Mobile Blender #b3d


Sometimes the news stories we cover are quite distasteful but none the less challenging. This time I was asked to show how a pedophile surrounded himself with images of abused children. I couldn’t and wouldn’t show any of those actual children as it would violate their right to privacy and could be titillating to boot. So I needed to create a metaphor that suited the narrative and could stretch to fill a large portion of the story for which we had absolutely NO pictures (or overlay/b-roll).

I settled on the idea of a child’s mobile, I had seen ones that could have photos hung from it. I could place the image of the perpetrator (since convicted) at the center and surround him with suggestive images of children. The pictures in themselves are not lewd or abusive but in context suggest very bad behaviour. I grabbed old images of my own kids and carefully cropped any parts that could identify them. Making sure to find ones with exposed skin and naivety, which amped up the creepyness. It proved very successful with music from a child’s toy playing in the background. Yuck.


To create the mobile I made a simple wire hook object and duplicated that down into a pyramid or tree of loops and hooks. Each one was parented to an empty (null object) and they were constrained in turn to higher empties. Then I placed the image objects at the end of each hook chain.


The background image was just a photo from my street mapped to a rather large plane, it didn’t have to be high res as I was going to shoot it out of focus anyway.



The images in the photos were photos mapped to mesh plane objects then attached or parented to curve objects (the white frames), which were extruded just a bit. I lofted holes in them as well. This seemed to save me memory rather than having lots of subsurfed mesh geometry.


I really wanted to use shallow depth of field to focus on the man at the center, and to bring an ethereal feeling to the images. I tried the defocus blur in Blender’s compositor but it failed around the edges. It is fine if the blur is not to extreme. So I switched to the Cycles render engine, which produces native accurate DOF effects. But it requires a LOT of samples to get a clean image. What to do?

Ask twitter of course! My tweep @quollism suggested that I hack the object’s material to simulate a light source.


I used a normal dot product on an emission node across all of the objects so that they would brighten and darken as the twisted in the simulated breeze. Only drawback is the lack of shadows. But you never notice because its such a high key image anyway.

I turned my attention to the metal hooks, which looked great in material view but not so hot in rendered view. I needed to get a reflection effect on them but I didn’t want to use up samples tracing them. Taking a leaf out of the OpenGL playbook I simply mapped them with the background image using the object’s reflection mapping coordinates. And a bit of light direction of course.


Finally I needed to add some more life to the rotation of the mobile, after all it must have some motivation too. So I added some breeze. Of course this doesn’t have simulated physics, pffft I’m much to lazy for that. Instead I set up random elements in the chain with some z rotation noise modifiers in the f-curve editor. As long as the constraints on the photos didn’t allow them to pass through the hooks I was safe.


All of this amounted to a reasonably fast render and proved easy to re-shoot from alternate angles so that I could stretch the initial animation. I could even swap out photos when the story had moved along and something else had to feature in the center.

The only thing that I added in post production was some of camera lens flares to give it more wispy ethereal-ness. I know that’s cheating but hey, all the rest was cheating too 😉


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