What can I do to get rid of ugly triangles I have a problem with baking textures and ambient occlusion. Weird triangles and artifacts appear at end of process. I have tried (i think) everything on internet like soldify, triangulate faces, recalculate, reinport from .obj format. I'm beginner with blender, so please, could someone find solution to this? All I can add: Corupted Meshes have been made new from plane surface like all others and I join them in to single object.


https://goo.gl/photos/h9463isytcmiqUyq7  

I think problem is with mesh. Because when I import mesh with other program where I can bake AO too, same problem happend.
After looking at your file the problem is very obvious.

You have a situation where your UV are laying on top of one another. For baking purposes you should never have your UVs position over one another. All islands must have their own space.

Imagine the renderer using those UV information you gave. First it renders A_island_uv portion of the mesh then render B_island_uv portion of the mesh over the previously rendered A_island_uv and no wonder it's a mess.

Check out the UVs after I corrected them the strange triangles are now gone.



FURTHER INSTRUCTIONS
All you need to do, for this scenario is to enter edit mode. Select a vertice on the UV island you want to move .. Hit L and that will select the whole island. Hit G to grab and move the island. Scale them up or down if need be and you are done.