PHASE 1: VISUAL DECONSTRUCTION - **Fabric Physics:** The source garment appears to be a heavy cotton flannel or "shacket" (shirt-jacket) material with a matte finish. It possesses medium stiffness, meaning it holds its shape at the collar and cuffs rather than draping loosely like silk. Light reflection should be diffuse with minimal specular highlights due to the fibrous texture. - **Key Features:** The distinctive brown and cream houndstooth/plaid pattern must be preserved with correct scaling. Critical details include the two chest pockets with buttoned flaps, the dark contrast buttons down the placket, and the structured collar. The simulation must handle the transition of the pattern across seams (sleeves to shoulder). PHASE 2: FIT & DRAPE SIMULATION - **Body Mapping:** The user has a straight, standing posture. The flannel shirt is boxier than the user's current fitted denim shirt; therefore, the simulation must allow for a slightly looser fit around the torso while maintaining the user's shoulder width. The fabric should hang vertically due to gravity, with minor bunching at the elbows where the user's arms are slightly bent. The hemline should fall naturally over the hips, likely untucked given the source style. - **Occlusion Handling:** The user's hands are visible. Specifically, the right hand is holding sunglasses/glasses. The new sleeve cuff must not obscure the hand or the object held. The red thread/bracelet on the right wrist must be segmented and layered *over* the new garment's sleeve cuff. PHASE 3: ENVIRONMENT & LIGHTING - **Light Match:** The user is in a high-contrast environment with strong directional sunlight coming from the left (viewer's left), casting distinct, hard grid-like shadows from the safety grill across the torso. The new garment MUST replicate these hard shadow lines. The illuminated areas should be bright, while the shadowed areas within the plaid pattern must be significantly darker to match the dynamic range of the scene. - **Color Calibration:** The source image has neutral studio lighting. The target scene has warm, natural sunlight. The beige/cream tones of the flannel shirt must be warmed slightly (shifted towards yellow/orange) to match the ambient temperature, while the dark brown checks must maintain contrast without becoming washed out by the bright sun. PHASE 4: IDENTITY PROTECTION - **Facial Lock:** The user's entire head, including the specific hairstyle, facial structure, ears, and neck skin tone, must be frozen and pixel-perfectly preserved. - **Body Integrity:** The simulation is strictly forbidden from altering the user's skeletal structure. Do not slim the waist or broaden the shoulders to match the source model's physique; the garment must drape over the user's existing body measurements.