turns black when rotating

Hi I i'm trying to render this logo out but I notice that it is black when it is sideways. No idea why it's doing this, any help or tips would be great. Thanks

[![enter image description here][2]][2]

enter image description here

  • $\begingroup$ Can you show screenshots of the object while in Edit mode ? Also could it be that there is some unrenderable object in the scene just behind this one and the black area is visible because this object partially gets inside of that one ? $\endgroup$
    – Mr Zak
    Mar 31 '16 at 21:27
  • $\begingroup$ gyazo.com/2e47b0c99ec3722435b64dec141b8204 gyazo.com/0f5fd0c309438bf2b8a4bd4b5416b2c6 gyazo.com/24c2ad76095f7cf2c63c6f2e34035613 sorry about the links i can't add more than two photos since i'm new. It doesn't appear to be because of some unrenderable object, I unhide everything and moved them and still showing up black. also when I rotate around the object it's not black. Only when I am viewing it completely sideways. $\endgroup$
    – Kevin Doan
    Mar 31 '16 at 21:33
  • 1
    $\begingroup$ Try recalculating normals in Edit mode with all selected (press Ctrl+N). If this doesn't solve please upload the file $\endgroup$
    – Mr Zak
    Mar 31 '16 at 21:40
  • $\begingroup$ did not work :/ thanks for helping here is the file: <img src="http://blend-exchange.giantcowfilms.com/embedImage.png?bid=1156" /> $\endgroup$
    – Kevin Doan
    Mar 31 '16 at 21:43
  • 1
    $\begingroup$ Tbh I don't see anything bad while it's rendered (images are other ones because yours weren't packed into blend, but I don't think this is the reason). The central face is very big 236-Ngon though, which could cause this behaviour because of bad shading of such enormous face; however to fix it you will need to use Grid Fill I think. $\endgroup$
    – Mr Zak
    Mar 31 '16 at 22:15

When you see black artifacts on rendered model and you know that all normals are facing correct direction, then most likely it's still bad shading of faces. It will be present because of inappropriate topology of the mesh.

Taking into consideration your example, the reason for black artifacts is Ngon (face with more than 4 vertices, in your case n = 256) in the middle of the mesh. More than that, this face is non-planar (the vertices which form it aren't located on the same imaginary plane):

Ngon in the middle of the mesh

To fix this first make the face flat (and vertex loop which forms this face being located on flat "surface" too); then either inset the face (more a workaround than a solution) or fill it with new faces.

Start with flattening Ngon.
Use scaling along normals for that (press Alt+Space, choose Normal and scale, see How to flatten a face to avoid distortion (make an ngon planar) for more info).

flatten Ngon

Insetting Ngon

Once face is flat inset it to avoid presence of Ngon near the curved area of the mesh. Press I and change Thickness value of insetting.

insetting Ngon

However this isn't the best solution as the vertices will start overlapping when insetted further than half of the original Ngon. This way is easier though as it creates less geometry which is easier to select / handle with.

Fill with new faces

Delete the big face (choose Faces in Delete menu), select boundary loop and use Grid Fill via Ctrl+F or Mesh > Faces menu in 3D View header:

filled faces

Note that this way create extra geometry at the cost of "all-quads". Beware that this can affect on render times / performance. Also it may be more difficult to handle with bigger amount of faces / verts. You may want to add created faces to a new vertex group while they are selected.

Do the same with second Ngon on the other side of mesh.


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