PHASE 1: VISUAL DECONSTRUCTION - **Fabric Physics:** The source garment is a heather grey cotton jersey knit. It is a matte fabric with low reflectivity and high flexibility. It should exhibit soft, rolling folds rather than sharp creases. The simulation must replicate the "micro-noise" texture of the heather grey pattern rather than a solid flat grey to maintain realism. - **Key Features:** The scoop neckline and wide tank-style straps are critical. The binding stitch along the neck and armholes must be preserved. The hemline appears straight but soft. The garment lacks buttons or distinct logos, focusing entirely on the knit texture and cut. PHASE 2: FIT & DRAPE SIMULATION - **Body Mapping:** The target user has a fuller figure than the source model. The tank top must stretch realistically across the bust and midsection without looking painted on; it needs to retain some slack near the waist. **Crucial:** Since the source is sleeveless and the user is wearing short sleeves, the simulation must generate realistic skin texture for the user's upper arms and shoulders where the red sleeves currently exist. The fabric must deform and compress where the user's arms press against the side of the torso. - **Occlusion Handling:** The user's arms are crossed over the stomach. This is a high-complexity occlusion. The grey tank top must be rendered *behind* the forearms and hands. A strict segmentation mask must be applied to the arms and hands to ensure the fabric tucks underneath them, creating realistic contact shadows where the arms press into the stomach area. PHASE 3: ENVIRONMENT & LIGHTING - **Light Match:** The user is in a room with mixed lighting—likely a ceiling source slightly to the left, casting soft shadows to the right. The grey fabric must accept shadows cast by the user's chin and, most importantly, the deep ambient occlusion shadows cast by the crossed arms onto the torso. The fabric should not look "brightly lit studio grey" but rather "indoor ambient grey." - **Color Calibration:** The environment has strong color contamination potential (blue curtain left, red brick right). The grey shirt acts as a neutral reflector; it should pick up a subtle blue spill on the left flank and a warm reddish tone on the right flank to integrate it into the physical space. PHASE 4: IDENTITY PROTECTION - **Facial Lock:** The user's entire head, including hair, hairline, face shape, and neck, must be frozen. The hands and wrists (including the bracelet/watch) must be preserved pixel-perfectly. - **Body Integrity:** Strict prohibition on body warping. The silhouette of the new garment will naturally be closer to the skin than the current loose red t-shirt, but the underlying volumetric mass of the user must remain unchanged. The generated skin for the shoulders/arms must match the user's facial skin tone exactly.