models were built for the refugee ships, although George recalled that he created a quick physical miniature for CG modeler Rob Coleman to develop his ideas from, rather than try to articulate his feedback without it. Other CG elements included the solar collapses and the Veridian III planet. Knoll used a digital version of the Enterprise-D for the warp effect; the limitations of the motion-control programming and slitscan effect for the original meant that the effect "barely holds up", Knoll said, whereas the CG recreation could keep consistent lighting throughout. While digital techniques were used for many sequences and ships, a few new models were physically built; these included the observatory, built by model shop foreman John Goodson. The climactic battle between the Enterprise and the Klingons over Veridian III was accomplished using traditional motion control, but without the budget for practical explosions and special breakaway models, impacts and battle damage were simulated with practical compositing tricks and computer-generated effects. The destruction of the Bird of Prey was a reuse of footage from The Undiscovered Country. Weapons fire and energy bolts were hand-animated, but Knoll had a different idea for the photon torpedoes. A fan of the impressive, arcing look of the torpedoes from The Motion Picture, Knoll scanned in footage from the film and turned to computer-generated effects. A simulator program created a similar look that could be animated from any point the effects artists wanted, without the expense and tedium required—shining lasers through a crystal in a smoky environment—to recreate the look optically. Carson described the Nexus energy ribbon as the true villain of the film; ILM was responsible for conceiving what the ribbon would look like with no natural frame of reference. "When creating something from scratch, it's always important to rough out the whole thing... because there are so many paths you can explore, it's easy to get bogged down," recalled effects co-supervisor Alex Seiden, who had worked as a technical director on the planetary explosion of Praxis from The Undiscovered Country. Knoll decided the ribbon was a rip through universes, filled with chaotic energy, taking inspiration from images he had seen of magnetic fields around Uranus from a Jet Propulsion Laboratory simulation. The airfoil-shaped core of the undulating ribbon was enhanced with electrical tendrils. To sell the ribbon's vastness in space shots where no sense of scale would be available, Seiden and George created a