the datablock previews fails to correctly frame an object if that object is an empty. Maybe it can't calculate it's extents of the linked geometry?

Philipp Oeser commented

2016-09-24 13:00:39 +02:00

Added subscriber: @lichtwerk

Philipp Oeser self-assigned this 2016-09-24 13:00:39 +02:00

Philipp Oeser commented

2016-09-24 13:00:39 +02:00

Confirmed.
@mont29 think this is your playground, but assigning to me cause I think I can get there and support this, will have a look (possibly this weekend). If it is real quick for you and you've got time, feel free to claim back...

Confirmed. @mont29 think this is your playground, but assigning to me cause I think I can get there and support this, will have a look (possibly this weekend). If it is real quick for you and you've got time, feel free to claim back...

Philipp Oeser commented

2016-09-24 15:36:25 +02:00

k, have it working for the case of group instances in groups, will do some further thinking/checking and post patch later/tomorrow...