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I cannot understand why this weird line in appearing in my coffee

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I decreased IOR of my glass and increased density of coffee. I moved light, checked if I have two materials and nothing is working.

It's still there even though I changed the camera view.

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    $\begingroup$ Double-check if the coffee is intersecting the cup glass at all places. You also may want to try moving the light, as it may be the light refracting through the cup walls and reflecting off the surface of the coffee $\endgroup$ – stphnl329 Jan 14 at 15:56
  • $\begingroup$ blender.stackexchange.com/questions/2823/… $\endgroup$ – user1853 Jan 14 at 16:53
  • $\begingroup$ @stphnl329 I checked it very carefully and it is intersecting it. I was moving the light to a various places and changing the light settings and nothing helped. I still have these two lines (this white one and black one a little lower). Going into the edit mode also didn't give me any clues because this line is not any of the edges so it has to be something with light or my materials. Thank you for the help! $\endgroup$ – Joanna Jan 14 at 17:11
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    $\begingroup$ From the images it looks as if it is either a reflection or refraction of the plate edge. Try hiding objects one by one and seeing if any affects it $\endgroup$ – Duarte Farrajota Ramos Jan 14 at 17:14
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    $\begingroup$ It is probably just the reflection of the cup edge, and should actually be there $\endgroup$ – Duarte Farrajota Ramos Jan 14 at 17:38
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It just occurred to me that this is probably a case of reversed normals seeing as the entire shading of the coffee is off. A Normal is a line that comes off perpendicular to a plane. Blender uses these to calculate lighting off the various faces of a mesh, but if they're facing the wrong way (inside rather than outside), then the shading of the object will not look right.

To check if the normals are facing the correct direction, open the Viewport Overlays drop-down menu, and check Face Orientation. If the normals are facing the right way (as in facing in the direction the object is meant to be viewed), than the object will appear blue. If not, it will be red.

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If this is the case, Tab into edit mode with the coffee selected, and press Shift+N to recalculate normals.

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