How to really make it only "one object"

Question

So after using the Ctrl+J method to make 1 object out of multiple ones I first thought: oh. nice.

In edit mode I sadly realized that the 1 object is still made up from several different parts. It is not like I think its looks ugly or anything. But editing and sculpting is really annoying when its like that. Needing to select the faces one by one etc.

How can I make my object just actually be 1 object without being made up from several parts?

Notes: - I don't have the object non-combined any more. that means I saved after doing Ctrl+J and I can't undo it.

Answer 1

This generally is not the "correct" or desirable way to model this.

Joining geometry with Ctrl + J will only group and turn it into one object, it will not alter you geometry in any way, nor will it "merge" volumes or faces. That is the job of a Boolean operation.

You can generally undo this step as described by Samir-Rahamtalla with P > Loose parts since the geometry will be exactly the same, and return to your "non merged" objects without loosing too much information, object centers will be lost though.

Boolean operations might work under certain circumstances, if you objects are closed watertight manifold meshes, and they don't have coplanar or coinciding faces.

In your case it will most likely fail since your faces are co-planar, and even if it does work, it will likely produce undesirable, uneven triangulated geometry, which in most cases will cause more problems down the road.

The "correct" way to mode something like this is to do it in edit mode by subdividing and extruding your mesh, so it will produce a "clean" geometry.

Answer 2

To separate the parts into individual objects press p in edit mode and select separate by loose parts.

Select one of the parts you want to combine and add a Boolean modifier. Set the Operation to Union then select one of the parts you want to add to the mesh.

Add more Boolean modifiers for the other parts.

When done you can apply the modifiers and have a single mesh or one object as you put it.

You can also use the Intersect (Boolean) tool in edit mode and set the operation to union and adjust the threshold to get all parts of the mesh to combine

You can get the tool quickly if you press Space and start typing intersect. The list will show two options. Select Intersect (Boolean).

Answer 3

Ray, when it comes to easy shapes like yours Duarte's way of modeling them is the easiest method to do them. If you are a beginner with 3D modeling it's crucial to learn the basics like extruding.

You might want to try the boolean modifier but don't expect to get instant good results. The amount of tweaking exceeds the time to do it like shown in Duarte's image.

It's also important to know what your model's purpose will be. Rendering out some pictures is a totally different thing compared to putting a model into a game engine.