Trans-scanning is the biological process by which a Transformer's built-in sensors choose and examine a new alternate mode. The process of disguising themselves, camouflaging their robotic natures, is as ingrained and natural in Transformers as changing color is in chameleons. Immediately after arriving on a new world in its transition form, a Transformer begins trans-scanning to choose and generate a new exostructure/disguise appropriate to both its size/body mass and its new locale.
Permanence vs. Fluidity of Scans
How permanent a trans-scanned alternate form becomes, as well as how easily a Transformer can scan and adopt a new one, are somewhat open to debate. There is much evidence to suggest they are quickly able to adopt new forms at will. Certainly Bumblebee was able to alter the features of his Camaro mode from an older to newer model with ease, but this is not the same as taking an entirely new form.
According to one source, any Transformer can trans-scan a new, appropriately massed alternate form at will, and their inner protoform core will generate a new exostructure or alter an existing one to that new appearance almost instantaneously.
However, other sources seem to disagree. The main evidence against this ease in switching forms being universal is the fact that it is treated as a "special power" for several Transformers. The Autobot and Decepticon Create-A-Bots, for instance, were able to switch between alt modes as diverse as trucks and helicopters on the fly, but this was apparently the result of some form of enhancement (installed by Wheeljack, in the case of the Autobot). Moreover, the Decepticon spy Frenzy possesses a similar ability, being equipped with a special "hyper-reactive" trans-scanning and reformatting processor, which allows him to scan and transform into anything at any given moment. The Create-A-Bots from the Revenge of the Fallen DS game can't change between different alt-modes once they have chosen their normal alt-mode, unlike their 2007 game counter-parts.
The fact that these few are singled out as having the ability to re-trans-scan at will would seem to suggest that once your average Transformer has selected an alternate mode, they can't take on an entirely new one under their own power. However, this is again contradicted in the prequel novel, Ghosts of Yesterday: Bumblebee transforms to a previously scanned mode on an empty alien world to escape an attack by Starscream, and he does so "hastily", indicating that his change from protoform was extremely swift. Prime himself transforms to cometary form on board the transport ship before launching down to aid his subordinate; again, this is indicated to be swift and not requiring a lot effort. As neither of these Transformers are noted with the above-named "special ability", it is indeed up in the air as to which of the two cases is the truth. Ultimately, no precise conclusions can be made, but traditionally, the Transformers mythos has long been peppered with such contradictions as this.
Behind the scenes
One piece of metatextual evidence which could be argued to support the fluidity argument indirectly is the fact that in the actual film, no two transformations by the same character were ever remotely identical. Although the vehicle and robot mode models were obviously always consistent, ILM animators have admitted that the actual transformations from mode A to B (and vice-versa) were unique every time they were performed, with the thousands of transforming parts moving around in significantly different orders and via different internal and external routes around the body each time a transformation took place. This was largely due to the fact that the transformations were not automated, but had to be "manually" animated each time, with the main focus being what part of the Transformer in question was facing the virtual camera and what would look interesting and "believable", rather than maintaining the consistency of any transformation method.
Thus, unlike most past depictions of Transformers (or, for that matter, all Transformers toys) individual Movieverse Transformers actually have no fixed "transformation scheme". This could be argued to support the suggestion that Cybertronians from the Movieverse have such fluid transformational abilities that they do not require set patterns or methods by which to change form, but rather move their parts around in an almost instinctive manner, possibly as determined by factors such as their current speed, terrain, or intent of action at the moment of transformation. This can most easily be seen with Optimus Prime. In the fight against Megatron in the forest during Revenge of the Fallen, his transformation took only a few seconds, while his very first transformation in front of Sam and Mikaela took well over 20 seconds to complete (most obviously for dramatic effect). Indeed, some transformations (most noticeably Barricade's first transformation on-screen) appear more akin to bodily locomotion than a proper procedure to shift from one form to another. This is especially enhanced when some parts continue to shift even after the overall transformation has been completed, such as the small moving parts seen when Bumblebee transforms in front of Sam and Mikaela. Then, Starscream at least momentarily flew in what appeared to be an in-between form of his robot and jet modes, his jet wings staying in their jet-mode positions even when all other parts have been shifted to form his robot mode, summarizing that the transformation ability of Transformers in the movieverse is closer to the color-changing ability of chameleons than in any other universe, being a process of free locomotion between two forms, or perhaps better-worded as poses, rather than transformation between two completely separate forms. The ultimate extension of this logic is that some of their additional transformational abilities (such as Bumblebee's previously unseen shoulder-mounted missile launchers used against Devastator) may not even be "designed in" when they trans-scan and reformat, but might even be spontaneously generated as needed.
The inclusion of Stealth Force mode seen in Dark of the Moon only adds evidence to this theory. Seeing as how Stealth Force mode is a halfway mode between robot mode and vehicle mode it seems that the Transformers are able to assume these halfway modes to have weapons as well as mobility.
- Trans Scanning Bumblebee
- Trans Scanning Optimus Prime
Japanese-only releases, these figures are able to transform into the Protoform, Transition, and Earth forms of their respective robots by utilizing snap-on armor.