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I found, that some faces are blinking (like Moire effect) while rotating in preview.

Is this normal?

Reboot didn't help. Blender version is 2.76

OS is Windows 10 prof.

Video is GeForce GTX 770.

Sample: https://www.youtube.com/watch?v=oQ6rB7XbShk

UPDATE

The following message appears upon start:

enter image description here

(AL lib: (EE) UpdateDeviceParams: Failed to set 44100hz, got 48000hz instead)

UPDATE

I found it is the problem of my model, since it affects only half of it:

enter image description here

I was extruding circle and the split is located exactly where I started. I.e., right half was extruded from the circle to the right, and the left half was extruded from the left vertices to the left.

Also I noticed extruding behavior changed when I was doing this: Unconstrained extrusion?

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    $\begingroup$ You have lots of overlapping faces in your model that cause Z-fighting (blender.stackexchange.com/questions/5441/…). See also related questions: blender.stackexchange.com/questions/21216/… or blender.stackexchange.com/questions/21/… $\endgroup$
    – Carlo
    Commented Nov 20, 2015 at 15:32
  • $\begingroup$ You also have a lot of inverted normals, try removing doubles with [W] > remove doubles, then recalculate the normals with [Ctrl]+[N]. $\endgroup$
    – PGmath
    Commented Nov 20, 2015 at 15:46
  • $\begingroup$ @carlo Just for the record, I would leave this question open. All of those questions are talking about the black squarish Z-fighting seen when rendered, this is referring to to the way it looks in the viewport. If I had this problem in the viewport (and didn't think to render it) I may not know that that is the same thing since they do look slightly different. $\endgroup$
    – PGmath
    Commented Nov 20, 2015 at 16:25

1 Answer 1

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The display glitch you are seeing on your model is a common 3D graphics artifact called Z-fighting.

From Wikipedia:

Z-fighting is a phenomenon in 3D rendering that occurs when two or more primitives have similar values in the z-buffer. It is particularly prevalent with coplanar polygons, where two faces occupy essentially the same space, with neither in front. Affected pixels are rendered with fragments from one polygon or the other arbitrarily, in a manner determined by the precision of the z-buffer.

Basically what is happening is when two coplanar faces occupy the exact same space Blender doesn't know which of the two faces to render. The faces are "fighting" which one is closer to the camera. So due to floating-point calculations in the distance to the camera (z-buffer), various points of the shared surface are rendered as one of the faces, and other parts are rendered as the other face. This results in the strange looking Moire-like glitch you are witnessing.

To fix this problem you can first try to remove double vertices with W > Remove Doubles. This will merge vertices which occupy essentially the same location, you can adjust the tolerance in the F6 parameters menu immediately after removing doubles. In some cases removing doubles won't be enough to fix the z-fighting, in these cases you will just have to go through manually and remove the overlapping faces.

I suggest you read up on manifold and non-manifold geometry.

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    $\begingroup$ Next time link the dupe, it'll save you the trouble of writing an answer $\endgroup$
    – J Sargent
    Commented Nov 20, 2015 at 16:19
  • $\begingroup$ @NᴏᴠɪᴄᴇIɴDɪsɢᴜɪsᴇ I wouldn't call it a duplicate, the other question is talking about the black squarish Z-fighting seen when rendered, this is referring to to the way it looks in the viewport. If I had this problem in the viewport (and didn't think to render it) I may not know that that is the same thing since they do look slightly different. $\endgroup$
    – PGmath
    Commented Nov 20, 2015 at 16:20
  • $\begingroup$ They both are visible in both cases $\endgroup$
    – J Sargent
    Commented Nov 20, 2015 at 16:56
  • $\begingroup$ @NᴏᴠɪᴄᴇIɴDɪsɢᴜɪsᴇ What I am saying is that they are the same problem, but (slightly) different manifestations of it. $\endgroup$
    – PGmath
    Commented Nov 20, 2015 at 16:58

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