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Lastes Blender versions break parenting in DEMO File - BMW scene
Closed, ResolvedPublicBUG

Description

System Information
Operating system: Windows 10
Graphics card: Vega 64

Blender Version
Broken: 2.82a and 2.83 -
Worked: 2.80

Short description of error
Downloaded Blender Demo Files (https://www.blender.org/download/demo-files/)

In case of BMW_27 file (dated 2016-02-26, one of the wheels parenting is lost in current versions. See attached photo of the discrepancy.

Exact steps for others to reproduce the error
Just opened the file in different blender builds.

NOTE - in latest build 94b8166a8b05 - part of the wheels vanish but render OK. this also occurs in Classroom file (chairs vanish but render OK)

Should I raise separate bug report on 2.83?

Event Timeline

Germano Cavalcante (mano-wii) changed the task status from Needs Triage to Confirmed.Wed, Mar 25, 7:28 PM
Germano Cavalcante (mano-wii) triaged this task as High priority.
Germano Cavalcante (mano-wii) changed the subtype of this task from "Report" to "Bug".

I can confirm.
This is a problem in the Workbench, if you switch to Eevee the missing objects reappear.

I am not able to reproduce. Using classroom.blend or bmw27_cpu.blend freshly downloaded from blender.org
rB671b6d41c408: CMake: Fix Blender.app creation/modification time Linux Intel

Here the problem is evident:

Operating system: Windows-10-10.0.18941 64 Bits
Graphics card: Radeon (TM) RX 480 Graphics ATI Technologies Inc. 4.5.13586 Core Profile Context 19.50.01.05 26.20.15001.5006

@Clément Foucault (fclem), can you repro the problem?

I can reproduce with proprietary drivers on linux. Seems linked to instanced rendering.

This is caused by MultiDrawIndirect in conjunction with (hypothetically) reading a default non enabled attribute (which should give default color of vec4(0.0, 0.0, 0.0, 1.0)). The attrib is not even always read.

if (materialIndex == 0) {
  color_interp = ac.rgb;
}

My instinct tells me that the driver creates a dummy VBO for non enabled attribs but this VBO is not configured correctly when doing MDI so we get an out of bound read and undefined behavior.

This is a bug in the GL driver implementation.

@Grzegorz Wereszko (Prodeous) can you upload the system-info.txt generated from blenders' Help menu to this ticket. This file contains information about the driver you are using.

Jeroen Bakker (jbakker) changed the task status from Confirmed to Needs Information from User.Thu, Mar 26, 5:11 PM

{F8429216}I used Radeon 20.3.1 drivers (latest). Note that all three version (as per origianl post) were done on the same system, so not a driver issue. eager to test that workaround when its out. but for completeness attached the requested system info file.

Another point, and the original BUG report. The "Parenting" of the wheel on the BMW27 file is broken after version 2.80. in 2.82a and latest the wheel is rotated almost 180*.. not a full 180, but definitley not as it should.

I can't replicate this with other files, but this file was pulled from blender demo files, so should be possible to replicate.