Black spots on the model At the modeling step, I've taken an issue with my model. Around the deleted parts of UV sphere appeared a lot of black spots, which I also have taken with imported model in Unreal Engine 4. 

Its looks like this:



And with enabled "Mesh analysis" (Distortion, with angles between 1 and 0 degrees)



How can I fix this issue? Or maybe it's a trouble of Blender?
I've seen this affect when using "smooth" shading on the model. Changing from Smooth to flat will probably fix this, but then your model also look - well - flat. You might want to subdivide your faces around the area a bit more, which should allow for a smoother shading (toggle back &amp; forth between smooth &amp; flat in Object mode to refresh the shading).