PHASE 1: VISUAL DECONSTRUCTION - **Fabric Physics:** The source garment is a jersey knit cotton or cotton-blend. It possesses a matte finish with low light reflectivity and soft, pliable drape properties. It is significantly softer and less structured than the stiff woven button-down the user is currently wearing. Simulation must replicate the natural micro-wrinkles typical of jersey fabric around the armholes and waist. - **Key Features:** - The large white "USPA" typography across the upper chest. - The neon yellow horizontal stripe containing "SINCE 1890" text. - The ribbed crew-neck collar structure. - The deep sleeveless armholes (muscle tee cut). - The specific Royal Blue color value. PHASE 2: FIT & DRAPE SIMULATION - **Body Mapping:** - **Arm Revelation (Critical):** Since the target is wearing a long-sleeve shirt and the source is sleeveless, the simulation must generate realistic skin texture and muscle definition for the user's biceps and forearms, matching the skin tone of his face/neck. - **Drape:** The jersey fabric must hang vertically from the acromion (shoulder point) due to gravity. Unlike the current tucked/structured shirt, the new garment should hang somewhat loose around the waist, creating slight vertical tension folds starting from the chest logo down to the hem. - **Occlusion Handling:** - **Hair:** The user's curly hair at the nape of the neck must be segmented and layered *over* the new crew-neck collar to maintain depth. - **Hands:** The hands are at the sides and do not overlap the torso, requiring no complex masking, but the wrist area where the current sleeves end must be cleanly erased and replaced with the user's wrist/hand transition. PHASE 3: ENVIRONMENT & LIGHTING - **Light Match:** The User Image features soft studio lighting originating from the front-right, casting soft shadows toward the back-left. The new Royal Blue garment must render with highlights on the right pectoral and shoulder area, and deeper shading on the left side of the torso to match the global illumination. - **Color Calibration:** The source image appears slightly more saturated. The blue of the new garment must be color-graded to match the neutral/warm white balance of the User Image. The white "USPA" text must reflect the ambient room light, avoiding pure #FFFFFF whiteness which would look artificial. PHASE 4: IDENTITY PROTECTION - **Facial Lock:** The user's face, including the jawline, ears, and the specific volume and curl pattern of the hair, must remain pixel-perfectly frozen. - **Body Integrity:** Strictly forbidden to slim the user's torso or alter the shoulder width. The user's athletic build must be preserved; the garment must adapt to the body, not the body to the garment. The generated skin on the arms must match the volumetric proportions suggested by the user's clothed shoulders.