I'm trying to create a glass bottle with a cork and the "map art" function isn't working properly. I turned a cork pattern into a symbol and applied it to the top and sides of the cork (which looks excellent btw), but as you can (barely) see in the picture it's leaving a white outline around the edge of the front and back. Is there a trick to fixing this that I'm not aware of yet? I'm still pretty new with illustrator.
This isn't a full screen version of the bottle so it's nearly impossible to see the white line.
...but as you can (barely) see...
I can't see it at all. Zoom into the problem area and take another screenshot.
It's probably just the way Illustrator antialiases (or doesn't) edges of bitmaps that are mapped to 3D Effect objects, and you may not be able to eliminate it completely without some kind of post-editing. There is a multitude of settings that may affect the rendering in a particular case; resolution of the mapped raster image, document raster effects setting, how you've scaled the raster image in the mapping window....
So without seeing your particular file, or at least knowing all the parameters, one can only guess. When mapping raster images, 3D Effect's rendering is affected by your Document Raster Effects setting. So that's a first thing you might try. (Don't go nuts with it; bear in mind the actual resolution needed for your final delivery purpose.) That will likely minimize the artifact, but may not eliminate it completely.
Illustrator's 3D Effect is not a high-end modeler or renderer. It's kind of a "down & dirty" feature for simple extrusions, etc. As such, it's often best to use it as a "construction guide" or a "rough out tool" for artwork that will be touched up or redrawn or enhanced after (or that is simply intended as a concept presentation, which doesn't need to be perfect anyway).
For example, depending on the resolution parameters involved, simply exporting the final as a raster image (which is often necessary anyway for final delivery) can effectively "smooth away" or "average out" edge artifacts. The fact that you had to mention that the undesirable artifact is difficult to see is a case-in-point. Your screenshot is your "final delivery" for the purpose of posting in this forum. At that screenshot's downsampled resolution, no one would notice the artifact that exists in your native file.
Example of what I mean by "post processing":
Always fundamental to getting comfortable with programs like Illustrator is to understand the basic principle that--regardless of what you see onscreen--you are always dealing with instances of a very few basic kinds of objects arranged in a front-to-back stack.
It follows then, that whenever you encounter behavior that is puzzling, you can discover alot (often including the solution you seek) by dissecting the seemingly "special" or "complex" objects you are dealing with, in order to understand what you are actually dealing with. In Illustrator, that means tearing things apart with commands like Expand, Expand Appearance, Ungroup, Clipping Mask>Release, etc., etc.
I think I see what you are referring to on the right and top side of the cork. But if this is printed in four color process I doubt that this will be something anyone will perceive except you.
It looks great, it's very well done or if you wish excellently and therefore leave it be.
This is where I am right now. I'm trying to put the sand in the bottle and "the whitness" is coming up on the edges of the sand. I had someone recommend upping the raster effects ppi, which nearly froze AI (changed to 750ppi), so I changed it back to 350 (what it was set at). It's hardly noticeable on the cork when zoomed at 100%, but is very noticeable on the sand, even when zoomed out. Here is are the zoomed in/out screenshots.