This paper proposes an interior design simulator with an inter-reflection between a marker and a glossy floor. The proposed method for rendering the inter-reflection consists of three processes: at first, a reflectance ratio
of the floor is estimated from the reflection on the floor and from the marker box directly. Then the roughness of the floor is estimated based on the sharpness of the reflected marker box image on the floor. Lastly, the marker box reflection is eliminated based on the surrounding colors of the marker box reflection.