Transitioning the overlap of multiple objects

Question

I'm trying to fade an object's regular solid surface into its wireframe.

I've got as far as duplicating the object and deleting vertices until I'm left with an area of overlap.

Is it possible to render this in such a way that there is a smooth transition at the area of overlap? Maybe there is a better way to achieve this effect?

Another example:

Answer 1

According to what you illustrated, I would propose a non-compositing way by using modifiers only:

1. Enter Edit Mode, Select one face as where the transition starts, ShiftS > Cursor to Selected to snap cursor to that face;
2. Select all faces, press Spacebar and search for Sort Mesh Elements, choose Cursor Distance in the popup menu, press F6 and toggle Reverse;
3. Create a duplication for the original object, repeat the last two steps on it, just leave Reverse untoggled;
4. Add Build modifier to the original object, toggle Reverse in the modifier stack;
5. Add a Wireframe modifier and a Build modifier to the duplicated object, leave Reverse untoggled this time.

After tweaking the modifier settings a bit, you will simply get something like this when playing animation:

Example file FYI.

Answer 2

You can do this using the compositor and different scenes. This method uses three scenes: one for the regular shaded sphere, one for the wireframe and one that we will use as a factor input to blend between the two. Maybe there are better ways to do this.

1. I am assuming you have you scene set up with a sphere, plane, and the lights.

   

2. Rename the current scene to something like sphere_shaded to be able to differentiate it better form the other we will create

   

3. Create a Full Copy of the scene and rename it to something like sphere_wireframe

   

4. Make sure you are in the sphere_wireframe scene: Select the sphere and add a Wireframe Modifier to it

   

5. Go back to the sphere_shaded scene and create another Full Copy, let's call it sphere_fac

6. In the sphere_fac scene delete everything besides the sphere and the camera

7. In the the same scene add a lamp, I will chose an area lamp but any other will do

8. Change the background of the scene to black

   • go the World Panel -> Surface -> Color

   

9. Position the light so that half of the sphere visible to the camera is getting light and the other half is in the shadows.

   • To make this task easier you can got into the camera view and turn and set the viewport type to rendered

   

10. Render out all scenes, F12

11. Switch to the Node Editor and switch to the compositing nodes. Enable use nodes and backrdrop

    

    

12. Add in the other render scenes

    • By default there should be one render scene already in the node view, duplicate it and form the name drop down choose the others.

    

13. Add a Color -> Mix node

    • Fac: plug in sphere_fac

    • Image: sphere_shaded

    • Image: sphere_wireframe

    

14. To get more control over the transition you can adjust the sphere_fac node a bit

    • RGB curves: good control, a little overkill I think for this

    • Brightness/Contrast: to simple

    • Color Ramp: simple, enough control

    I will use a Color Ramp in this case: Converter -> Color Ramp adjust the two slider on either side to your liking

    

---

Final Result

Same technique with a point lamp

Answer 3

You can achieve the same effect with the following material setup:

Detail of node setup:

If you want the blur to conform to the shape of the hole, put a black and white UV/image texture node in the factor slot of your mix shader instead. You will have to paint the texture yourself with texture painting or in photoshop, but once you have it UV mapped onto your object, it will achieve the effect you're looking for (I think).

See this, it tells you how to use an image mask as a mix factor for a material in cycles: Add different materials to different parts of a mesh?