A computer implemented method of interacting with a three dimensional image based lighting surface in order to adjust the lighting properties of the surface, the method comprising: defining an image plane and a user viewpoint for the lighting surface; rendering and displaying on a display of a computer a scene containing an object in situ within the lighting surface taking into account said image plane and said user viewpoint; by way of a user interaction with the displayed scene, receiving an identification of a point on the image plane; tracing a ray from the user viewpoint through the identified point on the image plane and either, • determining a surface intersection point of the ray with said surface or • determining an object intersection point of the ray with said object and tracing a further ray either being a reflection of the ray from the object or being normal to the surface of the object at said object intersection point, and determining a surface intersection point of the further ray with said surface, and adjusting the lighting properties of the surface in the region of the surface intersection point either by adding to the image based lighting surface, in the region of the said surface intersection point, a light source having a geometry including mapping the geometry of the light source onto the three dimensional image based lighting surface, or selecting a light source having a geometry in the region of the said surface intersection point and subtracting the selected light source or modifying the properties of the selected light source. defining an image plane and a user viewpoint for the lighting surface; rendering and displaying on a display of a computer a scene containing an object in situ within the lighting surface taking into account said image plane and said user viewpoint; by way of a user interaction with the displayed scene, receiving an identification of a point on the image plane; tracing a ray from the user viewpoint through the identified point on the image plane and either, • determining a surface intersection point of the ray with said surface or • determining an object intersection point of the ray with said object and tracing a further ray either being a reflection of the ray from the object or being normal to the surface of the object at said object intersection point, and determining a surface intersection point of the further ray with said surface, and • determining a surface intersection point of the ray with said surface or • determining an object intersection point of the ray with said object and tracing a further ray either being a reflection of the ray from the object or being normal to the surface of the object at said object intersection point, and determining a surface intersection point of the further ray with said surface, adjusting the lighting properties of the surface in the region of the surface intersection point either by adding to the image based lighting surface, in the region of the said surface intersection point, a light source having a geometry including mapping the geometry of the light source onto the three dimensional image based lighting surface, or selecting a light source having a geometry in the region of the said surface intersection point and subtracting the selected light source or modifying the properties of the selected light source. adding to the image based lighting surface, in the region of the said surface intersection point, a light source having a geometry including mapping the geometry of the light source onto the three dimensional image based lighting surface, or selecting a light source having a geometry in the region of the said surface intersection point and subtracting the selected light source or modifying the properties of the selected light source.