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Maniphest T36429

Bevel modifier with smooth shading - bug
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Description

--- Operating System, Graphics card ---
Windows 7 Pro, GeForce 550GTX

--- Blender version with error, and version that worked ---
2.68.0 r58368 official build

--- Short description of error ---
I'm trying to do a nice highly detailed building block. I want to use bevel modifier (with edge weights) because it's non destructive and gives me more freedom than doing "hard coded" subsurf with edge-loops everywhere. When I'm applying smooth shading on with more bevel step than 1 there's issue with visible edges between faces that should be smooth - everything is on the attached screenshot.

--- Steps for others to reproduce the error (preferably based on attached .blend file) ---
.blend file attached


Event Timeline

Luke (yoda) edited a custom field.Aug 10 2013, 9:40 AM
Luke (yoda) attached 1 file(s): F24224: bevel_bug1.png.
Luke (yoda) attached 1 file(s): F24225: lego_v2.0_test_3.blend.
Luke (yoda) added a comment.Aug 10 2013, 10:00 AM

Ok, after some additional tests it look like that only non glossy shading is affected - see second screenshot

Luke (yoda) attached 1 file(s): F24226: bevel_bug2.png.Aug 10 2013, 10:04 AM

[attachment]

Ton Roosendaal (ton) added a comment.Aug 23 2013, 6:39 PM

Howard: could you check this report? Thanks!

Howard Trickey (howardt) added a comment.Aug 23 2013, 7:21 PM

Thanks, I will look into this after I fix some other bugs in my queue (working some knife ones right now).

Howard Trickey (howardt) added a comment.Jan 24 2014, 9:06 PM

I looked at this and am not convinced that the bevel modifier is implicated here at all. I removed all modifiers and still could not get the faces to smooth shade with cycles. I think I will assign this to brecht to see if he can see what is going on. If it is the fault of Bevel, I guess it would be because bevel didn't properly propagate some flag or property to newly created edges, faces, or vertices. If someone could tell me what the property is, feel free to reassign this bug back to me.

Howard Trickey (howardt) reassigned this task from Howard Trickey (howardt) to Brecht Van Lommel (brecht).Jan 24 2014, 9:07 PM
Brecht Van Lommel (brecht) changed the task status from Unknown Status to Unknown Status.Feb 6 2014, 7:22 PM

This appears to be another instance of the dreaded shadow terminator problem:
http://archive.blender.org/development/release-logs/blender-234/misc-improvements/
http://www.geekshavefeelings.com/x/wp-content/uploads/2010/03/Its-Really-Not-a-Rendering-Bug-You-see....pdf

I'd like to find a better solution for this but it's not considered a bug at the moment. Basically what happens is that while the shading can make the geometry looks smooth, the true shape of the geometry can be revealed by the shadows. The only solution in Cycles now is to use more subdivision or tweak the light size and location to avoid it.