PHASE 1: VISUAL DECONSTRUCTION - **Fabric Physics:** The source garment is a structured woven cotton (likely poplin or broadcloth). Unlike the user's current ribbed knit top, this material has low elasticity. It requires a stiffer simulation with distinct fold lines rather than clinging to body contours. The surface is matte; specular highlights should be broad and diffused, typical of white cotton, avoiding any silky sheen. - **Key Features:** The sharp collar structure must be maintained without collapsing into the neck. The central button placket needs to remain vertically aligned, following the torso's centerline. The sleeveless armhole cuts and the subtle "princess dart" shaping on the sides must be preserved. The curved bottom hemline is essential. PHASE 2: FIT & DRAPE SIMULATION - **Body Mapping:** Due to the user's leaning pose against the barrier, the shirt must hang with a gravitational bias toward the user's right hip. The garment should not cling tightly to the waist; it needs to bridge the gap between the bust and hip with a straighter silhouette than the current top. **Crucial:** The system must synthesize realistic skin texture for the arms, as the source is sleeveless and the target is currently wearing long sleeves. - **Occlusion Handling:** The user's long, dark hair flows over both shoulders and the upper chest. This hair must be segmented and layered *over* the new shirt collar and shoulder seams. The right arm (resting on the barrier) creates a contact point; the new armhole must sit flush against the axilla without clipping into the barrier. PHASE 3: ENVIRONMENT & LIGHTING - **Light Match:** The target environment features harsh, high-altitude sunlight coming from the user's left (viewer's right). The simulation must cast deep, hard-edged shadows on the right side of the torso (viewer's left) and under the collar. The texture mapping must account for the high contrast of outdoor exposure. - **Color Calibration:** The studio white of the source cloth must be temperature-adjusted. Highlights should lean slightly warm (sunlight), while the shadowed areas (folds and the side away from the sun) should pick up a slight cool blue tint from the clear sky/lake reflection to integrate naturally. PHASE 4: IDENTITY PROTECTION - **Facial Lock:** The user's face, jawline, neck, and the red headband must be strictly frozen. The hairline interface with the forehead must remain untouched. - **Body Integrity:** The user's shoulder width, bust volume, and hip width must remain consistent. No slimming filters should be applied. The lower body (jeans) must remain completely masked out and unaltered. The generated skin for the arms must match the user's facial skin tone exactly.