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Earlier I've answered a question where the issue was that in edit mode, the 3D view fully or partially renders the mesh as if limit selection to visible was not ticked, when the 3D view clip start is set to 0.01 or lower, (or apparently when the 3D view clip end is set to 100000 or higher and view is set to Ortho - but I'm more interested in the first scenario).

If someone here knows, I'd really love to know why this is happening. The default values are 0.1 and 1000. So you'd expect not to run into such an issue when changing the values to 0.01 and 100 for example. By default 1 Blender unit equals 1 meter, this means that if you want to keep this default but work on an object that is the size of something that you can hold in your hand, then you'll run into this issue. Designing objects that are the size of your palm is not a very rare thing to do.

Furthermore, this issue does not happen when the 3D view is set to camera. Doesn't that prove that it should be able to work as expected in user view as well? Or is there even a way to get rid of this issue when working with a view clip start of 0.01 in Edit Mode? It should also be noted that sculpt mode is not affected either.

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  • $\begingroup$ Related: blender.stackexchange.com/a/1387/599 $\endgroup$
    – gandalf3 ♦
    Apr 4, 2016 at 0:36
  • $\begingroup$ Also Related: blender.stackexchange.com/a/23693/2217 $\endgroup$
    – David
    Apr 4, 2016 at 3:29
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    $\begingroup$ related, but in those links it's about having a huge range in between clips start and clip end. But no matter how low you set clip end, you won't get rid of the behavior described here when clicp start is set to 0.01. It seems like an arbitrary absolute limit. $\endgroup$
    – coCoKNIght
    Apr 4, 2016 at 5:13

2 Answers 2

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From my purely theoretical and limited technical knowledge on the matter real time rendered scenes (like in OpenGL or DirectX) use a Z depth buffer to determine the distance to camera of any object or vertex on screen.

That Z buffer is basically a black and white image of the screen, where for every pixel there can be a a value from 0 to 255 (black to white) for distance information. This image is then used to determine what is visible and what is not and build the viewport image. (There may be other wizardry involved for increased precision like double precision or using other color channels for more possible depth values, by my technical knowledge is limited here)

If the clipping distances (Start and End)are too far apart these 255 (or whatever) shades of grey are not gonna cut it and will not be enough for all the possible depth differences on screen, so artifacts and errors start appearing on screen, like the so called Z-Fighting on co-planar or coinciding faces, or these seemingly ghost-like edges and see-through faces in your mesh.

Now in theory changing clipping values but keeping them in sync should have no ill effects, but there are probably other variables like your graphics card capabilities, drivers, etc.

I would also like to know more about this, so if Blender developer, programmer or someone with more technical knowledge care correct me or enlighten us, I would be very grateful.

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This issue seems to be fixed since 2.8

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