So I combined these 3 shapes together and you can see the edges are still there. how can I fix this? How can I smoothen all the edges in that one shape?
It's easier to model the junctions in highly symmetrical objects like this than it seems.
Note that the origin of the spheres object never moves from the World origin. All moves are on the mesh, in Edit Mode.
- Starting with a 1/4 of a 16-segment, 8-ring sphere, aligned as shown, and an empty at the origin
- Assign a Mirror modifier in X, and an Array modifier, Count 3, with Object Offset based on the Empty, which is rotated in Z by 120 degrees. Check 'Merge' and 'First and Last' in the modifiers.
- In Edit Mode, G X move the mesh until the overlap is right for you
- Select all the entirely internal faces, (take a peek on the outside of the spheres, make sure there is no selection showing)
- Working on the 'original', delete the entirely internal faces
- On the partially internal faces, slide the internal vertices (G G) down their edges, until they meet their counterparts in the modifier-generated mesh. (Everything's symmetrical, you only have to do this half a dozen times)
- Once everything is neat and tidy, add a Z dimension to the Mirror modifier.
- After making a copy, and applying the modifiers, perhaps tweak. Here, I X> dissolved a few edges to get all quads, and (CtrlV > Smooth Vertex) eased the triple junction
- Throw on a Subdivision Surface modifier.
How did you combine the three spheres? The wrong way is to select the three spheres and then 'join' them. The reason it doesn't work is that this creates three sphere which sit trough one another (take a look in wireframe mode, shortcut z). The right way is to use the boolean modifier and set it to union. This creates one object with surface.