PHASE 1: VISUAL DECONSTRUCTION - **Fabric Physics:** The source garment is a heavy flannel or brushed cotton blend. It possesses a matte finish with high light absorption, contrasting significantly with the reflective leather jacket currently worn by the target. The simulation must render a "soft" structural integrity—folds should be rounder and less angular than the leather. - **Key Features:** The specific green-and-black buffalo check pattern must be preserved without distortion. Critical details include the two breast pockets (buttons included), the structured but soft collar, and the open-front drape style. The black crew-neck t-shirt visible underneath the flannel in the source image should be treated as part of the garment assembly to replace the target's current light-colored undershirt. PHASE 2: FIT & DRAPE SIMULATION - **Body Mapping:** The target user has hands inserted into trouser pockets. The new flannel shirt must simulate tension and bunching at the wrists and exhibit a "push-back" effect at the hips where the hands enter the pockets. Unlike the stiff leather which creates a triangular silhouette, the flannel should drape more vertically along the torso but gather naturally at the pocket entry points. - **Occlusion Handling:** The user's hands are partially obscured inside pockets; the hem of the flannel must interact physically with the wrist/pocket entry point, tucking behind the wrist or bunching above it. The user's chin and neck area must be cleared of the leather jacket collar, replacing it with the flannel collar sitting lower and softer against the trapezius muscles. PHASE 3: ENVIRONMENT & LIGHTING - **Light Match:** The target environment features harsh, high-altitude sunlight coming from the user's right (image left), creating high-contrast shadows. The source garment (currently in diffuse lighting) must be re-rendered with hard shadows on the wearer's left side (image right). The flannel texture requires bump mapping to show depth in the fabric weave under this intense directional light. - **Color Calibration:** The source green needs to be color-graded to match the cooler color temperature of the mountain environment (blue sky fill). The black squares in the plaid pattern must achieve the same black point as the shadows in the mountain rocks to ground the garment in the scene. PHASE 4: IDENTITY PROTECTION - **Facial Lock:** Absolute freeze required on the user's facial structure, facial hair (beard/mustache), hairstyle, and the sunglasses. The jawline boundary where the current jacket collar touches must be carefully segmented to remove the leather without eroding the jaw. - **Body Integrity:** Do not slim the user. While the flannel is thinner than the leather jacket, the user's shoulder width and torso volume must remain consistent. The simulation should reveal the user's natural build which is currently padded by the thick leather, without artificially reducing body mass.