Mesh Instances randomly not rendering (regression since 3.3)

[TokisanGames]

Godot version

3.3.4 official

System information

Win 10/64 NVIDIA GeForce GTX 1060/PCIe/SSE2

Issue description

Too frequently some meshes won't render in the editor, and sometimes in game. Switching to another scene and switching back, or closing and reopening will temporarily fix it.

We were developing on 3.2.1 and I never had the issue. As we explored the 3.3 branch I started noticing this error. It's frequent enough that it's a problem. It could have happened any time from 3.2.2.

@Arnklit Already reported this in #47051, and provided a test project, but it was closed prematurely. Though since it's intermittent I doubt the core devs will see it until they start making a large scene with tons of objects. @mbrlabs also confirmed the problem in that ticket.

It happens to all sorts of meshes. It has also affected @Zylann's heightmap terrain, one time, in the editor. One quad (say 5mx5m) was invisible and I couldn't get it to become visible until reloading the scene (prior to any of my gdnative work).

Here I'm building a house from a kit. I already had this scene open. I was in another scene, then switched back to it and saw this. I moved the camera closer for the shot:

I switched to the other scene, then came back, and the two meshes rendered again:

The floor is a fairly simple mesh with one wood material. The wall is more complex. Notice in the first picture you can see the shutter and glass. Here is the full object:

This wall object has separate glass and shutter meshes. The mesh that disappeared includes two materials, the same wood used on all objects in all of these pictures, and a rusty metal frame. Both materials on the mesh didn't render, and both materials are visible on all the other meshes.

The mesh instances have their mesh data stored in the tscn file. They were originally imported from fbx, but that file has already been deleted. The textures are separate dds files. The materials are separate binary files, though most of our other materials are tres. Here we are using MTLOD and an immediate geometry node, however I've experienced this on our meshes that are not using MTLOD. These shots are all close enough that we're only looking at LOD0.

I do not believe this is not an issue with LOD, file types or materials. It decides whether it is going to render these objects when the scene opens. Nothing I can do in the scene will get it to render. Not selecting it, moving it, changing visibility, or moving the camera. Only by switching or reopening scenes fixes (or breaks) these meshes.

My console is full of these errors, which repeat when I switch back and forth between my scenes sometimes.

ERROR: get: Condition "!id_map.has(p_rid.get_data())" is true. Returned: __null
   At: ./core/rid.h:150
ERROR: instance_set_transform: Condition "!instance" is true.
   At: servers/visual/visual_server_scene.cpp:713
ERROR: get: Condition "!id_map.has(p_rid.get_data())" is true. Returned: __null
   At: ./core/rid.h:150
ERROR: instance_set_scenario: Condition "!instance" is true.
   At: servers/visual/visual_server_scene.cpp:629
ERROR: get: Condition "!id_map.has(p_rid.get_data())" is true. Returned: __null
   At: ./core/rid.h:150
ERROR: instance_set_visible: Condition "!instance" is true.
   At: servers/visual/visual_server_scene.cpp:780
ERROR: get: Condition "!id_map.has(p_rid.get_data())" is true. Returned: __null
   At: ./core/rid.h:150
ERROR: instance_attach_skeleton: Condition "!instance" is true.
   At: servers/visual/visual_server_scene.cpp:913

Steps to reproduce

Build out a complex scene for a game with a lot of objects to greatly increase your likelihood of seeing the error.
Now at least 3 known gamedevs experience this problem.

Minimal reproduction project

Look in #47051

[Calinou]

Try disabling the BVH in the project settings and see if the issue persists.

[Zylann]

Last time I experienced meshes not rendering with RID errors was in #44642, although you might be hitting another variant of that if you also get it in game.

[lawnjelly]

Try disabling the BVH in the project settings and see if the issue persists.

It's worth a try (just in case there is some indirect effect), but these errors are coming from setting object data, not reading, and the BVH doesn't set anything on objects (or read if I remember correctly, all the data is sent in exactly the same way as octree). Although it could possibly be caused by the client code leaking objects in the BVH, i.e. creating them and not deleting them during a scene change. 🤔

Another experimental option to try if it is was the BVH, is rendering/threads/thread_safe_bvh. This may only be in the 3.4 betas I can't remember when it was added.

I'll see if I can reproduce it.

Also knowing whether it occurs in the latest 3.4 beta would be useful too, just in case it has been fixed since.

There's also an existing RID bug we found in 4.x (#49501) I can't remember if this same vulnerability exists in 3.x. reduz said he would do his own fix but it hasn't materialised yet.

The association with scene switching is interesting. I'm not really familiar with how the editor does scene switching, whether it detaches / attaches branches in a main scene tree or what. It could be there is a dangling reference, maybe a RID or ObjectID that is involved.

EDIT:
The addon in #47051 no longer seems compatible with 3.x dev, so that makes it less useful as an MRP.

[Arnklit]

Yeah I've been seeing this exact same issue on the last two complicated 3D scenes I've made for my "How Good Can I Make Godot Look" series. Sometimes meshes are just gone until you reopen. But yeah it was so random that I thought it was difficult to log a bug on it.

[akien-mga]

Likely the same issue as #50630, and I remember another one with GridMap tiles randomly disappearing but GitHub search is failing me.
#48790 might also be related.

[akien-mga]

For people who are able to reproduce the issue, it would be useful to test and track down which build first introduced the bug.

According to #47051 it dates back at least to 3.2.4 RC 5, and I haven't seen it reported against 3.2.3. So it would be good to confirm that 3.2.3 is not affected, and which 3.2.4 beta or RC build introduced the regression.
https://downloads.tuxfamily.org/godotengine/3.2.4/

[mbrlabs]

Yes i remember that issue. I did a lot of testing back then but could not reproduce it reliably (only happend in the editor for me so it was not that critical). I still occasionally have this problem when working on big scenes.

The earliest version i encountered this with was 3.2.4 beta3. See #47051 (comment)

[akien-mga]

So far it sounds like you might all be on Windows with Nvidia drivers? Not that it's necessarily a factor as that's the most common gamer config ;)