A selection from over 209 client variations I created for Harry Potter's "Patronus" Spell wand effect, circa 2003. (Probably Maya4 or 5)
The first version was a cool and wacky idea by the VFX Supervisor to use a cloth simulation as "electric liquid light" effect- cloth was simulated spinning in a cone and pulled through with keyframed vortexes. I ran the footage backwards to give it a look of emitting from the wand. This approach was quickly ditched as the "electric" was toned down.
The subsequent variations of the effect was created using primarily two software packages, AutoDesk's Maya using a custom plugin, and ILM's proprietary compositing software "CompTime".
In Maya, I tracked an emitter to Harry's wand which sprayed out particles at varying velocities. The particles would collide with a "shield" collision geometry constrained to the Dementor. The particles were not rendered in Maya, but instead used an amazing blobby system (before blobbies were uncool) written by Simon Eves as a test, but had since been abandoned due to some drawbacks and being reassigned. I Hacked the plugin together it held some interesting results. The system revolved around importing particles into the ILM custom lighting tool, IRENDER, as a surface. IRENDER relied on a custom PRman DSO which reads the particle pdb, surrounds it with a metaball, skins it with an implicit surface, and displays a single polygonal surface "ready" for lighting. At the point where two metaballs intersect, it would join the skin thus creating a smooth blob between the balls. Simply amazing at the time.
Since the DSO was a half abandoned, half baked test, it was never finished and thus was significantly limited to creating a new surface per frame. Typically in a production environment this would not work at all- no temporal adherence, no uv support, no motion blur, and on top of that, Simon had moved on to bigger and better projects- so no developer support either! Fortunately, the original artwork and script line called for an effect that could justify all of these drawbacks. "A blobby like light that swirls and pops from Harry's Wand!" sounded like a perfect fit for this half-baked technology I stumbled upon.
I was able to get a reflection pass, Fresnel pass and normals pass to render with some shader hackery - which was just enough to get it into CompTime, ILM's proprietary compositing system (much like AfterFX 3.0, but better!)
Using these passes, I was able to create literally hundreds of looks and variations for Director Alfonzo Curan. Good thing too, because this was Alfonzo's first FX film and one of the first major "emotional shots" for him to view. Suffice it to say, I ended up creating over 2009 official takes for him, each one catering to his whimsical and exploratory nature of "finding this effect for Harry", as he would say.
In the industry, when a Director loves the work and puts it in the move, we call this "Director Buyoff". Getting buyoff on this effect was enormously difficult as a result of a communication barrier between how to direct VFX work. Alfonzo was very accustomed to working with Actors and On-Set talent, but not so much on films with FX elements that are vital to the story.
What's presented here are selections in order of creation. Simulations in Maya, Surface Rendering in IRENDER, and Compositing tricks (such as using ILM's Lightsaber Plugin to create the glow and effect), and Renderman for the Dementor rendering and lighting interactions.
This was eventually rolled out for this Class Room Sequence, and earlier in the film on the Train. Thanks to Simon for the awesome setup, it saved my bacon! All in all, it was about 3-4 months of grueling development, but totally worth knowing I helped craft an icon of the HP universe.
VFX Supervisor: Bill George
VFX Producer: Sandra Scott
CG Supervisors: Euan MacDonald, Michael DiComo
Sequence Supervisor / Look Development: Anthony Shafer
Soundtrack: "Particle Man" They Might Be Giants
Editing: Final Cut 4 Studio
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