I've started learning blender recently and bumped into some weeeird stuff. The keyboard and guitar appea like that if I render with Cycles and can't figure out why. I already tried recalculating normals. Looks fine with Eevee.
That is a rendered image. Here is how it looks in edit mode. Anything else I can screenshot to make it more clear? Materials dont fix nor cause the problem. Thanks
The problem is that you have faces that's located at the same position. Take a look at example. Here is the default cube in cycles:
Nothing special. Now I duplicate the cube and move it in x direction, while Y and Z remains unchanged.
As you see, there is a black where faces overlaps.
Now I will move cube so that Y ans Z positions will be different:
This also apples on faces in the same objects. So any time then you will have overlapping faces, you will get this problem, like here at your guitar central part looks like there 2 faces overlaps each other at the middle:
EEVEE will also affect by this issue, but you should have different materials, so that you will see the glitch called z-fighting:
