Gradation Air

Commonly known as Projection (投影 touei), Gradation Air is a Magecraft that materializes objects, in accordance to the caster’s imagination, through the use of prana. Gradation comes from the fact that the created object slowly fades away after being created, and Air is an allusion to the fact that said object is made out of “nothing”.

Mechanics
The concept behind this Magecraft is rather simple, to shape prana into the material composition and design of an object that is being imagined by the magus. However, the world will recognize this item as a phantasm (something that does not belong to the natural world) and it will attempt to correct the inconsistency that is its existence by wiping it out. At this point the caster’s imagination plays an important role, as the better the magus can picture the object in his mind, the more stable the final result will be. The more perfect is the image of the object, the longer it will remain in the world. Still, regardless of how good the image is, it is impossible to create an everlasting object through Projection.

To most modern magi, Gradation Air is an incomplete Magecraft that is useless for anything other than immediate activities. This is not only because the object created will eventually fade away, but also because if something can be created with Projection, it is easier and more practical to craft said object with the appropriate techniques and raw materials. Therefore, most magi only use Projection to create dispensable tools that will only be used once in a particular moment, such as a sacrificial item to be forsaken in a ritual.

Also, while Gradation Air is a more complex form of Reinforcement, the former is ultimately inferior and less efficient than the latter. Comparatively speaking, if a magus uses Projection to recreate a sword while spending 10 units of prana in the process, he will get a weapon with an overall strength of 3 or 4. Meanwhile, if he uses that same prana to reinforce an existing blade, he will get a weapon with a power of 20 or 30. On a side note, Emiya Shirou has greater ease in performing Projection than Reinforcement.

If a magus needs to recreate a more lasting object with Projection, there are means to increase the stability of the final product, such as having technical knowledge of its construction or simply overlaying the desired shape on a material that has a similar composition. It is also possible to use Reinforcement to improve the capacities of the projected item.

Projection (Trace Version)
投影（トレース版）

The personal variation of Gradation Air that Emiya Shirou uses, referred as Tracing due the unique aria that he uses for its activation (Trace On). Shirou’s Tracing greatly differs from normal Projection in the fact that he does not reproduce only the shape and substance of an object, but also everything regarded to its creation and existence.In other words--not only the body of an item, but also its soul: the record of its existence and its history; a trait especially useful for ancient and legendary items which have amassed a substantial amount of mystery.

Shirou mentally divides the process of Tracing into eight steps, which include: Because of this “extra mile” on Shirou’s part, it is possible for him to produce incredibly stable ordinary items that can remain in the world for hours after he first creates them. Furthermore, whenever replicating mystical objects such as Noble Phantasms, he can produce such a faithful copy that even its magic powers and the skills that its true owners performed with it are available for him to use. The reason why he can surpass the usual limits of Projection Magecraft like that is because Shirou himself has a special talent to grasp the internal structure of objects just by glancing at them due to the properties of his Reality Marble, that records the history, composition and design of what he sees and then provides the necessary materials that he needs to reproduce it.
 * 1) Judging the concept of creation
 * 2) Hypothesizing the basic structure
 * 3) Duplicating the composition material
 * 4) Imitating the skill of its making
 * 5) Sympathizing with the experience of its growth
 * 6) Reproducing the accumulated years
 * 7) Excelling every manufacturing process

Strictly speaking, actual reproduction of the objects happens inside Shirou’s internal world and the Projection merely brings it into this world. In a sense, reproducing the object is like loading a bullet into a gun, while deploying it with Projection is like firing said gun. At higher level of proficiency, it is possible to reproduce multiple swords in advance and then deploy them later when they are in fact needed.

This method is not without its limitations though. For one thing it is even more dependent of the quality of Shirou’s image than regular Projection. If he does not go as far as reasoning the internal structure, the item will easily break apart upon physical impact. Furthermore, it is impossible for him to apply Reinforcement upon a replicated item if its image comes from the archives of his Reality Marble.

Although his capacity to perceive and record the properties of an item upon glance is extraordinary, the amount of information to create a mental image that he can acquire from sight alone is still limited and, as a consequence, the quality of the replicas will be inferior when compared to the original (in the case of Noble Phantasms, that means that the rank of his traced copies is decreased by one rank). The only exception to this rule is Avalon, which Shirou can replicate perfectly thanks to the fact that his own body preserved a complete record of the Noble Phantasm after being fused with it for over ten years. He also cannot replicate an object unless he has seen the original with his own eyes, even if he has the its blueprints to work with, which was the reason why he couldn’t recreate the Zelretch at first during the Heaven’s Feel scenario. Strangely enough, he had no trouble Tracing it and Caliburn after “seeing” them through the memories of Lizleihi Justica von Einzbern and Saber respectively. Though this could be because of the fact that in those cases he actually was the viewer, even if the eyes were not those of Emiya Shirou, they were for all intents and purposes connected to his mind.