Fig. 1. presents the concept of this tool:

Fig. 1. The MDeform tool.

I have created this add-on to implement the features that are missing in the standard Mesh Deform modifier. These are two things:

  • possibility to assign to the deforming mesh multiple objects in one step;
  • reverting of the deforming mesh to its initial shape when it is deactivated (i.e. unbound);
  • In the text below I am explaining the whole thing

    Here you can download the object_mdeform.py add-on file.

    To follow this tutorial, you should install this add-on into your Blender environment. (Here is the tutorial, which explains how to do that).

    Add-on activation

    This add-on is named MDeform (you will find it in the Object category) (Fig.2):

    Fig. 2. Activation of the MDeform add-on.

    If you want to activate it permanently, push the Save User Settings button.

    Add-on usage

    Begin with creating the deforming mesh object (Fig. 3):

    Fig. 3. Creation of the deforming mesh.

    In our example the „deformer” object is named Cube.003. Switch its display mode to Wire, to see the deformed objects inside.

    In Object Mode select the objects you want to deform (Fig. 4). Always select the deformer object as the last one. Then press the [W] key, to invoke the Set Deformer command:

    Fig. 4. Assigning objects to the deformer mesh.

    You can assign all the deformed objects at once. In case of complex assemblies you can invoke the Set Deformer command many times, selecting subsequent object groups.

    When you enter the Edit Mode of the deforming mesh, you will find additional Deformer panel at the bottom of the Property shelf (Fig. 5):

    Fig. 5. Deformer control panel

    To enter the object deformation mode, push the Bind objects button (Fig. 6):

    Fig. 6. Entering the deformation mode

    BEWARE: the operation of objects binding may take a few minutes (it depends on the face number of the deformed meshes).

    When it is completed, the Deformer panels changes its contents (Fig. 7):

    Fig. 7. Active deforming mesh and its panel

    From now on, every change in the shape of the mesh deforms objects assigned to it (Fig. 8):

    Fig. 8. Deforming the assigned objects
    Principle of operation

    How it works? Let’s switch into the Object Mode and examine one of the deformed objects (Fig. 9):

    Fig. 9. Details of the deformed objects

    Let’s come back to the reforming mesh. Sometimes during the work it turns out that you have to modify the shape of the deforming mesh. You cannot do it when it is active (because when you add new vertices, Blender turns off the deformation effect). To do it properly, deactivate the deforming mesh using the Unbind objects command (Fig. 10):

    Fig. 10. Deactivation of the deforming mesh

    In the result the reforming mesh receives the shape it had at the moment of pushing the Bind objects button (Fig. 11, see also Fig. 6):

    Fig. 11. The result of the mesh deactivation — reverting to its initial state

    Once the mesh his deactivated, you can modify its topology (Fig. 12):

    Fig. 12. Altering the deforming mesh

    Then you can push the Bind objects button again and try to deform the modified mesh. Once you manage to get the desired shape of the deformed objects — you can apply this change by pushing the Apply button (see Fig. 7).

    Sometimes when you push the Apply button, you may receive a warning, similar to the one shown in Fig. 13:

    Fig. 13 A warning during the Apply operation

    When you see it, check at the end of the list in the Info window which objects have caused this problem (Fig. 14):

    Fig. 14 A detailed message abort the problems with Mesh Deform modifier (contents of the Info window)

    Usually it means that you hale tried to apply the MDeform modifier to an object which shares its mesh with other objects. In such a case create a „single-user” duplicate of this mesh and push again the Deformer:Apply button.

    Usage example

    For what purpose we need this add-on? Well, once I had formed the P-40 model, I had received two original factory drawings of its fuselage. I put them on the appropriate views of my model. It turned out that I have to change the width of the entire fuselage, from the engine cowling to the end of the tail (Fig. 15):

    Rys. 15 Differences between the blueprint and my P-40B model

    The fuselage of this model is built of a number of accurately fitted elements: engine cowling panels, fairings, parts of the cockpit canopy, etc. If I modified each of them separately, I would probably spoil the shape of this model - it's hard to obtain the a perfectly smooth surface after such manual corrections. Besides, it would also require many hours of work. That's why I decided to change all these objects at once, using the MDeform add-on. This tool preserves the continuity between the deformed surfaces. It is a great advantage. Thus I begin with creation of a helper mesh around the fuselage (Fig. 16):

    Fig. 16. The deforming mesh, created around the fuselage

    Keep this mesh simple - in this case I have placed its few "bulkheads" in the key locations. (MDeform works well with the deforming meshes of a simple shape. They produce smoothly deformed meshes) (Fig. 17):

    Fig. 17. The key locations of the deforming mesh segments

    Assign all part of this fuselage to this mesh, and then Bind these objects. Then start to modify the mesh width. It will modify accordingly the width of the fuselage (Fig. 18):

    Fig. 18. Correcting the width of the mid-fuselage

    In a similar manner correct the width of the tail (Fig. 19):

    Fig. 19. Correcting the width of the tail

    This way we will quickly obtain a smoothly shaped fuselage that has correct width (Fig. 20):

    Fig. 20. The result of using the MDeform tool