Maniphest T47063

Perspective camera - start clipping value producing artefacts in viewport and render
Closed, Archived
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Assigned To
Brecht Van Lommel (brecht)
Authored By
Neil Larsen (Big_Fan)
Dec 27 2015, 2:57 AM
Tags
  • BF Blender
Subscribers
Brecht Van Lommel (brecht)
Neil Larsen (Big_Fan)

Description

System Information
Win7 pro
Nvidia Quadro K620

Blender Version
Broken: 2.76b
Worked: not sure which release this began - have noticed this occasionally before but could work around my intent and attributed it to some random hardware/driver issue however now believe its a bug or coders oversight.

Short description of error
When rendering a scene of models of large dimensions say 60-250m(BU) in perspective mode if the start of camera clipping is set to the minimum 0.001 it produces artefacts visible in the viewport and in the render. It appears a bit like a normal or doubles issue but isn't AFAIK. These are not apparent if the camera view is changed to orthographic or in smaller close scenes. If the start of clipping value is raised while in perspective the issue gradually diminishes and appears to be resolved by 0.1 or it was in the particular scene this was noticed in. The file is too big to share but pictures of issue are attached

pictures of bug.zip1 MBDownload
Possibly it arises as some sort of precision error or such.

Exact steps for others to reproduce the error
See attached pictures for evidence of issue

Related Objects

Event Timeline

Neil Larsen (Big_Fan) created this task.Dec 27 2015, 2:57 AM
Neil Larsen (Big_Fan) raised the priority of this task from to 90.
Neil Larsen (Big_Fan) updated the task description.
Neil Larsen (Big_Fan) added a project: BF Blender.
Neil Larsen (Big_Fan) edited a custom field.
Neil Larsen (Big_Fan) added a subscriber: Neil Larsen (Big_Fan).
Neil Larsen (Big_Fan) added a comment.Dec 27 2015, 3:09 AM

BTW the issue is independent of the using of Freestyle for rendering as in this case.

Brecht Van Lommel (brecht) changed the task status from Unknown Status to Archived.Dec 27 2015, 3:31 AM
Brecht Van Lommel (brecht) claimed this task.
Brecht Van Lommel (brecht) added a subscriber: Brecht Van Lommel (brecht).

See the explanation of clip start and end in the manual:
https://www.blender.org/manual/editors/3dview/display.html

It's not considered a bug, but a limitation of how OpenGL / DirectX / graphics cards work. The Blender renderer works the same way. It could be improved with rasterization methods that are better than what graphics cards do, but it's beyond the scope of the bug tracker.

Neil Larsen (Big_Fan) added a comment.Dec 27 2015, 5:41 AM

Ok thanks. I gather you have just added that wiki note for the benefit of others who see the same thing...
I think it is a little unsatisfactory that the UI setting allows the unwary user to experience this situation though. Honestly I feared my graphics card was developing a fault over the last year before I accidentally found a 'workaround' today. Call me dumb if you like.
Any how could there not be a simple avoidance of this issue by say making the start of clipping 0.0001 x the end value? So for example in the 3d view and for the camera a 1000BU end clip has a min start clip of 0.1. I am not sure anyone would want a scene bigger than 5000x5000x5000 for a city or sea scape or whatever but who knows... Maybe it is more complex than that. Thanks again.

Neil Larsen (Big_Fan) added a comment.Dec 27 2015, 6:03 AM

Last request - can you please use your moderator access to remove my attached pics. Thanks, and have a good New Year.

Brecht Van Lommel (brecht) added a comment.Dec 27 2015, 5:42 PM

That note has been in the documentation for a while, it's a common point of confusion that we unfortunately have no good solution for.

It's not possible to avoid the issue automatically, the appropriate clip start/end values depend on the scene, what improves the issue in one scene makes it worse in another.

I've removed the attachment file contents on the server, the file is still listed but if you click to download it will not work.

Richard Antalik (ISS) mentioned this in T76877: Orthographic Grid Artifacts when Clipping > 95km.May 19 2020, 1:18 PM