PHASE 1: VISUAL DECONSTRUCTION - **Fabric Physics:** The source garment is a heavy flannel or wool-blend "shacket" (shirt-jacket). It possesses high structural rigidity compared to the user's current athletic wear. It has a matte finish with high light absorption and practically no specular reflection. The fabric should behave with moderate stiffness, resisting small folds but creating deep, angular creases at major stress points (elbows, armpits). - **Key Features:** The distinctive brown and cream houndstooth/check pattern must be preserved with high fidelity. Essential geometry includes the structured collar, the dual chest pockets with buttoned flaps, the front button placket (worn open in source, implying a layered look), and the buttoned cuffs. The hemline is straight but slightly curved at the hips. PHASE 2: FIT & DRAPE SIMULATION - **Body Mapping:** The target user has a muscular, athletic build, significantly broader than the source model. The simulation must upsize the garment to accommodate the target's deltoids and chest without stretching the pattern. Unlike the current green t-shirt which clings to the skin, the flannel jacket must "bridge" gaps between muscle groups, hanging vertically from the widest points (shoulders/chest) rather than contouring the abdomen. The sleeves must extend fully to the wrist, replacing the currently exposed arms, and should bunch slightly at the bend of the target's right elbow. - **Occlusion Handling:** The transfer is relatively clean as the user has short hair and hands are positioned away from the torso. However, the neckline of the jacket must sit correctly around the target's muscular neck without clipping into the trapezius muscles. If the jacket is generated "open," a neutral undershirt or skin texture must replace the current green neckline. PHASE 3: ENVIRONMENT & LIGHTING - **Light Match:** The target environment utilizes warm, soft studio lighting with a peach/beige backdrop, casting shadows to the viewer's right. The source image is cooler. The jacket's albedo map must be color-graded to increase temperature (yellow/orange bias) to match the target scene. Shadows within the jacket folds must correspond to the target's existing light source (coming from the upper left). - **Color Calibration:** The cream/beige checks in the pattern need to reflect the ambient warm light of the target room, shifting slightly towards the background hue, rather than remaining the stark white/cool grey of the source studio. PHASE 4: IDENTITY PROTECTION - **Facial Lock:** Absolute freeze required on the user's facial structure, head shape, ears, and short hairstyle. The neck area above the collar line must remain unaltered. - **Body Integrity:** The user's legs (in black shorts) and the visible portions of the knees/calves must remain untouched. The simulation is strictly forbidden from narrowing the user's shoulders or chest to match the source model; the garment must adapt to the user's volume, not the other way around.