Grease pencil can't be instanciated using collection instance #72481

New Issue

Yannick Castaing · 2019-12-16T19:18:21+01:00

Yannick Castaing commented

2019-12-16 19:18:21 +01:00

System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.60

Blender Version
Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-11-20 14:27, hash: 26bd5ebd42
Worked: (optional)

Short description of error
When we are making more than one link of a same collection, from another scene, if this collection contains one grease pencil, this one can't be dupplicated, unlike other stuff (like geometry, or whatever).
(Maybe it's due to the fact that grease pencil is animated, but if animation playback is disabled, it shouldn't be a problem).

Exact steps for others to reproduce the error

create a scene
create a grease pencil monkey inside the default collection, which we can rename "plouf"
create a new scene
add the collection "plouf" as a collection instance
dupplicate or add again the collection "plouf"

the grease pencil is disappearing from the first instance of plouf, and goes to the second instance of plouf, whereas they are the the same

CollectionLinked.blend

**System Information** Operating system: Windows-10-10.0.17134 64 Bits Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.60 **Blender Version** Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-11-20 14:27, hash: `26bd5ebd42` Worked: (optional) **Short description of error** When we are making more than one link of a same collection, from another scene, if this collection contains one grease pencil, this one can't be dupplicated, unlike other stuff (like geometry, or whatever). (Maybe it's due to the fact that grease pencil is animated, but if animation playback is disabled, it shouldn't be a problem). **Exact steps for others to reproduce the error** - create a scene - create a grease pencil monkey inside the default collection, which we can rename "plouf" - create a new scene - add the collection "plouf" as a collection instance - dupplicate or add again the collection "plouf" the grease pencil is disappearing from the first instance of plouf, and goes to the second instance of plouf, whereas they are the the same [CollectionLinked.blend](https://archive.blender.org/developer/F8226699/CollectionLinked.blend) ![image.png](https://archive.blender.org/developer/F8226710/image.png)

Yannick Castaing commented

2019-12-16 19:18:21 +01:00

Added subscriber: @BoUBoU

Germano Cavalcante commented

2019-12-18 13:38:52 +01:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2019-12-18 13:38:52 +01:00

Similar to #63563, but in this case the stroke is visible.

Jacques Lucke commented

2020-01-22 15:04:54 +01:00

Added subscriber: @JacquesLucke

Jacques Lucke commented

2020-01-22 15:04:54 +01:00

When I try to open this file I get a stack-use-after-scope error when accessing ob->... in GPENCIL_draw_scene.

I found that the issue is that the pointer to ob is stored in a cache in GPENCIL_cache_populate. However, in this case, ob points to an object that lives on the stack in DEGObjectIterData.temp_dupli_object created by DEG_OBJECT_ITER_FOR_RENDER_ENGINE_BEGIN in DRW_draw_render_loop_ex.

This seems to be a deeper issue in the way grease pencil object duplis are drawn, but I don't understand the full context here...

@fclem, Should GPENCIL_cache_populate be allowed to store pointers to objects passed into it?

When I try to open this file I get a `stack-use-after-scope` error when accessing `ob->...` in `GPENCIL_draw_scene`. I found that the issue is that the pointer to `ob` is stored in a cache in `GPENCIL_cache_populate`. However, in this case, `ob` points to an object that lives on the stack in `DEGObjectIterData.temp_dupli_object` created by `DEG_OBJECT_ITER_FOR_RENDER_ENGINE_BEGIN` in `DRW_draw_render_loop_ex`. This seems to be a deeper issue in the way grease pencil object duplis are drawn, but I don't understand the full context here... @fclem, Should `GPENCIL_cache_populate` be allowed to store pointers to objects passed into it?

Jacques Lucke commented

2020-01-22 15:09:13 +01:00

Added subscriber: @fclem