Maniphest T60587

adaptive displacement seams between dupli faces
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Assigned To
Brecht Van Lommel (brecht)
Authored By
michael campbell (3di)
Jan 17 2019, 8:14 AM
Tags
  • BF Blender
Subscribers
Brecht Van Lommel (brecht)
Eclaires (EclairesRa)
Jacques Lucke (JacquesLucke)
michael campbell (3di)

Description

System Information
Operating system: win10
Graphics card: gtx 1070

Blender Version
Broken: 2.79b

There are visible seams between objects duplicated using dupli faces of a plane.

For example I have a section of road which needs to be 5km long and arrays are going to use too much memory, so I make a one face plane the exact size of the section of road, add an array to the plane, set its duplication method to face, and then parent the section of road to it. Add a subidivision modifier to the road, and turn on adaptive. I also set the texture co-ordinate node in the road material to object and populate the object to get the co-ordiantes from as the plane. The result is that although the texture is seamless, the micro displacement has a very noticeable crack between each duplication.

I'm guessing this is possible to fix, as the displacement works correctly if I use just an array on the road section even with merge disabled.

Event Timeline

michael campbell (3di) created this task.Jan 17 2019, 8:14 AM
Jacques Lucke (JacquesLucke) lowered the priority of this task from 90 to 30.Jan 17 2019, 10:30 AM
Jacques Lucke (JacquesLucke) added a subscriber: Jacques Lucke (JacquesLucke).

Please upload a simple .blend file that shows the issue (if you use textures, don't forget to pack them into the file). Also a screenshot would be helpful.

Brecht Van Lommel (brecht) changed the task status from Unknown Status to Unknown Status.Mar 8 2019, 5:06 PM
Brecht Van Lommel (brecht) claimed this task.
Brecht Van Lommel (brecht) added a subscriber: Brecht Van Lommel (brecht).

Closing due to lack information to investigate.

michael campbell (3di) changed the task status from Unknown Status to Unknown Status.Mar 8 2019, 5:32 PM

adaptive displacement bug.blend849 KBDownload

file attached.

michael campbell (3di) added a comment.Mar 8 2019, 5:35 PM

michael campbell (3di) added a comment.Mar 8 2019, 5:36 PM

texture is seamless between duplicates (see right hand object which has same material minus the displacement).

michael campbell (3di) added a comment.Mar 8 2019, 5:37 PM

normal map works correctly:

Brecht Van Lommel (brecht) changed the task status from Unknown Status to Unknown Status.Mar 8 2019, 6:18 PM

The Noise Texture is not seamless actually, it's intended to not show any repetitive patterns. You'd have to use an image texture or node setup that is seamless.

If you look closely at the textures on the left and right they are not the same.

Adaptive displacement is also not a good fit for this, since the number of subdivs on both ends may not be the same, it depends on distance to the camera.

michael campbell (3di) changed the task status from Unknown Status to Unknown Status.EditedMar 8 2019, 6:26 PM
michael campbell (3di) raised the priority of this task from 30 to Normal.

Hi, the object, mapping, and noise are identical on both left and right models. This is just an example file, the client file was using a seamless texture from poligon, and the results where the same. No matter how high the subdiv's are increased or how close the camera is, the result is still a visible seam between instances.

michael campbell (3di) added a comment.Mar 8 2019, 6:39 PM

with seamless texture:

michael campbell (3di) added a comment.Mar 8 2019, 6:45 PM

with displacement:

without displacement (same camera view):

michael campbell (3di) added a comment.Mar 8 2019, 6:56 PM

A fix would probably be to make sure a change in subdivision cant occur where two instances meet.

Brecht Van Lommel (brecht) triaged this task as 30 priority.Mar 8 2019, 7:08 PM

You can't use adaptive subdivision for this purpose, we don't consider that a bug.

If you have an example .blend without adaptive subdivision and with a seamless texture we can look at it. If not there is nothing to fix here.

michael campbell (3di) added a comment.Mar 8 2019, 7:11 PM

Here's the problem, the adaptive subdivision is being carried out on the first instance only, so that the end of the first instance is low poly, but then it meets back up with the high poly end when it's repeated. Would it be possible to perform the adaptive subdivision as it currently does, but limit the adaptivity to the inner part of the mesh, so that the outmost loop of polygons all get the same number of subdivisions as whatever the highest value on the mesh is (closest to camera).

michael campbell (3di) added a comment.EditedMar 8 2019, 7:12 PM
In T60587#636037, @Brecht Van Lommel (brecht) wrote:

You can't use adaptive subdivision for this purpose, we don't consider that a bug.

If you have an example .blend without adaptive subdivision and with a seamless texture we can look at it. If not there is nothing to fix here.

Brecht, i've just proposed a fix, can you see any problem with the logic? basically give the outer polygon loop of instanced models the same subidivion level so there's never a seam in displacement.

Brecht Van Lommel (brecht) changed the task status from Unknown Status to Unknown Status.Mar 8 2019, 7:15 PM

We have some ideas to do smarter adaptive subdivision for instances, for now the current behavior is as intended. Any improvements in this area are outside the scope of the bug tracker.

We would probably do uniform edge length subdivision for instances, possibly with a detail level based on the distance of the closest instances to the camera.

michael campbell (3di) added a comment.Mar 8 2019, 7:19 PM
In T60587#636042, @Brecht Van Lommel (brecht) wrote:

We have some ideas to do smarter adaptive subdivision for instances, for now the current behavior is as intended. Any improvements in this area are outside the scope of the bug tracker.

We would probably do uniform edge length subdivision for instances, possibly with a detail level based on the distance of the closest instances to the camera.

Yeah, that's basically what I'm suggesting. But definitely not uniform across the entire model, just at the outer polygons (or it's defeating the purpose of adaptivity in the first place). Perhaps not a bug, just an oversight. Would be great to get it fixed though :)

Eclaires (EclairesRa) added a subscriber: Eclaires (EclairesRa).Dec 11 2021, 7:49 PM

When you use displacement - texture displacing geometry what you have, but with separated geometry aka duplicates/instances (not connected verticies) its be doing that kind of artifacts, there is 2 solutions - 1 if its ok merge object duplicates (CTRL + J) and in edit mode press M (merge by distance). 2 you can set in texture extend instead of repeat (should fix problem if you use instances with displace modifier). if its subdivision it dont like separated geometry even when its merged (so you need to connect verticies in edit mode).